Research ArticleThree-Dimensional Lower Extremity Joint Loading ina Carved Ski and Snowboard Turn A Pilot Study
Miriam Klous12 Erich Muumlller2 and Hermann Schwameder2
1 Department of Health and Human Performance College of Charleston Charleston SC 29424 USA2Department of Sport Science and Kinesiology Christian Doppler Laboratory ldquoBiomechanics in SkiingrdquoUniversity of Salzburg 5400 Hallein Salzburg Austria
Correspondence should be addressed to Miriam Klous klousmcofcedu
Received 10 July 2014 Accepted 30 July 2014 Published 15 September 2014
Academic Editor Eddie Y K Ng
Copyright copy 2014 Miriam Klous et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited
A large number of injuries to the lower extremity occur in skiing and snowboarding Due to the difficulty of collecting 3D kinematicand kinetic datawith high accuracy a possible relationship between injury statistic and joint loading has not been studiedThereforethe purpose of the current study was to compare ankle and knee joint loading at the steering leg between carved ski and snowboardturns Kinetic data were collected using mobile force plates mounted under the toe and heel part of the binding on skies orsnowboard (KISTLER) Kinematic data were collected with five synchronized panning tilting and zooming cameras An extendedversion of the Yeadon model was applied to calculate inertial properties of the segments Ankle and knee joint forces and momentswere calculated using inverse dynamic analysis Results showed higher forces along the longitudinal axis in skiing and similar forcesfor skiing and snowboarding in anterior-posterior and mediolateral direction Joint moments were consistently greater during asnowboard turn but more fluctuations were observed in skiing Hence when comparing joint loading between carved ski andsnowboard turns one should differentiate between forces and moments including the direction of forces and moments and theturn phase
1 Introduction
Skiing and snowboarding are the prominent winter sportsand the general trend shows an increasing number of peopleparticipating in these sports [1ndash3] With the increased num-ber of practitioners the number of injuries increased Injurystatistics have shown that skiing injuries mainly involve thelower extremities predominantly the knee (181ndash367) [4ndash8] and the ankle joint (6ndash122) [6 9ndash11] In snowboardinginjuries occur when falling or during landings after a jumpand mainly the upper extremities are injured [7 8 12]However still a considerable number of injuries occur in thelower extremities with 64ndash17 in the knee joint and 49ndash16 in the ankle joint [7 13ndash16] These values clearly showthe vulnerability of the lower extremities in skiing and snow-boarding If we assume that higher joint loading is related toinjuries injury statistic would suggest greater knee joint load-ing in skiing and greater ankle joint loading in snowboarding
It has been suggested that the introduction of the carvedturning technique is contributing to the increase in the sever-ity of lower extremity injuries in skiing Based on biomechan-ical concepts described by Howe [17] external forces actingon skiersnowboarder include gravity and normal force snowfriction air resistance propulsion force and while turningcentripetal force The characteristically higher velocity andsmaller turn radius in carved turns increase the centripetalforce and thereby increase the lower extremity joint loadingThis concept applies to both skiing and snowboarding How-ever the magnitude and direction of joint loading for eachof the joints could vary between skiing and snowboardingdue to technique position and equipment differences Withthe use of soft boots in snowboarding a minimal amount ofmovement in the ankle is expected whereas in the stiff skiboots forces and moments are transferred to the knee jointThis would suggest higher joint loading in the ankle joint insnowboarding and higher joint loading in the knee joint in
Hindawi Publishing CorporationComputational and Mathematical Methods in MedicineVolume 2014 Article ID 340272 13 pageshttpdxdoiorg1011552014340272
2 Computational and Mathematical Methods in Medicine
skiing and would be in agreement with the injury statisticsdescribed previously
In a first attempt it is of special interest to obtain greaterinsight into the differences in ankle and knee joint loadingbetween a carved ski and snowboard turn The focus ofthe current study was on a carved turn since a carved turnis a common skill in both skiing and snowboarding andhigher joint loadings are predicted in this kind of turn Astudy of Urabe et al [18] on skiing reported larger numberof injuries at the outer leg The outer leg might experiencehigher forces and moments due to its steering functionTherefore the current study focused on the steeringleg In snowboarding steering is controlled by the rearleg
Several biomechanical studies estimated the joint loadingin skiing while turning [19ndash24] and on landing maneuversafter a jump [25 26] Also in snowboarding forces andmoments have been estimated at the boot sole with an alpineboard [27] and in lower extremity joints [28] Besides thestudies by Klous et al [23] and Kruger et al [28] none ofthe previous studies performed full three-dimensional (3D)inverse dynamic analysis in skiing or snowboarding withsufficient accuracyThis is due to the complexity to collect 3Dkinematic data accurately in a field experiment [20] Recentlywe developed a method to collect accurate 3D kinematic dataKlous et al [29] Comprehensive accuracy examination ofthe kinematic setup kinematic data collection and analysisled to photogrammetric errors of 11 9 and 13mm in 119909- 119910- and 119911-direction respectively The maximum errorcaused by skin movement artifacts was 39mm similar errorshave been reported in laboratory settings [30] Togetherwith the collected 3D kinetic data the kinematic dataserved as input for inverse dynamic analysis to determinelower extremity joint loading in full 3D with sufficientaccuracy
Therefore the main purpose of the current study wasto compare three-dimensional (3D) ankle and knee jointloading between carved ski and snowboard turns in thesteering leg in a real life situation with high accuracy Basedon the injury statistics and due to differences in techniqueposition and equipment (hard boot versus soft boot) betweenskiing and snowboarding it was hypothesized that at thesteering leg in a carved turn ankle joint loading was greaterin snowboarding and knee joint loading was greater in skiing
2 Methods
21 Subjects and Equipment Five male skilled subjects par-ticipated in the experiment three skiers (height 174 plusmn56 cm weight 75 plusmn 35 kg) on an all-round carver (length170 cm side cut 34mm ski radius 17m) and two regularsnowboarders (height 178 plusmn 28 cm weight 665 plusmn 49 kg)on a freestyle board (length 158 cm binding alignment 25∘front 10∘ rear binding distance between bindings 53 cm)Subjects were ski and snowboard teachers at national levelin Austria and had no history of injuries Subjects werewearing their own skisnowboard boots All subjects gavetheir informed consent
22 Kinematic Setup A detailed description of the kinematicsetup can be found in Klous et al [29] A schematic represen-tation of the kinematic setup is shown in Figure 1 includingthe course definition ((a) and (c)) and camera setup ((b) and(d)) for the ski turn ((a) and (b)) and snowboard turn ((c)and (d)) Briefly the course was set with five gates and datawere collected around the third gate Slope inclination was21∘ in skiing and 23∘ in snowboarding Kinematic data werecollected from edge change to the subsequent edge change(Figure 1 thick horizontal lines) with five synchronized pan-ning tilting and zooming cameras (Panasonic F15 50Hz)
A reference point system was set up on the hill todescribe the 3D movement of the skier and snowboarderfrom two-dimensional (2D) video data using panning tiltingand zooming cameras [29 31 32] The positions of thecamera tripods the reference points and the positions ofthe gates were measured using a theodolite The kinematicsetup allowed only one trajectory for skiing and one forsnowboarding Hence the radii of the ski and snowboardturn were similar but therefore the velocity of the turnsvaried Approximately 100 markers were attached to a tightfitting stretch-suit on the pelvis legs skisnowboard bootsand skiessnowboard This procedure was necessary to haveat least three markers per segment in sight of two successivecameras during the entire run which was required to perform3D kinematic analysis [33]
23 Kinetic Setup Stricker et al [34] described in detail thekinetic setup including a thorough analysis of the accuracy ofthe system Briefly kinetic data was collected with a mobileforce plate system (KISTLER CH 200Hz) consisting of 4six-component dynamometers that were mounted on the ski(two on each ski) or snowboard The measurement error ofthe dynamometers was 03 for 3D forces (119865 gt 292N) andranged from 40 to 83 for 3D torques The deviation ofthe calculated point of force application from its referencewas 14 and 88mm in mediolateral and anteroposteriordirection respectively Temperature had little impact onthe measurement accuracy of the dynamometers [34] Thestanding height from the snow to the bottom of the ski bootwas 8 cm Four cables connected the dynamometers with thecharging amplifiers in a backpack that also contained the dataloggers The additional weight of the complete measuringdevice was approximately 7 kg
24 Protocol Prior to the experiment three test runs wereperformed for warm-up and adjustment of measurementdevices Additionally subjects performed quiet stance trialsparallel and orthogonal to the fall line to allow definitionof local coordinate systems (LCSs) for each segment Datawere collected for a carved left turn in skiing and a carvedfront side (right) turn in snowboarding For both skiing andsnowboarding three runstrials were collected in which thesubject was clearly visible in all videos and the techniquewas performed correctly (controlled by visual inspection) Toallow synchronization of the kinetic and kinematic measur-ing devices in the data analysis the subject performed a jumpdirectly after the trial that was filmed by at least one camera
Computational and Mathematical Methods in Medicine 3
minus20
minus10
0
10
20
300 10 20 30 40 50
166
83
178
39
Dire
ctio
n of
fall
line (
m)
Across the slope (m)
(a)
0 10 20 30 40 50
20
10
0
10
20
30
153
168
160
44
241
108
170
166
21780
C1 C4
C3
C5C2
Across the slope (m)
Dire
ctio
n of
fall
line (
m)
(b)
0
minus20
minus10
10
20
30
Dire
ctio
n of
fall
line (
m)
minus10 0 10 20 30 40 50
Across the slope (m)
164
50
134
91
(c)
0
Dire
ctio
n of
fall
line (
m)
minus10 0 10 20 30 40 50
Across the slope (m)
C1
C2
C3
C4
C5
199
179
154
84
23275
150
33
164
211
20
10
10
20
30
(d)
Figure 1 Course definition (a and c) and camera setup (b and d) for the ski turn (a and b) and snowboard turn (c and d) including gates (e)cameras (998771) and the part of the turn that is analyzed (in between the thick lines)
A second reset of the kineticmeasuring devicewas performedafter the run to control for possible drift behaviors of thesystem
25 Data Analysis Kinematic and kinetic data analyses aswell as inverse dynamic calculations are described in detailin Klous et al [29] Briefly 3D marker coordinates were cal-culated from two successive cameras aftermanually digitizingall visiblemarkers for each video frame for each camera usingSIMI Motion (Version 70 Build 242) Data were filtered and
interpolated and the position and orientation of the segmentswere calculated using Cardan angles with mediolateral (119909)posterior-anterior (119910) and vertical (119911) rotation sequence[35 36] with software developed in Matlab (Version 65)Joint center positions were calculated using the sphere-fittingSCoREmethod [37] Kinetic data of the left and right leg weresynchronized and offset corrected and kinematic and kineticdata were also synchronized
Inertial properties of the lower extremities were calcu-lated applying the geometric model by Yeadon [38] The
4 Computational and Mathematical Methods in Medicine
+Fz
+Fy
+Fy
+Mz+Mx
+My
+Fz
+Fx
+Mz
+Mx
+My
+Fx
(a)
+Fz
+Fy
+Fy
+Mz
+Mz
+Mx
+My
+Fz
+Mx
+My
+Fx
+Fx
(b)
Figure 2 Definition of the local coordinate system (LCS) at the leg and the thigh of the steering leg in skiing (a) and snowboarding (b)
model was extended by adding skisnowboard boots to themodel The parts of the boot below the ankle were added tothe foot segment and the parts above the ankle were addedto the shank segment Density values from Dempster [39]were taken according to Yeadon [38] to calculate the inertialparameters of the segments The experimentally determineddensities for the inside and outside ski boot were 280 kgm3and 1400 kgm3 respectivelyThe experimentally determineddensities for the inside snowboard boot were 200 kgm3 andfor the outside boot 470 kgm3
Inverse dynamics analysis was applied to calculate netjoint forces and moments (net joint loading) from edgechanging to the subsequent one Since high frequencieskinematic movements were not expected the global positionof the center of mass (COM) as well as the orientation ofeach of the segments was filtered using a 4th order zero-phase Butterworth low-pass filter with a cutoff frequency of2Hz Kinematic angular and linear acceleration data weredetermined by numerical differentiation and kinetic andkinematic data were time-normalized to arbitrarily chosen201 data points before entering into the inverse dynamicanalysis Net joint forces and net moments at the ankle jointand knee jointwere calculated in the LCSof the calf and thighrespectively (Figure 2) Net joint forces were normalized tobody weight (BW) and net joint moments were normalizedto body mass The normalized net forces and net moments(referred to as joint forces and joint moments throughout theremaining paper) at the ankle joint represented the net forcesand net moments acting from the foot at the leg calculatedin the LCS of the leg The net forces and net moments atthe knee joint represented the net forces and net momentsacting from the leg at the thigh calculated in the LCS of thethigh The LCSs were defined with the 119910-axis in anterior-posterior direction (positive 119910-axis anterior) the 119911-axis alongthe length of the segment (positive 119911-axis proximal) andthe 119909-axis in mediolateral direction with the positive 119909-axis
pointing lateral for the steering (right) leg in both skiing andsnowboarding (Figure 2)
Due to the complexity of the experimental setup and therelated difficulty to collect accurate data only in two trialsa limited amount of interpolation was necessary to fulfillthe requirement of three markers in sight of two successivecameras during the entire run Therefore in the followingone representative carved ski turn and one representativecarved snowboard turn are presented comparatively Ankleand knee joint loading in the steering leg in skiing (outsideleg) and snowboarding (rear leg) were compared in thecurrent study Data were divided into three phases of equalduration (33) These phases correspond approximately tothe functional aspects of the turn initiation phase steeringphase I and steering phase II [40 41]
A skidding angle120573was calculated describing the skiddingcomponent in a turn [42 43] This angle was defined as theangle between the orientation vector (line from the front tothe rear binding piece of the ski) and the velocity vector of theankle of the skiersnowboarderrsquos leg In the current study anaverage skidding angle was calculated for skiing by averagingthe positions of the rear-binding piece of both skies the posi-tions of the front binding piece of both skies and the anklejoint position of the right and left leg In snowboarding anaverage ankle joint position was calculated With the angle 120573can objectively be verified that turns were carved Before cal-culating the skidding angle position data were filtered with a5Hz low-pass 4th order zero-lag Butterworth filter [23 42]
Since only one trial for each discipline is compared onlydescriptive statistics are reported with means and standarddeviations for each of the three phases of the turn
3 Results
31 Turning Technique A skidding angle 120573 was calculatedto verify the proper performance of the turning techniques(Figure 3) The average angle in skiing was 61∘ (plusmn32∘) and in
Computational and Mathematical Methods in Medicine 5
0
5
10
15
20
25
0 05 1 15 2 25
Skid
ding
angl
e (∘ )
Time (s)
Figure 3 Average skidding angle 120573 in a ski turn (black) and a frontside snowboard turn (grey)
snowboarding 92∘ (plusmn59∘) The average velocity was 139msand 111ms in skiing and snowboarding respectively Themaximum velocity in skiing was 165ms and in snowboard-ing 119ms Note that the ski and snowboard turn wereperformed with similar turning radii but different velocities
32 Ankle Joint Loading at the Steering Leg Time profilesof the mediolateral forces anteriorposterior forces andlongitudinal forces at the ankle joint in skiing and snow-boarding are shown in Figure 4 and Table 1 Mediolateralforces and anteriorposterior forces were clearly lower thanthe forces along the longitudinal axis In both skiing andsnowboarding ankle joint forces acted in posterior andupward direction Longitudinal forces in skiing were higherthan in snowboarding These forces increase up to 2-3 timesBW at 60 of the turn in skiing whereas in snowboardingthe longitudinal force was rather consistent at approximately1sdotBW Smaller forces in posterior direction showed morevariation in skiing than in snowboarding Average anklejoint forces in mediolateral were rather similar for skiingand snowboarding in the first two phases but higher insnowboarding in the last phase The ankle joint forces inanteriorposterior direction were similar for the last twophases but in the first phase the anteriorposterior force washigher in skiing The longitudinal forces were clearly greaterin skiing than in snowboarding in the first two phases andhigher in longitudinal direction than in the other directionsIn snowboarding the longitudinal force was more consistentthroughout the phases
During the turn predominantly an extension momentand abduction moment acted at the ankle joint in both ski-ing and snowboarding (Figure 5) Furthermore an internalrotation moment acted at the ankle joint in snowboardingand an external rotation moment in skiing Time profiles of
flexionextensionmoments showedmore variations in skiingthan in snowboarding with fluctuations between minus1 and7Nmkg whereas the extension moment in snowboardingvaried between 2 and 5Nmkg Averagemagnitudes (Table 2)showed higher flexionextension moments in snowboardingbut larger fluctuations in skiing in the first and second phaseof the turn represented by the large standard deviation (SD)A large abduction moment in skiing was observed in thesecond phase with peak values over 4Nmkg and an averagevalue of 17Nmkg In snowboarding the abduction momentwas approximately 0Nmkg in the first and second phases(see also Table 2) but increased up to 3Nmkg and averaged16Nmkg in the third phase The internal rotation momentclearly showed larger average magnitudes in all three phasesin snowboarding than in skiing (Table 2)
33 Knee Joint Loading Steering Leg Similar time profileswere observed for the forces in anteriorposterior directionfor skiing and snowboarding till approximately 70 of theturnwith slightly lower values in snowboarding (Figure 6) Inthe third part of the turn the force in the anterior directionis clearly higher in snowboarding than in skiing This isconfirmed by the average magnitudes for each of the threephases presented in Table 3 Anteriorposterior forces andforces along the longitudinal axis of the knee joint showedsimilar patterns in skiing Until 60 of the turn forcesincreased up to approximately 2sdotBW and then decreasedLongitudinal forces in snowboarding varied around 0sdotBWForces in mediallateral direction showed opposite timeprofiles at the steering leg for skiing and snowboarding Thelateral force in skiing showed a larger increase between 50and 75 of the turn and a smaller increase in the first 25 ofthe turn In snowboarding this increase was only observedbetween 50 and 75 of the turn in medial direction Averagemagnitudes for mediallateral forces for all three phases werelarger in skiing than in snowboarding
The time profiles of the moments at the knee joint wererather different for skiing and snowboarding (Figure 7) Inskiing the moment varied between flexion and extensionthroughout the turnwithmagnitudes between approximatelyminus2 and 4Nmkg In snowboarding a flexion moment actedat the knee joint throughout the turn with magnitudesup to 6Nmkg Average magnitudes were clearly higher insnowboarding for all three phases but the larger SD inskiing for all three phases represented the larger fluctuationsin skiing (Table 4) Furthermore in skiing an abductionmoment acted at the knee joint whereas in snowboarding anadductionmoment throughout the turn Averagemagnitudeswere clearly larger in skiing in phase 1 and in snowboarding inphase 3 In phase 2 average magnitudes were approximatelysimilar but in opposite directions (Table 4) Rather similartime profiles were observed for the internalexternal rotationmoment at the knee joint Both in skiing and snowboardingacted an internal rotation moment during most of theturn However average magnitudes were clearly higher insnowboarding than in skiing in the first and second phasesof the turn In the third phase these magnitudes were similar(see Table 4)
6 Computational and Mathematical Methods in Medicine
minus2
0
2
4
0 33 66 100
Fm
edl
atF
BW
Turn ()
(a)
minus2
0
2
4
0 33 66 100
Turn ()F
ant
posF
BW(b)
0 33 66 100
Turn ()
minus2
0
2
4
Flo
ngF
BW
(c)
Figure 4 Time profiles of the net medial (minus)lateral (+) forces (a) net anterior (+)posterior (minus) forces (b) and net forces around thelongitudinal axis (c) at the ankle joint for the steering leg in skiing (black) and snowboarding (grey)
Table 1 Average net ankle joint forces in medial (minus)lateral (+) direction (119865med-lat) anterior (+)posterior (minus) direction (119865ant-pos) and alongthe longitudinal axis (119865long) and standard deviations in the steering leg in skiing and snowboarding for each of the three phases
Computational and Mathematical Methods in Medicine 7
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()
Mfle
xex
tm (N
mk
g)
(a)
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()M
aba
dm
(Nm
kg)
(b)
0 33 66 100
Turn ()
minus6
minus4
minus2
0
2
4
6
8
m(N
mk
g)M
int
ext
(c)
Figure 5 Time profiles of the net flexion (+)extension (minus) moments (a) net adduction (+)abduction (minus) moments (b) and net internal(+)external (minus) moments (c) at the ankle joint for the steering leg in skiing (black) and snowboarding (grey)
Table 2 Average net ankle joint flexion (minus)extension (+) moments (119872flex-ext) net adduction (+)abduction (minus) moments (119872ad-ab) and netinternal (+)external (minus) rotation moments (119872int-ext) and standard deviations in the steering leg in skiing and snowboarding for each of thethree phases
8 Computational and Mathematical Methods in Medicine
0 33 66 100
Fm
edl
atF
BW
Turn ()
minus1
0
1
2
3
(a)
0 33 66 100
Turn ()
minus1
0
1
2
3
Fan
tpo
sF
BW(b)
0 33 66 100
Turn ()
minus1
0
1
2
3
Flo
ngF
BW
(c)
Figure 6 Time profiles of the net mediallateral forces (a) net anteriorposterior forces (b) and net forces around the longitudinal axis (c)at the knee joint for the steering leg in skiing (black) and snowboarding (grey)
Table 3 Average net knee joint forces in medial (minus)lateral (+) direction (119865med-lat) anterior (+)posterior (minus) direction (119865ant-pos) and alongthe longitudinal axis (119865long) and standard deviations in the steering leg in skiing and snowboarding for each of the three phases
Computational and Mathematical Methods in Medicine 9
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()
Mfle
xex
tm (N
mk
g)
(a)
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()M
aba
dm
(Nm
kg)
(b)
0 33 66 100
Turn ()
minus6
minus4
minus2
0
2
4
6
8
m(N
mk
g)M
int
ext
(c)
Figure 7 Time profiles of the net flexion (+)extension (minus) moments (a) net adduction (+)abduction (minus) moments (b) and net internal(+)external (minus) moments (c) at the knee joint for the steering leg in skiing (black) and snowboarding (grey)
Table 4 Average net knee joint flexion (+)extension (minus) moments (119872flex-ext) net adduction (+)abduction (minus) moments (119872ad-ab) and netinternal (+)external (minus) rotation moments (119872int-ext) and standard deviations in the steering leg in skiing and snowboarding for each of thethree phases
10 Computational and Mathematical Methods in Medicine
4 Discussion
The aim of this study was to compare the ankle and kneejoint loading at the steering leg between a carved ski andsnowboard turn Based on reported injury statistics and dueto differences in technique position and equipment betweenskiing and snowboarding it was hypothesized that ankle jointloading was greater in snowboarding and knee joint loadingwas greater in skiing However the current study showed adifferent outcomeWhile forcesweremostly similar for skiingand snowboarding the joint moments were consistentlygreater during a snowboard turn whereas in skiing muchmore fluctuations were observed during the turn particularlyin the first and second phase of the turn (represented by thegreater standard deviation in skiing in those two phases)Moreover forces along the longitudinal axis were higher inskiing than in snowboarding
Results showed that the carved turn demonstrated someskidding components The average skidding angle calculatedacross time was higher in snowboarding than in skiingwhich could be due to the rather steep slope to perform acarved turn in snowboarding Nevertheless both turns wererepresentative of a carved turn Results were in agreementwithMuller et al [43] andWagner [42] who reported averageskidding angles for the carving technique in skiing of 41∘Knunz et al [44] reported angles in a carved ski turn of 1-2∘for the outer leg and 7-8∘ for the inner leg in a (purely) carvedski turn
Forces in anteriorposterior and mediallateral directionat the ankle joint were similar and rather low for skiingand snowboarding As a consequence it is expected thatthe internalexternal rotation moment is also rather low asis observed in skiing However in snowboarding internalrotation moments reached magnitudes of approximately2Nmkg Consistent and larger values throughout the turnwere also observed for the flexionextension moment insnowboarding whereas the force along the longitudinal axiswas below 1sdotBW and the anteriorposterior force was evenlower Kruger et al [28] reported even larger peak values forthe flexionextension moment at the ankle joint comparedto the current study but do not report if these values area consequence of large kinetic or kinematic values Withthe low forces observed in the current study these relativelyhigh moments must be due to kinematics hence angularaccelerations of the segments or due to the different bodypositions in skiing and snowboarding which is representedby the position of the joint centres with respect to the forcevector The use of soft boots in snowboarding allowed shortbut fast rotational movements (ie kinematic parameters)whereas these movements were not possible with stiff skibootsThese equipment differences would explain the greaterjoint moments at the ankle joint in snowboarding Thiswas supported by a study of Delorme et al [45] thatcompared ankle joint kinematics between stiff and softboots in snowboarding This study reported that the useof soft boots leads to larger average dorsiplantar flexionangles and internalexternal rotation angles as well as largermaximum dorsiplantar flexion angles eversioninversionangles and internalexternal rotation angles larger minimal
internalexternal rotation angles and a larger range ofmotionin dorsiplantar flexion
In skiing the time pattern of the force along the longitu-dinal axis at the ankle joint showed similarities with the timepattern of the flexionextension and abductionadductionmoments but in opposite direction Hence opposite tosnowboarding the large moments in skiing seemed to bea consequence of the produced forces Note that in skiingthe flexionextension moment allowed the movement to thetiptail of the ski whereas the abductionadduction momentplaces the ski at the edges (see Figure 2) Fluctuations (rep-resented by the standard deviation) were much larger forthe moments than for the forces and also much larger inskiing than in snowboarding This might suggest that thegreater number of injuries at the ankle joint is caused by thespecific body position in snowboarding and the consistentlyhigh moments due to kinematic variables rather than largefluctuation as observed in the moments in skiing
At the knee joint both mediallateral forces and forcesalong the longitudinal axis were higher in skiing whereasthe anteriorposterior forces were similar for skiing andsnowboarding However the higher forces in skiing didnot result in consistently higher moments compared tosnowboarding The flexionextension moments in snow-boarding were required to place the snowboard at theedges just like the abductionadduction moment in ski-ing The flexionextension moments in snowboarding wereapproximately 3Nmkg whereas the abductionadductionmoments in skiing were approximately 10ndash15Nmkg Alsothe flexionextension moments in skiing were approximately1 Nmkg as were the abductionadductionmoments in snow-boarding In general moments were slightly lower at the kneejoint than at the ankle joint in snowboarding whereas inskiing the opposite was observed Again the larger momentsin snowboarding seemed not to be due to the high forcesbut due to the soft boot allowing larger accelerations and adifferent body position in snowboarding than in skiing
Even though the fluctuations were larger in snowboard-ing at the knee than at the ankle joint these variationswere still much lower in snowboarding than in skiing Thesefluctuations represent the loading and unloading that areclearly greater in skiing than in snowboarding In situationswhen a skier has to make a sudden adjustment these peakvalues would increase even further In skiing joint momentsincreased in the knee joint compared to the ankle jointwhereas in snowboarding the moments decreased Besidesthe knee joint forces being similar or greater in skiing thanin snowboarding also the peak forces and moments werelarger in skiing than in snowboarding except for the inter-nalexternal rotation moment Kruger et al [28] reportedclearly lower peak values for the flexionextension momentin snowboarding (33 less) than in the current study whichwould make differences between skiing and snowboardingeven more pronounced These three aspects together couldbe an explanation for the larger amount of knee injuries inskiing than in snowboarding
Even though the joint loading observed in the currentstudy is rather high one should realise that many otheraspects can explain the injury statistics as presented in
Computational and Mathematical Methods in Medicine 11
the current study The quality of the snow the technicaland physical capability of the skier or snowboarder andthe large number of skiers and snowboarders at the slopecould explain the many injuries that occur in skiing andsnowboarding The skier and snowboarder in the currentstudy carried additional equipment to allow measurementof ground reaction forces This equipment influenced theirweight and their standing heightWith their level of expertisethe skier and snowboarder did not report any influenceof this equipment Nevertheless the equipment might haveinfluenced their technique and performance Additionallythe differences in stiffness between ski and snowboard bootscould have influenced the results Due to the stiff ski bootpart of the loading might have been transferred to theboot and thereby reduced the ankle joint in skiing Inversedynamic calculations did not allow determining how muchof the ankle joint was transferred to the ski boot Hencethis could have caused overestimation of the ankle joint inskiing However where the current results showed largerankle joint in snowboarding the difference in ankle jointbetween skiing and snowboarding would have even beengreater if the ankle joint in skiing was overestimated Whencurrent results showed larger ankle joint in skiing thesedifferences might not have been as profound Both situationssupport the research hypothesis Also the magnitudes ofthe ankle joint forces and moments in skiing might havebeen lower but it is not to expect that the time patternswere influenced Furthermore the kinematic setup allowed aski and snowboard turn to be performed with similar radiibut different velocities The centripetal force (119865
119888) in a turn
is influenced by the velocity (119865119888= 119898V2119903) Although the
velocity in snowboarding was lower than in skiing the ankleand knee joint forces and moments were not consistentlylower than in skiing We speculate that if the snowboardturn was performed with higher velocities the forces andmoments at the ankle and knee joint would further increasedue to an increase of the centripetal force Furthermorevideos and data of ground reaction forces throughout thecollected data were similar Nevertheless the findings shouldbe interpreted with caution due to the single subject designAdditionally even though the applied method shows a goodaccuracy for on-snow data collection the results of inversedynamic calculations depend strongly on the accuracy of theinput data As is shown by McCaw amp DeVita [46] errorsin the input data are propagated in the inverse dynamicsprocedures thereby reducing the accuracy of the resultscalculated using this procedure Finally it is important toemphasise that we calculated forces and moments duringsuccessful turns which are not representative of the forcesand moments during unsuccessful turns that result in fallingandor injury
5 Conclusion
The expected higher ankle joint loading in snowboardingand higher knee joint loading in skiing that was based onreported injury statistics in the lower extremities in skiingand snowboarding and the differences in position technique
and equipment (soft boot versus hard boot) could not beconfirmed Ankle joint loading was not consistently greaterin snowboarding than in skiing and vice versa for the kneejoint loading When comparing skiing and snowboardingdifferentiationwas required between forces andmoments thedirection of the forces and moments and the phase of theturn thatwas consideredHowever there seemed to be a trendthat forces were larger in skiing and moments showed largefluctuations (loading-unloading) whereas in snowboardinghigh moments with a more consistent pattern were observedIn future research it is important to increase the number ofparticipants in the study and study joint loading of variousturning techniques
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors thank ski company Atomic for providing the testequipment They appreciate the helpful discussions with DrJosef Kroll
References
[1] K Grabler and G J Stirnweis ldquoWirstschaftsbericht derSeilbahnenmdashTrends Winter 2011-2011rdquo WKO die Seilbahnen2011 httpportalwkoatwkformat detailwkangid=1ampstid=621545ampdstid=329ampopennavid=0
[2] R Schonbachler and G Scharer Fakten und Zahlen zurSchweizer Seilbahbranche Seilbahnen Schweiz 2012 httpwwwseilbahnenorgdeBrancheFakten-ZahlenFakten-Zah-len
[3] N Laplante ldquo2008-2009 Canadian Skier and SnowboarderFacts and Statsrdquo 2009 httpxcskiorgnews200920Facts20and20Stats20final20draftpdf
[4] M KlousThree-dimensional joint loading on the lower extremi-ties in alpine skiing and snowboarding [PhD thesis] Universityof Salzburg Salzburg Austria 2007
[5] S Corra A Conci G Conforti G Sacco and F de GiorgildquoSkiing and snowboarding injuries and their impact on theemergency care system in South Tyrol a restrospective analysisfor the winter season 2001ndash2002rdquo Injury Control and SafetyPromotion vol 11 no 4 pp 281ndash285 2004
[6] M Langran and S Selvaraj ldquoSnow sports injuries in Scotlanda case-control studyrdquo British Journal of Sports Medicine vol 36no 2 pp 135ndash140 2002
[7] S Sulheim I Holme A Roslashdven A Ekeland and R BahrldquoRisk factors for injuries in alpine skiing telemark skiing andsnowboardingmdashcase-control studyrdquo British Journal of SportsMedicine vol 45 no 16 pp 1303ndash1309 2011
[8] S Kim N K Endres R J Johnson C F Ettlinger andJ E Shealy ldquoSnowboarding injuries trends over time andcomparisons with alpine skiing injuriesrdquoThe American Journalof Sports Medicine vol 40 no 4 pp 770ndash776 2012
[9] M Burtscher M Flatz R Sommersacher et al OsterreichischeSkiunfallerhebung Wintersaison 20022003 Osterreichischen
12 Computational and Mathematical Methods in Medicine
Skiverbandes in Kooperation mit dem Institut fur Sportwissen-schaften der Universitat Innsbruck 2003
[10] C Goulet G Regnier G Grimard P Valois and P VilleneuveldquoRisk factors associated with alpine skiing injuries in childrena case-control studyrdquoThe American Journal of Sports Medicinevol 27 no 5 pp 644ndash650 1999
[11] E J Bridges F Rouah and K M Johnston ldquoSnowbladinginjuries in Eastern Canadardquo British Journal of Sports Medicinevol 37 no 6 pp 511ndash515 2003
[12] D Ishimaru H Ogawa K Wakahara H Sumi Y Sumi andK Shimizu ldquoHip pads reduce the overall risk of injuries inrecreational snowboardersrdquo British Journal of Sports Medicinevol 46 no 15 pp 1055ndash1058 2012
[13] H Xiang K Kelleher B J Shields K J Brown and G ASmith ldquoSkiing- and snowboarding-related injuries treated inUS emergency departments 2002rdquo Journal of Trauma-InjuryInfection amp Critical Care vol 58 no 1 pp 112ndash118 2005
[14] C Made and L G Elmqvist ldquoA 10-year study of snowboardinjuries in Lapland Swedenrdquo Scandinavian Journal of Medicineand Science in Sports vol 14 no 2 pp 128ndash133 2004
[15] E Aschauer E Ritter and H ReschWintersport Unfallstatistik20022003 Universitatsklinik fur Unfallchirurgie und Sport-traumatologie Salzburg 2003
[16] T M Davidson and A T Laliotis ldquoSnowboarding injuries afour-year study with comparison with alpine ski injuriesrdquo TheWestern Journal of Medicine vol 164 no 3 pp 231ndash237 1996
[17] J Howe The New Skiing Mechanics McIntire PublishingWaterford UK 2nd edition 2001
[18] Y Urabe M Ochi K Onari and Y Ikuta ldquoAnterior cruciateligament injury in recreational alpine skiers analysis of mech-anisms and strategy for preventionrdquo Journal of OrthopaedicScience vol 7 no 1 pp 1ndash5 2002
[19] S M Maxwell and M L Hull ldquoMeasurement of strength andloading variables on the knee during alpine skiingrdquo Journal ofBiomechanics vol 22 no 6-7 pp 609ndash624 1989
[20] T P Quinn and C D Mote Jr ldquoPrediction of the loading alongthe leg during snow skiingrdquo Journal of Biomechanics vol 25 no6 pp 609ndash625 1992
[21] C Raschner E Muller and H Schwameder ldquoKinematic andkinetic analysis of slalom turns as a basis for the development ofspecific training methods to improve strength and endurancerdquoin Science and Skiing EMullerH Schwameder E Kornexl andC Raschner Eds pp 251ndash261 Chapman amp Hall CambridgeMass USA 1997
[22] M Brodie A Walmsley and W Page ldquoFusion motion capturea prototype system using inertial measurement units and GPSfor the biomechanical analysis of ski racingrdquo Sports Technologyvol 1 pp 17ndash28 2008
[23] M Klous E Muller and H Schwameder ldquoThree-dimensionalknee joint loading in alpine skiing a comparison between acarved and a skidded turnrdquo Journal of Applied Biomechanics vol28 no 6 pp 655ndash664 2012
[24] F Vaverka S Vodickova and M Elfmark ldquoKinetic analysis ofski turns based on measured ground reaction forcesrdquo Journal ofApplied Biomechanics vol 28 no 1 pp 41ndash47 2012
[25] L Read and W Herzog ldquoExternal loading at the knee joint forlanding movements in alpine skiingrdquo International Journal ofSport Biomechanics vol 8 pp 62ndash80 1992
[26] W Nachbauer P Kaps B Nigg et al ldquoA video technique forobtaining 3-D coordinates in alpine skiingrdquo Journal of AppliedBiomechanics vol 12 no 1 pp 104ndash115 1996
[27] B Knunz W Nachbauer K Schindelwig and F BrunnerldquoForces andmoments at the boot sole during snowboardingrdquo inScience and Skiing II E Muller H Schwameder C Raschner SLindinger and E Kornexl Eds pp 242ndash249 Kovac HamburgGermany 2001
[28] A Kruger P McAlpine F Borrani and J Edelmann-NusserldquoDetermination of three-dimensional joint loading within thelower extremities in snowboardingrdquo Proceedings of the Insti-tution of Mechanical Engineers H Journal of Engineering inMedicine vol 226 no 2 pp 170ndash175 2012
[29] M Klous EMuller andH Schwameder ldquoCollecting kinematicdata on a skisnowboard track with panning tilting and zoom-ing cameras is there sufficient accuracy for a biomechanicalanalysisrdquo Journal of Sports Sciences vol 28 no 12 pp 1345ndash1352 2010
[30] A Cappozzo F Catani A Leardini M G Benedetti and UDella Croce ldquoPosition and orientation in space of bones duringmovement experimental artefactsrdquo Clinical Biomechanics vol11 no 2 pp 90ndash100 1996
[31] V Drenk ldquoPanningmdashZusatzprogramm zur Behandlungschwenk- und neigbarer und in ihrere brennweite variierbarerKameras in Peak3DmdashDokumentationrdquo Institut fur Ange-wandte Traningswissenschaften e V Leipzig Germany 1993
[32] V Drenk ldquoBildmeszligverfahren fur schwenk-und neigbaresowie in ihrer Brennweite variierbare Kamerasrdquo Zeitschrift furAngewandte Trainingswissenschaft vol 1 pp 130ndash142 1994
[33] BM Nigg andWHerzog Biomechanics of theMusculo-skeletalSystem John Wiley amp Sons New York NY USA 3rd edition2007
[34] G Stricker P Scheiber E Lindenhofer and E MullerldquoDetermination of forces in alpine skiing and snowboardingvalidation of a mobile data acquisition systemrdquo EuropeanJournal of Sport Science vol 10 no 1 pp 31ndash41 2010
[35] D G E Robertson G E Caldwell J Hamill G Kamen andS N Whittlesey Research Methods in Biomechanics HumanKinetics Champaign Ill USA 2004
[36] V M Zatsiorsky Kinematics of Human Motion HumanKinetics Champaign Ill USA 1998
[37] R M Ehrig W R Taylor G N Duda and M O HellerldquoA survey of formal methods for determining the centre ofrotation of ball jointsrdquo Journal of Biomechanics vol 39 no 15pp 2798ndash2809 2006
[38] M R Yeadon ldquoThe simulation of aerial movement II Amathematical inertia model of the human bodyrdquo Journal ofBiomechanics vol 23 no 1 pp 67ndash74 1990
[39] W T Dempster ldquoSpace requirements of the seated operatorrdquoWADC Technical Report TR-55ndash159 Wright-Patterson AirForce Base Wright-Patterson Ohio USA 1955
[40] E Muller ldquoBiomechanische Analysen moderner alpinerSkilauftechniken in unterschiedlichen Schnee- Gelande-und Pistensituationenrdquo in Biomechanik der Sportarten Bd2biomechanik des alpinen skilaufs F Fetz and E Muller Eds pp1ndash49 Ferdinand Enke Stuttgart Germany 1991
[41] C Raschner C Schiefermuller G Zallinger E Hofer FBrunner and E Muller ldquoCarving turns versus traditionalparallel turnsmdasha comparative biomechanical analysisrdquo inScience and Skiing II E Muller H Schwameder C RaschnerS Lindinger and E Kornexl Eds pp 203ndash217 Dr KovacHamburg Germany 2001
[42] GWagnerMesstechnischeDifferzierung von genschnittenen undgerutschten Kurven im alpine Skilauf [MS thesis] University ofSalzburg 2006
Computational and Mathematical Methods in Medicine 13
[43] E Muller M Klous and G Wagner ldquoBiomechanical aspectsof turning techniques in alpine skiingrdquo in Science and SportsBridging the Gap T Reilly Ed pp 135ndash142 Shaker PublishingBV Maastricht The Netherlands 2008
[44] B Knunz W Nachbauer M Mossner K Schindelwig andF Brunner ldquoTrack analysis of giant slalom turns of WorldCup racersrdquo in Proceedings of the 5th Annual Congress of theEuropean College of Sport Science (ECSS rsquo00) pp 399ndash401Jyvaskyla Finland 2000
[45] S Delorme S Tavoularis and M Lamontagne ldquoKinematics ofthe ankle joint complex in snowboardingrdquo Journal of AppliedBiomechanics vol 21 no 4 pp 394ndash403 2005
[46] S T McCaw and P DeVita ldquoErrors in alignment of center ofpressure and foot coordinates affect predicted lower extremitytorquesrdquo Journal of Biomechanics vol 28 no 8 pp 985ndash9881995
2 Computational and Mathematical Methods in Medicine
skiing and would be in agreement with the injury statisticsdescribed previously
In a first attempt it is of special interest to obtain greaterinsight into the differences in ankle and knee joint loadingbetween a carved ski and snowboard turn The focus ofthe current study was on a carved turn since a carved turnis a common skill in both skiing and snowboarding andhigher joint loadings are predicted in this kind of turn Astudy of Urabe et al [18] on skiing reported larger numberof injuries at the outer leg The outer leg might experiencehigher forces and moments due to its steering functionTherefore the current study focused on the steeringleg In snowboarding steering is controlled by the rearleg
Several biomechanical studies estimated the joint loadingin skiing while turning [19ndash24] and on landing maneuversafter a jump [25 26] Also in snowboarding forces andmoments have been estimated at the boot sole with an alpineboard [27] and in lower extremity joints [28] Besides thestudies by Klous et al [23] and Kruger et al [28] none ofthe previous studies performed full three-dimensional (3D)inverse dynamic analysis in skiing or snowboarding withsufficient accuracyThis is due to the complexity to collect 3Dkinematic data accurately in a field experiment [20] Recentlywe developed a method to collect accurate 3D kinematic dataKlous et al [29] Comprehensive accuracy examination ofthe kinematic setup kinematic data collection and analysisled to photogrammetric errors of 11 9 and 13mm in 119909- 119910- and 119911-direction respectively The maximum errorcaused by skin movement artifacts was 39mm similar errorshave been reported in laboratory settings [30] Togetherwith the collected 3D kinetic data the kinematic dataserved as input for inverse dynamic analysis to determinelower extremity joint loading in full 3D with sufficientaccuracy
Therefore the main purpose of the current study wasto compare three-dimensional (3D) ankle and knee jointloading between carved ski and snowboard turns in thesteering leg in a real life situation with high accuracy Basedon the injury statistics and due to differences in techniqueposition and equipment (hard boot versus soft boot) betweenskiing and snowboarding it was hypothesized that at thesteering leg in a carved turn ankle joint loading was greaterin snowboarding and knee joint loading was greater in skiing
2 Methods
21 Subjects and Equipment Five male skilled subjects par-ticipated in the experiment three skiers (height 174 plusmn56 cm weight 75 plusmn 35 kg) on an all-round carver (length170 cm side cut 34mm ski radius 17m) and two regularsnowboarders (height 178 plusmn 28 cm weight 665 plusmn 49 kg)on a freestyle board (length 158 cm binding alignment 25∘front 10∘ rear binding distance between bindings 53 cm)Subjects were ski and snowboard teachers at national levelin Austria and had no history of injuries Subjects werewearing their own skisnowboard boots All subjects gavetheir informed consent
22 Kinematic Setup A detailed description of the kinematicsetup can be found in Klous et al [29] A schematic represen-tation of the kinematic setup is shown in Figure 1 includingthe course definition ((a) and (c)) and camera setup ((b) and(d)) for the ski turn ((a) and (b)) and snowboard turn ((c)and (d)) Briefly the course was set with five gates and datawere collected around the third gate Slope inclination was21∘ in skiing and 23∘ in snowboarding Kinematic data werecollected from edge change to the subsequent edge change(Figure 1 thick horizontal lines) with five synchronized pan-ning tilting and zooming cameras (Panasonic F15 50Hz)
A reference point system was set up on the hill todescribe the 3D movement of the skier and snowboarderfrom two-dimensional (2D) video data using panning tiltingand zooming cameras [29 31 32] The positions of thecamera tripods the reference points and the positions ofthe gates were measured using a theodolite The kinematicsetup allowed only one trajectory for skiing and one forsnowboarding Hence the radii of the ski and snowboardturn were similar but therefore the velocity of the turnsvaried Approximately 100 markers were attached to a tightfitting stretch-suit on the pelvis legs skisnowboard bootsand skiessnowboard This procedure was necessary to haveat least three markers per segment in sight of two successivecameras during the entire run which was required to perform3D kinematic analysis [33]
23 Kinetic Setup Stricker et al [34] described in detail thekinetic setup including a thorough analysis of the accuracy ofthe system Briefly kinetic data was collected with a mobileforce plate system (KISTLER CH 200Hz) consisting of 4six-component dynamometers that were mounted on the ski(two on each ski) or snowboard The measurement error ofthe dynamometers was 03 for 3D forces (119865 gt 292N) andranged from 40 to 83 for 3D torques The deviation ofthe calculated point of force application from its referencewas 14 and 88mm in mediolateral and anteroposteriordirection respectively Temperature had little impact onthe measurement accuracy of the dynamometers [34] Thestanding height from the snow to the bottom of the ski bootwas 8 cm Four cables connected the dynamometers with thecharging amplifiers in a backpack that also contained the dataloggers The additional weight of the complete measuringdevice was approximately 7 kg
24 Protocol Prior to the experiment three test runs wereperformed for warm-up and adjustment of measurementdevices Additionally subjects performed quiet stance trialsparallel and orthogonal to the fall line to allow definitionof local coordinate systems (LCSs) for each segment Datawere collected for a carved left turn in skiing and a carvedfront side (right) turn in snowboarding For both skiing andsnowboarding three runstrials were collected in which thesubject was clearly visible in all videos and the techniquewas performed correctly (controlled by visual inspection) Toallow synchronization of the kinetic and kinematic measur-ing devices in the data analysis the subject performed a jumpdirectly after the trial that was filmed by at least one camera
Computational and Mathematical Methods in Medicine 3
minus20
minus10
0
10
20
300 10 20 30 40 50
166
83
178
39
Dire
ctio
n of
fall
line (
m)
Across the slope (m)
(a)
0 10 20 30 40 50
20
10
0
10
20
30
153
168
160
44
241
108
170
166
21780
C1 C4
C3
C5C2
Across the slope (m)
Dire
ctio
n of
fall
line (
m)
(b)
0
minus20
minus10
10
20
30
Dire
ctio
n of
fall
line (
m)
minus10 0 10 20 30 40 50
Across the slope (m)
164
50
134
91
(c)
0
Dire
ctio
n of
fall
line (
m)
minus10 0 10 20 30 40 50
Across the slope (m)
C1
C2
C3
C4
C5
199
179
154
84
23275
150
33
164
211
20
10
10
20
30
(d)
Figure 1 Course definition (a and c) and camera setup (b and d) for the ski turn (a and b) and snowboard turn (c and d) including gates (e)cameras (998771) and the part of the turn that is analyzed (in between the thick lines)
A second reset of the kineticmeasuring devicewas performedafter the run to control for possible drift behaviors of thesystem
25 Data Analysis Kinematic and kinetic data analyses aswell as inverse dynamic calculations are described in detailin Klous et al [29] Briefly 3D marker coordinates were cal-culated from two successive cameras aftermanually digitizingall visiblemarkers for each video frame for each camera usingSIMI Motion (Version 70 Build 242) Data were filtered and
interpolated and the position and orientation of the segmentswere calculated using Cardan angles with mediolateral (119909)posterior-anterior (119910) and vertical (119911) rotation sequence[35 36] with software developed in Matlab (Version 65)Joint center positions were calculated using the sphere-fittingSCoREmethod [37] Kinetic data of the left and right leg weresynchronized and offset corrected and kinematic and kineticdata were also synchronized
Inertial properties of the lower extremities were calcu-lated applying the geometric model by Yeadon [38] The
4 Computational and Mathematical Methods in Medicine
+Fz
+Fy
+Fy
+Mz+Mx
+My
+Fz
+Fx
+Mz
+Mx
+My
+Fx
(a)
+Fz
+Fy
+Fy
+Mz
+Mz
+Mx
+My
+Fz
+Mx
+My
+Fx
+Fx
(b)
Figure 2 Definition of the local coordinate system (LCS) at the leg and the thigh of the steering leg in skiing (a) and snowboarding (b)
model was extended by adding skisnowboard boots to themodel The parts of the boot below the ankle were added tothe foot segment and the parts above the ankle were addedto the shank segment Density values from Dempster [39]were taken according to Yeadon [38] to calculate the inertialparameters of the segments The experimentally determineddensities for the inside and outside ski boot were 280 kgm3and 1400 kgm3 respectivelyThe experimentally determineddensities for the inside snowboard boot were 200 kgm3 andfor the outside boot 470 kgm3
Inverse dynamics analysis was applied to calculate netjoint forces and moments (net joint loading) from edgechanging to the subsequent one Since high frequencieskinematic movements were not expected the global positionof the center of mass (COM) as well as the orientation ofeach of the segments was filtered using a 4th order zero-phase Butterworth low-pass filter with a cutoff frequency of2Hz Kinematic angular and linear acceleration data weredetermined by numerical differentiation and kinetic andkinematic data were time-normalized to arbitrarily chosen201 data points before entering into the inverse dynamicanalysis Net joint forces and net moments at the ankle jointand knee jointwere calculated in the LCSof the calf and thighrespectively (Figure 2) Net joint forces were normalized tobody weight (BW) and net joint moments were normalizedto body mass The normalized net forces and net moments(referred to as joint forces and joint moments throughout theremaining paper) at the ankle joint represented the net forcesand net moments acting from the foot at the leg calculatedin the LCS of the leg The net forces and net moments atthe knee joint represented the net forces and net momentsacting from the leg at the thigh calculated in the LCS of thethigh The LCSs were defined with the 119910-axis in anterior-posterior direction (positive 119910-axis anterior) the 119911-axis alongthe length of the segment (positive 119911-axis proximal) andthe 119909-axis in mediolateral direction with the positive 119909-axis
pointing lateral for the steering (right) leg in both skiing andsnowboarding (Figure 2)
Due to the complexity of the experimental setup and therelated difficulty to collect accurate data only in two trialsa limited amount of interpolation was necessary to fulfillthe requirement of three markers in sight of two successivecameras during the entire run Therefore in the followingone representative carved ski turn and one representativecarved snowboard turn are presented comparatively Ankleand knee joint loading in the steering leg in skiing (outsideleg) and snowboarding (rear leg) were compared in thecurrent study Data were divided into three phases of equalduration (33) These phases correspond approximately tothe functional aspects of the turn initiation phase steeringphase I and steering phase II [40 41]
A skidding angle120573was calculated describing the skiddingcomponent in a turn [42 43] This angle was defined as theangle between the orientation vector (line from the front tothe rear binding piece of the ski) and the velocity vector of theankle of the skiersnowboarderrsquos leg In the current study anaverage skidding angle was calculated for skiing by averagingthe positions of the rear-binding piece of both skies the posi-tions of the front binding piece of both skies and the anklejoint position of the right and left leg In snowboarding anaverage ankle joint position was calculated With the angle 120573can objectively be verified that turns were carved Before cal-culating the skidding angle position data were filtered with a5Hz low-pass 4th order zero-lag Butterworth filter [23 42]
Since only one trial for each discipline is compared onlydescriptive statistics are reported with means and standarddeviations for each of the three phases of the turn
3 Results
31 Turning Technique A skidding angle 120573 was calculatedto verify the proper performance of the turning techniques(Figure 3) The average angle in skiing was 61∘ (plusmn32∘) and in
Computational and Mathematical Methods in Medicine 5
0
5
10
15
20
25
0 05 1 15 2 25
Skid
ding
angl
e (∘ )
Time (s)
Figure 3 Average skidding angle 120573 in a ski turn (black) and a frontside snowboard turn (grey)
snowboarding 92∘ (plusmn59∘) The average velocity was 139msand 111ms in skiing and snowboarding respectively Themaximum velocity in skiing was 165ms and in snowboard-ing 119ms Note that the ski and snowboard turn wereperformed with similar turning radii but different velocities
32 Ankle Joint Loading at the Steering Leg Time profilesof the mediolateral forces anteriorposterior forces andlongitudinal forces at the ankle joint in skiing and snow-boarding are shown in Figure 4 and Table 1 Mediolateralforces and anteriorposterior forces were clearly lower thanthe forces along the longitudinal axis In both skiing andsnowboarding ankle joint forces acted in posterior andupward direction Longitudinal forces in skiing were higherthan in snowboarding These forces increase up to 2-3 timesBW at 60 of the turn in skiing whereas in snowboardingthe longitudinal force was rather consistent at approximately1sdotBW Smaller forces in posterior direction showed morevariation in skiing than in snowboarding Average anklejoint forces in mediolateral were rather similar for skiingand snowboarding in the first two phases but higher insnowboarding in the last phase The ankle joint forces inanteriorposterior direction were similar for the last twophases but in the first phase the anteriorposterior force washigher in skiing The longitudinal forces were clearly greaterin skiing than in snowboarding in the first two phases andhigher in longitudinal direction than in the other directionsIn snowboarding the longitudinal force was more consistentthroughout the phases
During the turn predominantly an extension momentand abduction moment acted at the ankle joint in both ski-ing and snowboarding (Figure 5) Furthermore an internalrotation moment acted at the ankle joint in snowboardingand an external rotation moment in skiing Time profiles of
flexionextensionmoments showedmore variations in skiingthan in snowboarding with fluctuations between minus1 and7Nmkg whereas the extension moment in snowboardingvaried between 2 and 5Nmkg Averagemagnitudes (Table 2)showed higher flexionextension moments in snowboardingbut larger fluctuations in skiing in the first and second phaseof the turn represented by the large standard deviation (SD)A large abduction moment in skiing was observed in thesecond phase with peak values over 4Nmkg and an averagevalue of 17Nmkg In snowboarding the abduction momentwas approximately 0Nmkg in the first and second phases(see also Table 2) but increased up to 3Nmkg and averaged16Nmkg in the third phase The internal rotation momentclearly showed larger average magnitudes in all three phasesin snowboarding than in skiing (Table 2)
33 Knee Joint Loading Steering Leg Similar time profileswere observed for the forces in anteriorposterior directionfor skiing and snowboarding till approximately 70 of theturnwith slightly lower values in snowboarding (Figure 6) Inthe third part of the turn the force in the anterior directionis clearly higher in snowboarding than in skiing This isconfirmed by the average magnitudes for each of the threephases presented in Table 3 Anteriorposterior forces andforces along the longitudinal axis of the knee joint showedsimilar patterns in skiing Until 60 of the turn forcesincreased up to approximately 2sdotBW and then decreasedLongitudinal forces in snowboarding varied around 0sdotBWForces in mediallateral direction showed opposite timeprofiles at the steering leg for skiing and snowboarding Thelateral force in skiing showed a larger increase between 50and 75 of the turn and a smaller increase in the first 25 ofthe turn In snowboarding this increase was only observedbetween 50 and 75 of the turn in medial direction Averagemagnitudes for mediallateral forces for all three phases werelarger in skiing than in snowboarding
The time profiles of the moments at the knee joint wererather different for skiing and snowboarding (Figure 7) Inskiing the moment varied between flexion and extensionthroughout the turnwithmagnitudes between approximatelyminus2 and 4Nmkg In snowboarding a flexion moment actedat the knee joint throughout the turn with magnitudesup to 6Nmkg Average magnitudes were clearly higher insnowboarding for all three phases but the larger SD inskiing for all three phases represented the larger fluctuationsin skiing (Table 4) Furthermore in skiing an abductionmoment acted at the knee joint whereas in snowboarding anadductionmoment throughout the turn Averagemagnitudeswere clearly larger in skiing in phase 1 and in snowboarding inphase 3 In phase 2 average magnitudes were approximatelysimilar but in opposite directions (Table 4) Rather similartime profiles were observed for the internalexternal rotationmoment at the knee joint Both in skiing and snowboardingacted an internal rotation moment during most of theturn However average magnitudes were clearly higher insnowboarding than in skiing in the first and second phasesof the turn In the third phase these magnitudes were similar(see Table 4)
6 Computational and Mathematical Methods in Medicine
minus2
0
2
4
0 33 66 100
Fm
edl
atF
BW
Turn ()
(a)
minus2
0
2
4
0 33 66 100
Turn ()F
ant
posF
BW(b)
0 33 66 100
Turn ()
minus2
0
2
4
Flo
ngF
BW
(c)
Figure 4 Time profiles of the net medial (minus)lateral (+) forces (a) net anterior (+)posterior (minus) forces (b) and net forces around thelongitudinal axis (c) at the ankle joint for the steering leg in skiing (black) and snowboarding (grey)
Table 1 Average net ankle joint forces in medial (minus)lateral (+) direction (119865med-lat) anterior (+)posterior (minus) direction (119865ant-pos) and alongthe longitudinal axis (119865long) and standard deviations in the steering leg in skiing and snowboarding for each of the three phases
Computational and Mathematical Methods in Medicine 7
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()
Mfle
xex
tm (N
mk
g)
(a)
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()M
aba
dm
(Nm
kg)
(b)
0 33 66 100
Turn ()
minus6
minus4
minus2
0
2
4
6
8
m(N
mk
g)M
int
ext
(c)
Figure 5 Time profiles of the net flexion (+)extension (minus) moments (a) net adduction (+)abduction (minus) moments (b) and net internal(+)external (minus) moments (c) at the ankle joint for the steering leg in skiing (black) and snowboarding (grey)
Table 2 Average net ankle joint flexion (minus)extension (+) moments (119872flex-ext) net adduction (+)abduction (minus) moments (119872ad-ab) and netinternal (+)external (minus) rotation moments (119872int-ext) and standard deviations in the steering leg in skiing and snowboarding for each of thethree phases
8 Computational and Mathematical Methods in Medicine
0 33 66 100
Fm
edl
atF
BW
Turn ()
minus1
0
1
2
3
(a)
0 33 66 100
Turn ()
minus1
0
1
2
3
Fan
tpo
sF
BW(b)
0 33 66 100
Turn ()
minus1
0
1
2
3
Flo
ngF
BW
(c)
Figure 6 Time profiles of the net mediallateral forces (a) net anteriorposterior forces (b) and net forces around the longitudinal axis (c)at the knee joint for the steering leg in skiing (black) and snowboarding (grey)
Table 3 Average net knee joint forces in medial (minus)lateral (+) direction (119865med-lat) anterior (+)posterior (minus) direction (119865ant-pos) and alongthe longitudinal axis (119865long) and standard deviations in the steering leg in skiing and snowboarding for each of the three phases
Computational and Mathematical Methods in Medicine 9
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()
Mfle
xex
tm (N
mk
g)
(a)
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()M
aba
dm
(Nm
kg)
(b)
0 33 66 100
Turn ()
minus6
minus4
minus2
0
2
4
6
8
m(N
mk
g)M
int
ext
(c)
Figure 7 Time profiles of the net flexion (+)extension (minus) moments (a) net adduction (+)abduction (minus) moments (b) and net internal(+)external (minus) moments (c) at the knee joint for the steering leg in skiing (black) and snowboarding (grey)
Table 4 Average net knee joint flexion (+)extension (minus) moments (119872flex-ext) net adduction (+)abduction (minus) moments (119872ad-ab) and netinternal (+)external (minus) rotation moments (119872int-ext) and standard deviations in the steering leg in skiing and snowboarding for each of thethree phases
10 Computational and Mathematical Methods in Medicine
4 Discussion
The aim of this study was to compare the ankle and kneejoint loading at the steering leg between a carved ski andsnowboard turn Based on reported injury statistics and dueto differences in technique position and equipment betweenskiing and snowboarding it was hypothesized that ankle jointloading was greater in snowboarding and knee joint loadingwas greater in skiing However the current study showed adifferent outcomeWhile forcesweremostly similar for skiingand snowboarding the joint moments were consistentlygreater during a snowboard turn whereas in skiing muchmore fluctuations were observed during the turn particularlyin the first and second phase of the turn (represented by thegreater standard deviation in skiing in those two phases)Moreover forces along the longitudinal axis were higher inskiing than in snowboarding
Results showed that the carved turn demonstrated someskidding components The average skidding angle calculatedacross time was higher in snowboarding than in skiingwhich could be due to the rather steep slope to perform acarved turn in snowboarding Nevertheless both turns wererepresentative of a carved turn Results were in agreementwithMuller et al [43] andWagner [42] who reported averageskidding angles for the carving technique in skiing of 41∘Knunz et al [44] reported angles in a carved ski turn of 1-2∘for the outer leg and 7-8∘ for the inner leg in a (purely) carvedski turn
Forces in anteriorposterior and mediallateral directionat the ankle joint were similar and rather low for skiingand snowboarding As a consequence it is expected thatthe internalexternal rotation moment is also rather low asis observed in skiing However in snowboarding internalrotation moments reached magnitudes of approximately2Nmkg Consistent and larger values throughout the turnwere also observed for the flexionextension moment insnowboarding whereas the force along the longitudinal axiswas below 1sdotBW and the anteriorposterior force was evenlower Kruger et al [28] reported even larger peak values forthe flexionextension moment at the ankle joint comparedto the current study but do not report if these values area consequence of large kinetic or kinematic values Withthe low forces observed in the current study these relativelyhigh moments must be due to kinematics hence angularaccelerations of the segments or due to the different bodypositions in skiing and snowboarding which is representedby the position of the joint centres with respect to the forcevector The use of soft boots in snowboarding allowed shortbut fast rotational movements (ie kinematic parameters)whereas these movements were not possible with stiff skibootsThese equipment differences would explain the greaterjoint moments at the ankle joint in snowboarding Thiswas supported by a study of Delorme et al [45] thatcompared ankle joint kinematics between stiff and softboots in snowboarding This study reported that the useof soft boots leads to larger average dorsiplantar flexionangles and internalexternal rotation angles as well as largermaximum dorsiplantar flexion angles eversioninversionangles and internalexternal rotation angles larger minimal
internalexternal rotation angles and a larger range ofmotionin dorsiplantar flexion
In skiing the time pattern of the force along the longitu-dinal axis at the ankle joint showed similarities with the timepattern of the flexionextension and abductionadductionmoments but in opposite direction Hence opposite tosnowboarding the large moments in skiing seemed to bea consequence of the produced forces Note that in skiingthe flexionextension moment allowed the movement to thetiptail of the ski whereas the abductionadduction momentplaces the ski at the edges (see Figure 2) Fluctuations (rep-resented by the standard deviation) were much larger forthe moments than for the forces and also much larger inskiing than in snowboarding This might suggest that thegreater number of injuries at the ankle joint is caused by thespecific body position in snowboarding and the consistentlyhigh moments due to kinematic variables rather than largefluctuation as observed in the moments in skiing
At the knee joint both mediallateral forces and forcesalong the longitudinal axis were higher in skiing whereasthe anteriorposterior forces were similar for skiing andsnowboarding However the higher forces in skiing didnot result in consistently higher moments compared tosnowboarding The flexionextension moments in snow-boarding were required to place the snowboard at theedges just like the abductionadduction moment in ski-ing The flexionextension moments in snowboarding wereapproximately 3Nmkg whereas the abductionadductionmoments in skiing were approximately 10ndash15Nmkg Alsothe flexionextension moments in skiing were approximately1 Nmkg as were the abductionadductionmoments in snow-boarding In general moments were slightly lower at the kneejoint than at the ankle joint in snowboarding whereas inskiing the opposite was observed Again the larger momentsin snowboarding seemed not to be due to the high forcesbut due to the soft boot allowing larger accelerations and adifferent body position in snowboarding than in skiing
Even though the fluctuations were larger in snowboard-ing at the knee than at the ankle joint these variationswere still much lower in snowboarding than in skiing Thesefluctuations represent the loading and unloading that areclearly greater in skiing than in snowboarding In situationswhen a skier has to make a sudden adjustment these peakvalues would increase even further In skiing joint momentsincreased in the knee joint compared to the ankle jointwhereas in snowboarding the moments decreased Besidesthe knee joint forces being similar or greater in skiing thanin snowboarding also the peak forces and moments werelarger in skiing than in snowboarding except for the inter-nalexternal rotation moment Kruger et al [28] reportedclearly lower peak values for the flexionextension momentin snowboarding (33 less) than in the current study whichwould make differences between skiing and snowboardingeven more pronounced These three aspects together couldbe an explanation for the larger amount of knee injuries inskiing than in snowboarding
Even though the joint loading observed in the currentstudy is rather high one should realise that many otheraspects can explain the injury statistics as presented in
Computational and Mathematical Methods in Medicine 11
the current study The quality of the snow the technicaland physical capability of the skier or snowboarder andthe large number of skiers and snowboarders at the slopecould explain the many injuries that occur in skiing andsnowboarding The skier and snowboarder in the currentstudy carried additional equipment to allow measurementof ground reaction forces This equipment influenced theirweight and their standing heightWith their level of expertisethe skier and snowboarder did not report any influenceof this equipment Nevertheless the equipment might haveinfluenced their technique and performance Additionallythe differences in stiffness between ski and snowboard bootscould have influenced the results Due to the stiff ski bootpart of the loading might have been transferred to theboot and thereby reduced the ankle joint in skiing Inversedynamic calculations did not allow determining how muchof the ankle joint was transferred to the ski boot Hencethis could have caused overestimation of the ankle joint inskiing However where the current results showed largerankle joint in snowboarding the difference in ankle jointbetween skiing and snowboarding would have even beengreater if the ankle joint in skiing was overestimated Whencurrent results showed larger ankle joint in skiing thesedifferences might not have been as profound Both situationssupport the research hypothesis Also the magnitudes ofthe ankle joint forces and moments in skiing might havebeen lower but it is not to expect that the time patternswere influenced Furthermore the kinematic setup allowed aski and snowboard turn to be performed with similar radiibut different velocities The centripetal force (119865
119888) in a turn
is influenced by the velocity (119865119888= 119898V2119903) Although the
velocity in snowboarding was lower than in skiing the ankleand knee joint forces and moments were not consistentlylower than in skiing We speculate that if the snowboardturn was performed with higher velocities the forces andmoments at the ankle and knee joint would further increasedue to an increase of the centripetal force Furthermorevideos and data of ground reaction forces throughout thecollected data were similar Nevertheless the findings shouldbe interpreted with caution due to the single subject designAdditionally even though the applied method shows a goodaccuracy for on-snow data collection the results of inversedynamic calculations depend strongly on the accuracy of theinput data As is shown by McCaw amp DeVita [46] errorsin the input data are propagated in the inverse dynamicsprocedures thereby reducing the accuracy of the resultscalculated using this procedure Finally it is important toemphasise that we calculated forces and moments duringsuccessful turns which are not representative of the forcesand moments during unsuccessful turns that result in fallingandor injury
5 Conclusion
The expected higher ankle joint loading in snowboardingand higher knee joint loading in skiing that was based onreported injury statistics in the lower extremities in skiingand snowboarding and the differences in position technique
and equipment (soft boot versus hard boot) could not beconfirmed Ankle joint loading was not consistently greaterin snowboarding than in skiing and vice versa for the kneejoint loading When comparing skiing and snowboardingdifferentiationwas required between forces andmoments thedirection of the forces and moments and the phase of theturn thatwas consideredHowever there seemed to be a trendthat forces were larger in skiing and moments showed largefluctuations (loading-unloading) whereas in snowboardinghigh moments with a more consistent pattern were observedIn future research it is important to increase the number ofparticipants in the study and study joint loading of variousturning techniques
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors thank ski company Atomic for providing the testequipment They appreciate the helpful discussions with DrJosef Kroll
References
[1] K Grabler and G J Stirnweis ldquoWirstschaftsbericht derSeilbahnenmdashTrends Winter 2011-2011rdquo WKO die Seilbahnen2011 httpportalwkoatwkformat detailwkangid=1ampstid=621545ampdstid=329ampopennavid=0
[2] R Schonbachler and G Scharer Fakten und Zahlen zurSchweizer Seilbahbranche Seilbahnen Schweiz 2012 httpwwwseilbahnenorgdeBrancheFakten-ZahlenFakten-Zah-len
[3] N Laplante ldquo2008-2009 Canadian Skier and SnowboarderFacts and Statsrdquo 2009 httpxcskiorgnews200920Facts20and20Stats20final20draftpdf
[4] M KlousThree-dimensional joint loading on the lower extremi-ties in alpine skiing and snowboarding [PhD thesis] Universityof Salzburg Salzburg Austria 2007
[5] S Corra A Conci G Conforti G Sacco and F de GiorgildquoSkiing and snowboarding injuries and their impact on theemergency care system in South Tyrol a restrospective analysisfor the winter season 2001ndash2002rdquo Injury Control and SafetyPromotion vol 11 no 4 pp 281ndash285 2004
[6] M Langran and S Selvaraj ldquoSnow sports injuries in Scotlanda case-control studyrdquo British Journal of Sports Medicine vol 36no 2 pp 135ndash140 2002
[7] S Sulheim I Holme A Roslashdven A Ekeland and R BahrldquoRisk factors for injuries in alpine skiing telemark skiing andsnowboardingmdashcase-control studyrdquo British Journal of SportsMedicine vol 45 no 16 pp 1303ndash1309 2011
[8] S Kim N K Endres R J Johnson C F Ettlinger andJ E Shealy ldquoSnowboarding injuries trends over time andcomparisons with alpine skiing injuriesrdquoThe American Journalof Sports Medicine vol 40 no 4 pp 770ndash776 2012
[9] M Burtscher M Flatz R Sommersacher et al OsterreichischeSkiunfallerhebung Wintersaison 20022003 Osterreichischen
12 Computational and Mathematical Methods in Medicine
Skiverbandes in Kooperation mit dem Institut fur Sportwissen-schaften der Universitat Innsbruck 2003
[10] C Goulet G Regnier G Grimard P Valois and P VilleneuveldquoRisk factors associated with alpine skiing injuries in childrena case-control studyrdquoThe American Journal of Sports Medicinevol 27 no 5 pp 644ndash650 1999
[11] E J Bridges F Rouah and K M Johnston ldquoSnowbladinginjuries in Eastern Canadardquo British Journal of Sports Medicinevol 37 no 6 pp 511ndash515 2003
[12] D Ishimaru H Ogawa K Wakahara H Sumi Y Sumi andK Shimizu ldquoHip pads reduce the overall risk of injuries inrecreational snowboardersrdquo British Journal of Sports Medicinevol 46 no 15 pp 1055ndash1058 2012
[13] H Xiang K Kelleher B J Shields K J Brown and G ASmith ldquoSkiing- and snowboarding-related injuries treated inUS emergency departments 2002rdquo Journal of Trauma-InjuryInfection amp Critical Care vol 58 no 1 pp 112ndash118 2005
[14] C Made and L G Elmqvist ldquoA 10-year study of snowboardinjuries in Lapland Swedenrdquo Scandinavian Journal of Medicineand Science in Sports vol 14 no 2 pp 128ndash133 2004
[15] E Aschauer E Ritter and H ReschWintersport Unfallstatistik20022003 Universitatsklinik fur Unfallchirurgie und Sport-traumatologie Salzburg 2003
[16] T M Davidson and A T Laliotis ldquoSnowboarding injuries afour-year study with comparison with alpine ski injuriesrdquo TheWestern Journal of Medicine vol 164 no 3 pp 231ndash237 1996
[17] J Howe The New Skiing Mechanics McIntire PublishingWaterford UK 2nd edition 2001
[18] Y Urabe M Ochi K Onari and Y Ikuta ldquoAnterior cruciateligament injury in recreational alpine skiers analysis of mech-anisms and strategy for preventionrdquo Journal of OrthopaedicScience vol 7 no 1 pp 1ndash5 2002
[19] S M Maxwell and M L Hull ldquoMeasurement of strength andloading variables on the knee during alpine skiingrdquo Journal ofBiomechanics vol 22 no 6-7 pp 609ndash624 1989
[20] T P Quinn and C D Mote Jr ldquoPrediction of the loading alongthe leg during snow skiingrdquo Journal of Biomechanics vol 25 no6 pp 609ndash625 1992
[21] C Raschner E Muller and H Schwameder ldquoKinematic andkinetic analysis of slalom turns as a basis for the development ofspecific training methods to improve strength and endurancerdquoin Science and Skiing EMullerH Schwameder E Kornexl andC Raschner Eds pp 251ndash261 Chapman amp Hall CambridgeMass USA 1997
[22] M Brodie A Walmsley and W Page ldquoFusion motion capturea prototype system using inertial measurement units and GPSfor the biomechanical analysis of ski racingrdquo Sports Technologyvol 1 pp 17ndash28 2008
[23] M Klous E Muller and H Schwameder ldquoThree-dimensionalknee joint loading in alpine skiing a comparison between acarved and a skidded turnrdquo Journal of Applied Biomechanics vol28 no 6 pp 655ndash664 2012
[24] F Vaverka S Vodickova and M Elfmark ldquoKinetic analysis ofski turns based on measured ground reaction forcesrdquo Journal ofApplied Biomechanics vol 28 no 1 pp 41ndash47 2012
[25] L Read and W Herzog ldquoExternal loading at the knee joint forlanding movements in alpine skiingrdquo International Journal ofSport Biomechanics vol 8 pp 62ndash80 1992
[26] W Nachbauer P Kaps B Nigg et al ldquoA video technique forobtaining 3-D coordinates in alpine skiingrdquo Journal of AppliedBiomechanics vol 12 no 1 pp 104ndash115 1996
[27] B Knunz W Nachbauer K Schindelwig and F BrunnerldquoForces andmoments at the boot sole during snowboardingrdquo inScience and Skiing II E Muller H Schwameder C Raschner SLindinger and E Kornexl Eds pp 242ndash249 Kovac HamburgGermany 2001
[28] A Kruger P McAlpine F Borrani and J Edelmann-NusserldquoDetermination of three-dimensional joint loading within thelower extremities in snowboardingrdquo Proceedings of the Insti-tution of Mechanical Engineers H Journal of Engineering inMedicine vol 226 no 2 pp 170ndash175 2012
[29] M Klous EMuller andH Schwameder ldquoCollecting kinematicdata on a skisnowboard track with panning tilting and zoom-ing cameras is there sufficient accuracy for a biomechanicalanalysisrdquo Journal of Sports Sciences vol 28 no 12 pp 1345ndash1352 2010
[30] A Cappozzo F Catani A Leardini M G Benedetti and UDella Croce ldquoPosition and orientation in space of bones duringmovement experimental artefactsrdquo Clinical Biomechanics vol11 no 2 pp 90ndash100 1996
[31] V Drenk ldquoPanningmdashZusatzprogramm zur Behandlungschwenk- und neigbarer und in ihrere brennweite variierbarerKameras in Peak3DmdashDokumentationrdquo Institut fur Ange-wandte Traningswissenschaften e V Leipzig Germany 1993
[32] V Drenk ldquoBildmeszligverfahren fur schwenk-und neigbaresowie in ihrer Brennweite variierbare Kamerasrdquo Zeitschrift furAngewandte Trainingswissenschaft vol 1 pp 130ndash142 1994
[33] BM Nigg andWHerzog Biomechanics of theMusculo-skeletalSystem John Wiley amp Sons New York NY USA 3rd edition2007
[34] G Stricker P Scheiber E Lindenhofer and E MullerldquoDetermination of forces in alpine skiing and snowboardingvalidation of a mobile data acquisition systemrdquo EuropeanJournal of Sport Science vol 10 no 1 pp 31ndash41 2010
[35] D G E Robertson G E Caldwell J Hamill G Kamen andS N Whittlesey Research Methods in Biomechanics HumanKinetics Champaign Ill USA 2004
[36] V M Zatsiorsky Kinematics of Human Motion HumanKinetics Champaign Ill USA 1998
[37] R M Ehrig W R Taylor G N Duda and M O HellerldquoA survey of formal methods for determining the centre ofrotation of ball jointsrdquo Journal of Biomechanics vol 39 no 15pp 2798ndash2809 2006
[38] M R Yeadon ldquoThe simulation of aerial movement II Amathematical inertia model of the human bodyrdquo Journal ofBiomechanics vol 23 no 1 pp 67ndash74 1990
[39] W T Dempster ldquoSpace requirements of the seated operatorrdquoWADC Technical Report TR-55ndash159 Wright-Patterson AirForce Base Wright-Patterson Ohio USA 1955
[40] E Muller ldquoBiomechanische Analysen moderner alpinerSkilauftechniken in unterschiedlichen Schnee- Gelande-und Pistensituationenrdquo in Biomechanik der Sportarten Bd2biomechanik des alpinen skilaufs F Fetz and E Muller Eds pp1ndash49 Ferdinand Enke Stuttgart Germany 1991
[41] C Raschner C Schiefermuller G Zallinger E Hofer FBrunner and E Muller ldquoCarving turns versus traditionalparallel turnsmdasha comparative biomechanical analysisrdquo inScience and Skiing II E Muller H Schwameder C RaschnerS Lindinger and E Kornexl Eds pp 203ndash217 Dr KovacHamburg Germany 2001
[42] GWagnerMesstechnischeDifferzierung von genschnittenen undgerutschten Kurven im alpine Skilauf [MS thesis] University ofSalzburg 2006
Computational and Mathematical Methods in Medicine 13
[43] E Muller M Klous and G Wagner ldquoBiomechanical aspectsof turning techniques in alpine skiingrdquo in Science and SportsBridging the Gap T Reilly Ed pp 135ndash142 Shaker PublishingBV Maastricht The Netherlands 2008
[44] B Knunz W Nachbauer M Mossner K Schindelwig andF Brunner ldquoTrack analysis of giant slalom turns of WorldCup racersrdquo in Proceedings of the 5th Annual Congress of theEuropean College of Sport Science (ECSS rsquo00) pp 399ndash401Jyvaskyla Finland 2000
[45] S Delorme S Tavoularis and M Lamontagne ldquoKinematics ofthe ankle joint complex in snowboardingrdquo Journal of AppliedBiomechanics vol 21 no 4 pp 394ndash403 2005
[46] S T McCaw and P DeVita ldquoErrors in alignment of center ofpressure and foot coordinates affect predicted lower extremitytorquesrdquo Journal of Biomechanics vol 28 no 8 pp 985ndash9881995
Computational and Mathematical Methods in Medicine 3
minus20
minus10
0
10
20
300 10 20 30 40 50
166
83
178
39
Dire
ctio
n of
fall
line (
m)
Across the slope (m)
(a)
0 10 20 30 40 50
20
10
0
10
20
30
153
168
160
44
241
108
170
166
21780
C1 C4
C3
C5C2
Across the slope (m)
Dire
ctio
n of
fall
line (
m)
(b)
0
minus20
minus10
10
20
30
Dire
ctio
n of
fall
line (
m)
minus10 0 10 20 30 40 50
Across the slope (m)
164
50
134
91
(c)
0
Dire
ctio
n of
fall
line (
m)
minus10 0 10 20 30 40 50
Across the slope (m)
C1
C2
C3
C4
C5
199
179
154
84
23275
150
33
164
211
20
10
10
20
30
(d)
Figure 1 Course definition (a and c) and camera setup (b and d) for the ski turn (a and b) and snowboard turn (c and d) including gates (e)cameras (998771) and the part of the turn that is analyzed (in between the thick lines)
A second reset of the kineticmeasuring devicewas performedafter the run to control for possible drift behaviors of thesystem
25 Data Analysis Kinematic and kinetic data analyses aswell as inverse dynamic calculations are described in detailin Klous et al [29] Briefly 3D marker coordinates were cal-culated from two successive cameras aftermanually digitizingall visiblemarkers for each video frame for each camera usingSIMI Motion (Version 70 Build 242) Data were filtered and
interpolated and the position and orientation of the segmentswere calculated using Cardan angles with mediolateral (119909)posterior-anterior (119910) and vertical (119911) rotation sequence[35 36] with software developed in Matlab (Version 65)Joint center positions were calculated using the sphere-fittingSCoREmethod [37] Kinetic data of the left and right leg weresynchronized and offset corrected and kinematic and kineticdata were also synchronized
Inertial properties of the lower extremities were calcu-lated applying the geometric model by Yeadon [38] The
4 Computational and Mathematical Methods in Medicine
+Fz
+Fy
+Fy
+Mz+Mx
+My
+Fz
+Fx
+Mz
+Mx
+My
+Fx
(a)
+Fz
+Fy
+Fy
+Mz
+Mz
+Mx
+My
+Fz
+Mx
+My
+Fx
+Fx
(b)
Figure 2 Definition of the local coordinate system (LCS) at the leg and the thigh of the steering leg in skiing (a) and snowboarding (b)
model was extended by adding skisnowboard boots to themodel The parts of the boot below the ankle were added tothe foot segment and the parts above the ankle were addedto the shank segment Density values from Dempster [39]were taken according to Yeadon [38] to calculate the inertialparameters of the segments The experimentally determineddensities for the inside and outside ski boot were 280 kgm3and 1400 kgm3 respectivelyThe experimentally determineddensities for the inside snowboard boot were 200 kgm3 andfor the outside boot 470 kgm3
Inverse dynamics analysis was applied to calculate netjoint forces and moments (net joint loading) from edgechanging to the subsequent one Since high frequencieskinematic movements were not expected the global positionof the center of mass (COM) as well as the orientation ofeach of the segments was filtered using a 4th order zero-phase Butterworth low-pass filter with a cutoff frequency of2Hz Kinematic angular and linear acceleration data weredetermined by numerical differentiation and kinetic andkinematic data were time-normalized to arbitrarily chosen201 data points before entering into the inverse dynamicanalysis Net joint forces and net moments at the ankle jointand knee jointwere calculated in the LCSof the calf and thighrespectively (Figure 2) Net joint forces were normalized tobody weight (BW) and net joint moments were normalizedto body mass The normalized net forces and net moments(referred to as joint forces and joint moments throughout theremaining paper) at the ankle joint represented the net forcesand net moments acting from the foot at the leg calculatedin the LCS of the leg The net forces and net moments atthe knee joint represented the net forces and net momentsacting from the leg at the thigh calculated in the LCS of thethigh The LCSs were defined with the 119910-axis in anterior-posterior direction (positive 119910-axis anterior) the 119911-axis alongthe length of the segment (positive 119911-axis proximal) andthe 119909-axis in mediolateral direction with the positive 119909-axis
pointing lateral for the steering (right) leg in both skiing andsnowboarding (Figure 2)
Due to the complexity of the experimental setup and therelated difficulty to collect accurate data only in two trialsa limited amount of interpolation was necessary to fulfillthe requirement of three markers in sight of two successivecameras during the entire run Therefore in the followingone representative carved ski turn and one representativecarved snowboard turn are presented comparatively Ankleand knee joint loading in the steering leg in skiing (outsideleg) and snowboarding (rear leg) were compared in thecurrent study Data were divided into three phases of equalduration (33) These phases correspond approximately tothe functional aspects of the turn initiation phase steeringphase I and steering phase II [40 41]
A skidding angle120573was calculated describing the skiddingcomponent in a turn [42 43] This angle was defined as theangle between the orientation vector (line from the front tothe rear binding piece of the ski) and the velocity vector of theankle of the skiersnowboarderrsquos leg In the current study anaverage skidding angle was calculated for skiing by averagingthe positions of the rear-binding piece of both skies the posi-tions of the front binding piece of both skies and the anklejoint position of the right and left leg In snowboarding anaverage ankle joint position was calculated With the angle 120573can objectively be verified that turns were carved Before cal-culating the skidding angle position data were filtered with a5Hz low-pass 4th order zero-lag Butterworth filter [23 42]
Since only one trial for each discipline is compared onlydescriptive statistics are reported with means and standarddeviations for each of the three phases of the turn
3 Results
31 Turning Technique A skidding angle 120573 was calculatedto verify the proper performance of the turning techniques(Figure 3) The average angle in skiing was 61∘ (plusmn32∘) and in
Computational and Mathematical Methods in Medicine 5
0
5
10
15
20
25
0 05 1 15 2 25
Skid
ding
angl
e (∘ )
Time (s)
Figure 3 Average skidding angle 120573 in a ski turn (black) and a frontside snowboard turn (grey)
snowboarding 92∘ (plusmn59∘) The average velocity was 139msand 111ms in skiing and snowboarding respectively Themaximum velocity in skiing was 165ms and in snowboard-ing 119ms Note that the ski and snowboard turn wereperformed with similar turning radii but different velocities
32 Ankle Joint Loading at the Steering Leg Time profilesof the mediolateral forces anteriorposterior forces andlongitudinal forces at the ankle joint in skiing and snow-boarding are shown in Figure 4 and Table 1 Mediolateralforces and anteriorposterior forces were clearly lower thanthe forces along the longitudinal axis In both skiing andsnowboarding ankle joint forces acted in posterior andupward direction Longitudinal forces in skiing were higherthan in snowboarding These forces increase up to 2-3 timesBW at 60 of the turn in skiing whereas in snowboardingthe longitudinal force was rather consistent at approximately1sdotBW Smaller forces in posterior direction showed morevariation in skiing than in snowboarding Average anklejoint forces in mediolateral were rather similar for skiingand snowboarding in the first two phases but higher insnowboarding in the last phase The ankle joint forces inanteriorposterior direction were similar for the last twophases but in the first phase the anteriorposterior force washigher in skiing The longitudinal forces were clearly greaterin skiing than in snowboarding in the first two phases andhigher in longitudinal direction than in the other directionsIn snowboarding the longitudinal force was more consistentthroughout the phases
During the turn predominantly an extension momentand abduction moment acted at the ankle joint in both ski-ing and snowboarding (Figure 5) Furthermore an internalrotation moment acted at the ankle joint in snowboardingand an external rotation moment in skiing Time profiles of
flexionextensionmoments showedmore variations in skiingthan in snowboarding with fluctuations between minus1 and7Nmkg whereas the extension moment in snowboardingvaried between 2 and 5Nmkg Averagemagnitudes (Table 2)showed higher flexionextension moments in snowboardingbut larger fluctuations in skiing in the first and second phaseof the turn represented by the large standard deviation (SD)A large abduction moment in skiing was observed in thesecond phase with peak values over 4Nmkg and an averagevalue of 17Nmkg In snowboarding the abduction momentwas approximately 0Nmkg in the first and second phases(see also Table 2) but increased up to 3Nmkg and averaged16Nmkg in the third phase The internal rotation momentclearly showed larger average magnitudes in all three phasesin snowboarding than in skiing (Table 2)
33 Knee Joint Loading Steering Leg Similar time profileswere observed for the forces in anteriorposterior directionfor skiing and snowboarding till approximately 70 of theturnwith slightly lower values in snowboarding (Figure 6) Inthe third part of the turn the force in the anterior directionis clearly higher in snowboarding than in skiing This isconfirmed by the average magnitudes for each of the threephases presented in Table 3 Anteriorposterior forces andforces along the longitudinal axis of the knee joint showedsimilar patterns in skiing Until 60 of the turn forcesincreased up to approximately 2sdotBW and then decreasedLongitudinal forces in snowboarding varied around 0sdotBWForces in mediallateral direction showed opposite timeprofiles at the steering leg for skiing and snowboarding Thelateral force in skiing showed a larger increase between 50and 75 of the turn and a smaller increase in the first 25 ofthe turn In snowboarding this increase was only observedbetween 50 and 75 of the turn in medial direction Averagemagnitudes for mediallateral forces for all three phases werelarger in skiing than in snowboarding
The time profiles of the moments at the knee joint wererather different for skiing and snowboarding (Figure 7) Inskiing the moment varied between flexion and extensionthroughout the turnwithmagnitudes between approximatelyminus2 and 4Nmkg In snowboarding a flexion moment actedat the knee joint throughout the turn with magnitudesup to 6Nmkg Average magnitudes were clearly higher insnowboarding for all three phases but the larger SD inskiing for all three phases represented the larger fluctuationsin skiing (Table 4) Furthermore in skiing an abductionmoment acted at the knee joint whereas in snowboarding anadductionmoment throughout the turn Averagemagnitudeswere clearly larger in skiing in phase 1 and in snowboarding inphase 3 In phase 2 average magnitudes were approximatelysimilar but in opposite directions (Table 4) Rather similartime profiles were observed for the internalexternal rotationmoment at the knee joint Both in skiing and snowboardingacted an internal rotation moment during most of theturn However average magnitudes were clearly higher insnowboarding than in skiing in the first and second phasesof the turn In the third phase these magnitudes were similar(see Table 4)
6 Computational and Mathematical Methods in Medicine
minus2
0
2
4
0 33 66 100
Fm
edl
atF
BW
Turn ()
(a)
minus2
0
2
4
0 33 66 100
Turn ()F
ant
posF
BW(b)
0 33 66 100
Turn ()
minus2
0
2
4
Flo
ngF
BW
(c)
Figure 4 Time profiles of the net medial (minus)lateral (+) forces (a) net anterior (+)posterior (minus) forces (b) and net forces around thelongitudinal axis (c) at the ankle joint for the steering leg in skiing (black) and snowboarding (grey)
Table 1 Average net ankle joint forces in medial (minus)lateral (+) direction (119865med-lat) anterior (+)posterior (minus) direction (119865ant-pos) and alongthe longitudinal axis (119865long) and standard deviations in the steering leg in skiing and snowboarding for each of the three phases
Computational and Mathematical Methods in Medicine 7
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()
Mfle
xex
tm (N
mk
g)
(a)
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()M
aba
dm
(Nm
kg)
(b)
0 33 66 100
Turn ()
minus6
minus4
minus2
0
2
4
6
8
m(N
mk
g)M
int
ext
(c)
Figure 5 Time profiles of the net flexion (+)extension (minus) moments (a) net adduction (+)abduction (minus) moments (b) and net internal(+)external (minus) moments (c) at the ankle joint for the steering leg in skiing (black) and snowboarding (grey)
Table 2 Average net ankle joint flexion (minus)extension (+) moments (119872flex-ext) net adduction (+)abduction (minus) moments (119872ad-ab) and netinternal (+)external (minus) rotation moments (119872int-ext) and standard deviations in the steering leg in skiing and snowboarding for each of thethree phases
8 Computational and Mathematical Methods in Medicine
0 33 66 100
Fm
edl
atF
BW
Turn ()
minus1
0
1
2
3
(a)
0 33 66 100
Turn ()
minus1
0
1
2
3
Fan
tpo
sF
BW(b)
0 33 66 100
Turn ()
minus1
0
1
2
3
Flo
ngF
BW
(c)
Figure 6 Time profiles of the net mediallateral forces (a) net anteriorposterior forces (b) and net forces around the longitudinal axis (c)at the knee joint for the steering leg in skiing (black) and snowboarding (grey)
Table 3 Average net knee joint forces in medial (minus)lateral (+) direction (119865med-lat) anterior (+)posterior (minus) direction (119865ant-pos) and alongthe longitudinal axis (119865long) and standard deviations in the steering leg in skiing and snowboarding for each of the three phases
Computational and Mathematical Methods in Medicine 9
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()
Mfle
xex
tm (N
mk
g)
(a)
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()M
aba
dm
(Nm
kg)
(b)
0 33 66 100
Turn ()
minus6
minus4
minus2
0
2
4
6
8
m(N
mk
g)M
int
ext
(c)
Figure 7 Time profiles of the net flexion (+)extension (minus) moments (a) net adduction (+)abduction (minus) moments (b) and net internal(+)external (minus) moments (c) at the knee joint for the steering leg in skiing (black) and snowboarding (grey)
Table 4 Average net knee joint flexion (+)extension (minus) moments (119872flex-ext) net adduction (+)abduction (minus) moments (119872ad-ab) and netinternal (+)external (minus) rotation moments (119872int-ext) and standard deviations in the steering leg in skiing and snowboarding for each of thethree phases
10 Computational and Mathematical Methods in Medicine
4 Discussion
The aim of this study was to compare the ankle and kneejoint loading at the steering leg between a carved ski andsnowboard turn Based on reported injury statistics and dueto differences in technique position and equipment betweenskiing and snowboarding it was hypothesized that ankle jointloading was greater in snowboarding and knee joint loadingwas greater in skiing However the current study showed adifferent outcomeWhile forcesweremostly similar for skiingand snowboarding the joint moments were consistentlygreater during a snowboard turn whereas in skiing muchmore fluctuations were observed during the turn particularlyin the first and second phase of the turn (represented by thegreater standard deviation in skiing in those two phases)Moreover forces along the longitudinal axis were higher inskiing than in snowboarding
Results showed that the carved turn demonstrated someskidding components The average skidding angle calculatedacross time was higher in snowboarding than in skiingwhich could be due to the rather steep slope to perform acarved turn in snowboarding Nevertheless both turns wererepresentative of a carved turn Results were in agreementwithMuller et al [43] andWagner [42] who reported averageskidding angles for the carving technique in skiing of 41∘Knunz et al [44] reported angles in a carved ski turn of 1-2∘for the outer leg and 7-8∘ for the inner leg in a (purely) carvedski turn
Forces in anteriorposterior and mediallateral directionat the ankle joint were similar and rather low for skiingand snowboarding As a consequence it is expected thatthe internalexternal rotation moment is also rather low asis observed in skiing However in snowboarding internalrotation moments reached magnitudes of approximately2Nmkg Consistent and larger values throughout the turnwere also observed for the flexionextension moment insnowboarding whereas the force along the longitudinal axiswas below 1sdotBW and the anteriorposterior force was evenlower Kruger et al [28] reported even larger peak values forthe flexionextension moment at the ankle joint comparedto the current study but do not report if these values area consequence of large kinetic or kinematic values Withthe low forces observed in the current study these relativelyhigh moments must be due to kinematics hence angularaccelerations of the segments or due to the different bodypositions in skiing and snowboarding which is representedby the position of the joint centres with respect to the forcevector The use of soft boots in snowboarding allowed shortbut fast rotational movements (ie kinematic parameters)whereas these movements were not possible with stiff skibootsThese equipment differences would explain the greaterjoint moments at the ankle joint in snowboarding Thiswas supported by a study of Delorme et al [45] thatcompared ankle joint kinematics between stiff and softboots in snowboarding This study reported that the useof soft boots leads to larger average dorsiplantar flexionangles and internalexternal rotation angles as well as largermaximum dorsiplantar flexion angles eversioninversionangles and internalexternal rotation angles larger minimal
internalexternal rotation angles and a larger range ofmotionin dorsiplantar flexion
In skiing the time pattern of the force along the longitu-dinal axis at the ankle joint showed similarities with the timepattern of the flexionextension and abductionadductionmoments but in opposite direction Hence opposite tosnowboarding the large moments in skiing seemed to bea consequence of the produced forces Note that in skiingthe flexionextension moment allowed the movement to thetiptail of the ski whereas the abductionadduction momentplaces the ski at the edges (see Figure 2) Fluctuations (rep-resented by the standard deviation) were much larger forthe moments than for the forces and also much larger inskiing than in snowboarding This might suggest that thegreater number of injuries at the ankle joint is caused by thespecific body position in snowboarding and the consistentlyhigh moments due to kinematic variables rather than largefluctuation as observed in the moments in skiing
At the knee joint both mediallateral forces and forcesalong the longitudinal axis were higher in skiing whereasthe anteriorposterior forces were similar for skiing andsnowboarding However the higher forces in skiing didnot result in consistently higher moments compared tosnowboarding The flexionextension moments in snow-boarding were required to place the snowboard at theedges just like the abductionadduction moment in ski-ing The flexionextension moments in snowboarding wereapproximately 3Nmkg whereas the abductionadductionmoments in skiing were approximately 10ndash15Nmkg Alsothe flexionextension moments in skiing were approximately1 Nmkg as were the abductionadductionmoments in snow-boarding In general moments were slightly lower at the kneejoint than at the ankle joint in snowboarding whereas inskiing the opposite was observed Again the larger momentsin snowboarding seemed not to be due to the high forcesbut due to the soft boot allowing larger accelerations and adifferent body position in snowboarding than in skiing
Even though the fluctuations were larger in snowboard-ing at the knee than at the ankle joint these variationswere still much lower in snowboarding than in skiing Thesefluctuations represent the loading and unloading that areclearly greater in skiing than in snowboarding In situationswhen a skier has to make a sudden adjustment these peakvalues would increase even further In skiing joint momentsincreased in the knee joint compared to the ankle jointwhereas in snowboarding the moments decreased Besidesthe knee joint forces being similar or greater in skiing thanin snowboarding also the peak forces and moments werelarger in skiing than in snowboarding except for the inter-nalexternal rotation moment Kruger et al [28] reportedclearly lower peak values for the flexionextension momentin snowboarding (33 less) than in the current study whichwould make differences between skiing and snowboardingeven more pronounced These three aspects together couldbe an explanation for the larger amount of knee injuries inskiing than in snowboarding
Even though the joint loading observed in the currentstudy is rather high one should realise that many otheraspects can explain the injury statistics as presented in
Computational and Mathematical Methods in Medicine 11
the current study The quality of the snow the technicaland physical capability of the skier or snowboarder andthe large number of skiers and snowboarders at the slopecould explain the many injuries that occur in skiing andsnowboarding The skier and snowboarder in the currentstudy carried additional equipment to allow measurementof ground reaction forces This equipment influenced theirweight and their standing heightWith their level of expertisethe skier and snowboarder did not report any influenceof this equipment Nevertheless the equipment might haveinfluenced their technique and performance Additionallythe differences in stiffness between ski and snowboard bootscould have influenced the results Due to the stiff ski bootpart of the loading might have been transferred to theboot and thereby reduced the ankle joint in skiing Inversedynamic calculations did not allow determining how muchof the ankle joint was transferred to the ski boot Hencethis could have caused overestimation of the ankle joint inskiing However where the current results showed largerankle joint in snowboarding the difference in ankle jointbetween skiing and snowboarding would have even beengreater if the ankle joint in skiing was overestimated Whencurrent results showed larger ankle joint in skiing thesedifferences might not have been as profound Both situationssupport the research hypothesis Also the magnitudes ofthe ankle joint forces and moments in skiing might havebeen lower but it is not to expect that the time patternswere influenced Furthermore the kinematic setup allowed aski and snowboard turn to be performed with similar radiibut different velocities The centripetal force (119865
119888) in a turn
is influenced by the velocity (119865119888= 119898V2119903) Although the
velocity in snowboarding was lower than in skiing the ankleand knee joint forces and moments were not consistentlylower than in skiing We speculate that if the snowboardturn was performed with higher velocities the forces andmoments at the ankle and knee joint would further increasedue to an increase of the centripetal force Furthermorevideos and data of ground reaction forces throughout thecollected data were similar Nevertheless the findings shouldbe interpreted with caution due to the single subject designAdditionally even though the applied method shows a goodaccuracy for on-snow data collection the results of inversedynamic calculations depend strongly on the accuracy of theinput data As is shown by McCaw amp DeVita [46] errorsin the input data are propagated in the inverse dynamicsprocedures thereby reducing the accuracy of the resultscalculated using this procedure Finally it is important toemphasise that we calculated forces and moments duringsuccessful turns which are not representative of the forcesand moments during unsuccessful turns that result in fallingandor injury
5 Conclusion
The expected higher ankle joint loading in snowboardingand higher knee joint loading in skiing that was based onreported injury statistics in the lower extremities in skiingand snowboarding and the differences in position technique
and equipment (soft boot versus hard boot) could not beconfirmed Ankle joint loading was not consistently greaterin snowboarding than in skiing and vice versa for the kneejoint loading When comparing skiing and snowboardingdifferentiationwas required between forces andmoments thedirection of the forces and moments and the phase of theturn thatwas consideredHowever there seemed to be a trendthat forces were larger in skiing and moments showed largefluctuations (loading-unloading) whereas in snowboardinghigh moments with a more consistent pattern were observedIn future research it is important to increase the number ofparticipants in the study and study joint loading of variousturning techniques
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors thank ski company Atomic for providing the testequipment They appreciate the helpful discussions with DrJosef Kroll
References
[1] K Grabler and G J Stirnweis ldquoWirstschaftsbericht derSeilbahnenmdashTrends Winter 2011-2011rdquo WKO die Seilbahnen2011 httpportalwkoatwkformat detailwkangid=1ampstid=621545ampdstid=329ampopennavid=0
[2] R Schonbachler and G Scharer Fakten und Zahlen zurSchweizer Seilbahbranche Seilbahnen Schweiz 2012 httpwwwseilbahnenorgdeBrancheFakten-ZahlenFakten-Zah-len
[3] N Laplante ldquo2008-2009 Canadian Skier and SnowboarderFacts and Statsrdquo 2009 httpxcskiorgnews200920Facts20and20Stats20final20draftpdf
[4] M KlousThree-dimensional joint loading on the lower extremi-ties in alpine skiing and snowboarding [PhD thesis] Universityof Salzburg Salzburg Austria 2007
[5] S Corra A Conci G Conforti G Sacco and F de GiorgildquoSkiing and snowboarding injuries and their impact on theemergency care system in South Tyrol a restrospective analysisfor the winter season 2001ndash2002rdquo Injury Control and SafetyPromotion vol 11 no 4 pp 281ndash285 2004
[6] M Langran and S Selvaraj ldquoSnow sports injuries in Scotlanda case-control studyrdquo British Journal of Sports Medicine vol 36no 2 pp 135ndash140 2002
[7] S Sulheim I Holme A Roslashdven A Ekeland and R BahrldquoRisk factors for injuries in alpine skiing telemark skiing andsnowboardingmdashcase-control studyrdquo British Journal of SportsMedicine vol 45 no 16 pp 1303ndash1309 2011
[8] S Kim N K Endres R J Johnson C F Ettlinger andJ E Shealy ldquoSnowboarding injuries trends over time andcomparisons with alpine skiing injuriesrdquoThe American Journalof Sports Medicine vol 40 no 4 pp 770ndash776 2012
[9] M Burtscher M Flatz R Sommersacher et al OsterreichischeSkiunfallerhebung Wintersaison 20022003 Osterreichischen
12 Computational and Mathematical Methods in Medicine
Skiverbandes in Kooperation mit dem Institut fur Sportwissen-schaften der Universitat Innsbruck 2003
[10] C Goulet G Regnier G Grimard P Valois and P VilleneuveldquoRisk factors associated with alpine skiing injuries in childrena case-control studyrdquoThe American Journal of Sports Medicinevol 27 no 5 pp 644ndash650 1999
[11] E J Bridges F Rouah and K M Johnston ldquoSnowbladinginjuries in Eastern Canadardquo British Journal of Sports Medicinevol 37 no 6 pp 511ndash515 2003
[12] D Ishimaru H Ogawa K Wakahara H Sumi Y Sumi andK Shimizu ldquoHip pads reduce the overall risk of injuries inrecreational snowboardersrdquo British Journal of Sports Medicinevol 46 no 15 pp 1055ndash1058 2012
[13] H Xiang K Kelleher B J Shields K J Brown and G ASmith ldquoSkiing- and snowboarding-related injuries treated inUS emergency departments 2002rdquo Journal of Trauma-InjuryInfection amp Critical Care vol 58 no 1 pp 112ndash118 2005
[14] C Made and L G Elmqvist ldquoA 10-year study of snowboardinjuries in Lapland Swedenrdquo Scandinavian Journal of Medicineand Science in Sports vol 14 no 2 pp 128ndash133 2004
[15] E Aschauer E Ritter and H ReschWintersport Unfallstatistik20022003 Universitatsklinik fur Unfallchirurgie und Sport-traumatologie Salzburg 2003
[16] T M Davidson and A T Laliotis ldquoSnowboarding injuries afour-year study with comparison with alpine ski injuriesrdquo TheWestern Journal of Medicine vol 164 no 3 pp 231ndash237 1996
[17] J Howe The New Skiing Mechanics McIntire PublishingWaterford UK 2nd edition 2001
[18] Y Urabe M Ochi K Onari and Y Ikuta ldquoAnterior cruciateligament injury in recreational alpine skiers analysis of mech-anisms and strategy for preventionrdquo Journal of OrthopaedicScience vol 7 no 1 pp 1ndash5 2002
[19] S M Maxwell and M L Hull ldquoMeasurement of strength andloading variables on the knee during alpine skiingrdquo Journal ofBiomechanics vol 22 no 6-7 pp 609ndash624 1989
[20] T P Quinn and C D Mote Jr ldquoPrediction of the loading alongthe leg during snow skiingrdquo Journal of Biomechanics vol 25 no6 pp 609ndash625 1992
[21] C Raschner E Muller and H Schwameder ldquoKinematic andkinetic analysis of slalom turns as a basis for the development ofspecific training methods to improve strength and endurancerdquoin Science and Skiing EMullerH Schwameder E Kornexl andC Raschner Eds pp 251ndash261 Chapman amp Hall CambridgeMass USA 1997
[22] M Brodie A Walmsley and W Page ldquoFusion motion capturea prototype system using inertial measurement units and GPSfor the biomechanical analysis of ski racingrdquo Sports Technologyvol 1 pp 17ndash28 2008
[23] M Klous E Muller and H Schwameder ldquoThree-dimensionalknee joint loading in alpine skiing a comparison between acarved and a skidded turnrdquo Journal of Applied Biomechanics vol28 no 6 pp 655ndash664 2012
[24] F Vaverka S Vodickova and M Elfmark ldquoKinetic analysis ofski turns based on measured ground reaction forcesrdquo Journal ofApplied Biomechanics vol 28 no 1 pp 41ndash47 2012
[25] L Read and W Herzog ldquoExternal loading at the knee joint forlanding movements in alpine skiingrdquo International Journal ofSport Biomechanics vol 8 pp 62ndash80 1992
[26] W Nachbauer P Kaps B Nigg et al ldquoA video technique forobtaining 3-D coordinates in alpine skiingrdquo Journal of AppliedBiomechanics vol 12 no 1 pp 104ndash115 1996
[27] B Knunz W Nachbauer K Schindelwig and F BrunnerldquoForces andmoments at the boot sole during snowboardingrdquo inScience and Skiing II E Muller H Schwameder C Raschner SLindinger and E Kornexl Eds pp 242ndash249 Kovac HamburgGermany 2001
[28] A Kruger P McAlpine F Borrani and J Edelmann-NusserldquoDetermination of three-dimensional joint loading within thelower extremities in snowboardingrdquo Proceedings of the Insti-tution of Mechanical Engineers H Journal of Engineering inMedicine vol 226 no 2 pp 170ndash175 2012
[29] M Klous EMuller andH Schwameder ldquoCollecting kinematicdata on a skisnowboard track with panning tilting and zoom-ing cameras is there sufficient accuracy for a biomechanicalanalysisrdquo Journal of Sports Sciences vol 28 no 12 pp 1345ndash1352 2010
[30] A Cappozzo F Catani A Leardini M G Benedetti and UDella Croce ldquoPosition and orientation in space of bones duringmovement experimental artefactsrdquo Clinical Biomechanics vol11 no 2 pp 90ndash100 1996
[31] V Drenk ldquoPanningmdashZusatzprogramm zur Behandlungschwenk- und neigbarer und in ihrere brennweite variierbarerKameras in Peak3DmdashDokumentationrdquo Institut fur Ange-wandte Traningswissenschaften e V Leipzig Germany 1993
[32] V Drenk ldquoBildmeszligverfahren fur schwenk-und neigbaresowie in ihrer Brennweite variierbare Kamerasrdquo Zeitschrift furAngewandte Trainingswissenschaft vol 1 pp 130ndash142 1994
[33] BM Nigg andWHerzog Biomechanics of theMusculo-skeletalSystem John Wiley amp Sons New York NY USA 3rd edition2007
[34] G Stricker P Scheiber E Lindenhofer and E MullerldquoDetermination of forces in alpine skiing and snowboardingvalidation of a mobile data acquisition systemrdquo EuropeanJournal of Sport Science vol 10 no 1 pp 31ndash41 2010
[35] D G E Robertson G E Caldwell J Hamill G Kamen andS N Whittlesey Research Methods in Biomechanics HumanKinetics Champaign Ill USA 2004
[36] V M Zatsiorsky Kinematics of Human Motion HumanKinetics Champaign Ill USA 1998
[37] R M Ehrig W R Taylor G N Duda and M O HellerldquoA survey of formal methods for determining the centre ofrotation of ball jointsrdquo Journal of Biomechanics vol 39 no 15pp 2798ndash2809 2006
[38] M R Yeadon ldquoThe simulation of aerial movement II Amathematical inertia model of the human bodyrdquo Journal ofBiomechanics vol 23 no 1 pp 67ndash74 1990
[39] W T Dempster ldquoSpace requirements of the seated operatorrdquoWADC Technical Report TR-55ndash159 Wright-Patterson AirForce Base Wright-Patterson Ohio USA 1955
[40] E Muller ldquoBiomechanische Analysen moderner alpinerSkilauftechniken in unterschiedlichen Schnee- Gelande-und Pistensituationenrdquo in Biomechanik der Sportarten Bd2biomechanik des alpinen skilaufs F Fetz and E Muller Eds pp1ndash49 Ferdinand Enke Stuttgart Germany 1991
[41] C Raschner C Schiefermuller G Zallinger E Hofer FBrunner and E Muller ldquoCarving turns versus traditionalparallel turnsmdasha comparative biomechanical analysisrdquo inScience and Skiing II E Muller H Schwameder C RaschnerS Lindinger and E Kornexl Eds pp 203ndash217 Dr KovacHamburg Germany 2001
[42] GWagnerMesstechnischeDifferzierung von genschnittenen undgerutschten Kurven im alpine Skilauf [MS thesis] University ofSalzburg 2006
Computational and Mathematical Methods in Medicine 13
[43] E Muller M Klous and G Wagner ldquoBiomechanical aspectsof turning techniques in alpine skiingrdquo in Science and SportsBridging the Gap T Reilly Ed pp 135ndash142 Shaker PublishingBV Maastricht The Netherlands 2008
[44] B Knunz W Nachbauer M Mossner K Schindelwig andF Brunner ldquoTrack analysis of giant slalom turns of WorldCup racersrdquo in Proceedings of the 5th Annual Congress of theEuropean College of Sport Science (ECSS rsquo00) pp 399ndash401Jyvaskyla Finland 2000
[45] S Delorme S Tavoularis and M Lamontagne ldquoKinematics ofthe ankle joint complex in snowboardingrdquo Journal of AppliedBiomechanics vol 21 no 4 pp 394ndash403 2005
[46] S T McCaw and P DeVita ldquoErrors in alignment of center ofpressure and foot coordinates affect predicted lower extremitytorquesrdquo Journal of Biomechanics vol 28 no 8 pp 985ndash9881995
4 Computational and Mathematical Methods in Medicine
+Fz
+Fy
+Fy
+Mz+Mx
+My
+Fz
+Fx
+Mz
+Mx
+My
+Fx
(a)
+Fz
+Fy
+Fy
+Mz
+Mz
+Mx
+My
+Fz
+Mx
+My
+Fx
+Fx
(b)
Figure 2 Definition of the local coordinate system (LCS) at the leg and the thigh of the steering leg in skiing (a) and snowboarding (b)
model was extended by adding skisnowboard boots to themodel The parts of the boot below the ankle were added tothe foot segment and the parts above the ankle were addedto the shank segment Density values from Dempster [39]were taken according to Yeadon [38] to calculate the inertialparameters of the segments The experimentally determineddensities for the inside and outside ski boot were 280 kgm3and 1400 kgm3 respectivelyThe experimentally determineddensities for the inside snowboard boot were 200 kgm3 andfor the outside boot 470 kgm3
Inverse dynamics analysis was applied to calculate netjoint forces and moments (net joint loading) from edgechanging to the subsequent one Since high frequencieskinematic movements were not expected the global positionof the center of mass (COM) as well as the orientation ofeach of the segments was filtered using a 4th order zero-phase Butterworth low-pass filter with a cutoff frequency of2Hz Kinematic angular and linear acceleration data weredetermined by numerical differentiation and kinetic andkinematic data were time-normalized to arbitrarily chosen201 data points before entering into the inverse dynamicanalysis Net joint forces and net moments at the ankle jointand knee jointwere calculated in the LCSof the calf and thighrespectively (Figure 2) Net joint forces were normalized tobody weight (BW) and net joint moments were normalizedto body mass The normalized net forces and net moments(referred to as joint forces and joint moments throughout theremaining paper) at the ankle joint represented the net forcesand net moments acting from the foot at the leg calculatedin the LCS of the leg The net forces and net moments atthe knee joint represented the net forces and net momentsacting from the leg at the thigh calculated in the LCS of thethigh The LCSs were defined with the 119910-axis in anterior-posterior direction (positive 119910-axis anterior) the 119911-axis alongthe length of the segment (positive 119911-axis proximal) andthe 119909-axis in mediolateral direction with the positive 119909-axis
pointing lateral for the steering (right) leg in both skiing andsnowboarding (Figure 2)
Due to the complexity of the experimental setup and therelated difficulty to collect accurate data only in two trialsa limited amount of interpolation was necessary to fulfillthe requirement of three markers in sight of two successivecameras during the entire run Therefore in the followingone representative carved ski turn and one representativecarved snowboard turn are presented comparatively Ankleand knee joint loading in the steering leg in skiing (outsideleg) and snowboarding (rear leg) were compared in thecurrent study Data were divided into three phases of equalduration (33) These phases correspond approximately tothe functional aspects of the turn initiation phase steeringphase I and steering phase II [40 41]
A skidding angle120573was calculated describing the skiddingcomponent in a turn [42 43] This angle was defined as theangle between the orientation vector (line from the front tothe rear binding piece of the ski) and the velocity vector of theankle of the skiersnowboarderrsquos leg In the current study anaverage skidding angle was calculated for skiing by averagingthe positions of the rear-binding piece of both skies the posi-tions of the front binding piece of both skies and the anklejoint position of the right and left leg In snowboarding anaverage ankle joint position was calculated With the angle 120573can objectively be verified that turns were carved Before cal-culating the skidding angle position data were filtered with a5Hz low-pass 4th order zero-lag Butterworth filter [23 42]
Since only one trial for each discipline is compared onlydescriptive statistics are reported with means and standarddeviations for each of the three phases of the turn
3 Results
31 Turning Technique A skidding angle 120573 was calculatedto verify the proper performance of the turning techniques(Figure 3) The average angle in skiing was 61∘ (plusmn32∘) and in
Computational and Mathematical Methods in Medicine 5
0
5
10
15
20
25
0 05 1 15 2 25
Skid
ding
angl
e (∘ )
Time (s)
Figure 3 Average skidding angle 120573 in a ski turn (black) and a frontside snowboard turn (grey)
snowboarding 92∘ (plusmn59∘) The average velocity was 139msand 111ms in skiing and snowboarding respectively Themaximum velocity in skiing was 165ms and in snowboard-ing 119ms Note that the ski and snowboard turn wereperformed with similar turning radii but different velocities
32 Ankle Joint Loading at the Steering Leg Time profilesof the mediolateral forces anteriorposterior forces andlongitudinal forces at the ankle joint in skiing and snow-boarding are shown in Figure 4 and Table 1 Mediolateralforces and anteriorposterior forces were clearly lower thanthe forces along the longitudinal axis In both skiing andsnowboarding ankle joint forces acted in posterior andupward direction Longitudinal forces in skiing were higherthan in snowboarding These forces increase up to 2-3 timesBW at 60 of the turn in skiing whereas in snowboardingthe longitudinal force was rather consistent at approximately1sdotBW Smaller forces in posterior direction showed morevariation in skiing than in snowboarding Average anklejoint forces in mediolateral were rather similar for skiingand snowboarding in the first two phases but higher insnowboarding in the last phase The ankle joint forces inanteriorposterior direction were similar for the last twophases but in the first phase the anteriorposterior force washigher in skiing The longitudinal forces were clearly greaterin skiing than in snowboarding in the first two phases andhigher in longitudinal direction than in the other directionsIn snowboarding the longitudinal force was more consistentthroughout the phases
During the turn predominantly an extension momentand abduction moment acted at the ankle joint in both ski-ing and snowboarding (Figure 5) Furthermore an internalrotation moment acted at the ankle joint in snowboardingand an external rotation moment in skiing Time profiles of
flexionextensionmoments showedmore variations in skiingthan in snowboarding with fluctuations between minus1 and7Nmkg whereas the extension moment in snowboardingvaried between 2 and 5Nmkg Averagemagnitudes (Table 2)showed higher flexionextension moments in snowboardingbut larger fluctuations in skiing in the first and second phaseof the turn represented by the large standard deviation (SD)A large abduction moment in skiing was observed in thesecond phase with peak values over 4Nmkg and an averagevalue of 17Nmkg In snowboarding the abduction momentwas approximately 0Nmkg in the first and second phases(see also Table 2) but increased up to 3Nmkg and averaged16Nmkg in the third phase The internal rotation momentclearly showed larger average magnitudes in all three phasesin snowboarding than in skiing (Table 2)
33 Knee Joint Loading Steering Leg Similar time profileswere observed for the forces in anteriorposterior directionfor skiing and snowboarding till approximately 70 of theturnwith slightly lower values in snowboarding (Figure 6) Inthe third part of the turn the force in the anterior directionis clearly higher in snowboarding than in skiing This isconfirmed by the average magnitudes for each of the threephases presented in Table 3 Anteriorposterior forces andforces along the longitudinal axis of the knee joint showedsimilar patterns in skiing Until 60 of the turn forcesincreased up to approximately 2sdotBW and then decreasedLongitudinal forces in snowboarding varied around 0sdotBWForces in mediallateral direction showed opposite timeprofiles at the steering leg for skiing and snowboarding Thelateral force in skiing showed a larger increase between 50and 75 of the turn and a smaller increase in the first 25 ofthe turn In snowboarding this increase was only observedbetween 50 and 75 of the turn in medial direction Averagemagnitudes for mediallateral forces for all three phases werelarger in skiing than in snowboarding
The time profiles of the moments at the knee joint wererather different for skiing and snowboarding (Figure 7) Inskiing the moment varied between flexion and extensionthroughout the turnwithmagnitudes between approximatelyminus2 and 4Nmkg In snowboarding a flexion moment actedat the knee joint throughout the turn with magnitudesup to 6Nmkg Average magnitudes were clearly higher insnowboarding for all three phases but the larger SD inskiing for all three phases represented the larger fluctuationsin skiing (Table 4) Furthermore in skiing an abductionmoment acted at the knee joint whereas in snowboarding anadductionmoment throughout the turn Averagemagnitudeswere clearly larger in skiing in phase 1 and in snowboarding inphase 3 In phase 2 average magnitudes were approximatelysimilar but in opposite directions (Table 4) Rather similartime profiles were observed for the internalexternal rotationmoment at the knee joint Both in skiing and snowboardingacted an internal rotation moment during most of theturn However average magnitudes were clearly higher insnowboarding than in skiing in the first and second phasesof the turn In the third phase these magnitudes were similar(see Table 4)
6 Computational and Mathematical Methods in Medicine
minus2
0
2
4
0 33 66 100
Fm
edl
atF
BW
Turn ()
(a)
minus2
0
2
4
0 33 66 100
Turn ()F
ant
posF
BW(b)
0 33 66 100
Turn ()
minus2
0
2
4
Flo
ngF
BW
(c)
Figure 4 Time profiles of the net medial (minus)lateral (+) forces (a) net anterior (+)posterior (minus) forces (b) and net forces around thelongitudinal axis (c) at the ankle joint for the steering leg in skiing (black) and snowboarding (grey)
Table 1 Average net ankle joint forces in medial (minus)lateral (+) direction (119865med-lat) anterior (+)posterior (minus) direction (119865ant-pos) and alongthe longitudinal axis (119865long) and standard deviations in the steering leg in skiing and snowboarding for each of the three phases
Computational and Mathematical Methods in Medicine 7
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()
Mfle
xex
tm (N
mk
g)
(a)
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()M
aba
dm
(Nm
kg)
(b)
0 33 66 100
Turn ()
minus6
minus4
minus2
0
2
4
6
8
m(N
mk
g)M
int
ext
(c)
Figure 5 Time profiles of the net flexion (+)extension (minus) moments (a) net adduction (+)abduction (minus) moments (b) and net internal(+)external (minus) moments (c) at the ankle joint for the steering leg in skiing (black) and snowboarding (grey)
Table 2 Average net ankle joint flexion (minus)extension (+) moments (119872flex-ext) net adduction (+)abduction (minus) moments (119872ad-ab) and netinternal (+)external (minus) rotation moments (119872int-ext) and standard deviations in the steering leg in skiing and snowboarding for each of thethree phases
8 Computational and Mathematical Methods in Medicine
0 33 66 100
Fm
edl
atF
BW
Turn ()
minus1
0
1
2
3
(a)
0 33 66 100
Turn ()
minus1
0
1
2
3
Fan
tpo
sF
BW(b)
0 33 66 100
Turn ()
minus1
0
1
2
3
Flo
ngF
BW
(c)
Figure 6 Time profiles of the net mediallateral forces (a) net anteriorposterior forces (b) and net forces around the longitudinal axis (c)at the knee joint for the steering leg in skiing (black) and snowboarding (grey)
Table 3 Average net knee joint forces in medial (minus)lateral (+) direction (119865med-lat) anterior (+)posterior (minus) direction (119865ant-pos) and alongthe longitudinal axis (119865long) and standard deviations in the steering leg in skiing and snowboarding for each of the three phases
Computational and Mathematical Methods in Medicine 9
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()
Mfle
xex
tm (N
mk
g)
(a)
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()M
aba
dm
(Nm
kg)
(b)
0 33 66 100
Turn ()
minus6
minus4
minus2
0
2
4
6
8
m(N
mk
g)M
int
ext
(c)
Figure 7 Time profiles of the net flexion (+)extension (minus) moments (a) net adduction (+)abduction (minus) moments (b) and net internal(+)external (minus) moments (c) at the knee joint for the steering leg in skiing (black) and snowboarding (grey)
Table 4 Average net knee joint flexion (+)extension (minus) moments (119872flex-ext) net adduction (+)abduction (minus) moments (119872ad-ab) and netinternal (+)external (minus) rotation moments (119872int-ext) and standard deviations in the steering leg in skiing and snowboarding for each of thethree phases
10 Computational and Mathematical Methods in Medicine
4 Discussion
The aim of this study was to compare the ankle and kneejoint loading at the steering leg between a carved ski andsnowboard turn Based on reported injury statistics and dueto differences in technique position and equipment betweenskiing and snowboarding it was hypothesized that ankle jointloading was greater in snowboarding and knee joint loadingwas greater in skiing However the current study showed adifferent outcomeWhile forcesweremostly similar for skiingand snowboarding the joint moments were consistentlygreater during a snowboard turn whereas in skiing muchmore fluctuations were observed during the turn particularlyin the first and second phase of the turn (represented by thegreater standard deviation in skiing in those two phases)Moreover forces along the longitudinal axis were higher inskiing than in snowboarding
Results showed that the carved turn demonstrated someskidding components The average skidding angle calculatedacross time was higher in snowboarding than in skiingwhich could be due to the rather steep slope to perform acarved turn in snowboarding Nevertheless both turns wererepresentative of a carved turn Results were in agreementwithMuller et al [43] andWagner [42] who reported averageskidding angles for the carving technique in skiing of 41∘Knunz et al [44] reported angles in a carved ski turn of 1-2∘for the outer leg and 7-8∘ for the inner leg in a (purely) carvedski turn
Forces in anteriorposterior and mediallateral directionat the ankle joint were similar and rather low for skiingand snowboarding As a consequence it is expected thatthe internalexternal rotation moment is also rather low asis observed in skiing However in snowboarding internalrotation moments reached magnitudes of approximately2Nmkg Consistent and larger values throughout the turnwere also observed for the flexionextension moment insnowboarding whereas the force along the longitudinal axiswas below 1sdotBW and the anteriorposterior force was evenlower Kruger et al [28] reported even larger peak values forthe flexionextension moment at the ankle joint comparedto the current study but do not report if these values area consequence of large kinetic or kinematic values Withthe low forces observed in the current study these relativelyhigh moments must be due to kinematics hence angularaccelerations of the segments or due to the different bodypositions in skiing and snowboarding which is representedby the position of the joint centres with respect to the forcevector The use of soft boots in snowboarding allowed shortbut fast rotational movements (ie kinematic parameters)whereas these movements were not possible with stiff skibootsThese equipment differences would explain the greaterjoint moments at the ankle joint in snowboarding Thiswas supported by a study of Delorme et al [45] thatcompared ankle joint kinematics between stiff and softboots in snowboarding This study reported that the useof soft boots leads to larger average dorsiplantar flexionangles and internalexternal rotation angles as well as largermaximum dorsiplantar flexion angles eversioninversionangles and internalexternal rotation angles larger minimal
internalexternal rotation angles and a larger range ofmotionin dorsiplantar flexion
In skiing the time pattern of the force along the longitu-dinal axis at the ankle joint showed similarities with the timepattern of the flexionextension and abductionadductionmoments but in opposite direction Hence opposite tosnowboarding the large moments in skiing seemed to bea consequence of the produced forces Note that in skiingthe flexionextension moment allowed the movement to thetiptail of the ski whereas the abductionadduction momentplaces the ski at the edges (see Figure 2) Fluctuations (rep-resented by the standard deviation) were much larger forthe moments than for the forces and also much larger inskiing than in snowboarding This might suggest that thegreater number of injuries at the ankle joint is caused by thespecific body position in snowboarding and the consistentlyhigh moments due to kinematic variables rather than largefluctuation as observed in the moments in skiing
At the knee joint both mediallateral forces and forcesalong the longitudinal axis were higher in skiing whereasthe anteriorposterior forces were similar for skiing andsnowboarding However the higher forces in skiing didnot result in consistently higher moments compared tosnowboarding The flexionextension moments in snow-boarding were required to place the snowboard at theedges just like the abductionadduction moment in ski-ing The flexionextension moments in snowboarding wereapproximately 3Nmkg whereas the abductionadductionmoments in skiing were approximately 10ndash15Nmkg Alsothe flexionextension moments in skiing were approximately1 Nmkg as were the abductionadductionmoments in snow-boarding In general moments were slightly lower at the kneejoint than at the ankle joint in snowboarding whereas inskiing the opposite was observed Again the larger momentsin snowboarding seemed not to be due to the high forcesbut due to the soft boot allowing larger accelerations and adifferent body position in snowboarding than in skiing
Even though the fluctuations were larger in snowboard-ing at the knee than at the ankle joint these variationswere still much lower in snowboarding than in skiing Thesefluctuations represent the loading and unloading that areclearly greater in skiing than in snowboarding In situationswhen a skier has to make a sudden adjustment these peakvalues would increase even further In skiing joint momentsincreased in the knee joint compared to the ankle jointwhereas in snowboarding the moments decreased Besidesthe knee joint forces being similar or greater in skiing thanin snowboarding also the peak forces and moments werelarger in skiing than in snowboarding except for the inter-nalexternal rotation moment Kruger et al [28] reportedclearly lower peak values for the flexionextension momentin snowboarding (33 less) than in the current study whichwould make differences between skiing and snowboardingeven more pronounced These three aspects together couldbe an explanation for the larger amount of knee injuries inskiing than in snowboarding
Even though the joint loading observed in the currentstudy is rather high one should realise that many otheraspects can explain the injury statistics as presented in
Computational and Mathematical Methods in Medicine 11
the current study The quality of the snow the technicaland physical capability of the skier or snowboarder andthe large number of skiers and snowboarders at the slopecould explain the many injuries that occur in skiing andsnowboarding The skier and snowboarder in the currentstudy carried additional equipment to allow measurementof ground reaction forces This equipment influenced theirweight and their standing heightWith their level of expertisethe skier and snowboarder did not report any influenceof this equipment Nevertheless the equipment might haveinfluenced their technique and performance Additionallythe differences in stiffness between ski and snowboard bootscould have influenced the results Due to the stiff ski bootpart of the loading might have been transferred to theboot and thereby reduced the ankle joint in skiing Inversedynamic calculations did not allow determining how muchof the ankle joint was transferred to the ski boot Hencethis could have caused overestimation of the ankle joint inskiing However where the current results showed largerankle joint in snowboarding the difference in ankle jointbetween skiing and snowboarding would have even beengreater if the ankle joint in skiing was overestimated Whencurrent results showed larger ankle joint in skiing thesedifferences might not have been as profound Both situationssupport the research hypothesis Also the magnitudes ofthe ankle joint forces and moments in skiing might havebeen lower but it is not to expect that the time patternswere influenced Furthermore the kinematic setup allowed aski and snowboard turn to be performed with similar radiibut different velocities The centripetal force (119865
119888) in a turn
is influenced by the velocity (119865119888= 119898V2119903) Although the
velocity in snowboarding was lower than in skiing the ankleand knee joint forces and moments were not consistentlylower than in skiing We speculate that if the snowboardturn was performed with higher velocities the forces andmoments at the ankle and knee joint would further increasedue to an increase of the centripetal force Furthermorevideos and data of ground reaction forces throughout thecollected data were similar Nevertheless the findings shouldbe interpreted with caution due to the single subject designAdditionally even though the applied method shows a goodaccuracy for on-snow data collection the results of inversedynamic calculations depend strongly on the accuracy of theinput data As is shown by McCaw amp DeVita [46] errorsin the input data are propagated in the inverse dynamicsprocedures thereby reducing the accuracy of the resultscalculated using this procedure Finally it is important toemphasise that we calculated forces and moments duringsuccessful turns which are not representative of the forcesand moments during unsuccessful turns that result in fallingandor injury
5 Conclusion
The expected higher ankle joint loading in snowboardingand higher knee joint loading in skiing that was based onreported injury statistics in the lower extremities in skiingand snowboarding and the differences in position technique
and equipment (soft boot versus hard boot) could not beconfirmed Ankle joint loading was not consistently greaterin snowboarding than in skiing and vice versa for the kneejoint loading When comparing skiing and snowboardingdifferentiationwas required between forces andmoments thedirection of the forces and moments and the phase of theturn thatwas consideredHowever there seemed to be a trendthat forces were larger in skiing and moments showed largefluctuations (loading-unloading) whereas in snowboardinghigh moments with a more consistent pattern were observedIn future research it is important to increase the number ofparticipants in the study and study joint loading of variousturning techniques
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors thank ski company Atomic for providing the testequipment They appreciate the helpful discussions with DrJosef Kroll
References
[1] K Grabler and G J Stirnweis ldquoWirstschaftsbericht derSeilbahnenmdashTrends Winter 2011-2011rdquo WKO die Seilbahnen2011 httpportalwkoatwkformat detailwkangid=1ampstid=621545ampdstid=329ampopennavid=0
[2] R Schonbachler and G Scharer Fakten und Zahlen zurSchweizer Seilbahbranche Seilbahnen Schweiz 2012 httpwwwseilbahnenorgdeBrancheFakten-ZahlenFakten-Zah-len
[3] N Laplante ldquo2008-2009 Canadian Skier and SnowboarderFacts and Statsrdquo 2009 httpxcskiorgnews200920Facts20and20Stats20final20draftpdf
[4] M KlousThree-dimensional joint loading on the lower extremi-ties in alpine skiing and snowboarding [PhD thesis] Universityof Salzburg Salzburg Austria 2007
[5] S Corra A Conci G Conforti G Sacco and F de GiorgildquoSkiing and snowboarding injuries and their impact on theemergency care system in South Tyrol a restrospective analysisfor the winter season 2001ndash2002rdquo Injury Control and SafetyPromotion vol 11 no 4 pp 281ndash285 2004
[6] M Langran and S Selvaraj ldquoSnow sports injuries in Scotlanda case-control studyrdquo British Journal of Sports Medicine vol 36no 2 pp 135ndash140 2002
[7] S Sulheim I Holme A Roslashdven A Ekeland and R BahrldquoRisk factors for injuries in alpine skiing telemark skiing andsnowboardingmdashcase-control studyrdquo British Journal of SportsMedicine vol 45 no 16 pp 1303ndash1309 2011
[8] S Kim N K Endres R J Johnson C F Ettlinger andJ E Shealy ldquoSnowboarding injuries trends over time andcomparisons with alpine skiing injuriesrdquoThe American Journalof Sports Medicine vol 40 no 4 pp 770ndash776 2012
[9] M Burtscher M Flatz R Sommersacher et al OsterreichischeSkiunfallerhebung Wintersaison 20022003 Osterreichischen
12 Computational and Mathematical Methods in Medicine
Skiverbandes in Kooperation mit dem Institut fur Sportwissen-schaften der Universitat Innsbruck 2003
[10] C Goulet G Regnier G Grimard P Valois and P VilleneuveldquoRisk factors associated with alpine skiing injuries in childrena case-control studyrdquoThe American Journal of Sports Medicinevol 27 no 5 pp 644ndash650 1999
[11] E J Bridges F Rouah and K M Johnston ldquoSnowbladinginjuries in Eastern Canadardquo British Journal of Sports Medicinevol 37 no 6 pp 511ndash515 2003
[12] D Ishimaru H Ogawa K Wakahara H Sumi Y Sumi andK Shimizu ldquoHip pads reduce the overall risk of injuries inrecreational snowboardersrdquo British Journal of Sports Medicinevol 46 no 15 pp 1055ndash1058 2012
[13] H Xiang K Kelleher B J Shields K J Brown and G ASmith ldquoSkiing- and snowboarding-related injuries treated inUS emergency departments 2002rdquo Journal of Trauma-InjuryInfection amp Critical Care vol 58 no 1 pp 112ndash118 2005
[14] C Made and L G Elmqvist ldquoA 10-year study of snowboardinjuries in Lapland Swedenrdquo Scandinavian Journal of Medicineand Science in Sports vol 14 no 2 pp 128ndash133 2004
[15] E Aschauer E Ritter and H ReschWintersport Unfallstatistik20022003 Universitatsklinik fur Unfallchirurgie und Sport-traumatologie Salzburg 2003
[16] T M Davidson and A T Laliotis ldquoSnowboarding injuries afour-year study with comparison with alpine ski injuriesrdquo TheWestern Journal of Medicine vol 164 no 3 pp 231ndash237 1996
[17] J Howe The New Skiing Mechanics McIntire PublishingWaterford UK 2nd edition 2001
[18] Y Urabe M Ochi K Onari and Y Ikuta ldquoAnterior cruciateligament injury in recreational alpine skiers analysis of mech-anisms and strategy for preventionrdquo Journal of OrthopaedicScience vol 7 no 1 pp 1ndash5 2002
[19] S M Maxwell and M L Hull ldquoMeasurement of strength andloading variables on the knee during alpine skiingrdquo Journal ofBiomechanics vol 22 no 6-7 pp 609ndash624 1989
[20] T P Quinn and C D Mote Jr ldquoPrediction of the loading alongthe leg during snow skiingrdquo Journal of Biomechanics vol 25 no6 pp 609ndash625 1992
[21] C Raschner E Muller and H Schwameder ldquoKinematic andkinetic analysis of slalom turns as a basis for the development ofspecific training methods to improve strength and endurancerdquoin Science and Skiing EMullerH Schwameder E Kornexl andC Raschner Eds pp 251ndash261 Chapman amp Hall CambridgeMass USA 1997
[22] M Brodie A Walmsley and W Page ldquoFusion motion capturea prototype system using inertial measurement units and GPSfor the biomechanical analysis of ski racingrdquo Sports Technologyvol 1 pp 17ndash28 2008
[23] M Klous E Muller and H Schwameder ldquoThree-dimensionalknee joint loading in alpine skiing a comparison between acarved and a skidded turnrdquo Journal of Applied Biomechanics vol28 no 6 pp 655ndash664 2012
[24] F Vaverka S Vodickova and M Elfmark ldquoKinetic analysis ofski turns based on measured ground reaction forcesrdquo Journal ofApplied Biomechanics vol 28 no 1 pp 41ndash47 2012
[25] L Read and W Herzog ldquoExternal loading at the knee joint forlanding movements in alpine skiingrdquo International Journal ofSport Biomechanics vol 8 pp 62ndash80 1992
[26] W Nachbauer P Kaps B Nigg et al ldquoA video technique forobtaining 3-D coordinates in alpine skiingrdquo Journal of AppliedBiomechanics vol 12 no 1 pp 104ndash115 1996
[27] B Knunz W Nachbauer K Schindelwig and F BrunnerldquoForces andmoments at the boot sole during snowboardingrdquo inScience and Skiing II E Muller H Schwameder C Raschner SLindinger and E Kornexl Eds pp 242ndash249 Kovac HamburgGermany 2001
[28] A Kruger P McAlpine F Borrani and J Edelmann-NusserldquoDetermination of three-dimensional joint loading within thelower extremities in snowboardingrdquo Proceedings of the Insti-tution of Mechanical Engineers H Journal of Engineering inMedicine vol 226 no 2 pp 170ndash175 2012
[29] M Klous EMuller andH Schwameder ldquoCollecting kinematicdata on a skisnowboard track with panning tilting and zoom-ing cameras is there sufficient accuracy for a biomechanicalanalysisrdquo Journal of Sports Sciences vol 28 no 12 pp 1345ndash1352 2010
[30] A Cappozzo F Catani A Leardini M G Benedetti and UDella Croce ldquoPosition and orientation in space of bones duringmovement experimental artefactsrdquo Clinical Biomechanics vol11 no 2 pp 90ndash100 1996
[31] V Drenk ldquoPanningmdashZusatzprogramm zur Behandlungschwenk- und neigbarer und in ihrere brennweite variierbarerKameras in Peak3DmdashDokumentationrdquo Institut fur Ange-wandte Traningswissenschaften e V Leipzig Germany 1993
[32] V Drenk ldquoBildmeszligverfahren fur schwenk-und neigbaresowie in ihrer Brennweite variierbare Kamerasrdquo Zeitschrift furAngewandte Trainingswissenschaft vol 1 pp 130ndash142 1994
[33] BM Nigg andWHerzog Biomechanics of theMusculo-skeletalSystem John Wiley amp Sons New York NY USA 3rd edition2007
[34] G Stricker P Scheiber E Lindenhofer and E MullerldquoDetermination of forces in alpine skiing and snowboardingvalidation of a mobile data acquisition systemrdquo EuropeanJournal of Sport Science vol 10 no 1 pp 31ndash41 2010
[35] D G E Robertson G E Caldwell J Hamill G Kamen andS N Whittlesey Research Methods in Biomechanics HumanKinetics Champaign Ill USA 2004
[36] V M Zatsiorsky Kinematics of Human Motion HumanKinetics Champaign Ill USA 1998
[37] R M Ehrig W R Taylor G N Duda and M O HellerldquoA survey of formal methods for determining the centre ofrotation of ball jointsrdquo Journal of Biomechanics vol 39 no 15pp 2798ndash2809 2006
[38] M R Yeadon ldquoThe simulation of aerial movement II Amathematical inertia model of the human bodyrdquo Journal ofBiomechanics vol 23 no 1 pp 67ndash74 1990
[39] W T Dempster ldquoSpace requirements of the seated operatorrdquoWADC Technical Report TR-55ndash159 Wright-Patterson AirForce Base Wright-Patterson Ohio USA 1955
[40] E Muller ldquoBiomechanische Analysen moderner alpinerSkilauftechniken in unterschiedlichen Schnee- Gelande-und Pistensituationenrdquo in Biomechanik der Sportarten Bd2biomechanik des alpinen skilaufs F Fetz and E Muller Eds pp1ndash49 Ferdinand Enke Stuttgart Germany 1991
[41] C Raschner C Schiefermuller G Zallinger E Hofer FBrunner and E Muller ldquoCarving turns versus traditionalparallel turnsmdasha comparative biomechanical analysisrdquo inScience and Skiing II E Muller H Schwameder C RaschnerS Lindinger and E Kornexl Eds pp 203ndash217 Dr KovacHamburg Germany 2001
[42] GWagnerMesstechnischeDifferzierung von genschnittenen undgerutschten Kurven im alpine Skilauf [MS thesis] University ofSalzburg 2006
Computational and Mathematical Methods in Medicine 13
[43] E Muller M Klous and G Wagner ldquoBiomechanical aspectsof turning techniques in alpine skiingrdquo in Science and SportsBridging the Gap T Reilly Ed pp 135ndash142 Shaker PublishingBV Maastricht The Netherlands 2008
[44] B Knunz W Nachbauer M Mossner K Schindelwig andF Brunner ldquoTrack analysis of giant slalom turns of WorldCup racersrdquo in Proceedings of the 5th Annual Congress of theEuropean College of Sport Science (ECSS rsquo00) pp 399ndash401Jyvaskyla Finland 2000
[45] S Delorme S Tavoularis and M Lamontagne ldquoKinematics ofthe ankle joint complex in snowboardingrdquo Journal of AppliedBiomechanics vol 21 no 4 pp 394ndash403 2005
[46] S T McCaw and P DeVita ldquoErrors in alignment of center ofpressure and foot coordinates affect predicted lower extremitytorquesrdquo Journal of Biomechanics vol 28 no 8 pp 985ndash9881995
Computational and Mathematical Methods in Medicine 5
0
5
10
15
20
25
0 05 1 15 2 25
Skid
ding
angl
e (∘ )
Time (s)
Figure 3 Average skidding angle 120573 in a ski turn (black) and a frontside snowboard turn (grey)
snowboarding 92∘ (plusmn59∘) The average velocity was 139msand 111ms in skiing and snowboarding respectively Themaximum velocity in skiing was 165ms and in snowboard-ing 119ms Note that the ski and snowboard turn wereperformed with similar turning radii but different velocities
32 Ankle Joint Loading at the Steering Leg Time profilesof the mediolateral forces anteriorposterior forces andlongitudinal forces at the ankle joint in skiing and snow-boarding are shown in Figure 4 and Table 1 Mediolateralforces and anteriorposterior forces were clearly lower thanthe forces along the longitudinal axis In both skiing andsnowboarding ankle joint forces acted in posterior andupward direction Longitudinal forces in skiing were higherthan in snowboarding These forces increase up to 2-3 timesBW at 60 of the turn in skiing whereas in snowboardingthe longitudinal force was rather consistent at approximately1sdotBW Smaller forces in posterior direction showed morevariation in skiing than in snowboarding Average anklejoint forces in mediolateral were rather similar for skiingand snowboarding in the first two phases but higher insnowboarding in the last phase The ankle joint forces inanteriorposterior direction were similar for the last twophases but in the first phase the anteriorposterior force washigher in skiing The longitudinal forces were clearly greaterin skiing than in snowboarding in the first two phases andhigher in longitudinal direction than in the other directionsIn snowboarding the longitudinal force was more consistentthroughout the phases
During the turn predominantly an extension momentand abduction moment acted at the ankle joint in both ski-ing and snowboarding (Figure 5) Furthermore an internalrotation moment acted at the ankle joint in snowboardingand an external rotation moment in skiing Time profiles of
flexionextensionmoments showedmore variations in skiingthan in snowboarding with fluctuations between minus1 and7Nmkg whereas the extension moment in snowboardingvaried between 2 and 5Nmkg Averagemagnitudes (Table 2)showed higher flexionextension moments in snowboardingbut larger fluctuations in skiing in the first and second phaseof the turn represented by the large standard deviation (SD)A large abduction moment in skiing was observed in thesecond phase with peak values over 4Nmkg and an averagevalue of 17Nmkg In snowboarding the abduction momentwas approximately 0Nmkg in the first and second phases(see also Table 2) but increased up to 3Nmkg and averaged16Nmkg in the third phase The internal rotation momentclearly showed larger average magnitudes in all three phasesin snowboarding than in skiing (Table 2)
33 Knee Joint Loading Steering Leg Similar time profileswere observed for the forces in anteriorposterior directionfor skiing and snowboarding till approximately 70 of theturnwith slightly lower values in snowboarding (Figure 6) Inthe third part of the turn the force in the anterior directionis clearly higher in snowboarding than in skiing This isconfirmed by the average magnitudes for each of the threephases presented in Table 3 Anteriorposterior forces andforces along the longitudinal axis of the knee joint showedsimilar patterns in skiing Until 60 of the turn forcesincreased up to approximately 2sdotBW and then decreasedLongitudinal forces in snowboarding varied around 0sdotBWForces in mediallateral direction showed opposite timeprofiles at the steering leg for skiing and snowboarding Thelateral force in skiing showed a larger increase between 50and 75 of the turn and a smaller increase in the first 25 ofthe turn In snowboarding this increase was only observedbetween 50 and 75 of the turn in medial direction Averagemagnitudes for mediallateral forces for all three phases werelarger in skiing than in snowboarding
The time profiles of the moments at the knee joint wererather different for skiing and snowboarding (Figure 7) Inskiing the moment varied between flexion and extensionthroughout the turnwithmagnitudes between approximatelyminus2 and 4Nmkg In snowboarding a flexion moment actedat the knee joint throughout the turn with magnitudesup to 6Nmkg Average magnitudes were clearly higher insnowboarding for all three phases but the larger SD inskiing for all three phases represented the larger fluctuationsin skiing (Table 4) Furthermore in skiing an abductionmoment acted at the knee joint whereas in snowboarding anadductionmoment throughout the turn Averagemagnitudeswere clearly larger in skiing in phase 1 and in snowboarding inphase 3 In phase 2 average magnitudes were approximatelysimilar but in opposite directions (Table 4) Rather similartime profiles were observed for the internalexternal rotationmoment at the knee joint Both in skiing and snowboardingacted an internal rotation moment during most of theturn However average magnitudes were clearly higher insnowboarding than in skiing in the first and second phasesof the turn In the third phase these magnitudes were similar(see Table 4)
6 Computational and Mathematical Methods in Medicine
minus2
0
2
4
0 33 66 100
Fm
edl
atF
BW
Turn ()
(a)
minus2
0
2
4
0 33 66 100
Turn ()F
ant
posF
BW(b)
0 33 66 100
Turn ()
minus2
0
2
4
Flo
ngF
BW
(c)
Figure 4 Time profiles of the net medial (minus)lateral (+) forces (a) net anterior (+)posterior (minus) forces (b) and net forces around thelongitudinal axis (c) at the ankle joint for the steering leg in skiing (black) and snowboarding (grey)
Table 1 Average net ankle joint forces in medial (minus)lateral (+) direction (119865med-lat) anterior (+)posterior (minus) direction (119865ant-pos) and alongthe longitudinal axis (119865long) and standard deviations in the steering leg in skiing and snowboarding for each of the three phases
Computational and Mathematical Methods in Medicine 7
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()
Mfle
xex
tm (N
mk
g)
(a)
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()M
aba
dm
(Nm
kg)
(b)
0 33 66 100
Turn ()
minus6
minus4
minus2
0
2
4
6
8
m(N
mk
g)M
int
ext
(c)
Figure 5 Time profiles of the net flexion (+)extension (minus) moments (a) net adduction (+)abduction (minus) moments (b) and net internal(+)external (minus) moments (c) at the ankle joint for the steering leg in skiing (black) and snowboarding (grey)
Table 2 Average net ankle joint flexion (minus)extension (+) moments (119872flex-ext) net adduction (+)abduction (minus) moments (119872ad-ab) and netinternal (+)external (minus) rotation moments (119872int-ext) and standard deviations in the steering leg in skiing and snowboarding for each of thethree phases
8 Computational and Mathematical Methods in Medicine
0 33 66 100
Fm
edl
atF
BW
Turn ()
minus1
0
1
2
3
(a)
0 33 66 100
Turn ()
minus1
0
1
2
3
Fan
tpo
sF
BW(b)
0 33 66 100
Turn ()
minus1
0
1
2
3
Flo
ngF
BW
(c)
Figure 6 Time profiles of the net mediallateral forces (a) net anteriorposterior forces (b) and net forces around the longitudinal axis (c)at the knee joint for the steering leg in skiing (black) and snowboarding (grey)
Table 3 Average net knee joint forces in medial (minus)lateral (+) direction (119865med-lat) anterior (+)posterior (minus) direction (119865ant-pos) and alongthe longitudinal axis (119865long) and standard deviations in the steering leg in skiing and snowboarding for each of the three phases
Computational and Mathematical Methods in Medicine 9
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()
Mfle
xex
tm (N
mk
g)
(a)
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()M
aba
dm
(Nm
kg)
(b)
0 33 66 100
Turn ()
minus6
minus4
minus2
0
2
4
6
8
m(N
mk
g)M
int
ext
(c)
Figure 7 Time profiles of the net flexion (+)extension (minus) moments (a) net adduction (+)abduction (minus) moments (b) and net internal(+)external (minus) moments (c) at the knee joint for the steering leg in skiing (black) and snowboarding (grey)
Table 4 Average net knee joint flexion (+)extension (minus) moments (119872flex-ext) net adduction (+)abduction (minus) moments (119872ad-ab) and netinternal (+)external (minus) rotation moments (119872int-ext) and standard deviations in the steering leg in skiing and snowboarding for each of thethree phases
10 Computational and Mathematical Methods in Medicine
4 Discussion
The aim of this study was to compare the ankle and kneejoint loading at the steering leg between a carved ski andsnowboard turn Based on reported injury statistics and dueto differences in technique position and equipment betweenskiing and snowboarding it was hypothesized that ankle jointloading was greater in snowboarding and knee joint loadingwas greater in skiing However the current study showed adifferent outcomeWhile forcesweremostly similar for skiingand snowboarding the joint moments were consistentlygreater during a snowboard turn whereas in skiing muchmore fluctuations were observed during the turn particularlyin the first and second phase of the turn (represented by thegreater standard deviation in skiing in those two phases)Moreover forces along the longitudinal axis were higher inskiing than in snowboarding
Results showed that the carved turn demonstrated someskidding components The average skidding angle calculatedacross time was higher in snowboarding than in skiingwhich could be due to the rather steep slope to perform acarved turn in snowboarding Nevertheless both turns wererepresentative of a carved turn Results were in agreementwithMuller et al [43] andWagner [42] who reported averageskidding angles for the carving technique in skiing of 41∘Knunz et al [44] reported angles in a carved ski turn of 1-2∘for the outer leg and 7-8∘ for the inner leg in a (purely) carvedski turn
Forces in anteriorposterior and mediallateral directionat the ankle joint were similar and rather low for skiingand snowboarding As a consequence it is expected thatthe internalexternal rotation moment is also rather low asis observed in skiing However in snowboarding internalrotation moments reached magnitudes of approximately2Nmkg Consistent and larger values throughout the turnwere also observed for the flexionextension moment insnowboarding whereas the force along the longitudinal axiswas below 1sdotBW and the anteriorposterior force was evenlower Kruger et al [28] reported even larger peak values forthe flexionextension moment at the ankle joint comparedto the current study but do not report if these values area consequence of large kinetic or kinematic values Withthe low forces observed in the current study these relativelyhigh moments must be due to kinematics hence angularaccelerations of the segments or due to the different bodypositions in skiing and snowboarding which is representedby the position of the joint centres with respect to the forcevector The use of soft boots in snowboarding allowed shortbut fast rotational movements (ie kinematic parameters)whereas these movements were not possible with stiff skibootsThese equipment differences would explain the greaterjoint moments at the ankle joint in snowboarding Thiswas supported by a study of Delorme et al [45] thatcompared ankle joint kinematics between stiff and softboots in snowboarding This study reported that the useof soft boots leads to larger average dorsiplantar flexionangles and internalexternal rotation angles as well as largermaximum dorsiplantar flexion angles eversioninversionangles and internalexternal rotation angles larger minimal
internalexternal rotation angles and a larger range ofmotionin dorsiplantar flexion
In skiing the time pattern of the force along the longitu-dinal axis at the ankle joint showed similarities with the timepattern of the flexionextension and abductionadductionmoments but in opposite direction Hence opposite tosnowboarding the large moments in skiing seemed to bea consequence of the produced forces Note that in skiingthe flexionextension moment allowed the movement to thetiptail of the ski whereas the abductionadduction momentplaces the ski at the edges (see Figure 2) Fluctuations (rep-resented by the standard deviation) were much larger forthe moments than for the forces and also much larger inskiing than in snowboarding This might suggest that thegreater number of injuries at the ankle joint is caused by thespecific body position in snowboarding and the consistentlyhigh moments due to kinematic variables rather than largefluctuation as observed in the moments in skiing
At the knee joint both mediallateral forces and forcesalong the longitudinal axis were higher in skiing whereasthe anteriorposterior forces were similar for skiing andsnowboarding However the higher forces in skiing didnot result in consistently higher moments compared tosnowboarding The flexionextension moments in snow-boarding were required to place the snowboard at theedges just like the abductionadduction moment in ski-ing The flexionextension moments in snowboarding wereapproximately 3Nmkg whereas the abductionadductionmoments in skiing were approximately 10ndash15Nmkg Alsothe flexionextension moments in skiing were approximately1 Nmkg as were the abductionadductionmoments in snow-boarding In general moments were slightly lower at the kneejoint than at the ankle joint in snowboarding whereas inskiing the opposite was observed Again the larger momentsin snowboarding seemed not to be due to the high forcesbut due to the soft boot allowing larger accelerations and adifferent body position in snowboarding than in skiing
Even though the fluctuations were larger in snowboard-ing at the knee than at the ankle joint these variationswere still much lower in snowboarding than in skiing Thesefluctuations represent the loading and unloading that areclearly greater in skiing than in snowboarding In situationswhen a skier has to make a sudden adjustment these peakvalues would increase even further In skiing joint momentsincreased in the knee joint compared to the ankle jointwhereas in snowboarding the moments decreased Besidesthe knee joint forces being similar or greater in skiing thanin snowboarding also the peak forces and moments werelarger in skiing than in snowboarding except for the inter-nalexternal rotation moment Kruger et al [28] reportedclearly lower peak values for the flexionextension momentin snowboarding (33 less) than in the current study whichwould make differences between skiing and snowboardingeven more pronounced These three aspects together couldbe an explanation for the larger amount of knee injuries inskiing than in snowboarding
Even though the joint loading observed in the currentstudy is rather high one should realise that many otheraspects can explain the injury statistics as presented in
Computational and Mathematical Methods in Medicine 11
the current study The quality of the snow the technicaland physical capability of the skier or snowboarder andthe large number of skiers and snowboarders at the slopecould explain the many injuries that occur in skiing andsnowboarding The skier and snowboarder in the currentstudy carried additional equipment to allow measurementof ground reaction forces This equipment influenced theirweight and their standing heightWith their level of expertisethe skier and snowboarder did not report any influenceof this equipment Nevertheless the equipment might haveinfluenced their technique and performance Additionallythe differences in stiffness between ski and snowboard bootscould have influenced the results Due to the stiff ski bootpart of the loading might have been transferred to theboot and thereby reduced the ankle joint in skiing Inversedynamic calculations did not allow determining how muchof the ankle joint was transferred to the ski boot Hencethis could have caused overestimation of the ankle joint inskiing However where the current results showed largerankle joint in snowboarding the difference in ankle jointbetween skiing and snowboarding would have even beengreater if the ankle joint in skiing was overestimated Whencurrent results showed larger ankle joint in skiing thesedifferences might not have been as profound Both situationssupport the research hypothesis Also the magnitudes ofthe ankle joint forces and moments in skiing might havebeen lower but it is not to expect that the time patternswere influenced Furthermore the kinematic setup allowed aski and snowboard turn to be performed with similar radiibut different velocities The centripetal force (119865
119888) in a turn
is influenced by the velocity (119865119888= 119898V2119903) Although the
velocity in snowboarding was lower than in skiing the ankleand knee joint forces and moments were not consistentlylower than in skiing We speculate that if the snowboardturn was performed with higher velocities the forces andmoments at the ankle and knee joint would further increasedue to an increase of the centripetal force Furthermorevideos and data of ground reaction forces throughout thecollected data were similar Nevertheless the findings shouldbe interpreted with caution due to the single subject designAdditionally even though the applied method shows a goodaccuracy for on-snow data collection the results of inversedynamic calculations depend strongly on the accuracy of theinput data As is shown by McCaw amp DeVita [46] errorsin the input data are propagated in the inverse dynamicsprocedures thereby reducing the accuracy of the resultscalculated using this procedure Finally it is important toemphasise that we calculated forces and moments duringsuccessful turns which are not representative of the forcesand moments during unsuccessful turns that result in fallingandor injury
5 Conclusion
The expected higher ankle joint loading in snowboardingand higher knee joint loading in skiing that was based onreported injury statistics in the lower extremities in skiingand snowboarding and the differences in position technique
and equipment (soft boot versus hard boot) could not beconfirmed Ankle joint loading was not consistently greaterin snowboarding than in skiing and vice versa for the kneejoint loading When comparing skiing and snowboardingdifferentiationwas required between forces andmoments thedirection of the forces and moments and the phase of theturn thatwas consideredHowever there seemed to be a trendthat forces were larger in skiing and moments showed largefluctuations (loading-unloading) whereas in snowboardinghigh moments with a more consistent pattern were observedIn future research it is important to increase the number ofparticipants in the study and study joint loading of variousturning techniques
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors thank ski company Atomic for providing the testequipment They appreciate the helpful discussions with DrJosef Kroll
References
[1] K Grabler and G J Stirnweis ldquoWirstschaftsbericht derSeilbahnenmdashTrends Winter 2011-2011rdquo WKO die Seilbahnen2011 httpportalwkoatwkformat detailwkangid=1ampstid=621545ampdstid=329ampopennavid=0
[2] R Schonbachler and G Scharer Fakten und Zahlen zurSchweizer Seilbahbranche Seilbahnen Schweiz 2012 httpwwwseilbahnenorgdeBrancheFakten-ZahlenFakten-Zah-len
[3] N Laplante ldquo2008-2009 Canadian Skier and SnowboarderFacts and Statsrdquo 2009 httpxcskiorgnews200920Facts20and20Stats20final20draftpdf
[4] M KlousThree-dimensional joint loading on the lower extremi-ties in alpine skiing and snowboarding [PhD thesis] Universityof Salzburg Salzburg Austria 2007
[5] S Corra A Conci G Conforti G Sacco and F de GiorgildquoSkiing and snowboarding injuries and their impact on theemergency care system in South Tyrol a restrospective analysisfor the winter season 2001ndash2002rdquo Injury Control and SafetyPromotion vol 11 no 4 pp 281ndash285 2004
[6] M Langran and S Selvaraj ldquoSnow sports injuries in Scotlanda case-control studyrdquo British Journal of Sports Medicine vol 36no 2 pp 135ndash140 2002
[7] S Sulheim I Holme A Roslashdven A Ekeland and R BahrldquoRisk factors for injuries in alpine skiing telemark skiing andsnowboardingmdashcase-control studyrdquo British Journal of SportsMedicine vol 45 no 16 pp 1303ndash1309 2011
[8] S Kim N K Endres R J Johnson C F Ettlinger andJ E Shealy ldquoSnowboarding injuries trends over time andcomparisons with alpine skiing injuriesrdquoThe American Journalof Sports Medicine vol 40 no 4 pp 770ndash776 2012
[9] M Burtscher M Flatz R Sommersacher et al OsterreichischeSkiunfallerhebung Wintersaison 20022003 Osterreichischen
12 Computational and Mathematical Methods in Medicine
Skiverbandes in Kooperation mit dem Institut fur Sportwissen-schaften der Universitat Innsbruck 2003
[10] C Goulet G Regnier G Grimard P Valois and P VilleneuveldquoRisk factors associated with alpine skiing injuries in childrena case-control studyrdquoThe American Journal of Sports Medicinevol 27 no 5 pp 644ndash650 1999
[11] E J Bridges F Rouah and K M Johnston ldquoSnowbladinginjuries in Eastern Canadardquo British Journal of Sports Medicinevol 37 no 6 pp 511ndash515 2003
[12] D Ishimaru H Ogawa K Wakahara H Sumi Y Sumi andK Shimizu ldquoHip pads reduce the overall risk of injuries inrecreational snowboardersrdquo British Journal of Sports Medicinevol 46 no 15 pp 1055ndash1058 2012
[13] H Xiang K Kelleher B J Shields K J Brown and G ASmith ldquoSkiing- and snowboarding-related injuries treated inUS emergency departments 2002rdquo Journal of Trauma-InjuryInfection amp Critical Care vol 58 no 1 pp 112ndash118 2005
[14] C Made and L G Elmqvist ldquoA 10-year study of snowboardinjuries in Lapland Swedenrdquo Scandinavian Journal of Medicineand Science in Sports vol 14 no 2 pp 128ndash133 2004
[15] E Aschauer E Ritter and H ReschWintersport Unfallstatistik20022003 Universitatsklinik fur Unfallchirurgie und Sport-traumatologie Salzburg 2003
[16] T M Davidson and A T Laliotis ldquoSnowboarding injuries afour-year study with comparison with alpine ski injuriesrdquo TheWestern Journal of Medicine vol 164 no 3 pp 231ndash237 1996
[17] J Howe The New Skiing Mechanics McIntire PublishingWaterford UK 2nd edition 2001
[18] Y Urabe M Ochi K Onari and Y Ikuta ldquoAnterior cruciateligament injury in recreational alpine skiers analysis of mech-anisms and strategy for preventionrdquo Journal of OrthopaedicScience vol 7 no 1 pp 1ndash5 2002
[19] S M Maxwell and M L Hull ldquoMeasurement of strength andloading variables on the knee during alpine skiingrdquo Journal ofBiomechanics vol 22 no 6-7 pp 609ndash624 1989
[20] T P Quinn and C D Mote Jr ldquoPrediction of the loading alongthe leg during snow skiingrdquo Journal of Biomechanics vol 25 no6 pp 609ndash625 1992
[21] C Raschner E Muller and H Schwameder ldquoKinematic andkinetic analysis of slalom turns as a basis for the development ofspecific training methods to improve strength and endurancerdquoin Science and Skiing EMullerH Schwameder E Kornexl andC Raschner Eds pp 251ndash261 Chapman amp Hall CambridgeMass USA 1997
[22] M Brodie A Walmsley and W Page ldquoFusion motion capturea prototype system using inertial measurement units and GPSfor the biomechanical analysis of ski racingrdquo Sports Technologyvol 1 pp 17ndash28 2008
[23] M Klous E Muller and H Schwameder ldquoThree-dimensionalknee joint loading in alpine skiing a comparison between acarved and a skidded turnrdquo Journal of Applied Biomechanics vol28 no 6 pp 655ndash664 2012
[24] F Vaverka S Vodickova and M Elfmark ldquoKinetic analysis ofski turns based on measured ground reaction forcesrdquo Journal ofApplied Biomechanics vol 28 no 1 pp 41ndash47 2012
[25] L Read and W Herzog ldquoExternal loading at the knee joint forlanding movements in alpine skiingrdquo International Journal ofSport Biomechanics vol 8 pp 62ndash80 1992
[26] W Nachbauer P Kaps B Nigg et al ldquoA video technique forobtaining 3-D coordinates in alpine skiingrdquo Journal of AppliedBiomechanics vol 12 no 1 pp 104ndash115 1996
[27] B Knunz W Nachbauer K Schindelwig and F BrunnerldquoForces andmoments at the boot sole during snowboardingrdquo inScience and Skiing II E Muller H Schwameder C Raschner SLindinger and E Kornexl Eds pp 242ndash249 Kovac HamburgGermany 2001
[28] A Kruger P McAlpine F Borrani and J Edelmann-NusserldquoDetermination of three-dimensional joint loading within thelower extremities in snowboardingrdquo Proceedings of the Insti-tution of Mechanical Engineers H Journal of Engineering inMedicine vol 226 no 2 pp 170ndash175 2012
[29] M Klous EMuller andH Schwameder ldquoCollecting kinematicdata on a skisnowboard track with panning tilting and zoom-ing cameras is there sufficient accuracy for a biomechanicalanalysisrdquo Journal of Sports Sciences vol 28 no 12 pp 1345ndash1352 2010
[30] A Cappozzo F Catani A Leardini M G Benedetti and UDella Croce ldquoPosition and orientation in space of bones duringmovement experimental artefactsrdquo Clinical Biomechanics vol11 no 2 pp 90ndash100 1996
[31] V Drenk ldquoPanningmdashZusatzprogramm zur Behandlungschwenk- und neigbarer und in ihrere brennweite variierbarerKameras in Peak3DmdashDokumentationrdquo Institut fur Ange-wandte Traningswissenschaften e V Leipzig Germany 1993
[32] V Drenk ldquoBildmeszligverfahren fur schwenk-und neigbaresowie in ihrer Brennweite variierbare Kamerasrdquo Zeitschrift furAngewandte Trainingswissenschaft vol 1 pp 130ndash142 1994
[33] BM Nigg andWHerzog Biomechanics of theMusculo-skeletalSystem John Wiley amp Sons New York NY USA 3rd edition2007
[34] G Stricker P Scheiber E Lindenhofer and E MullerldquoDetermination of forces in alpine skiing and snowboardingvalidation of a mobile data acquisition systemrdquo EuropeanJournal of Sport Science vol 10 no 1 pp 31ndash41 2010
[35] D G E Robertson G E Caldwell J Hamill G Kamen andS N Whittlesey Research Methods in Biomechanics HumanKinetics Champaign Ill USA 2004
[36] V M Zatsiorsky Kinematics of Human Motion HumanKinetics Champaign Ill USA 1998
[37] R M Ehrig W R Taylor G N Duda and M O HellerldquoA survey of formal methods for determining the centre ofrotation of ball jointsrdquo Journal of Biomechanics vol 39 no 15pp 2798ndash2809 2006
[38] M R Yeadon ldquoThe simulation of aerial movement II Amathematical inertia model of the human bodyrdquo Journal ofBiomechanics vol 23 no 1 pp 67ndash74 1990
[39] W T Dempster ldquoSpace requirements of the seated operatorrdquoWADC Technical Report TR-55ndash159 Wright-Patterson AirForce Base Wright-Patterson Ohio USA 1955
[40] E Muller ldquoBiomechanische Analysen moderner alpinerSkilauftechniken in unterschiedlichen Schnee- Gelande-und Pistensituationenrdquo in Biomechanik der Sportarten Bd2biomechanik des alpinen skilaufs F Fetz and E Muller Eds pp1ndash49 Ferdinand Enke Stuttgart Germany 1991
[41] C Raschner C Schiefermuller G Zallinger E Hofer FBrunner and E Muller ldquoCarving turns versus traditionalparallel turnsmdasha comparative biomechanical analysisrdquo inScience and Skiing II E Muller H Schwameder C RaschnerS Lindinger and E Kornexl Eds pp 203ndash217 Dr KovacHamburg Germany 2001
[42] GWagnerMesstechnischeDifferzierung von genschnittenen undgerutschten Kurven im alpine Skilauf [MS thesis] University ofSalzburg 2006
Computational and Mathematical Methods in Medicine 13
[43] E Muller M Klous and G Wagner ldquoBiomechanical aspectsof turning techniques in alpine skiingrdquo in Science and SportsBridging the Gap T Reilly Ed pp 135ndash142 Shaker PublishingBV Maastricht The Netherlands 2008
[44] B Knunz W Nachbauer M Mossner K Schindelwig andF Brunner ldquoTrack analysis of giant slalom turns of WorldCup racersrdquo in Proceedings of the 5th Annual Congress of theEuropean College of Sport Science (ECSS rsquo00) pp 399ndash401Jyvaskyla Finland 2000
[45] S Delorme S Tavoularis and M Lamontagne ldquoKinematics ofthe ankle joint complex in snowboardingrdquo Journal of AppliedBiomechanics vol 21 no 4 pp 394ndash403 2005
[46] S T McCaw and P DeVita ldquoErrors in alignment of center ofpressure and foot coordinates affect predicted lower extremitytorquesrdquo Journal of Biomechanics vol 28 no 8 pp 985ndash9881995
6 Computational and Mathematical Methods in Medicine
minus2
0
2
4
0 33 66 100
Fm
edl
atF
BW
Turn ()
(a)
minus2
0
2
4
0 33 66 100
Turn ()F
ant
posF
BW(b)
0 33 66 100
Turn ()
minus2
0
2
4
Flo
ngF
BW
(c)
Figure 4 Time profiles of the net medial (minus)lateral (+) forces (a) net anterior (+)posterior (minus) forces (b) and net forces around thelongitudinal axis (c) at the ankle joint for the steering leg in skiing (black) and snowboarding (grey)
Table 1 Average net ankle joint forces in medial (minus)lateral (+) direction (119865med-lat) anterior (+)posterior (minus) direction (119865ant-pos) and alongthe longitudinal axis (119865long) and standard deviations in the steering leg in skiing and snowboarding for each of the three phases
Computational and Mathematical Methods in Medicine 7
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()
Mfle
xex
tm (N
mk
g)
(a)
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()M
aba
dm
(Nm
kg)
(b)
0 33 66 100
Turn ()
minus6
minus4
minus2
0
2
4
6
8
m(N
mk
g)M
int
ext
(c)
Figure 5 Time profiles of the net flexion (+)extension (minus) moments (a) net adduction (+)abduction (minus) moments (b) and net internal(+)external (minus) moments (c) at the ankle joint for the steering leg in skiing (black) and snowboarding (grey)
Table 2 Average net ankle joint flexion (minus)extension (+) moments (119872flex-ext) net adduction (+)abduction (minus) moments (119872ad-ab) and netinternal (+)external (minus) rotation moments (119872int-ext) and standard deviations in the steering leg in skiing and snowboarding for each of thethree phases
8 Computational and Mathematical Methods in Medicine
0 33 66 100
Fm
edl
atF
BW
Turn ()
minus1
0
1
2
3
(a)
0 33 66 100
Turn ()
minus1
0
1
2
3
Fan
tpo
sF
BW(b)
0 33 66 100
Turn ()
minus1
0
1
2
3
Flo
ngF
BW
(c)
Figure 6 Time profiles of the net mediallateral forces (a) net anteriorposterior forces (b) and net forces around the longitudinal axis (c)at the knee joint for the steering leg in skiing (black) and snowboarding (grey)
Table 3 Average net knee joint forces in medial (minus)lateral (+) direction (119865med-lat) anterior (+)posterior (minus) direction (119865ant-pos) and alongthe longitudinal axis (119865long) and standard deviations in the steering leg in skiing and snowboarding for each of the three phases
Computational and Mathematical Methods in Medicine 9
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()
Mfle
xex
tm (N
mk
g)
(a)
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()M
aba
dm
(Nm
kg)
(b)
0 33 66 100
Turn ()
minus6
minus4
minus2
0
2
4
6
8
m(N
mk
g)M
int
ext
(c)
Figure 7 Time profiles of the net flexion (+)extension (minus) moments (a) net adduction (+)abduction (minus) moments (b) and net internal(+)external (minus) moments (c) at the knee joint for the steering leg in skiing (black) and snowboarding (grey)
Table 4 Average net knee joint flexion (+)extension (minus) moments (119872flex-ext) net adduction (+)abduction (minus) moments (119872ad-ab) and netinternal (+)external (minus) rotation moments (119872int-ext) and standard deviations in the steering leg in skiing and snowboarding for each of thethree phases
10 Computational and Mathematical Methods in Medicine
4 Discussion
The aim of this study was to compare the ankle and kneejoint loading at the steering leg between a carved ski andsnowboard turn Based on reported injury statistics and dueto differences in technique position and equipment betweenskiing and snowboarding it was hypothesized that ankle jointloading was greater in snowboarding and knee joint loadingwas greater in skiing However the current study showed adifferent outcomeWhile forcesweremostly similar for skiingand snowboarding the joint moments were consistentlygreater during a snowboard turn whereas in skiing muchmore fluctuations were observed during the turn particularlyin the first and second phase of the turn (represented by thegreater standard deviation in skiing in those two phases)Moreover forces along the longitudinal axis were higher inskiing than in snowboarding
Results showed that the carved turn demonstrated someskidding components The average skidding angle calculatedacross time was higher in snowboarding than in skiingwhich could be due to the rather steep slope to perform acarved turn in snowboarding Nevertheless both turns wererepresentative of a carved turn Results were in agreementwithMuller et al [43] andWagner [42] who reported averageskidding angles for the carving technique in skiing of 41∘Knunz et al [44] reported angles in a carved ski turn of 1-2∘for the outer leg and 7-8∘ for the inner leg in a (purely) carvedski turn
Forces in anteriorposterior and mediallateral directionat the ankle joint were similar and rather low for skiingand snowboarding As a consequence it is expected thatthe internalexternal rotation moment is also rather low asis observed in skiing However in snowboarding internalrotation moments reached magnitudes of approximately2Nmkg Consistent and larger values throughout the turnwere also observed for the flexionextension moment insnowboarding whereas the force along the longitudinal axiswas below 1sdotBW and the anteriorposterior force was evenlower Kruger et al [28] reported even larger peak values forthe flexionextension moment at the ankle joint comparedto the current study but do not report if these values area consequence of large kinetic or kinematic values Withthe low forces observed in the current study these relativelyhigh moments must be due to kinematics hence angularaccelerations of the segments or due to the different bodypositions in skiing and snowboarding which is representedby the position of the joint centres with respect to the forcevector The use of soft boots in snowboarding allowed shortbut fast rotational movements (ie kinematic parameters)whereas these movements were not possible with stiff skibootsThese equipment differences would explain the greaterjoint moments at the ankle joint in snowboarding Thiswas supported by a study of Delorme et al [45] thatcompared ankle joint kinematics between stiff and softboots in snowboarding This study reported that the useof soft boots leads to larger average dorsiplantar flexionangles and internalexternal rotation angles as well as largermaximum dorsiplantar flexion angles eversioninversionangles and internalexternal rotation angles larger minimal
internalexternal rotation angles and a larger range ofmotionin dorsiplantar flexion
In skiing the time pattern of the force along the longitu-dinal axis at the ankle joint showed similarities with the timepattern of the flexionextension and abductionadductionmoments but in opposite direction Hence opposite tosnowboarding the large moments in skiing seemed to bea consequence of the produced forces Note that in skiingthe flexionextension moment allowed the movement to thetiptail of the ski whereas the abductionadduction momentplaces the ski at the edges (see Figure 2) Fluctuations (rep-resented by the standard deviation) were much larger forthe moments than for the forces and also much larger inskiing than in snowboarding This might suggest that thegreater number of injuries at the ankle joint is caused by thespecific body position in snowboarding and the consistentlyhigh moments due to kinematic variables rather than largefluctuation as observed in the moments in skiing
At the knee joint both mediallateral forces and forcesalong the longitudinal axis were higher in skiing whereasthe anteriorposterior forces were similar for skiing andsnowboarding However the higher forces in skiing didnot result in consistently higher moments compared tosnowboarding The flexionextension moments in snow-boarding were required to place the snowboard at theedges just like the abductionadduction moment in ski-ing The flexionextension moments in snowboarding wereapproximately 3Nmkg whereas the abductionadductionmoments in skiing were approximately 10ndash15Nmkg Alsothe flexionextension moments in skiing were approximately1 Nmkg as were the abductionadductionmoments in snow-boarding In general moments were slightly lower at the kneejoint than at the ankle joint in snowboarding whereas inskiing the opposite was observed Again the larger momentsin snowboarding seemed not to be due to the high forcesbut due to the soft boot allowing larger accelerations and adifferent body position in snowboarding than in skiing
Even though the fluctuations were larger in snowboard-ing at the knee than at the ankle joint these variationswere still much lower in snowboarding than in skiing Thesefluctuations represent the loading and unloading that areclearly greater in skiing than in snowboarding In situationswhen a skier has to make a sudden adjustment these peakvalues would increase even further In skiing joint momentsincreased in the knee joint compared to the ankle jointwhereas in snowboarding the moments decreased Besidesthe knee joint forces being similar or greater in skiing thanin snowboarding also the peak forces and moments werelarger in skiing than in snowboarding except for the inter-nalexternal rotation moment Kruger et al [28] reportedclearly lower peak values for the flexionextension momentin snowboarding (33 less) than in the current study whichwould make differences between skiing and snowboardingeven more pronounced These three aspects together couldbe an explanation for the larger amount of knee injuries inskiing than in snowboarding
Even though the joint loading observed in the currentstudy is rather high one should realise that many otheraspects can explain the injury statistics as presented in
Computational and Mathematical Methods in Medicine 11
the current study The quality of the snow the technicaland physical capability of the skier or snowboarder andthe large number of skiers and snowboarders at the slopecould explain the many injuries that occur in skiing andsnowboarding The skier and snowboarder in the currentstudy carried additional equipment to allow measurementof ground reaction forces This equipment influenced theirweight and their standing heightWith their level of expertisethe skier and snowboarder did not report any influenceof this equipment Nevertheless the equipment might haveinfluenced their technique and performance Additionallythe differences in stiffness between ski and snowboard bootscould have influenced the results Due to the stiff ski bootpart of the loading might have been transferred to theboot and thereby reduced the ankle joint in skiing Inversedynamic calculations did not allow determining how muchof the ankle joint was transferred to the ski boot Hencethis could have caused overestimation of the ankle joint inskiing However where the current results showed largerankle joint in snowboarding the difference in ankle jointbetween skiing and snowboarding would have even beengreater if the ankle joint in skiing was overestimated Whencurrent results showed larger ankle joint in skiing thesedifferences might not have been as profound Both situationssupport the research hypothesis Also the magnitudes ofthe ankle joint forces and moments in skiing might havebeen lower but it is not to expect that the time patternswere influenced Furthermore the kinematic setup allowed aski and snowboard turn to be performed with similar radiibut different velocities The centripetal force (119865
119888) in a turn
is influenced by the velocity (119865119888= 119898V2119903) Although the
velocity in snowboarding was lower than in skiing the ankleand knee joint forces and moments were not consistentlylower than in skiing We speculate that if the snowboardturn was performed with higher velocities the forces andmoments at the ankle and knee joint would further increasedue to an increase of the centripetal force Furthermorevideos and data of ground reaction forces throughout thecollected data were similar Nevertheless the findings shouldbe interpreted with caution due to the single subject designAdditionally even though the applied method shows a goodaccuracy for on-snow data collection the results of inversedynamic calculations depend strongly on the accuracy of theinput data As is shown by McCaw amp DeVita [46] errorsin the input data are propagated in the inverse dynamicsprocedures thereby reducing the accuracy of the resultscalculated using this procedure Finally it is important toemphasise that we calculated forces and moments duringsuccessful turns which are not representative of the forcesand moments during unsuccessful turns that result in fallingandor injury
5 Conclusion
The expected higher ankle joint loading in snowboardingand higher knee joint loading in skiing that was based onreported injury statistics in the lower extremities in skiingand snowboarding and the differences in position technique
and equipment (soft boot versus hard boot) could not beconfirmed Ankle joint loading was not consistently greaterin snowboarding than in skiing and vice versa for the kneejoint loading When comparing skiing and snowboardingdifferentiationwas required between forces andmoments thedirection of the forces and moments and the phase of theturn thatwas consideredHowever there seemed to be a trendthat forces were larger in skiing and moments showed largefluctuations (loading-unloading) whereas in snowboardinghigh moments with a more consistent pattern were observedIn future research it is important to increase the number ofparticipants in the study and study joint loading of variousturning techniques
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors thank ski company Atomic for providing the testequipment They appreciate the helpful discussions with DrJosef Kroll
References
[1] K Grabler and G J Stirnweis ldquoWirstschaftsbericht derSeilbahnenmdashTrends Winter 2011-2011rdquo WKO die Seilbahnen2011 httpportalwkoatwkformat detailwkangid=1ampstid=621545ampdstid=329ampopennavid=0
[2] R Schonbachler and G Scharer Fakten und Zahlen zurSchweizer Seilbahbranche Seilbahnen Schweiz 2012 httpwwwseilbahnenorgdeBrancheFakten-ZahlenFakten-Zah-len
[3] N Laplante ldquo2008-2009 Canadian Skier and SnowboarderFacts and Statsrdquo 2009 httpxcskiorgnews200920Facts20and20Stats20final20draftpdf
[4] M KlousThree-dimensional joint loading on the lower extremi-ties in alpine skiing and snowboarding [PhD thesis] Universityof Salzburg Salzburg Austria 2007
[5] S Corra A Conci G Conforti G Sacco and F de GiorgildquoSkiing and snowboarding injuries and their impact on theemergency care system in South Tyrol a restrospective analysisfor the winter season 2001ndash2002rdquo Injury Control and SafetyPromotion vol 11 no 4 pp 281ndash285 2004
[6] M Langran and S Selvaraj ldquoSnow sports injuries in Scotlanda case-control studyrdquo British Journal of Sports Medicine vol 36no 2 pp 135ndash140 2002
[7] S Sulheim I Holme A Roslashdven A Ekeland and R BahrldquoRisk factors for injuries in alpine skiing telemark skiing andsnowboardingmdashcase-control studyrdquo British Journal of SportsMedicine vol 45 no 16 pp 1303ndash1309 2011
[8] S Kim N K Endres R J Johnson C F Ettlinger andJ E Shealy ldquoSnowboarding injuries trends over time andcomparisons with alpine skiing injuriesrdquoThe American Journalof Sports Medicine vol 40 no 4 pp 770ndash776 2012
[9] M Burtscher M Flatz R Sommersacher et al OsterreichischeSkiunfallerhebung Wintersaison 20022003 Osterreichischen
12 Computational and Mathematical Methods in Medicine
Skiverbandes in Kooperation mit dem Institut fur Sportwissen-schaften der Universitat Innsbruck 2003
[10] C Goulet G Regnier G Grimard P Valois and P VilleneuveldquoRisk factors associated with alpine skiing injuries in childrena case-control studyrdquoThe American Journal of Sports Medicinevol 27 no 5 pp 644ndash650 1999
[11] E J Bridges F Rouah and K M Johnston ldquoSnowbladinginjuries in Eastern Canadardquo British Journal of Sports Medicinevol 37 no 6 pp 511ndash515 2003
[12] D Ishimaru H Ogawa K Wakahara H Sumi Y Sumi andK Shimizu ldquoHip pads reduce the overall risk of injuries inrecreational snowboardersrdquo British Journal of Sports Medicinevol 46 no 15 pp 1055ndash1058 2012
[13] H Xiang K Kelleher B J Shields K J Brown and G ASmith ldquoSkiing- and snowboarding-related injuries treated inUS emergency departments 2002rdquo Journal of Trauma-InjuryInfection amp Critical Care vol 58 no 1 pp 112ndash118 2005
[14] C Made and L G Elmqvist ldquoA 10-year study of snowboardinjuries in Lapland Swedenrdquo Scandinavian Journal of Medicineand Science in Sports vol 14 no 2 pp 128ndash133 2004
[15] E Aschauer E Ritter and H ReschWintersport Unfallstatistik20022003 Universitatsklinik fur Unfallchirurgie und Sport-traumatologie Salzburg 2003
[16] T M Davidson and A T Laliotis ldquoSnowboarding injuries afour-year study with comparison with alpine ski injuriesrdquo TheWestern Journal of Medicine vol 164 no 3 pp 231ndash237 1996
[17] J Howe The New Skiing Mechanics McIntire PublishingWaterford UK 2nd edition 2001
[18] Y Urabe M Ochi K Onari and Y Ikuta ldquoAnterior cruciateligament injury in recreational alpine skiers analysis of mech-anisms and strategy for preventionrdquo Journal of OrthopaedicScience vol 7 no 1 pp 1ndash5 2002
[19] S M Maxwell and M L Hull ldquoMeasurement of strength andloading variables on the knee during alpine skiingrdquo Journal ofBiomechanics vol 22 no 6-7 pp 609ndash624 1989
[20] T P Quinn and C D Mote Jr ldquoPrediction of the loading alongthe leg during snow skiingrdquo Journal of Biomechanics vol 25 no6 pp 609ndash625 1992
[21] C Raschner E Muller and H Schwameder ldquoKinematic andkinetic analysis of slalom turns as a basis for the development ofspecific training methods to improve strength and endurancerdquoin Science and Skiing EMullerH Schwameder E Kornexl andC Raschner Eds pp 251ndash261 Chapman amp Hall CambridgeMass USA 1997
[22] M Brodie A Walmsley and W Page ldquoFusion motion capturea prototype system using inertial measurement units and GPSfor the biomechanical analysis of ski racingrdquo Sports Technologyvol 1 pp 17ndash28 2008
[23] M Klous E Muller and H Schwameder ldquoThree-dimensionalknee joint loading in alpine skiing a comparison between acarved and a skidded turnrdquo Journal of Applied Biomechanics vol28 no 6 pp 655ndash664 2012
[24] F Vaverka S Vodickova and M Elfmark ldquoKinetic analysis ofski turns based on measured ground reaction forcesrdquo Journal ofApplied Biomechanics vol 28 no 1 pp 41ndash47 2012
[25] L Read and W Herzog ldquoExternal loading at the knee joint forlanding movements in alpine skiingrdquo International Journal ofSport Biomechanics vol 8 pp 62ndash80 1992
[26] W Nachbauer P Kaps B Nigg et al ldquoA video technique forobtaining 3-D coordinates in alpine skiingrdquo Journal of AppliedBiomechanics vol 12 no 1 pp 104ndash115 1996
[27] B Knunz W Nachbauer K Schindelwig and F BrunnerldquoForces andmoments at the boot sole during snowboardingrdquo inScience and Skiing II E Muller H Schwameder C Raschner SLindinger and E Kornexl Eds pp 242ndash249 Kovac HamburgGermany 2001
[28] A Kruger P McAlpine F Borrani and J Edelmann-NusserldquoDetermination of three-dimensional joint loading within thelower extremities in snowboardingrdquo Proceedings of the Insti-tution of Mechanical Engineers H Journal of Engineering inMedicine vol 226 no 2 pp 170ndash175 2012
[29] M Klous EMuller andH Schwameder ldquoCollecting kinematicdata on a skisnowboard track with panning tilting and zoom-ing cameras is there sufficient accuracy for a biomechanicalanalysisrdquo Journal of Sports Sciences vol 28 no 12 pp 1345ndash1352 2010
[30] A Cappozzo F Catani A Leardini M G Benedetti and UDella Croce ldquoPosition and orientation in space of bones duringmovement experimental artefactsrdquo Clinical Biomechanics vol11 no 2 pp 90ndash100 1996
[31] V Drenk ldquoPanningmdashZusatzprogramm zur Behandlungschwenk- und neigbarer und in ihrere brennweite variierbarerKameras in Peak3DmdashDokumentationrdquo Institut fur Ange-wandte Traningswissenschaften e V Leipzig Germany 1993
[32] V Drenk ldquoBildmeszligverfahren fur schwenk-und neigbaresowie in ihrer Brennweite variierbare Kamerasrdquo Zeitschrift furAngewandte Trainingswissenschaft vol 1 pp 130ndash142 1994
[33] BM Nigg andWHerzog Biomechanics of theMusculo-skeletalSystem John Wiley amp Sons New York NY USA 3rd edition2007
[34] G Stricker P Scheiber E Lindenhofer and E MullerldquoDetermination of forces in alpine skiing and snowboardingvalidation of a mobile data acquisition systemrdquo EuropeanJournal of Sport Science vol 10 no 1 pp 31ndash41 2010
[35] D G E Robertson G E Caldwell J Hamill G Kamen andS N Whittlesey Research Methods in Biomechanics HumanKinetics Champaign Ill USA 2004
[36] V M Zatsiorsky Kinematics of Human Motion HumanKinetics Champaign Ill USA 1998
[37] R M Ehrig W R Taylor G N Duda and M O HellerldquoA survey of formal methods for determining the centre ofrotation of ball jointsrdquo Journal of Biomechanics vol 39 no 15pp 2798ndash2809 2006
[38] M R Yeadon ldquoThe simulation of aerial movement II Amathematical inertia model of the human bodyrdquo Journal ofBiomechanics vol 23 no 1 pp 67ndash74 1990
[39] W T Dempster ldquoSpace requirements of the seated operatorrdquoWADC Technical Report TR-55ndash159 Wright-Patterson AirForce Base Wright-Patterson Ohio USA 1955
[40] E Muller ldquoBiomechanische Analysen moderner alpinerSkilauftechniken in unterschiedlichen Schnee- Gelande-und Pistensituationenrdquo in Biomechanik der Sportarten Bd2biomechanik des alpinen skilaufs F Fetz and E Muller Eds pp1ndash49 Ferdinand Enke Stuttgart Germany 1991
[41] C Raschner C Schiefermuller G Zallinger E Hofer FBrunner and E Muller ldquoCarving turns versus traditionalparallel turnsmdasha comparative biomechanical analysisrdquo inScience and Skiing II E Muller H Schwameder C RaschnerS Lindinger and E Kornexl Eds pp 203ndash217 Dr KovacHamburg Germany 2001
[42] GWagnerMesstechnischeDifferzierung von genschnittenen undgerutschten Kurven im alpine Skilauf [MS thesis] University ofSalzburg 2006
Computational and Mathematical Methods in Medicine 13
[43] E Muller M Klous and G Wagner ldquoBiomechanical aspectsof turning techniques in alpine skiingrdquo in Science and SportsBridging the Gap T Reilly Ed pp 135ndash142 Shaker PublishingBV Maastricht The Netherlands 2008
[44] B Knunz W Nachbauer M Mossner K Schindelwig andF Brunner ldquoTrack analysis of giant slalom turns of WorldCup racersrdquo in Proceedings of the 5th Annual Congress of theEuropean College of Sport Science (ECSS rsquo00) pp 399ndash401Jyvaskyla Finland 2000
[45] S Delorme S Tavoularis and M Lamontagne ldquoKinematics ofthe ankle joint complex in snowboardingrdquo Journal of AppliedBiomechanics vol 21 no 4 pp 394ndash403 2005
[46] S T McCaw and P DeVita ldquoErrors in alignment of center ofpressure and foot coordinates affect predicted lower extremitytorquesrdquo Journal of Biomechanics vol 28 no 8 pp 985ndash9881995
Computational and Mathematical Methods in Medicine 7
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()
Mfle
xex
tm (N
mk
g)
(a)
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()M
aba
dm
(Nm
kg)
(b)
0 33 66 100
Turn ()
minus6
minus4
minus2
0
2
4
6
8
m(N
mk
g)M
int
ext
(c)
Figure 5 Time profiles of the net flexion (+)extension (minus) moments (a) net adduction (+)abduction (minus) moments (b) and net internal(+)external (minus) moments (c) at the ankle joint for the steering leg in skiing (black) and snowboarding (grey)
Table 2 Average net ankle joint flexion (minus)extension (+) moments (119872flex-ext) net adduction (+)abduction (minus) moments (119872ad-ab) and netinternal (+)external (minus) rotation moments (119872int-ext) and standard deviations in the steering leg in skiing and snowboarding for each of thethree phases
8 Computational and Mathematical Methods in Medicine
0 33 66 100
Fm
edl
atF
BW
Turn ()
minus1
0
1
2
3
(a)
0 33 66 100
Turn ()
minus1
0
1
2
3
Fan
tpo
sF
BW(b)
0 33 66 100
Turn ()
minus1
0
1
2
3
Flo
ngF
BW
(c)
Figure 6 Time profiles of the net mediallateral forces (a) net anteriorposterior forces (b) and net forces around the longitudinal axis (c)at the knee joint for the steering leg in skiing (black) and snowboarding (grey)
Table 3 Average net knee joint forces in medial (minus)lateral (+) direction (119865med-lat) anterior (+)posterior (minus) direction (119865ant-pos) and alongthe longitudinal axis (119865long) and standard deviations in the steering leg in skiing and snowboarding for each of the three phases
Computational and Mathematical Methods in Medicine 9
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()
Mfle
xex
tm (N
mk
g)
(a)
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()M
aba
dm
(Nm
kg)
(b)
0 33 66 100
Turn ()
minus6
minus4
minus2
0
2
4
6
8
m(N
mk
g)M
int
ext
(c)
Figure 7 Time profiles of the net flexion (+)extension (minus) moments (a) net adduction (+)abduction (minus) moments (b) and net internal(+)external (minus) moments (c) at the knee joint for the steering leg in skiing (black) and snowboarding (grey)
Table 4 Average net knee joint flexion (+)extension (minus) moments (119872flex-ext) net adduction (+)abduction (minus) moments (119872ad-ab) and netinternal (+)external (minus) rotation moments (119872int-ext) and standard deviations in the steering leg in skiing and snowboarding for each of thethree phases
10 Computational and Mathematical Methods in Medicine
4 Discussion
The aim of this study was to compare the ankle and kneejoint loading at the steering leg between a carved ski andsnowboard turn Based on reported injury statistics and dueto differences in technique position and equipment betweenskiing and snowboarding it was hypothesized that ankle jointloading was greater in snowboarding and knee joint loadingwas greater in skiing However the current study showed adifferent outcomeWhile forcesweremostly similar for skiingand snowboarding the joint moments were consistentlygreater during a snowboard turn whereas in skiing muchmore fluctuations were observed during the turn particularlyin the first and second phase of the turn (represented by thegreater standard deviation in skiing in those two phases)Moreover forces along the longitudinal axis were higher inskiing than in snowboarding
Results showed that the carved turn demonstrated someskidding components The average skidding angle calculatedacross time was higher in snowboarding than in skiingwhich could be due to the rather steep slope to perform acarved turn in snowboarding Nevertheless both turns wererepresentative of a carved turn Results were in agreementwithMuller et al [43] andWagner [42] who reported averageskidding angles for the carving technique in skiing of 41∘Knunz et al [44] reported angles in a carved ski turn of 1-2∘for the outer leg and 7-8∘ for the inner leg in a (purely) carvedski turn
Forces in anteriorposterior and mediallateral directionat the ankle joint were similar and rather low for skiingand snowboarding As a consequence it is expected thatthe internalexternal rotation moment is also rather low asis observed in skiing However in snowboarding internalrotation moments reached magnitudes of approximately2Nmkg Consistent and larger values throughout the turnwere also observed for the flexionextension moment insnowboarding whereas the force along the longitudinal axiswas below 1sdotBW and the anteriorposterior force was evenlower Kruger et al [28] reported even larger peak values forthe flexionextension moment at the ankle joint comparedto the current study but do not report if these values area consequence of large kinetic or kinematic values Withthe low forces observed in the current study these relativelyhigh moments must be due to kinematics hence angularaccelerations of the segments or due to the different bodypositions in skiing and snowboarding which is representedby the position of the joint centres with respect to the forcevector The use of soft boots in snowboarding allowed shortbut fast rotational movements (ie kinematic parameters)whereas these movements were not possible with stiff skibootsThese equipment differences would explain the greaterjoint moments at the ankle joint in snowboarding Thiswas supported by a study of Delorme et al [45] thatcompared ankle joint kinematics between stiff and softboots in snowboarding This study reported that the useof soft boots leads to larger average dorsiplantar flexionangles and internalexternal rotation angles as well as largermaximum dorsiplantar flexion angles eversioninversionangles and internalexternal rotation angles larger minimal
internalexternal rotation angles and a larger range ofmotionin dorsiplantar flexion
In skiing the time pattern of the force along the longitu-dinal axis at the ankle joint showed similarities with the timepattern of the flexionextension and abductionadductionmoments but in opposite direction Hence opposite tosnowboarding the large moments in skiing seemed to bea consequence of the produced forces Note that in skiingthe flexionextension moment allowed the movement to thetiptail of the ski whereas the abductionadduction momentplaces the ski at the edges (see Figure 2) Fluctuations (rep-resented by the standard deviation) were much larger forthe moments than for the forces and also much larger inskiing than in snowboarding This might suggest that thegreater number of injuries at the ankle joint is caused by thespecific body position in snowboarding and the consistentlyhigh moments due to kinematic variables rather than largefluctuation as observed in the moments in skiing
At the knee joint both mediallateral forces and forcesalong the longitudinal axis were higher in skiing whereasthe anteriorposterior forces were similar for skiing andsnowboarding However the higher forces in skiing didnot result in consistently higher moments compared tosnowboarding The flexionextension moments in snow-boarding were required to place the snowboard at theedges just like the abductionadduction moment in ski-ing The flexionextension moments in snowboarding wereapproximately 3Nmkg whereas the abductionadductionmoments in skiing were approximately 10ndash15Nmkg Alsothe flexionextension moments in skiing were approximately1 Nmkg as were the abductionadductionmoments in snow-boarding In general moments were slightly lower at the kneejoint than at the ankle joint in snowboarding whereas inskiing the opposite was observed Again the larger momentsin snowboarding seemed not to be due to the high forcesbut due to the soft boot allowing larger accelerations and adifferent body position in snowboarding than in skiing
Even though the fluctuations were larger in snowboard-ing at the knee than at the ankle joint these variationswere still much lower in snowboarding than in skiing Thesefluctuations represent the loading and unloading that areclearly greater in skiing than in snowboarding In situationswhen a skier has to make a sudden adjustment these peakvalues would increase even further In skiing joint momentsincreased in the knee joint compared to the ankle jointwhereas in snowboarding the moments decreased Besidesthe knee joint forces being similar or greater in skiing thanin snowboarding also the peak forces and moments werelarger in skiing than in snowboarding except for the inter-nalexternal rotation moment Kruger et al [28] reportedclearly lower peak values for the flexionextension momentin snowboarding (33 less) than in the current study whichwould make differences between skiing and snowboardingeven more pronounced These three aspects together couldbe an explanation for the larger amount of knee injuries inskiing than in snowboarding
Even though the joint loading observed in the currentstudy is rather high one should realise that many otheraspects can explain the injury statistics as presented in
Computational and Mathematical Methods in Medicine 11
the current study The quality of the snow the technicaland physical capability of the skier or snowboarder andthe large number of skiers and snowboarders at the slopecould explain the many injuries that occur in skiing andsnowboarding The skier and snowboarder in the currentstudy carried additional equipment to allow measurementof ground reaction forces This equipment influenced theirweight and their standing heightWith their level of expertisethe skier and snowboarder did not report any influenceof this equipment Nevertheless the equipment might haveinfluenced their technique and performance Additionallythe differences in stiffness between ski and snowboard bootscould have influenced the results Due to the stiff ski bootpart of the loading might have been transferred to theboot and thereby reduced the ankle joint in skiing Inversedynamic calculations did not allow determining how muchof the ankle joint was transferred to the ski boot Hencethis could have caused overestimation of the ankle joint inskiing However where the current results showed largerankle joint in snowboarding the difference in ankle jointbetween skiing and snowboarding would have even beengreater if the ankle joint in skiing was overestimated Whencurrent results showed larger ankle joint in skiing thesedifferences might not have been as profound Both situationssupport the research hypothesis Also the magnitudes ofthe ankle joint forces and moments in skiing might havebeen lower but it is not to expect that the time patternswere influenced Furthermore the kinematic setup allowed aski and snowboard turn to be performed with similar radiibut different velocities The centripetal force (119865
119888) in a turn
is influenced by the velocity (119865119888= 119898V2119903) Although the
velocity in snowboarding was lower than in skiing the ankleand knee joint forces and moments were not consistentlylower than in skiing We speculate that if the snowboardturn was performed with higher velocities the forces andmoments at the ankle and knee joint would further increasedue to an increase of the centripetal force Furthermorevideos and data of ground reaction forces throughout thecollected data were similar Nevertheless the findings shouldbe interpreted with caution due to the single subject designAdditionally even though the applied method shows a goodaccuracy for on-snow data collection the results of inversedynamic calculations depend strongly on the accuracy of theinput data As is shown by McCaw amp DeVita [46] errorsin the input data are propagated in the inverse dynamicsprocedures thereby reducing the accuracy of the resultscalculated using this procedure Finally it is important toemphasise that we calculated forces and moments duringsuccessful turns which are not representative of the forcesand moments during unsuccessful turns that result in fallingandor injury
5 Conclusion
The expected higher ankle joint loading in snowboardingand higher knee joint loading in skiing that was based onreported injury statistics in the lower extremities in skiingand snowboarding and the differences in position technique
and equipment (soft boot versus hard boot) could not beconfirmed Ankle joint loading was not consistently greaterin snowboarding than in skiing and vice versa for the kneejoint loading When comparing skiing and snowboardingdifferentiationwas required between forces andmoments thedirection of the forces and moments and the phase of theturn thatwas consideredHowever there seemed to be a trendthat forces were larger in skiing and moments showed largefluctuations (loading-unloading) whereas in snowboardinghigh moments with a more consistent pattern were observedIn future research it is important to increase the number ofparticipants in the study and study joint loading of variousturning techniques
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors thank ski company Atomic for providing the testequipment They appreciate the helpful discussions with DrJosef Kroll
References
[1] K Grabler and G J Stirnweis ldquoWirstschaftsbericht derSeilbahnenmdashTrends Winter 2011-2011rdquo WKO die Seilbahnen2011 httpportalwkoatwkformat detailwkangid=1ampstid=621545ampdstid=329ampopennavid=0
[2] R Schonbachler and G Scharer Fakten und Zahlen zurSchweizer Seilbahbranche Seilbahnen Schweiz 2012 httpwwwseilbahnenorgdeBrancheFakten-ZahlenFakten-Zah-len
[3] N Laplante ldquo2008-2009 Canadian Skier and SnowboarderFacts and Statsrdquo 2009 httpxcskiorgnews200920Facts20and20Stats20final20draftpdf
[4] M KlousThree-dimensional joint loading on the lower extremi-ties in alpine skiing and snowboarding [PhD thesis] Universityof Salzburg Salzburg Austria 2007
[5] S Corra A Conci G Conforti G Sacco and F de GiorgildquoSkiing and snowboarding injuries and their impact on theemergency care system in South Tyrol a restrospective analysisfor the winter season 2001ndash2002rdquo Injury Control and SafetyPromotion vol 11 no 4 pp 281ndash285 2004
[6] M Langran and S Selvaraj ldquoSnow sports injuries in Scotlanda case-control studyrdquo British Journal of Sports Medicine vol 36no 2 pp 135ndash140 2002
[7] S Sulheim I Holme A Roslashdven A Ekeland and R BahrldquoRisk factors for injuries in alpine skiing telemark skiing andsnowboardingmdashcase-control studyrdquo British Journal of SportsMedicine vol 45 no 16 pp 1303ndash1309 2011
[8] S Kim N K Endres R J Johnson C F Ettlinger andJ E Shealy ldquoSnowboarding injuries trends over time andcomparisons with alpine skiing injuriesrdquoThe American Journalof Sports Medicine vol 40 no 4 pp 770ndash776 2012
[9] M Burtscher M Flatz R Sommersacher et al OsterreichischeSkiunfallerhebung Wintersaison 20022003 Osterreichischen
12 Computational and Mathematical Methods in Medicine
Skiverbandes in Kooperation mit dem Institut fur Sportwissen-schaften der Universitat Innsbruck 2003
[10] C Goulet G Regnier G Grimard P Valois and P VilleneuveldquoRisk factors associated with alpine skiing injuries in childrena case-control studyrdquoThe American Journal of Sports Medicinevol 27 no 5 pp 644ndash650 1999
[11] E J Bridges F Rouah and K M Johnston ldquoSnowbladinginjuries in Eastern Canadardquo British Journal of Sports Medicinevol 37 no 6 pp 511ndash515 2003
[12] D Ishimaru H Ogawa K Wakahara H Sumi Y Sumi andK Shimizu ldquoHip pads reduce the overall risk of injuries inrecreational snowboardersrdquo British Journal of Sports Medicinevol 46 no 15 pp 1055ndash1058 2012
[13] H Xiang K Kelleher B J Shields K J Brown and G ASmith ldquoSkiing- and snowboarding-related injuries treated inUS emergency departments 2002rdquo Journal of Trauma-InjuryInfection amp Critical Care vol 58 no 1 pp 112ndash118 2005
[14] C Made and L G Elmqvist ldquoA 10-year study of snowboardinjuries in Lapland Swedenrdquo Scandinavian Journal of Medicineand Science in Sports vol 14 no 2 pp 128ndash133 2004
[15] E Aschauer E Ritter and H ReschWintersport Unfallstatistik20022003 Universitatsklinik fur Unfallchirurgie und Sport-traumatologie Salzburg 2003
[16] T M Davidson and A T Laliotis ldquoSnowboarding injuries afour-year study with comparison with alpine ski injuriesrdquo TheWestern Journal of Medicine vol 164 no 3 pp 231ndash237 1996
[17] J Howe The New Skiing Mechanics McIntire PublishingWaterford UK 2nd edition 2001
[18] Y Urabe M Ochi K Onari and Y Ikuta ldquoAnterior cruciateligament injury in recreational alpine skiers analysis of mech-anisms and strategy for preventionrdquo Journal of OrthopaedicScience vol 7 no 1 pp 1ndash5 2002
[19] S M Maxwell and M L Hull ldquoMeasurement of strength andloading variables on the knee during alpine skiingrdquo Journal ofBiomechanics vol 22 no 6-7 pp 609ndash624 1989
[20] T P Quinn and C D Mote Jr ldquoPrediction of the loading alongthe leg during snow skiingrdquo Journal of Biomechanics vol 25 no6 pp 609ndash625 1992
[21] C Raschner E Muller and H Schwameder ldquoKinematic andkinetic analysis of slalom turns as a basis for the development ofspecific training methods to improve strength and endurancerdquoin Science and Skiing EMullerH Schwameder E Kornexl andC Raschner Eds pp 251ndash261 Chapman amp Hall CambridgeMass USA 1997
[22] M Brodie A Walmsley and W Page ldquoFusion motion capturea prototype system using inertial measurement units and GPSfor the biomechanical analysis of ski racingrdquo Sports Technologyvol 1 pp 17ndash28 2008
[23] M Klous E Muller and H Schwameder ldquoThree-dimensionalknee joint loading in alpine skiing a comparison between acarved and a skidded turnrdquo Journal of Applied Biomechanics vol28 no 6 pp 655ndash664 2012
[24] F Vaverka S Vodickova and M Elfmark ldquoKinetic analysis ofski turns based on measured ground reaction forcesrdquo Journal ofApplied Biomechanics vol 28 no 1 pp 41ndash47 2012
[25] L Read and W Herzog ldquoExternal loading at the knee joint forlanding movements in alpine skiingrdquo International Journal ofSport Biomechanics vol 8 pp 62ndash80 1992
[26] W Nachbauer P Kaps B Nigg et al ldquoA video technique forobtaining 3-D coordinates in alpine skiingrdquo Journal of AppliedBiomechanics vol 12 no 1 pp 104ndash115 1996
[27] B Knunz W Nachbauer K Schindelwig and F BrunnerldquoForces andmoments at the boot sole during snowboardingrdquo inScience and Skiing II E Muller H Schwameder C Raschner SLindinger and E Kornexl Eds pp 242ndash249 Kovac HamburgGermany 2001
[28] A Kruger P McAlpine F Borrani and J Edelmann-NusserldquoDetermination of three-dimensional joint loading within thelower extremities in snowboardingrdquo Proceedings of the Insti-tution of Mechanical Engineers H Journal of Engineering inMedicine vol 226 no 2 pp 170ndash175 2012
[29] M Klous EMuller andH Schwameder ldquoCollecting kinematicdata on a skisnowboard track with panning tilting and zoom-ing cameras is there sufficient accuracy for a biomechanicalanalysisrdquo Journal of Sports Sciences vol 28 no 12 pp 1345ndash1352 2010
[30] A Cappozzo F Catani A Leardini M G Benedetti and UDella Croce ldquoPosition and orientation in space of bones duringmovement experimental artefactsrdquo Clinical Biomechanics vol11 no 2 pp 90ndash100 1996
[31] V Drenk ldquoPanningmdashZusatzprogramm zur Behandlungschwenk- und neigbarer und in ihrere brennweite variierbarerKameras in Peak3DmdashDokumentationrdquo Institut fur Ange-wandte Traningswissenschaften e V Leipzig Germany 1993
[32] V Drenk ldquoBildmeszligverfahren fur schwenk-und neigbaresowie in ihrer Brennweite variierbare Kamerasrdquo Zeitschrift furAngewandte Trainingswissenschaft vol 1 pp 130ndash142 1994
[33] BM Nigg andWHerzog Biomechanics of theMusculo-skeletalSystem John Wiley amp Sons New York NY USA 3rd edition2007
[34] G Stricker P Scheiber E Lindenhofer and E MullerldquoDetermination of forces in alpine skiing and snowboardingvalidation of a mobile data acquisition systemrdquo EuropeanJournal of Sport Science vol 10 no 1 pp 31ndash41 2010
[35] D G E Robertson G E Caldwell J Hamill G Kamen andS N Whittlesey Research Methods in Biomechanics HumanKinetics Champaign Ill USA 2004
[36] V M Zatsiorsky Kinematics of Human Motion HumanKinetics Champaign Ill USA 1998
[37] R M Ehrig W R Taylor G N Duda and M O HellerldquoA survey of formal methods for determining the centre ofrotation of ball jointsrdquo Journal of Biomechanics vol 39 no 15pp 2798ndash2809 2006
[38] M R Yeadon ldquoThe simulation of aerial movement II Amathematical inertia model of the human bodyrdquo Journal ofBiomechanics vol 23 no 1 pp 67ndash74 1990
[39] W T Dempster ldquoSpace requirements of the seated operatorrdquoWADC Technical Report TR-55ndash159 Wright-Patterson AirForce Base Wright-Patterson Ohio USA 1955
[40] E Muller ldquoBiomechanische Analysen moderner alpinerSkilauftechniken in unterschiedlichen Schnee- Gelande-und Pistensituationenrdquo in Biomechanik der Sportarten Bd2biomechanik des alpinen skilaufs F Fetz and E Muller Eds pp1ndash49 Ferdinand Enke Stuttgart Germany 1991
[41] C Raschner C Schiefermuller G Zallinger E Hofer FBrunner and E Muller ldquoCarving turns versus traditionalparallel turnsmdasha comparative biomechanical analysisrdquo inScience and Skiing II E Muller H Schwameder C RaschnerS Lindinger and E Kornexl Eds pp 203ndash217 Dr KovacHamburg Germany 2001
[42] GWagnerMesstechnischeDifferzierung von genschnittenen undgerutschten Kurven im alpine Skilauf [MS thesis] University ofSalzburg 2006
Computational and Mathematical Methods in Medicine 13
[43] E Muller M Klous and G Wagner ldquoBiomechanical aspectsof turning techniques in alpine skiingrdquo in Science and SportsBridging the Gap T Reilly Ed pp 135ndash142 Shaker PublishingBV Maastricht The Netherlands 2008
[44] B Knunz W Nachbauer M Mossner K Schindelwig andF Brunner ldquoTrack analysis of giant slalom turns of WorldCup racersrdquo in Proceedings of the 5th Annual Congress of theEuropean College of Sport Science (ECSS rsquo00) pp 399ndash401Jyvaskyla Finland 2000
[45] S Delorme S Tavoularis and M Lamontagne ldquoKinematics ofthe ankle joint complex in snowboardingrdquo Journal of AppliedBiomechanics vol 21 no 4 pp 394ndash403 2005
[46] S T McCaw and P DeVita ldquoErrors in alignment of center ofpressure and foot coordinates affect predicted lower extremitytorquesrdquo Journal of Biomechanics vol 28 no 8 pp 985ndash9881995
8 Computational and Mathematical Methods in Medicine
0 33 66 100
Fm
edl
atF
BW
Turn ()
minus1
0
1
2
3
(a)
0 33 66 100
Turn ()
minus1
0
1
2
3
Fan
tpo
sF
BW(b)
0 33 66 100
Turn ()
minus1
0
1
2
3
Flo
ngF
BW
(c)
Figure 6 Time profiles of the net mediallateral forces (a) net anteriorposterior forces (b) and net forces around the longitudinal axis (c)at the knee joint for the steering leg in skiing (black) and snowboarding (grey)
Table 3 Average net knee joint forces in medial (minus)lateral (+) direction (119865med-lat) anterior (+)posterior (minus) direction (119865ant-pos) and alongthe longitudinal axis (119865long) and standard deviations in the steering leg in skiing and snowboarding for each of the three phases
Computational and Mathematical Methods in Medicine 9
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()
Mfle
xex
tm (N
mk
g)
(a)
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()M
aba
dm
(Nm
kg)
(b)
0 33 66 100
Turn ()
minus6
minus4
minus2
0
2
4
6
8
m(N
mk
g)M
int
ext
(c)
Figure 7 Time profiles of the net flexion (+)extension (minus) moments (a) net adduction (+)abduction (minus) moments (b) and net internal(+)external (minus) moments (c) at the knee joint for the steering leg in skiing (black) and snowboarding (grey)
Table 4 Average net knee joint flexion (+)extension (minus) moments (119872flex-ext) net adduction (+)abduction (minus) moments (119872ad-ab) and netinternal (+)external (minus) rotation moments (119872int-ext) and standard deviations in the steering leg in skiing and snowboarding for each of thethree phases
10 Computational and Mathematical Methods in Medicine
4 Discussion
The aim of this study was to compare the ankle and kneejoint loading at the steering leg between a carved ski andsnowboard turn Based on reported injury statistics and dueto differences in technique position and equipment betweenskiing and snowboarding it was hypothesized that ankle jointloading was greater in snowboarding and knee joint loadingwas greater in skiing However the current study showed adifferent outcomeWhile forcesweremostly similar for skiingand snowboarding the joint moments were consistentlygreater during a snowboard turn whereas in skiing muchmore fluctuations were observed during the turn particularlyin the first and second phase of the turn (represented by thegreater standard deviation in skiing in those two phases)Moreover forces along the longitudinal axis were higher inskiing than in snowboarding
Results showed that the carved turn demonstrated someskidding components The average skidding angle calculatedacross time was higher in snowboarding than in skiingwhich could be due to the rather steep slope to perform acarved turn in snowboarding Nevertheless both turns wererepresentative of a carved turn Results were in agreementwithMuller et al [43] andWagner [42] who reported averageskidding angles for the carving technique in skiing of 41∘Knunz et al [44] reported angles in a carved ski turn of 1-2∘for the outer leg and 7-8∘ for the inner leg in a (purely) carvedski turn
Forces in anteriorposterior and mediallateral directionat the ankle joint were similar and rather low for skiingand snowboarding As a consequence it is expected thatthe internalexternal rotation moment is also rather low asis observed in skiing However in snowboarding internalrotation moments reached magnitudes of approximately2Nmkg Consistent and larger values throughout the turnwere also observed for the flexionextension moment insnowboarding whereas the force along the longitudinal axiswas below 1sdotBW and the anteriorposterior force was evenlower Kruger et al [28] reported even larger peak values forthe flexionextension moment at the ankle joint comparedto the current study but do not report if these values area consequence of large kinetic or kinematic values Withthe low forces observed in the current study these relativelyhigh moments must be due to kinematics hence angularaccelerations of the segments or due to the different bodypositions in skiing and snowboarding which is representedby the position of the joint centres with respect to the forcevector The use of soft boots in snowboarding allowed shortbut fast rotational movements (ie kinematic parameters)whereas these movements were not possible with stiff skibootsThese equipment differences would explain the greaterjoint moments at the ankle joint in snowboarding Thiswas supported by a study of Delorme et al [45] thatcompared ankle joint kinematics between stiff and softboots in snowboarding This study reported that the useof soft boots leads to larger average dorsiplantar flexionangles and internalexternal rotation angles as well as largermaximum dorsiplantar flexion angles eversioninversionangles and internalexternal rotation angles larger minimal
internalexternal rotation angles and a larger range ofmotionin dorsiplantar flexion
In skiing the time pattern of the force along the longitu-dinal axis at the ankle joint showed similarities with the timepattern of the flexionextension and abductionadductionmoments but in opposite direction Hence opposite tosnowboarding the large moments in skiing seemed to bea consequence of the produced forces Note that in skiingthe flexionextension moment allowed the movement to thetiptail of the ski whereas the abductionadduction momentplaces the ski at the edges (see Figure 2) Fluctuations (rep-resented by the standard deviation) were much larger forthe moments than for the forces and also much larger inskiing than in snowboarding This might suggest that thegreater number of injuries at the ankle joint is caused by thespecific body position in snowboarding and the consistentlyhigh moments due to kinematic variables rather than largefluctuation as observed in the moments in skiing
At the knee joint both mediallateral forces and forcesalong the longitudinal axis were higher in skiing whereasthe anteriorposterior forces were similar for skiing andsnowboarding However the higher forces in skiing didnot result in consistently higher moments compared tosnowboarding The flexionextension moments in snow-boarding were required to place the snowboard at theedges just like the abductionadduction moment in ski-ing The flexionextension moments in snowboarding wereapproximately 3Nmkg whereas the abductionadductionmoments in skiing were approximately 10ndash15Nmkg Alsothe flexionextension moments in skiing were approximately1 Nmkg as were the abductionadductionmoments in snow-boarding In general moments were slightly lower at the kneejoint than at the ankle joint in snowboarding whereas inskiing the opposite was observed Again the larger momentsin snowboarding seemed not to be due to the high forcesbut due to the soft boot allowing larger accelerations and adifferent body position in snowboarding than in skiing
Even though the fluctuations were larger in snowboard-ing at the knee than at the ankle joint these variationswere still much lower in snowboarding than in skiing Thesefluctuations represent the loading and unloading that areclearly greater in skiing than in snowboarding In situationswhen a skier has to make a sudden adjustment these peakvalues would increase even further In skiing joint momentsincreased in the knee joint compared to the ankle jointwhereas in snowboarding the moments decreased Besidesthe knee joint forces being similar or greater in skiing thanin snowboarding also the peak forces and moments werelarger in skiing than in snowboarding except for the inter-nalexternal rotation moment Kruger et al [28] reportedclearly lower peak values for the flexionextension momentin snowboarding (33 less) than in the current study whichwould make differences between skiing and snowboardingeven more pronounced These three aspects together couldbe an explanation for the larger amount of knee injuries inskiing than in snowboarding
Even though the joint loading observed in the currentstudy is rather high one should realise that many otheraspects can explain the injury statistics as presented in
Computational and Mathematical Methods in Medicine 11
the current study The quality of the snow the technicaland physical capability of the skier or snowboarder andthe large number of skiers and snowboarders at the slopecould explain the many injuries that occur in skiing andsnowboarding The skier and snowboarder in the currentstudy carried additional equipment to allow measurementof ground reaction forces This equipment influenced theirweight and their standing heightWith their level of expertisethe skier and snowboarder did not report any influenceof this equipment Nevertheless the equipment might haveinfluenced their technique and performance Additionallythe differences in stiffness between ski and snowboard bootscould have influenced the results Due to the stiff ski bootpart of the loading might have been transferred to theboot and thereby reduced the ankle joint in skiing Inversedynamic calculations did not allow determining how muchof the ankle joint was transferred to the ski boot Hencethis could have caused overestimation of the ankle joint inskiing However where the current results showed largerankle joint in snowboarding the difference in ankle jointbetween skiing and snowboarding would have even beengreater if the ankle joint in skiing was overestimated Whencurrent results showed larger ankle joint in skiing thesedifferences might not have been as profound Both situationssupport the research hypothesis Also the magnitudes ofthe ankle joint forces and moments in skiing might havebeen lower but it is not to expect that the time patternswere influenced Furthermore the kinematic setup allowed aski and snowboard turn to be performed with similar radiibut different velocities The centripetal force (119865
119888) in a turn
is influenced by the velocity (119865119888= 119898V2119903) Although the
velocity in snowboarding was lower than in skiing the ankleand knee joint forces and moments were not consistentlylower than in skiing We speculate that if the snowboardturn was performed with higher velocities the forces andmoments at the ankle and knee joint would further increasedue to an increase of the centripetal force Furthermorevideos and data of ground reaction forces throughout thecollected data were similar Nevertheless the findings shouldbe interpreted with caution due to the single subject designAdditionally even though the applied method shows a goodaccuracy for on-snow data collection the results of inversedynamic calculations depend strongly on the accuracy of theinput data As is shown by McCaw amp DeVita [46] errorsin the input data are propagated in the inverse dynamicsprocedures thereby reducing the accuracy of the resultscalculated using this procedure Finally it is important toemphasise that we calculated forces and moments duringsuccessful turns which are not representative of the forcesand moments during unsuccessful turns that result in fallingandor injury
5 Conclusion
The expected higher ankle joint loading in snowboardingand higher knee joint loading in skiing that was based onreported injury statistics in the lower extremities in skiingand snowboarding and the differences in position technique
and equipment (soft boot versus hard boot) could not beconfirmed Ankle joint loading was not consistently greaterin snowboarding than in skiing and vice versa for the kneejoint loading When comparing skiing and snowboardingdifferentiationwas required between forces andmoments thedirection of the forces and moments and the phase of theturn thatwas consideredHowever there seemed to be a trendthat forces were larger in skiing and moments showed largefluctuations (loading-unloading) whereas in snowboardinghigh moments with a more consistent pattern were observedIn future research it is important to increase the number ofparticipants in the study and study joint loading of variousturning techniques
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors thank ski company Atomic for providing the testequipment They appreciate the helpful discussions with DrJosef Kroll
References
[1] K Grabler and G J Stirnweis ldquoWirstschaftsbericht derSeilbahnenmdashTrends Winter 2011-2011rdquo WKO die Seilbahnen2011 httpportalwkoatwkformat detailwkangid=1ampstid=621545ampdstid=329ampopennavid=0
[2] R Schonbachler and G Scharer Fakten und Zahlen zurSchweizer Seilbahbranche Seilbahnen Schweiz 2012 httpwwwseilbahnenorgdeBrancheFakten-ZahlenFakten-Zah-len
[3] N Laplante ldquo2008-2009 Canadian Skier and SnowboarderFacts and Statsrdquo 2009 httpxcskiorgnews200920Facts20and20Stats20final20draftpdf
[4] M KlousThree-dimensional joint loading on the lower extremi-ties in alpine skiing and snowboarding [PhD thesis] Universityof Salzburg Salzburg Austria 2007
[5] S Corra A Conci G Conforti G Sacco and F de GiorgildquoSkiing and snowboarding injuries and their impact on theemergency care system in South Tyrol a restrospective analysisfor the winter season 2001ndash2002rdquo Injury Control and SafetyPromotion vol 11 no 4 pp 281ndash285 2004
[6] M Langran and S Selvaraj ldquoSnow sports injuries in Scotlanda case-control studyrdquo British Journal of Sports Medicine vol 36no 2 pp 135ndash140 2002
[7] S Sulheim I Holme A Roslashdven A Ekeland and R BahrldquoRisk factors for injuries in alpine skiing telemark skiing andsnowboardingmdashcase-control studyrdquo British Journal of SportsMedicine vol 45 no 16 pp 1303ndash1309 2011
[8] S Kim N K Endres R J Johnson C F Ettlinger andJ E Shealy ldquoSnowboarding injuries trends over time andcomparisons with alpine skiing injuriesrdquoThe American Journalof Sports Medicine vol 40 no 4 pp 770ndash776 2012
[9] M Burtscher M Flatz R Sommersacher et al OsterreichischeSkiunfallerhebung Wintersaison 20022003 Osterreichischen
12 Computational and Mathematical Methods in Medicine
Skiverbandes in Kooperation mit dem Institut fur Sportwissen-schaften der Universitat Innsbruck 2003
[10] C Goulet G Regnier G Grimard P Valois and P VilleneuveldquoRisk factors associated with alpine skiing injuries in childrena case-control studyrdquoThe American Journal of Sports Medicinevol 27 no 5 pp 644ndash650 1999
[11] E J Bridges F Rouah and K M Johnston ldquoSnowbladinginjuries in Eastern Canadardquo British Journal of Sports Medicinevol 37 no 6 pp 511ndash515 2003
[12] D Ishimaru H Ogawa K Wakahara H Sumi Y Sumi andK Shimizu ldquoHip pads reduce the overall risk of injuries inrecreational snowboardersrdquo British Journal of Sports Medicinevol 46 no 15 pp 1055ndash1058 2012
[13] H Xiang K Kelleher B J Shields K J Brown and G ASmith ldquoSkiing- and snowboarding-related injuries treated inUS emergency departments 2002rdquo Journal of Trauma-InjuryInfection amp Critical Care vol 58 no 1 pp 112ndash118 2005
[14] C Made and L G Elmqvist ldquoA 10-year study of snowboardinjuries in Lapland Swedenrdquo Scandinavian Journal of Medicineand Science in Sports vol 14 no 2 pp 128ndash133 2004
[15] E Aschauer E Ritter and H ReschWintersport Unfallstatistik20022003 Universitatsklinik fur Unfallchirurgie und Sport-traumatologie Salzburg 2003
[16] T M Davidson and A T Laliotis ldquoSnowboarding injuries afour-year study with comparison with alpine ski injuriesrdquo TheWestern Journal of Medicine vol 164 no 3 pp 231ndash237 1996
[17] J Howe The New Skiing Mechanics McIntire PublishingWaterford UK 2nd edition 2001
[18] Y Urabe M Ochi K Onari and Y Ikuta ldquoAnterior cruciateligament injury in recreational alpine skiers analysis of mech-anisms and strategy for preventionrdquo Journal of OrthopaedicScience vol 7 no 1 pp 1ndash5 2002
[19] S M Maxwell and M L Hull ldquoMeasurement of strength andloading variables on the knee during alpine skiingrdquo Journal ofBiomechanics vol 22 no 6-7 pp 609ndash624 1989
[20] T P Quinn and C D Mote Jr ldquoPrediction of the loading alongthe leg during snow skiingrdquo Journal of Biomechanics vol 25 no6 pp 609ndash625 1992
[21] C Raschner E Muller and H Schwameder ldquoKinematic andkinetic analysis of slalom turns as a basis for the development ofspecific training methods to improve strength and endurancerdquoin Science and Skiing EMullerH Schwameder E Kornexl andC Raschner Eds pp 251ndash261 Chapman amp Hall CambridgeMass USA 1997
[22] M Brodie A Walmsley and W Page ldquoFusion motion capturea prototype system using inertial measurement units and GPSfor the biomechanical analysis of ski racingrdquo Sports Technologyvol 1 pp 17ndash28 2008
[23] M Klous E Muller and H Schwameder ldquoThree-dimensionalknee joint loading in alpine skiing a comparison between acarved and a skidded turnrdquo Journal of Applied Biomechanics vol28 no 6 pp 655ndash664 2012
[24] F Vaverka S Vodickova and M Elfmark ldquoKinetic analysis ofski turns based on measured ground reaction forcesrdquo Journal ofApplied Biomechanics vol 28 no 1 pp 41ndash47 2012
[25] L Read and W Herzog ldquoExternal loading at the knee joint forlanding movements in alpine skiingrdquo International Journal ofSport Biomechanics vol 8 pp 62ndash80 1992
[26] W Nachbauer P Kaps B Nigg et al ldquoA video technique forobtaining 3-D coordinates in alpine skiingrdquo Journal of AppliedBiomechanics vol 12 no 1 pp 104ndash115 1996
[27] B Knunz W Nachbauer K Schindelwig and F BrunnerldquoForces andmoments at the boot sole during snowboardingrdquo inScience and Skiing II E Muller H Schwameder C Raschner SLindinger and E Kornexl Eds pp 242ndash249 Kovac HamburgGermany 2001
[28] A Kruger P McAlpine F Borrani and J Edelmann-NusserldquoDetermination of three-dimensional joint loading within thelower extremities in snowboardingrdquo Proceedings of the Insti-tution of Mechanical Engineers H Journal of Engineering inMedicine vol 226 no 2 pp 170ndash175 2012
[29] M Klous EMuller andH Schwameder ldquoCollecting kinematicdata on a skisnowboard track with panning tilting and zoom-ing cameras is there sufficient accuracy for a biomechanicalanalysisrdquo Journal of Sports Sciences vol 28 no 12 pp 1345ndash1352 2010
[30] A Cappozzo F Catani A Leardini M G Benedetti and UDella Croce ldquoPosition and orientation in space of bones duringmovement experimental artefactsrdquo Clinical Biomechanics vol11 no 2 pp 90ndash100 1996
[31] V Drenk ldquoPanningmdashZusatzprogramm zur Behandlungschwenk- und neigbarer und in ihrere brennweite variierbarerKameras in Peak3DmdashDokumentationrdquo Institut fur Ange-wandte Traningswissenschaften e V Leipzig Germany 1993
[32] V Drenk ldquoBildmeszligverfahren fur schwenk-und neigbaresowie in ihrer Brennweite variierbare Kamerasrdquo Zeitschrift furAngewandte Trainingswissenschaft vol 1 pp 130ndash142 1994
[33] BM Nigg andWHerzog Biomechanics of theMusculo-skeletalSystem John Wiley amp Sons New York NY USA 3rd edition2007
[34] G Stricker P Scheiber E Lindenhofer and E MullerldquoDetermination of forces in alpine skiing and snowboardingvalidation of a mobile data acquisition systemrdquo EuropeanJournal of Sport Science vol 10 no 1 pp 31ndash41 2010
[35] D G E Robertson G E Caldwell J Hamill G Kamen andS N Whittlesey Research Methods in Biomechanics HumanKinetics Champaign Ill USA 2004
[36] V M Zatsiorsky Kinematics of Human Motion HumanKinetics Champaign Ill USA 1998
[37] R M Ehrig W R Taylor G N Duda and M O HellerldquoA survey of formal methods for determining the centre ofrotation of ball jointsrdquo Journal of Biomechanics vol 39 no 15pp 2798ndash2809 2006
[38] M R Yeadon ldquoThe simulation of aerial movement II Amathematical inertia model of the human bodyrdquo Journal ofBiomechanics vol 23 no 1 pp 67ndash74 1990
[39] W T Dempster ldquoSpace requirements of the seated operatorrdquoWADC Technical Report TR-55ndash159 Wright-Patterson AirForce Base Wright-Patterson Ohio USA 1955
[40] E Muller ldquoBiomechanische Analysen moderner alpinerSkilauftechniken in unterschiedlichen Schnee- Gelande-und Pistensituationenrdquo in Biomechanik der Sportarten Bd2biomechanik des alpinen skilaufs F Fetz and E Muller Eds pp1ndash49 Ferdinand Enke Stuttgart Germany 1991
[41] C Raschner C Schiefermuller G Zallinger E Hofer FBrunner and E Muller ldquoCarving turns versus traditionalparallel turnsmdasha comparative biomechanical analysisrdquo inScience and Skiing II E Muller H Schwameder C RaschnerS Lindinger and E Kornexl Eds pp 203ndash217 Dr KovacHamburg Germany 2001
[42] GWagnerMesstechnischeDifferzierung von genschnittenen undgerutschten Kurven im alpine Skilauf [MS thesis] University ofSalzburg 2006
Computational and Mathematical Methods in Medicine 13
[43] E Muller M Klous and G Wagner ldquoBiomechanical aspectsof turning techniques in alpine skiingrdquo in Science and SportsBridging the Gap T Reilly Ed pp 135ndash142 Shaker PublishingBV Maastricht The Netherlands 2008
[44] B Knunz W Nachbauer M Mossner K Schindelwig andF Brunner ldquoTrack analysis of giant slalom turns of WorldCup racersrdquo in Proceedings of the 5th Annual Congress of theEuropean College of Sport Science (ECSS rsquo00) pp 399ndash401Jyvaskyla Finland 2000
[45] S Delorme S Tavoularis and M Lamontagne ldquoKinematics ofthe ankle joint complex in snowboardingrdquo Journal of AppliedBiomechanics vol 21 no 4 pp 394ndash403 2005
[46] S T McCaw and P DeVita ldquoErrors in alignment of center ofpressure and foot coordinates affect predicted lower extremitytorquesrdquo Journal of Biomechanics vol 28 no 8 pp 985ndash9881995
Computational and Mathematical Methods in Medicine 9
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()
Mfle
xex
tm (N
mk
g)
(a)
minus6
minus4
minus2
0
2
4
6
8
0 33 66 100
Turn ()M
aba
dm
(Nm
kg)
(b)
0 33 66 100
Turn ()
minus6
minus4
minus2
0
2
4
6
8
m(N
mk
g)M
int
ext
(c)
Figure 7 Time profiles of the net flexion (+)extension (minus) moments (a) net adduction (+)abduction (minus) moments (b) and net internal(+)external (minus) moments (c) at the knee joint for the steering leg in skiing (black) and snowboarding (grey)
Table 4 Average net knee joint flexion (+)extension (minus) moments (119872flex-ext) net adduction (+)abduction (minus) moments (119872ad-ab) and netinternal (+)external (minus) rotation moments (119872int-ext) and standard deviations in the steering leg in skiing and snowboarding for each of thethree phases
10 Computational and Mathematical Methods in Medicine
4 Discussion
The aim of this study was to compare the ankle and kneejoint loading at the steering leg between a carved ski andsnowboard turn Based on reported injury statistics and dueto differences in technique position and equipment betweenskiing and snowboarding it was hypothesized that ankle jointloading was greater in snowboarding and knee joint loadingwas greater in skiing However the current study showed adifferent outcomeWhile forcesweremostly similar for skiingand snowboarding the joint moments were consistentlygreater during a snowboard turn whereas in skiing muchmore fluctuations were observed during the turn particularlyin the first and second phase of the turn (represented by thegreater standard deviation in skiing in those two phases)Moreover forces along the longitudinal axis were higher inskiing than in snowboarding
Results showed that the carved turn demonstrated someskidding components The average skidding angle calculatedacross time was higher in snowboarding than in skiingwhich could be due to the rather steep slope to perform acarved turn in snowboarding Nevertheless both turns wererepresentative of a carved turn Results were in agreementwithMuller et al [43] andWagner [42] who reported averageskidding angles for the carving technique in skiing of 41∘Knunz et al [44] reported angles in a carved ski turn of 1-2∘for the outer leg and 7-8∘ for the inner leg in a (purely) carvedski turn
Forces in anteriorposterior and mediallateral directionat the ankle joint were similar and rather low for skiingand snowboarding As a consequence it is expected thatthe internalexternal rotation moment is also rather low asis observed in skiing However in snowboarding internalrotation moments reached magnitudes of approximately2Nmkg Consistent and larger values throughout the turnwere also observed for the flexionextension moment insnowboarding whereas the force along the longitudinal axiswas below 1sdotBW and the anteriorposterior force was evenlower Kruger et al [28] reported even larger peak values forthe flexionextension moment at the ankle joint comparedto the current study but do not report if these values area consequence of large kinetic or kinematic values Withthe low forces observed in the current study these relativelyhigh moments must be due to kinematics hence angularaccelerations of the segments or due to the different bodypositions in skiing and snowboarding which is representedby the position of the joint centres with respect to the forcevector The use of soft boots in snowboarding allowed shortbut fast rotational movements (ie kinematic parameters)whereas these movements were not possible with stiff skibootsThese equipment differences would explain the greaterjoint moments at the ankle joint in snowboarding Thiswas supported by a study of Delorme et al [45] thatcompared ankle joint kinematics between stiff and softboots in snowboarding This study reported that the useof soft boots leads to larger average dorsiplantar flexionangles and internalexternal rotation angles as well as largermaximum dorsiplantar flexion angles eversioninversionangles and internalexternal rotation angles larger minimal
internalexternal rotation angles and a larger range ofmotionin dorsiplantar flexion
In skiing the time pattern of the force along the longitu-dinal axis at the ankle joint showed similarities with the timepattern of the flexionextension and abductionadductionmoments but in opposite direction Hence opposite tosnowboarding the large moments in skiing seemed to bea consequence of the produced forces Note that in skiingthe flexionextension moment allowed the movement to thetiptail of the ski whereas the abductionadduction momentplaces the ski at the edges (see Figure 2) Fluctuations (rep-resented by the standard deviation) were much larger forthe moments than for the forces and also much larger inskiing than in snowboarding This might suggest that thegreater number of injuries at the ankle joint is caused by thespecific body position in snowboarding and the consistentlyhigh moments due to kinematic variables rather than largefluctuation as observed in the moments in skiing
At the knee joint both mediallateral forces and forcesalong the longitudinal axis were higher in skiing whereasthe anteriorposterior forces were similar for skiing andsnowboarding However the higher forces in skiing didnot result in consistently higher moments compared tosnowboarding The flexionextension moments in snow-boarding were required to place the snowboard at theedges just like the abductionadduction moment in ski-ing The flexionextension moments in snowboarding wereapproximately 3Nmkg whereas the abductionadductionmoments in skiing were approximately 10ndash15Nmkg Alsothe flexionextension moments in skiing were approximately1 Nmkg as were the abductionadductionmoments in snow-boarding In general moments were slightly lower at the kneejoint than at the ankle joint in snowboarding whereas inskiing the opposite was observed Again the larger momentsin snowboarding seemed not to be due to the high forcesbut due to the soft boot allowing larger accelerations and adifferent body position in snowboarding than in skiing
Even though the fluctuations were larger in snowboard-ing at the knee than at the ankle joint these variationswere still much lower in snowboarding than in skiing Thesefluctuations represent the loading and unloading that areclearly greater in skiing than in snowboarding In situationswhen a skier has to make a sudden adjustment these peakvalues would increase even further In skiing joint momentsincreased in the knee joint compared to the ankle jointwhereas in snowboarding the moments decreased Besidesthe knee joint forces being similar or greater in skiing thanin snowboarding also the peak forces and moments werelarger in skiing than in snowboarding except for the inter-nalexternal rotation moment Kruger et al [28] reportedclearly lower peak values for the flexionextension momentin snowboarding (33 less) than in the current study whichwould make differences between skiing and snowboardingeven more pronounced These three aspects together couldbe an explanation for the larger amount of knee injuries inskiing than in snowboarding
Even though the joint loading observed in the currentstudy is rather high one should realise that many otheraspects can explain the injury statistics as presented in
Computational and Mathematical Methods in Medicine 11
the current study The quality of the snow the technicaland physical capability of the skier or snowboarder andthe large number of skiers and snowboarders at the slopecould explain the many injuries that occur in skiing andsnowboarding The skier and snowboarder in the currentstudy carried additional equipment to allow measurementof ground reaction forces This equipment influenced theirweight and their standing heightWith their level of expertisethe skier and snowboarder did not report any influenceof this equipment Nevertheless the equipment might haveinfluenced their technique and performance Additionallythe differences in stiffness between ski and snowboard bootscould have influenced the results Due to the stiff ski bootpart of the loading might have been transferred to theboot and thereby reduced the ankle joint in skiing Inversedynamic calculations did not allow determining how muchof the ankle joint was transferred to the ski boot Hencethis could have caused overestimation of the ankle joint inskiing However where the current results showed largerankle joint in snowboarding the difference in ankle jointbetween skiing and snowboarding would have even beengreater if the ankle joint in skiing was overestimated Whencurrent results showed larger ankle joint in skiing thesedifferences might not have been as profound Both situationssupport the research hypothesis Also the magnitudes ofthe ankle joint forces and moments in skiing might havebeen lower but it is not to expect that the time patternswere influenced Furthermore the kinematic setup allowed aski and snowboard turn to be performed with similar radiibut different velocities The centripetal force (119865
119888) in a turn
is influenced by the velocity (119865119888= 119898V2119903) Although the
velocity in snowboarding was lower than in skiing the ankleand knee joint forces and moments were not consistentlylower than in skiing We speculate that if the snowboardturn was performed with higher velocities the forces andmoments at the ankle and knee joint would further increasedue to an increase of the centripetal force Furthermorevideos and data of ground reaction forces throughout thecollected data were similar Nevertheless the findings shouldbe interpreted with caution due to the single subject designAdditionally even though the applied method shows a goodaccuracy for on-snow data collection the results of inversedynamic calculations depend strongly on the accuracy of theinput data As is shown by McCaw amp DeVita [46] errorsin the input data are propagated in the inverse dynamicsprocedures thereby reducing the accuracy of the resultscalculated using this procedure Finally it is important toemphasise that we calculated forces and moments duringsuccessful turns which are not representative of the forcesand moments during unsuccessful turns that result in fallingandor injury
5 Conclusion
The expected higher ankle joint loading in snowboardingand higher knee joint loading in skiing that was based onreported injury statistics in the lower extremities in skiingand snowboarding and the differences in position technique
and equipment (soft boot versus hard boot) could not beconfirmed Ankle joint loading was not consistently greaterin snowboarding than in skiing and vice versa for the kneejoint loading When comparing skiing and snowboardingdifferentiationwas required between forces andmoments thedirection of the forces and moments and the phase of theturn thatwas consideredHowever there seemed to be a trendthat forces were larger in skiing and moments showed largefluctuations (loading-unloading) whereas in snowboardinghigh moments with a more consistent pattern were observedIn future research it is important to increase the number ofparticipants in the study and study joint loading of variousturning techniques
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors thank ski company Atomic for providing the testequipment They appreciate the helpful discussions with DrJosef Kroll
References
[1] K Grabler and G J Stirnweis ldquoWirstschaftsbericht derSeilbahnenmdashTrends Winter 2011-2011rdquo WKO die Seilbahnen2011 httpportalwkoatwkformat detailwkangid=1ampstid=621545ampdstid=329ampopennavid=0
[2] R Schonbachler and G Scharer Fakten und Zahlen zurSchweizer Seilbahbranche Seilbahnen Schweiz 2012 httpwwwseilbahnenorgdeBrancheFakten-ZahlenFakten-Zah-len
[3] N Laplante ldquo2008-2009 Canadian Skier and SnowboarderFacts and Statsrdquo 2009 httpxcskiorgnews200920Facts20and20Stats20final20draftpdf
[4] M KlousThree-dimensional joint loading on the lower extremi-ties in alpine skiing and snowboarding [PhD thesis] Universityof Salzburg Salzburg Austria 2007
[5] S Corra A Conci G Conforti G Sacco and F de GiorgildquoSkiing and snowboarding injuries and their impact on theemergency care system in South Tyrol a restrospective analysisfor the winter season 2001ndash2002rdquo Injury Control and SafetyPromotion vol 11 no 4 pp 281ndash285 2004
[6] M Langran and S Selvaraj ldquoSnow sports injuries in Scotlanda case-control studyrdquo British Journal of Sports Medicine vol 36no 2 pp 135ndash140 2002
[7] S Sulheim I Holme A Roslashdven A Ekeland and R BahrldquoRisk factors for injuries in alpine skiing telemark skiing andsnowboardingmdashcase-control studyrdquo British Journal of SportsMedicine vol 45 no 16 pp 1303ndash1309 2011
[8] S Kim N K Endres R J Johnson C F Ettlinger andJ E Shealy ldquoSnowboarding injuries trends over time andcomparisons with alpine skiing injuriesrdquoThe American Journalof Sports Medicine vol 40 no 4 pp 770ndash776 2012
[9] M Burtscher M Flatz R Sommersacher et al OsterreichischeSkiunfallerhebung Wintersaison 20022003 Osterreichischen
12 Computational and Mathematical Methods in Medicine
Skiverbandes in Kooperation mit dem Institut fur Sportwissen-schaften der Universitat Innsbruck 2003
[10] C Goulet G Regnier G Grimard P Valois and P VilleneuveldquoRisk factors associated with alpine skiing injuries in childrena case-control studyrdquoThe American Journal of Sports Medicinevol 27 no 5 pp 644ndash650 1999
[11] E J Bridges F Rouah and K M Johnston ldquoSnowbladinginjuries in Eastern Canadardquo British Journal of Sports Medicinevol 37 no 6 pp 511ndash515 2003
[12] D Ishimaru H Ogawa K Wakahara H Sumi Y Sumi andK Shimizu ldquoHip pads reduce the overall risk of injuries inrecreational snowboardersrdquo British Journal of Sports Medicinevol 46 no 15 pp 1055ndash1058 2012
[13] H Xiang K Kelleher B J Shields K J Brown and G ASmith ldquoSkiing- and snowboarding-related injuries treated inUS emergency departments 2002rdquo Journal of Trauma-InjuryInfection amp Critical Care vol 58 no 1 pp 112ndash118 2005
[14] C Made and L G Elmqvist ldquoA 10-year study of snowboardinjuries in Lapland Swedenrdquo Scandinavian Journal of Medicineand Science in Sports vol 14 no 2 pp 128ndash133 2004
[15] E Aschauer E Ritter and H ReschWintersport Unfallstatistik20022003 Universitatsklinik fur Unfallchirurgie und Sport-traumatologie Salzburg 2003
[16] T M Davidson and A T Laliotis ldquoSnowboarding injuries afour-year study with comparison with alpine ski injuriesrdquo TheWestern Journal of Medicine vol 164 no 3 pp 231ndash237 1996
[17] J Howe The New Skiing Mechanics McIntire PublishingWaterford UK 2nd edition 2001
[18] Y Urabe M Ochi K Onari and Y Ikuta ldquoAnterior cruciateligament injury in recreational alpine skiers analysis of mech-anisms and strategy for preventionrdquo Journal of OrthopaedicScience vol 7 no 1 pp 1ndash5 2002
[19] S M Maxwell and M L Hull ldquoMeasurement of strength andloading variables on the knee during alpine skiingrdquo Journal ofBiomechanics vol 22 no 6-7 pp 609ndash624 1989
[20] T P Quinn and C D Mote Jr ldquoPrediction of the loading alongthe leg during snow skiingrdquo Journal of Biomechanics vol 25 no6 pp 609ndash625 1992
[21] C Raschner E Muller and H Schwameder ldquoKinematic andkinetic analysis of slalom turns as a basis for the development ofspecific training methods to improve strength and endurancerdquoin Science and Skiing EMullerH Schwameder E Kornexl andC Raschner Eds pp 251ndash261 Chapman amp Hall CambridgeMass USA 1997
[22] M Brodie A Walmsley and W Page ldquoFusion motion capturea prototype system using inertial measurement units and GPSfor the biomechanical analysis of ski racingrdquo Sports Technologyvol 1 pp 17ndash28 2008
[23] M Klous E Muller and H Schwameder ldquoThree-dimensionalknee joint loading in alpine skiing a comparison between acarved and a skidded turnrdquo Journal of Applied Biomechanics vol28 no 6 pp 655ndash664 2012
[24] F Vaverka S Vodickova and M Elfmark ldquoKinetic analysis ofski turns based on measured ground reaction forcesrdquo Journal ofApplied Biomechanics vol 28 no 1 pp 41ndash47 2012
[25] L Read and W Herzog ldquoExternal loading at the knee joint forlanding movements in alpine skiingrdquo International Journal ofSport Biomechanics vol 8 pp 62ndash80 1992
[26] W Nachbauer P Kaps B Nigg et al ldquoA video technique forobtaining 3-D coordinates in alpine skiingrdquo Journal of AppliedBiomechanics vol 12 no 1 pp 104ndash115 1996
[27] B Knunz W Nachbauer K Schindelwig and F BrunnerldquoForces andmoments at the boot sole during snowboardingrdquo inScience and Skiing II E Muller H Schwameder C Raschner SLindinger and E Kornexl Eds pp 242ndash249 Kovac HamburgGermany 2001
[28] A Kruger P McAlpine F Borrani and J Edelmann-NusserldquoDetermination of three-dimensional joint loading within thelower extremities in snowboardingrdquo Proceedings of the Insti-tution of Mechanical Engineers H Journal of Engineering inMedicine vol 226 no 2 pp 170ndash175 2012
[29] M Klous EMuller andH Schwameder ldquoCollecting kinematicdata on a skisnowboard track with panning tilting and zoom-ing cameras is there sufficient accuracy for a biomechanicalanalysisrdquo Journal of Sports Sciences vol 28 no 12 pp 1345ndash1352 2010
[30] A Cappozzo F Catani A Leardini M G Benedetti and UDella Croce ldquoPosition and orientation in space of bones duringmovement experimental artefactsrdquo Clinical Biomechanics vol11 no 2 pp 90ndash100 1996
[31] V Drenk ldquoPanningmdashZusatzprogramm zur Behandlungschwenk- und neigbarer und in ihrere brennweite variierbarerKameras in Peak3DmdashDokumentationrdquo Institut fur Ange-wandte Traningswissenschaften e V Leipzig Germany 1993
[32] V Drenk ldquoBildmeszligverfahren fur schwenk-und neigbaresowie in ihrer Brennweite variierbare Kamerasrdquo Zeitschrift furAngewandte Trainingswissenschaft vol 1 pp 130ndash142 1994
[33] BM Nigg andWHerzog Biomechanics of theMusculo-skeletalSystem John Wiley amp Sons New York NY USA 3rd edition2007
[34] G Stricker P Scheiber E Lindenhofer and E MullerldquoDetermination of forces in alpine skiing and snowboardingvalidation of a mobile data acquisition systemrdquo EuropeanJournal of Sport Science vol 10 no 1 pp 31ndash41 2010
[35] D G E Robertson G E Caldwell J Hamill G Kamen andS N Whittlesey Research Methods in Biomechanics HumanKinetics Champaign Ill USA 2004
[36] V M Zatsiorsky Kinematics of Human Motion HumanKinetics Champaign Ill USA 1998
[37] R M Ehrig W R Taylor G N Duda and M O HellerldquoA survey of formal methods for determining the centre ofrotation of ball jointsrdquo Journal of Biomechanics vol 39 no 15pp 2798ndash2809 2006
[38] M R Yeadon ldquoThe simulation of aerial movement II Amathematical inertia model of the human bodyrdquo Journal ofBiomechanics vol 23 no 1 pp 67ndash74 1990
[39] W T Dempster ldquoSpace requirements of the seated operatorrdquoWADC Technical Report TR-55ndash159 Wright-Patterson AirForce Base Wright-Patterson Ohio USA 1955
[40] E Muller ldquoBiomechanische Analysen moderner alpinerSkilauftechniken in unterschiedlichen Schnee- Gelande-und Pistensituationenrdquo in Biomechanik der Sportarten Bd2biomechanik des alpinen skilaufs F Fetz and E Muller Eds pp1ndash49 Ferdinand Enke Stuttgart Germany 1991
[41] C Raschner C Schiefermuller G Zallinger E Hofer FBrunner and E Muller ldquoCarving turns versus traditionalparallel turnsmdasha comparative biomechanical analysisrdquo inScience and Skiing II E Muller H Schwameder C RaschnerS Lindinger and E Kornexl Eds pp 203ndash217 Dr KovacHamburg Germany 2001
[42] GWagnerMesstechnischeDifferzierung von genschnittenen undgerutschten Kurven im alpine Skilauf [MS thesis] University ofSalzburg 2006
Computational and Mathematical Methods in Medicine 13
[43] E Muller M Klous and G Wagner ldquoBiomechanical aspectsof turning techniques in alpine skiingrdquo in Science and SportsBridging the Gap T Reilly Ed pp 135ndash142 Shaker PublishingBV Maastricht The Netherlands 2008
[44] B Knunz W Nachbauer M Mossner K Schindelwig andF Brunner ldquoTrack analysis of giant slalom turns of WorldCup racersrdquo in Proceedings of the 5th Annual Congress of theEuropean College of Sport Science (ECSS rsquo00) pp 399ndash401Jyvaskyla Finland 2000
[45] S Delorme S Tavoularis and M Lamontagne ldquoKinematics ofthe ankle joint complex in snowboardingrdquo Journal of AppliedBiomechanics vol 21 no 4 pp 394ndash403 2005
[46] S T McCaw and P DeVita ldquoErrors in alignment of center ofpressure and foot coordinates affect predicted lower extremitytorquesrdquo Journal of Biomechanics vol 28 no 8 pp 985ndash9881995
10 Computational and Mathematical Methods in Medicine
4 Discussion
The aim of this study was to compare the ankle and kneejoint loading at the steering leg between a carved ski andsnowboard turn Based on reported injury statistics and dueto differences in technique position and equipment betweenskiing and snowboarding it was hypothesized that ankle jointloading was greater in snowboarding and knee joint loadingwas greater in skiing However the current study showed adifferent outcomeWhile forcesweremostly similar for skiingand snowboarding the joint moments were consistentlygreater during a snowboard turn whereas in skiing muchmore fluctuations were observed during the turn particularlyin the first and second phase of the turn (represented by thegreater standard deviation in skiing in those two phases)Moreover forces along the longitudinal axis were higher inskiing than in snowboarding
Results showed that the carved turn demonstrated someskidding components The average skidding angle calculatedacross time was higher in snowboarding than in skiingwhich could be due to the rather steep slope to perform acarved turn in snowboarding Nevertheless both turns wererepresentative of a carved turn Results were in agreementwithMuller et al [43] andWagner [42] who reported averageskidding angles for the carving technique in skiing of 41∘Knunz et al [44] reported angles in a carved ski turn of 1-2∘for the outer leg and 7-8∘ for the inner leg in a (purely) carvedski turn
Forces in anteriorposterior and mediallateral directionat the ankle joint were similar and rather low for skiingand snowboarding As a consequence it is expected thatthe internalexternal rotation moment is also rather low asis observed in skiing However in snowboarding internalrotation moments reached magnitudes of approximately2Nmkg Consistent and larger values throughout the turnwere also observed for the flexionextension moment insnowboarding whereas the force along the longitudinal axiswas below 1sdotBW and the anteriorposterior force was evenlower Kruger et al [28] reported even larger peak values forthe flexionextension moment at the ankle joint comparedto the current study but do not report if these values area consequence of large kinetic or kinematic values Withthe low forces observed in the current study these relativelyhigh moments must be due to kinematics hence angularaccelerations of the segments or due to the different bodypositions in skiing and snowboarding which is representedby the position of the joint centres with respect to the forcevector The use of soft boots in snowboarding allowed shortbut fast rotational movements (ie kinematic parameters)whereas these movements were not possible with stiff skibootsThese equipment differences would explain the greaterjoint moments at the ankle joint in snowboarding Thiswas supported by a study of Delorme et al [45] thatcompared ankle joint kinematics between stiff and softboots in snowboarding This study reported that the useof soft boots leads to larger average dorsiplantar flexionangles and internalexternal rotation angles as well as largermaximum dorsiplantar flexion angles eversioninversionangles and internalexternal rotation angles larger minimal
internalexternal rotation angles and a larger range ofmotionin dorsiplantar flexion
In skiing the time pattern of the force along the longitu-dinal axis at the ankle joint showed similarities with the timepattern of the flexionextension and abductionadductionmoments but in opposite direction Hence opposite tosnowboarding the large moments in skiing seemed to bea consequence of the produced forces Note that in skiingthe flexionextension moment allowed the movement to thetiptail of the ski whereas the abductionadduction momentplaces the ski at the edges (see Figure 2) Fluctuations (rep-resented by the standard deviation) were much larger forthe moments than for the forces and also much larger inskiing than in snowboarding This might suggest that thegreater number of injuries at the ankle joint is caused by thespecific body position in snowboarding and the consistentlyhigh moments due to kinematic variables rather than largefluctuation as observed in the moments in skiing
At the knee joint both mediallateral forces and forcesalong the longitudinal axis were higher in skiing whereasthe anteriorposterior forces were similar for skiing andsnowboarding However the higher forces in skiing didnot result in consistently higher moments compared tosnowboarding The flexionextension moments in snow-boarding were required to place the snowboard at theedges just like the abductionadduction moment in ski-ing The flexionextension moments in snowboarding wereapproximately 3Nmkg whereas the abductionadductionmoments in skiing were approximately 10ndash15Nmkg Alsothe flexionextension moments in skiing were approximately1 Nmkg as were the abductionadductionmoments in snow-boarding In general moments were slightly lower at the kneejoint than at the ankle joint in snowboarding whereas inskiing the opposite was observed Again the larger momentsin snowboarding seemed not to be due to the high forcesbut due to the soft boot allowing larger accelerations and adifferent body position in snowboarding than in skiing
Even though the fluctuations were larger in snowboard-ing at the knee than at the ankle joint these variationswere still much lower in snowboarding than in skiing Thesefluctuations represent the loading and unloading that areclearly greater in skiing than in snowboarding In situationswhen a skier has to make a sudden adjustment these peakvalues would increase even further In skiing joint momentsincreased in the knee joint compared to the ankle jointwhereas in snowboarding the moments decreased Besidesthe knee joint forces being similar or greater in skiing thanin snowboarding also the peak forces and moments werelarger in skiing than in snowboarding except for the inter-nalexternal rotation moment Kruger et al [28] reportedclearly lower peak values for the flexionextension momentin snowboarding (33 less) than in the current study whichwould make differences between skiing and snowboardingeven more pronounced These three aspects together couldbe an explanation for the larger amount of knee injuries inskiing than in snowboarding
Even though the joint loading observed in the currentstudy is rather high one should realise that many otheraspects can explain the injury statistics as presented in
Computational and Mathematical Methods in Medicine 11
the current study The quality of the snow the technicaland physical capability of the skier or snowboarder andthe large number of skiers and snowboarders at the slopecould explain the many injuries that occur in skiing andsnowboarding The skier and snowboarder in the currentstudy carried additional equipment to allow measurementof ground reaction forces This equipment influenced theirweight and their standing heightWith their level of expertisethe skier and snowboarder did not report any influenceof this equipment Nevertheless the equipment might haveinfluenced their technique and performance Additionallythe differences in stiffness between ski and snowboard bootscould have influenced the results Due to the stiff ski bootpart of the loading might have been transferred to theboot and thereby reduced the ankle joint in skiing Inversedynamic calculations did not allow determining how muchof the ankle joint was transferred to the ski boot Hencethis could have caused overestimation of the ankle joint inskiing However where the current results showed largerankle joint in snowboarding the difference in ankle jointbetween skiing and snowboarding would have even beengreater if the ankle joint in skiing was overestimated Whencurrent results showed larger ankle joint in skiing thesedifferences might not have been as profound Both situationssupport the research hypothesis Also the magnitudes ofthe ankle joint forces and moments in skiing might havebeen lower but it is not to expect that the time patternswere influenced Furthermore the kinematic setup allowed aski and snowboard turn to be performed with similar radiibut different velocities The centripetal force (119865
119888) in a turn
is influenced by the velocity (119865119888= 119898V2119903) Although the
velocity in snowboarding was lower than in skiing the ankleand knee joint forces and moments were not consistentlylower than in skiing We speculate that if the snowboardturn was performed with higher velocities the forces andmoments at the ankle and knee joint would further increasedue to an increase of the centripetal force Furthermorevideos and data of ground reaction forces throughout thecollected data were similar Nevertheless the findings shouldbe interpreted with caution due to the single subject designAdditionally even though the applied method shows a goodaccuracy for on-snow data collection the results of inversedynamic calculations depend strongly on the accuracy of theinput data As is shown by McCaw amp DeVita [46] errorsin the input data are propagated in the inverse dynamicsprocedures thereby reducing the accuracy of the resultscalculated using this procedure Finally it is important toemphasise that we calculated forces and moments duringsuccessful turns which are not representative of the forcesand moments during unsuccessful turns that result in fallingandor injury
5 Conclusion
The expected higher ankle joint loading in snowboardingand higher knee joint loading in skiing that was based onreported injury statistics in the lower extremities in skiingand snowboarding and the differences in position technique
and equipment (soft boot versus hard boot) could not beconfirmed Ankle joint loading was not consistently greaterin snowboarding than in skiing and vice versa for the kneejoint loading When comparing skiing and snowboardingdifferentiationwas required between forces andmoments thedirection of the forces and moments and the phase of theturn thatwas consideredHowever there seemed to be a trendthat forces were larger in skiing and moments showed largefluctuations (loading-unloading) whereas in snowboardinghigh moments with a more consistent pattern were observedIn future research it is important to increase the number ofparticipants in the study and study joint loading of variousturning techniques
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors thank ski company Atomic for providing the testequipment They appreciate the helpful discussions with DrJosef Kroll
References
[1] K Grabler and G J Stirnweis ldquoWirstschaftsbericht derSeilbahnenmdashTrends Winter 2011-2011rdquo WKO die Seilbahnen2011 httpportalwkoatwkformat detailwkangid=1ampstid=621545ampdstid=329ampopennavid=0
[2] R Schonbachler and G Scharer Fakten und Zahlen zurSchweizer Seilbahbranche Seilbahnen Schweiz 2012 httpwwwseilbahnenorgdeBrancheFakten-ZahlenFakten-Zah-len
[3] N Laplante ldquo2008-2009 Canadian Skier and SnowboarderFacts and Statsrdquo 2009 httpxcskiorgnews200920Facts20and20Stats20final20draftpdf
[4] M KlousThree-dimensional joint loading on the lower extremi-ties in alpine skiing and snowboarding [PhD thesis] Universityof Salzburg Salzburg Austria 2007
[5] S Corra A Conci G Conforti G Sacco and F de GiorgildquoSkiing and snowboarding injuries and their impact on theemergency care system in South Tyrol a restrospective analysisfor the winter season 2001ndash2002rdquo Injury Control and SafetyPromotion vol 11 no 4 pp 281ndash285 2004
[6] M Langran and S Selvaraj ldquoSnow sports injuries in Scotlanda case-control studyrdquo British Journal of Sports Medicine vol 36no 2 pp 135ndash140 2002
[7] S Sulheim I Holme A Roslashdven A Ekeland and R BahrldquoRisk factors for injuries in alpine skiing telemark skiing andsnowboardingmdashcase-control studyrdquo British Journal of SportsMedicine vol 45 no 16 pp 1303ndash1309 2011
[8] S Kim N K Endres R J Johnson C F Ettlinger andJ E Shealy ldquoSnowboarding injuries trends over time andcomparisons with alpine skiing injuriesrdquoThe American Journalof Sports Medicine vol 40 no 4 pp 770ndash776 2012
[9] M Burtscher M Flatz R Sommersacher et al OsterreichischeSkiunfallerhebung Wintersaison 20022003 Osterreichischen
12 Computational and Mathematical Methods in Medicine
Skiverbandes in Kooperation mit dem Institut fur Sportwissen-schaften der Universitat Innsbruck 2003
[10] C Goulet G Regnier G Grimard P Valois and P VilleneuveldquoRisk factors associated with alpine skiing injuries in childrena case-control studyrdquoThe American Journal of Sports Medicinevol 27 no 5 pp 644ndash650 1999
[11] E J Bridges F Rouah and K M Johnston ldquoSnowbladinginjuries in Eastern Canadardquo British Journal of Sports Medicinevol 37 no 6 pp 511ndash515 2003
[12] D Ishimaru H Ogawa K Wakahara H Sumi Y Sumi andK Shimizu ldquoHip pads reduce the overall risk of injuries inrecreational snowboardersrdquo British Journal of Sports Medicinevol 46 no 15 pp 1055ndash1058 2012
[13] H Xiang K Kelleher B J Shields K J Brown and G ASmith ldquoSkiing- and snowboarding-related injuries treated inUS emergency departments 2002rdquo Journal of Trauma-InjuryInfection amp Critical Care vol 58 no 1 pp 112ndash118 2005
[14] C Made and L G Elmqvist ldquoA 10-year study of snowboardinjuries in Lapland Swedenrdquo Scandinavian Journal of Medicineand Science in Sports vol 14 no 2 pp 128ndash133 2004
[15] E Aschauer E Ritter and H ReschWintersport Unfallstatistik20022003 Universitatsklinik fur Unfallchirurgie und Sport-traumatologie Salzburg 2003
[16] T M Davidson and A T Laliotis ldquoSnowboarding injuries afour-year study with comparison with alpine ski injuriesrdquo TheWestern Journal of Medicine vol 164 no 3 pp 231ndash237 1996
[17] J Howe The New Skiing Mechanics McIntire PublishingWaterford UK 2nd edition 2001
[18] Y Urabe M Ochi K Onari and Y Ikuta ldquoAnterior cruciateligament injury in recreational alpine skiers analysis of mech-anisms and strategy for preventionrdquo Journal of OrthopaedicScience vol 7 no 1 pp 1ndash5 2002
[19] S M Maxwell and M L Hull ldquoMeasurement of strength andloading variables on the knee during alpine skiingrdquo Journal ofBiomechanics vol 22 no 6-7 pp 609ndash624 1989
[20] T P Quinn and C D Mote Jr ldquoPrediction of the loading alongthe leg during snow skiingrdquo Journal of Biomechanics vol 25 no6 pp 609ndash625 1992
[21] C Raschner E Muller and H Schwameder ldquoKinematic andkinetic analysis of slalom turns as a basis for the development ofspecific training methods to improve strength and endurancerdquoin Science and Skiing EMullerH Schwameder E Kornexl andC Raschner Eds pp 251ndash261 Chapman amp Hall CambridgeMass USA 1997
[22] M Brodie A Walmsley and W Page ldquoFusion motion capturea prototype system using inertial measurement units and GPSfor the biomechanical analysis of ski racingrdquo Sports Technologyvol 1 pp 17ndash28 2008
[23] M Klous E Muller and H Schwameder ldquoThree-dimensionalknee joint loading in alpine skiing a comparison between acarved and a skidded turnrdquo Journal of Applied Biomechanics vol28 no 6 pp 655ndash664 2012
[24] F Vaverka S Vodickova and M Elfmark ldquoKinetic analysis ofski turns based on measured ground reaction forcesrdquo Journal ofApplied Biomechanics vol 28 no 1 pp 41ndash47 2012
[25] L Read and W Herzog ldquoExternal loading at the knee joint forlanding movements in alpine skiingrdquo International Journal ofSport Biomechanics vol 8 pp 62ndash80 1992
[26] W Nachbauer P Kaps B Nigg et al ldquoA video technique forobtaining 3-D coordinates in alpine skiingrdquo Journal of AppliedBiomechanics vol 12 no 1 pp 104ndash115 1996
[27] B Knunz W Nachbauer K Schindelwig and F BrunnerldquoForces andmoments at the boot sole during snowboardingrdquo inScience and Skiing II E Muller H Schwameder C Raschner SLindinger and E Kornexl Eds pp 242ndash249 Kovac HamburgGermany 2001
[28] A Kruger P McAlpine F Borrani and J Edelmann-NusserldquoDetermination of three-dimensional joint loading within thelower extremities in snowboardingrdquo Proceedings of the Insti-tution of Mechanical Engineers H Journal of Engineering inMedicine vol 226 no 2 pp 170ndash175 2012
[29] M Klous EMuller andH Schwameder ldquoCollecting kinematicdata on a skisnowboard track with panning tilting and zoom-ing cameras is there sufficient accuracy for a biomechanicalanalysisrdquo Journal of Sports Sciences vol 28 no 12 pp 1345ndash1352 2010
[30] A Cappozzo F Catani A Leardini M G Benedetti and UDella Croce ldquoPosition and orientation in space of bones duringmovement experimental artefactsrdquo Clinical Biomechanics vol11 no 2 pp 90ndash100 1996
[31] V Drenk ldquoPanningmdashZusatzprogramm zur Behandlungschwenk- und neigbarer und in ihrere brennweite variierbarerKameras in Peak3DmdashDokumentationrdquo Institut fur Ange-wandte Traningswissenschaften e V Leipzig Germany 1993
[32] V Drenk ldquoBildmeszligverfahren fur schwenk-und neigbaresowie in ihrer Brennweite variierbare Kamerasrdquo Zeitschrift furAngewandte Trainingswissenschaft vol 1 pp 130ndash142 1994
[33] BM Nigg andWHerzog Biomechanics of theMusculo-skeletalSystem John Wiley amp Sons New York NY USA 3rd edition2007
[34] G Stricker P Scheiber E Lindenhofer and E MullerldquoDetermination of forces in alpine skiing and snowboardingvalidation of a mobile data acquisition systemrdquo EuropeanJournal of Sport Science vol 10 no 1 pp 31ndash41 2010
[35] D G E Robertson G E Caldwell J Hamill G Kamen andS N Whittlesey Research Methods in Biomechanics HumanKinetics Champaign Ill USA 2004
[36] V M Zatsiorsky Kinematics of Human Motion HumanKinetics Champaign Ill USA 1998
[37] R M Ehrig W R Taylor G N Duda and M O HellerldquoA survey of formal methods for determining the centre ofrotation of ball jointsrdquo Journal of Biomechanics vol 39 no 15pp 2798ndash2809 2006
[38] M R Yeadon ldquoThe simulation of aerial movement II Amathematical inertia model of the human bodyrdquo Journal ofBiomechanics vol 23 no 1 pp 67ndash74 1990
[39] W T Dempster ldquoSpace requirements of the seated operatorrdquoWADC Technical Report TR-55ndash159 Wright-Patterson AirForce Base Wright-Patterson Ohio USA 1955
[40] E Muller ldquoBiomechanische Analysen moderner alpinerSkilauftechniken in unterschiedlichen Schnee- Gelande-und Pistensituationenrdquo in Biomechanik der Sportarten Bd2biomechanik des alpinen skilaufs F Fetz and E Muller Eds pp1ndash49 Ferdinand Enke Stuttgart Germany 1991
[41] C Raschner C Schiefermuller G Zallinger E Hofer FBrunner and E Muller ldquoCarving turns versus traditionalparallel turnsmdasha comparative biomechanical analysisrdquo inScience and Skiing II E Muller H Schwameder C RaschnerS Lindinger and E Kornexl Eds pp 203ndash217 Dr KovacHamburg Germany 2001
[42] GWagnerMesstechnischeDifferzierung von genschnittenen undgerutschten Kurven im alpine Skilauf [MS thesis] University ofSalzburg 2006
Computational and Mathematical Methods in Medicine 13
[43] E Muller M Klous and G Wagner ldquoBiomechanical aspectsof turning techniques in alpine skiingrdquo in Science and SportsBridging the Gap T Reilly Ed pp 135ndash142 Shaker PublishingBV Maastricht The Netherlands 2008
[44] B Knunz W Nachbauer M Mossner K Schindelwig andF Brunner ldquoTrack analysis of giant slalom turns of WorldCup racersrdquo in Proceedings of the 5th Annual Congress of theEuropean College of Sport Science (ECSS rsquo00) pp 399ndash401Jyvaskyla Finland 2000
[45] S Delorme S Tavoularis and M Lamontagne ldquoKinematics ofthe ankle joint complex in snowboardingrdquo Journal of AppliedBiomechanics vol 21 no 4 pp 394ndash403 2005
[46] S T McCaw and P DeVita ldquoErrors in alignment of center ofpressure and foot coordinates affect predicted lower extremitytorquesrdquo Journal of Biomechanics vol 28 no 8 pp 985ndash9881995
Computational and Mathematical Methods in Medicine 11
the current study The quality of the snow the technicaland physical capability of the skier or snowboarder andthe large number of skiers and snowboarders at the slopecould explain the many injuries that occur in skiing andsnowboarding The skier and snowboarder in the currentstudy carried additional equipment to allow measurementof ground reaction forces This equipment influenced theirweight and their standing heightWith their level of expertisethe skier and snowboarder did not report any influenceof this equipment Nevertheless the equipment might haveinfluenced their technique and performance Additionallythe differences in stiffness between ski and snowboard bootscould have influenced the results Due to the stiff ski bootpart of the loading might have been transferred to theboot and thereby reduced the ankle joint in skiing Inversedynamic calculations did not allow determining how muchof the ankle joint was transferred to the ski boot Hencethis could have caused overestimation of the ankle joint inskiing However where the current results showed largerankle joint in snowboarding the difference in ankle jointbetween skiing and snowboarding would have even beengreater if the ankle joint in skiing was overestimated Whencurrent results showed larger ankle joint in skiing thesedifferences might not have been as profound Both situationssupport the research hypothesis Also the magnitudes ofthe ankle joint forces and moments in skiing might havebeen lower but it is not to expect that the time patternswere influenced Furthermore the kinematic setup allowed aski and snowboard turn to be performed with similar radiibut different velocities The centripetal force (119865
119888) in a turn
is influenced by the velocity (119865119888= 119898V2119903) Although the
velocity in snowboarding was lower than in skiing the ankleand knee joint forces and moments were not consistentlylower than in skiing We speculate that if the snowboardturn was performed with higher velocities the forces andmoments at the ankle and knee joint would further increasedue to an increase of the centripetal force Furthermorevideos and data of ground reaction forces throughout thecollected data were similar Nevertheless the findings shouldbe interpreted with caution due to the single subject designAdditionally even though the applied method shows a goodaccuracy for on-snow data collection the results of inversedynamic calculations depend strongly on the accuracy of theinput data As is shown by McCaw amp DeVita [46] errorsin the input data are propagated in the inverse dynamicsprocedures thereby reducing the accuracy of the resultscalculated using this procedure Finally it is important toemphasise that we calculated forces and moments duringsuccessful turns which are not representative of the forcesand moments during unsuccessful turns that result in fallingandor injury
5 Conclusion
The expected higher ankle joint loading in snowboardingand higher knee joint loading in skiing that was based onreported injury statistics in the lower extremities in skiingand snowboarding and the differences in position technique
and equipment (soft boot versus hard boot) could not beconfirmed Ankle joint loading was not consistently greaterin snowboarding than in skiing and vice versa for the kneejoint loading When comparing skiing and snowboardingdifferentiationwas required between forces andmoments thedirection of the forces and moments and the phase of theturn thatwas consideredHowever there seemed to be a trendthat forces were larger in skiing and moments showed largefluctuations (loading-unloading) whereas in snowboardinghigh moments with a more consistent pattern were observedIn future research it is important to increase the number ofparticipants in the study and study joint loading of variousturning techniques
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors thank ski company Atomic for providing the testequipment They appreciate the helpful discussions with DrJosef Kroll
References
[1] K Grabler and G J Stirnweis ldquoWirstschaftsbericht derSeilbahnenmdashTrends Winter 2011-2011rdquo WKO die Seilbahnen2011 httpportalwkoatwkformat detailwkangid=1ampstid=621545ampdstid=329ampopennavid=0
[2] R Schonbachler and G Scharer Fakten und Zahlen zurSchweizer Seilbahbranche Seilbahnen Schweiz 2012 httpwwwseilbahnenorgdeBrancheFakten-ZahlenFakten-Zah-len
[3] N Laplante ldquo2008-2009 Canadian Skier and SnowboarderFacts and Statsrdquo 2009 httpxcskiorgnews200920Facts20and20Stats20final20draftpdf
[4] M KlousThree-dimensional joint loading on the lower extremi-ties in alpine skiing and snowboarding [PhD thesis] Universityof Salzburg Salzburg Austria 2007
[5] S Corra A Conci G Conforti G Sacco and F de GiorgildquoSkiing and snowboarding injuries and their impact on theemergency care system in South Tyrol a restrospective analysisfor the winter season 2001ndash2002rdquo Injury Control and SafetyPromotion vol 11 no 4 pp 281ndash285 2004
[6] M Langran and S Selvaraj ldquoSnow sports injuries in Scotlanda case-control studyrdquo British Journal of Sports Medicine vol 36no 2 pp 135ndash140 2002
[7] S Sulheim I Holme A Roslashdven A Ekeland and R BahrldquoRisk factors for injuries in alpine skiing telemark skiing andsnowboardingmdashcase-control studyrdquo British Journal of SportsMedicine vol 45 no 16 pp 1303ndash1309 2011
[8] S Kim N K Endres R J Johnson C F Ettlinger andJ E Shealy ldquoSnowboarding injuries trends over time andcomparisons with alpine skiing injuriesrdquoThe American Journalof Sports Medicine vol 40 no 4 pp 770ndash776 2012
[9] M Burtscher M Flatz R Sommersacher et al OsterreichischeSkiunfallerhebung Wintersaison 20022003 Osterreichischen
12 Computational and Mathematical Methods in Medicine
Skiverbandes in Kooperation mit dem Institut fur Sportwissen-schaften der Universitat Innsbruck 2003
[10] C Goulet G Regnier G Grimard P Valois and P VilleneuveldquoRisk factors associated with alpine skiing injuries in childrena case-control studyrdquoThe American Journal of Sports Medicinevol 27 no 5 pp 644ndash650 1999
[11] E J Bridges F Rouah and K M Johnston ldquoSnowbladinginjuries in Eastern Canadardquo British Journal of Sports Medicinevol 37 no 6 pp 511ndash515 2003
[12] D Ishimaru H Ogawa K Wakahara H Sumi Y Sumi andK Shimizu ldquoHip pads reduce the overall risk of injuries inrecreational snowboardersrdquo British Journal of Sports Medicinevol 46 no 15 pp 1055ndash1058 2012
[13] H Xiang K Kelleher B J Shields K J Brown and G ASmith ldquoSkiing- and snowboarding-related injuries treated inUS emergency departments 2002rdquo Journal of Trauma-InjuryInfection amp Critical Care vol 58 no 1 pp 112ndash118 2005
[14] C Made and L G Elmqvist ldquoA 10-year study of snowboardinjuries in Lapland Swedenrdquo Scandinavian Journal of Medicineand Science in Sports vol 14 no 2 pp 128ndash133 2004
[15] E Aschauer E Ritter and H ReschWintersport Unfallstatistik20022003 Universitatsklinik fur Unfallchirurgie und Sport-traumatologie Salzburg 2003
[16] T M Davidson and A T Laliotis ldquoSnowboarding injuries afour-year study with comparison with alpine ski injuriesrdquo TheWestern Journal of Medicine vol 164 no 3 pp 231ndash237 1996
[17] J Howe The New Skiing Mechanics McIntire PublishingWaterford UK 2nd edition 2001
[18] Y Urabe M Ochi K Onari and Y Ikuta ldquoAnterior cruciateligament injury in recreational alpine skiers analysis of mech-anisms and strategy for preventionrdquo Journal of OrthopaedicScience vol 7 no 1 pp 1ndash5 2002
[19] S M Maxwell and M L Hull ldquoMeasurement of strength andloading variables on the knee during alpine skiingrdquo Journal ofBiomechanics vol 22 no 6-7 pp 609ndash624 1989
[20] T P Quinn and C D Mote Jr ldquoPrediction of the loading alongthe leg during snow skiingrdquo Journal of Biomechanics vol 25 no6 pp 609ndash625 1992
[21] C Raschner E Muller and H Schwameder ldquoKinematic andkinetic analysis of slalom turns as a basis for the development ofspecific training methods to improve strength and endurancerdquoin Science and Skiing EMullerH Schwameder E Kornexl andC Raschner Eds pp 251ndash261 Chapman amp Hall CambridgeMass USA 1997
[22] M Brodie A Walmsley and W Page ldquoFusion motion capturea prototype system using inertial measurement units and GPSfor the biomechanical analysis of ski racingrdquo Sports Technologyvol 1 pp 17ndash28 2008
[23] M Klous E Muller and H Schwameder ldquoThree-dimensionalknee joint loading in alpine skiing a comparison between acarved and a skidded turnrdquo Journal of Applied Biomechanics vol28 no 6 pp 655ndash664 2012
[24] F Vaverka S Vodickova and M Elfmark ldquoKinetic analysis ofski turns based on measured ground reaction forcesrdquo Journal ofApplied Biomechanics vol 28 no 1 pp 41ndash47 2012
[25] L Read and W Herzog ldquoExternal loading at the knee joint forlanding movements in alpine skiingrdquo International Journal ofSport Biomechanics vol 8 pp 62ndash80 1992
[26] W Nachbauer P Kaps B Nigg et al ldquoA video technique forobtaining 3-D coordinates in alpine skiingrdquo Journal of AppliedBiomechanics vol 12 no 1 pp 104ndash115 1996
[27] B Knunz W Nachbauer K Schindelwig and F BrunnerldquoForces andmoments at the boot sole during snowboardingrdquo inScience and Skiing II E Muller H Schwameder C Raschner SLindinger and E Kornexl Eds pp 242ndash249 Kovac HamburgGermany 2001
[28] A Kruger P McAlpine F Borrani and J Edelmann-NusserldquoDetermination of three-dimensional joint loading within thelower extremities in snowboardingrdquo Proceedings of the Insti-tution of Mechanical Engineers H Journal of Engineering inMedicine vol 226 no 2 pp 170ndash175 2012
[29] M Klous EMuller andH Schwameder ldquoCollecting kinematicdata on a skisnowboard track with panning tilting and zoom-ing cameras is there sufficient accuracy for a biomechanicalanalysisrdquo Journal of Sports Sciences vol 28 no 12 pp 1345ndash1352 2010
[30] A Cappozzo F Catani A Leardini M G Benedetti and UDella Croce ldquoPosition and orientation in space of bones duringmovement experimental artefactsrdquo Clinical Biomechanics vol11 no 2 pp 90ndash100 1996
[31] V Drenk ldquoPanningmdashZusatzprogramm zur Behandlungschwenk- und neigbarer und in ihrere brennweite variierbarerKameras in Peak3DmdashDokumentationrdquo Institut fur Ange-wandte Traningswissenschaften e V Leipzig Germany 1993
[32] V Drenk ldquoBildmeszligverfahren fur schwenk-und neigbaresowie in ihrer Brennweite variierbare Kamerasrdquo Zeitschrift furAngewandte Trainingswissenschaft vol 1 pp 130ndash142 1994
[33] BM Nigg andWHerzog Biomechanics of theMusculo-skeletalSystem John Wiley amp Sons New York NY USA 3rd edition2007
[34] G Stricker P Scheiber E Lindenhofer and E MullerldquoDetermination of forces in alpine skiing and snowboardingvalidation of a mobile data acquisition systemrdquo EuropeanJournal of Sport Science vol 10 no 1 pp 31ndash41 2010
[35] D G E Robertson G E Caldwell J Hamill G Kamen andS N Whittlesey Research Methods in Biomechanics HumanKinetics Champaign Ill USA 2004
[36] V M Zatsiorsky Kinematics of Human Motion HumanKinetics Champaign Ill USA 1998
[37] R M Ehrig W R Taylor G N Duda and M O HellerldquoA survey of formal methods for determining the centre ofrotation of ball jointsrdquo Journal of Biomechanics vol 39 no 15pp 2798ndash2809 2006
[38] M R Yeadon ldquoThe simulation of aerial movement II Amathematical inertia model of the human bodyrdquo Journal ofBiomechanics vol 23 no 1 pp 67ndash74 1990
[39] W T Dempster ldquoSpace requirements of the seated operatorrdquoWADC Technical Report TR-55ndash159 Wright-Patterson AirForce Base Wright-Patterson Ohio USA 1955
[40] E Muller ldquoBiomechanische Analysen moderner alpinerSkilauftechniken in unterschiedlichen Schnee- Gelande-und Pistensituationenrdquo in Biomechanik der Sportarten Bd2biomechanik des alpinen skilaufs F Fetz and E Muller Eds pp1ndash49 Ferdinand Enke Stuttgart Germany 1991
[41] C Raschner C Schiefermuller G Zallinger E Hofer FBrunner and E Muller ldquoCarving turns versus traditionalparallel turnsmdasha comparative biomechanical analysisrdquo inScience and Skiing II E Muller H Schwameder C RaschnerS Lindinger and E Kornexl Eds pp 203ndash217 Dr KovacHamburg Germany 2001
[42] GWagnerMesstechnischeDifferzierung von genschnittenen undgerutschten Kurven im alpine Skilauf [MS thesis] University ofSalzburg 2006
Computational and Mathematical Methods in Medicine 13
[43] E Muller M Klous and G Wagner ldquoBiomechanical aspectsof turning techniques in alpine skiingrdquo in Science and SportsBridging the Gap T Reilly Ed pp 135ndash142 Shaker PublishingBV Maastricht The Netherlands 2008
[44] B Knunz W Nachbauer M Mossner K Schindelwig andF Brunner ldquoTrack analysis of giant slalom turns of WorldCup racersrdquo in Proceedings of the 5th Annual Congress of theEuropean College of Sport Science (ECSS rsquo00) pp 399ndash401Jyvaskyla Finland 2000
[45] S Delorme S Tavoularis and M Lamontagne ldquoKinematics ofthe ankle joint complex in snowboardingrdquo Journal of AppliedBiomechanics vol 21 no 4 pp 394ndash403 2005
[46] S T McCaw and P DeVita ldquoErrors in alignment of center ofpressure and foot coordinates affect predicted lower extremitytorquesrdquo Journal of Biomechanics vol 28 no 8 pp 985ndash9881995
12 Computational and Mathematical Methods in Medicine
Skiverbandes in Kooperation mit dem Institut fur Sportwissen-schaften der Universitat Innsbruck 2003
[10] C Goulet G Regnier G Grimard P Valois and P VilleneuveldquoRisk factors associated with alpine skiing injuries in childrena case-control studyrdquoThe American Journal of Sports Medicinevol 27 no 5 pp 644ndash650 1999
[11] E J Bridges F Rouah and K M Johnston ldquoSnowbladinginjuries in Eastern Canadardquo British Journal of Sports Medicinevol 37 no 6 pp 511ndash515 2003
[12] D Ishimaru H Ogawa K Wakahara H Sumi Y Sumi andK Shimizu ldquoHip pads reduce the overall risk of injuries inrecreational snowboardersrdquo British Journal of Sports Medicinevol 46 no 15 pp 1055ndash1058 2012
[13] H Xiang K Kelleher B J Shields K J Brown and G ASmith ldquoSkiing- and snowboarding-related injuries treated inUS emergency departments 2002rdquo Journal of Trauma-InjuryInfection amp Critical Care vol 58 no 1 pp 112ndash118 2005
[14] C Made and L G Elmqvist ldquoA 10-year study of snowboardinjuries in Lapland Swedenrdquo Scandinavian Journal of Medicineand Science in Sports vol 14 no 2 pp 128ndash133 2004
[15] E Aschauer E Ritter and H ReschWintersport Unfallstatistik20022003 Universitatsklinik fur Unfallchirurgie und Sport-traumatologie Salzburg 2003
[16] T M Davidson and A T Laliotis ldquoSnowboarding injuries afour-year study with comparison with alpine ski injuriesrdquo TheWestern Journal of Medicine vol 164 no 3 pp 231ndash237 1996
[17] J Howe The New Skiing Mechanics McIntire PublishingWaterford UK 2nd edition 2001
[18] Y Urabe M Ochi K Onari and Y Ikuta ldquoAnterior cruciateligament injury in recreational alpine skiers analysis of mech-anisms and strategy for preventionrdquo Journal of OrthopaedicScience vol 7 no 1 pp 1ndash5 2002
[19] S M Maxwell and M L Hull ldquoMeasurement of strength andloading variables on the knee during alpine skiingrdquo Journal ofBiomechanics vol 22 no 6-7 pp 609ndash624 1989
[20] T P Quinn and C D Mote Jr ldquoPrediction of the loading alongthe leg during snow skiingrdquo Journal of Biomechanics vol 25 no6 pp 609ndash625 1992
[21] C Raschner E Muller and H Schwameder ldquoKinematic andkinetic analysis of slalom turns as a basis for the development ofspecific training methods to improve strength and endurancerdquoin Science and Skiing EMullerH Schwameder E Kornexl andC Raschner Eds pp 251ndash261 Chapman amp Hall CambridgeMass USA 1997
[22] M Brodie A Walmsley and W Page ldquoFusion motion capturea prototype system using inertial measurement units and GPSfor the biomechanical analysis of ski racingrdquo Sports Technologyvol 1 pp 17ndash28 2008
[23] M Klous E Muller and H Schwameder ldquoThree-dimensionalknee joint loading in alpine skiing a comparison between acarved and a skidded turnrdquo Journal of Applied Biomechanics vol28 no 6 pp 655ndash664 2012
[24] F Vaverka S Vodickova and M Elfmark ldquoKinetic analysis ofski turns based on measured ground reaction forcesrdquo Journal ofApplied Biomechanics vol 28 no 1 pp 41ndash47 2012
[25] L Read and W Herzog ldquoExternal loading at the knee joint forlanding movements in alpine skiingrdquo International Journal ofSport Biomechanics vol 8 pp 62ndash80 1992
[26] W Nachbauer P Kaps B Nigg et al ldquoA video technique forobtaining 3-D coordinates in alpine skiingrdquo Journal of AppliedBiomechanics vol 12 no 1 pp 104ndash115 1996
[27] B Knunz W Nachbauer K Schindelwig and F BrunnerldquoForces andmoments at the boot sole during snowboardingrdquo inScience and Skiing II E Muller H Schwameder C Raschner SLindinger and E Kornexl Eds pp 242ndash249 Kovac HamburgGermany 2001
[28] A Kruger P McAlpine F Borrani and J Edelmann-NusserldquoDetermination of three-dimensional joint loading within thelower extremities in snowboardingrdquo Proceedings of the Insti-tution of Mechanical Engineers H Journal of Engineering inMedicine vol 226 no 2 pp 170ndash175 2012
[29] M Klous EMuller andH Schwameder ldquoCollecting kinematicdata on a skisnowboard track with panning tilting and zoom-ing cameras is there sufficient accuracy for a biomechanicalanalysisrdquo Journal of Sports Sciences vol 28 no 12 pp 1345ndash1352 2010
[30] A Cappozzo F Catani A Leardini M G Benedetti and UDella Croce ldquoPosition and orientation in space of bones duringmovement experimental artefactsrdquo Clinical Biomechanics vol11 no 2 pp 90ndash100 1996
[31] V Drenk ldquoPanningmdashZusatzprogramm zur Behandlungschwenk- und neigbarer und in ihrere brennweite variierbarerKameras in Peak3DmdashDokumentationrdquo Institut fur Ange-wandte Traningswissenschaften e V Leipzig Germany 1993
[32] V Drenk ldquoBildmeszligverfahren fur schwenk-und neigbaresowie in ihrer Brennweite variierbare Kamerasrdquo Zeitschrift furAngewandte Trainingswissenschaft vol 1 pp 130ndash142 1994
[33] BM Nigg andWHerzog Biomechanics of theMusculo-skeletalSystem John Wiley amp Sons New York NY USA 3rd edition2007
[34] G Stricker P Scheiber E Lindenhofer and E MullerldquoDetermination of forces in alpine skiing and snowboardingvalidation of a mobile data acquisition systemrdquo EuropeanJournal of Sport Science vol 10 no 1 pp 31ndash41 2010
[35] D G E Robertson G E Caldwell J Hamill G Kamen andS N Whittlesey Research Methods in Biomechanics HumanKinetics Champaign Ill USA 2004
[36] V M Zatsiorsky Kinematics of Human Motion HumanKinetics Champaign Ill USA 1998
[37] R M Ehrig W R Taylor G N Duda and M O HellerldquoA survey of formal methods for determining the centre ofrotation of ball jointsrdquo Journal of Biomechanics vol 39 no 15pp 2798ndash2809 2006
[38] M R Yeadon ldquoThe simulation of aerial movement II Amathematical inertia model of the human bodyrdquo Journal ofBiomechanics vol 23 no 1 pp 67ndash74 1990
[39] W T Dempster ldquoSpace requirements of the seated operatorrdquoWADC Technical Report TR-55ndash159 Wright-Patterson AirForce Base Wright-Patterson Ohio USA 1955
[40] E Muller ldquoBiomechanische Analysen moderner alpinerSkilauftechniken in unterschiedlichen Schnee- Gelande-und Pistensituationenrdquo in Biomechanik der Sportarten Bd2biomechanik des alpinen skilaufs F Fetz and E Muller Eds pp1ndash49 Ferdinand Enke Stuttgart Germany 1991
[41] C Raschner C Schiefermuller G Zallinger E Hofer FBrunner and E Muller ldquoCarving turns versus traditionalparallel turnsmdasha comparative biomechanical analysisrdquo inScience and Skiing II E Muller H Schwameder C RaschnerS Lindinger and E Kornexl Eds pp 203ndash217 Dr KovacHamburg Germany 2001
[42] GWagnerMesstechnischeDifferzierung von genschnittenen undgerutschten Kurven im alpine Skilauf [MS thesis] University ofSalzburg 2006
Computational and Mathematical Methods in Medicine 13
[43] E Muller M Klous and G Wagner ldquoBiomechanical aspectsof turning techniques in alpine skiingrdquo in Science and SportsBridging the Gap T Reilly Ed pp 135ndash142 Shaker PublishingBV Maastricht The Netherlands 2008
[44] B Knunz W Nachbauer M Mossner K Schindelwig andF Brunner ldquoTrack analysis of giant slalom turns of WorldCup racersrdquo in Proceedings of the 5th Annual Congress of theEuropean College of Sport Science (ECSS rsquo00) pp 399ndash401Jyvaskyla Finland 2000
[45] S Delorme S Tavoularis and M Lamontagne ldquoKinematics ofthe ankle joint complex in snowboardingrdquo Journal of AppliedBiomechanics vol 21 no 4 pp 394ndash403 2005
[46] S T McCaw and P DeVita ldquoErrors in alignment of center ofpressure and foot coordinates affect predicted lower extremitytorquesrdquo Journal of Biomechanics vol 28 no 8 pp 985ndash9881995
Computational and Mathematical Methods in Medicine 13
[43] E Muller M Klous and G Wagner ldquoBiomechanical aspectsof turning techniques in alpine skiingrdquo in Science and SportsBridging the Gap T Reilly Ed pp 135ndash142 Shaker PublishingBV Maastricht The Netherlands 2008
[44] B Knunz W Nachbauer M Mossner K Schindelwig andF Brunner ldquoTrack analysis of giant slalom turns of WorldCup racersrdquo in Proceedings of the 5th Annual Congress of theEuropean College of Sport Science (ECSS rsquo00) pp 399ndash401Jyvaskyla Finland 2000
[45] S Delorme S Tavoularis and M Lamontagne ldquoKinematics ofthe ankle joint complex in snowboardingrdquo Journal of AppliedBiomechanics vol 21 no 4 pp 394ndash403 2005
[46] S T McCaw and P DeVita ldquoErrors in alignment of center ofpressure and foot coordinates affect predicted lower extremitytorquesrdquo Journal of Biomechanics vol 28 no 8 pp 985ndash9881995
