A Gender Comparison of Lower ExtremityA Gender Comparison of Lower Extremity Landing Biomechanics Utilizing Different Tasks:

Implications in ACL Injury Researchp j y

Adam HernandezErik Swartz, PhD ATCS a t , CDain LaRoche, PhD

Anterior Cruciate LigamentAnterior Cruciate Ligament• One of 4 main ligaments in the knee• Provides stability within the kneeProvides stability within the knee • Injury of ACL can severely inhibit athletic

performance• Typically surgically repaired• 6 month rehabilitation period

ProblemProblem

• Female athletes areFemale athletes are 4 to 6 times more likely to sustain an yACL injury than their male counterparts.4,5,6

IntroductionIntroduction• Motion capture and electromyography (EMG) have been used

to examine differences in males and females:– Studies found that women land with a straighter knee than men– Studies found that women land with a straighter knee than men

and are also quadriceps dominant.3,4, 9, 10

• Methods used in these Studies:– Drop landings from a height standard (i.e., 60 cm)1,7

– Functional tasks (i.e., vertical jump).2,3,8, 9

• Standard heights may not be appropriate for all subjects and may elicit abnormal landing biomechanics in some subjects.2

Purpose of This StudyPurpose of This Study• Examine gender differences in leg

biomechanics during different landingbiomechanics during different landing tasks, a drop landing and a functional vertical jump landingvertical jump landing.

VS.Female Male

SubjectsSubjects•17 subjects: 9 Female, 8 Male

•No history of significant knee injury

•Recreationally active

•Between 18 and 24 years old•No history of significant knee injury

•Recruited from UNH and community

•Between 18 and 24 years old

Subject Demographics (Average±SD)

Male Female

Age (years) 21 50�1 20 20 56�1 24Age (years) 21.50�1.20 20.56�1.24Height (cm) 173.25�2.8

2161.11�6.01

Weight (kg) 75.58�7.92 57.58�11.65Max Vertical Jump (cm) 60.97�5.81 33.13�9.76

InstrumentsInstruments•6 camera, Hi-Res 3-D Kinematic Motion Capture System

–EVaRT version 7 –Motion Analysis Inc., Santa Rosa, CA–Sampling Rate 120 Hz

•EMG Data –EMG 100. BIOPAC System Inc., Santa Barbara, CA

S li R t f 1080 MH–Sampling Rate of 1080 MHz

•Force PlatformModel OR6 7 2000; Advanced Technologies Ins–Model OR6-7-2000; Advanced Technologies Ins.

Watertown, MA–Sampling rate 960 Hz

Methods and ProcedureMethods and Procedure• Consent• Health history questionnairey q• Laboratory clothing and shoes• 5-minute treadmill/stationary bike warm-up• 12-retro-reflective markers placed on dominant leg• 7 Electromyography (EMG) markers placed on

quadriceps (quad) and hamstrings (ham) of dominantquadriceps (quad) and hamstrings (ham) of dominant leg.

ProcedureProcedure• 2 landing tasks, random

order– Self-initiated vertical jump (VJ)– Drop landing (DL)

• Subjects completed 6 successful trials in each conditioncondition

• Success:– Right foot on force plate– Balance

ProcedureProcedure

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ProcedureProcedure

Q i kTi ™ d QuickTime™ and aMicrosoft Video 1 decompressorare needed to see this picture.

Data AnalysisData Analysis• Dependent Variable:

– Maximum knee flexion (MKF) angle during landing – Pre and post quadriceps and hamstring activation

• Individual trials exported (Excel)– Group means

• Import into SPSS software 13.0

• Two-way ANOVA (gender x task). – Alpha level= .05 or lessAlpha level .05 or less

Kinematics ResultsKinematics ResultsMaximum Knee FlexionMaximum Knee Flexion

60708090 *

102030405060

Deg

rees males

females

010

vertical jump drop landing

Condition

• Drop Landing– Male= 75.55± 8.46

F l 67 52 6 31

•Vertical Jump–Male= 83.38± 18.90

* (P = .001)

– Female= 67.52± 6.31 –Female= 66.22±15.01

EMG ResultsEMG Results• In both the VJ and DJ, no differences were

found in EMG activation between males and females in the:– Quadriceps (quad)– Hamstrings (ham)Hamstrings (ham)– Quadriceps/ Hamstrings ration (quad/ham)

Discussion of ResultsDiscussion of Results• No gender difference in muscle activation of quad,

ham, and quad/ham ratio before or after landing.Chappell et al3 4 reported women were quad dominant– Chappell et al3,4 reported women were quad dominant

• MKF similar between gender in DL.H ston8 and others reported females landed ith less knee– Huston8 and others reported females landed with less knee flexion from standard height drops (40, 60 cm).

• Gender differences existed during the VJ Men had• Gender differences existed during the VJ. Men had greater MKF than women.– Early study conducted by Swartz et al9 found no gender

differences during vertical jumpdifferences during vertical jump

• Why the conflicting results?

ConclusionConclusion• On average men are capable of jumping at

the same height of the drop jump height,the same height of the drop jump height, while females can only jump half of the height.

Gender Mean Max Vertical Jump (cm) ±SDMale 60.97 ±5.81

• Researchers should continue to question

Female 33.13 ±9.76

Researchers should continue to question the appropriateness of heights when creating research methodology.

Thank YouThank You• Hamel Center for Undergraduate

ResearchResearch

D E ik S t PhD• Dr. Erik Swartz, PhD

• Dr. Dain LaRoche, PhD

Questions?Questions?

ReferencesReferences1. Barber-Westin S.D., Fleckenstein C., Noyes F.R., Walsh C., et al. “ The Drop-Jump Screening Test:

Difference in Lower Limb Control By Gender and Effect of Neuromuscular Training in Female Athletes.” American Journal of Sports Medicine. 33: 197, 2005.

2. Caster, B. Bates, B. “The Assessment of Mechanical and Neuromuscular Response Strategies During Landing.” Medicine and Science in Sports and Exercise. 27(5):736-734 (1995).

3. Chappell, J., et al. “A Comparison of Knee Kinetics Between Male and Female Recreational Athletes in Stop-Jump Tasks.” The American Journal of Sports Medicine. 30(2): 261-267, 2002.

4. Chappell, J., et al. “Kinematics and Electromyography of Landing Preparation in Vertical Stop-Jump: Risks for Noncontact Anterior Cruciate Ligament Injury.” The American Journal of Sports Medicine. 35: 235-242, 2007.

5. Ford K. R., Hewett T.E., Myer G.D. “Anterior Cruciate Ligament Injuries in Female Athletes: Part 1, Mechanisms and Risk Factors.” American Journal of Sports Medicine. 34: 299, 2006.

6. Ford K. R., Hewett T.E., Myer G.D. “Anterior Cruciate Ligament Injuries in Female Athletes: Part 2, A Meta-Analysis of Neuromuscular Interventions Aimed at Injury Prevention.” American Journal of Sports Medicine. 34: 490, 2006.

7. Hewett, T.E., et al. “Biomechanical Measures of Neuromuscular Control and Valgus Loading of the Knee Predict Anterior Cruciate Ligament Injury Risk in Female Athletes.” American Journal of Sports Medicine. 33: 492-501, 2005.

8. Huston, L.J., et al. “Gender Differences in Knee Angle When Landing From a Drop-Jump.” American Journal of Knee Surgery. 14: 215-220, 2001.

9. Swartz, E., et al. “Effects of Developmental Stage and Sex on Lower Extremity Kinematics and Vertical Ground Reaction Forces During Landing.” Journal of Athletic Training. 40 (1): 9-14, 2005.