Complementary Therapies in Medicine (2014) 22, 662—669
Available online at www.sciencedirect.com
j ourna l ho me pa g e: www.elsev ierhea l th .com/ journa ls /c t im
Muscle utilization patterns vary by skilllevels of the practitioners across specificyoga poses (asanas)
Meng Nia, Kiersten Mooneyb, Anoop Balachandrana,Luca Richardsb, Kysha Harriell a, Joseph F. Signorilea,c,∗
a Laboratory of Neuromuscular Research and Active Aging, Department of Kinesiology and Sports Sciences,University of Miami, Coral Gables, FL, United Statesb Bala Vinyasa Yoga, Naples, FL, United Statesc Miller School of Medicine, Center on Aging, University of Miami, Miami, FL, United StatesAvailable online 30 June 2014
∗ Corresponding author at: Department of Kinesiology and Sport Sciences, University of Miami, 1507 Levante Ave, Max Orovitz, Room 114,Coral Gables, FL 33146, United States. Tel.: +1 305 284 3105; fax: +1 305 284 4183.
PosesChr chair (Utkaasana)DogDWN downward facing dog (Adho Mukha Svanasana)DogUP upward facing dog (Urdhva Mukha Svanasana)FFold forward fold (Uttanasana)HLift halfway lift (Urdhva Mukha Uttanasana)MntDWN mountain pose with arms down (Tadasana)MntUP mountain pose with arms up (Urdhva Has-
tasana)PlnkHI high plank (Dandasana)PlnkLOW low plank (Chaturanga Dandasana)WarNO-DOM non-dominant side warrior 1 pose (Virab-
hadrasana I)WarDOM dominant side warrior 1 pose
Skill levelsADV advanced groupINST instructor groupNOV novice group
Introduction
Yoga, originated in ancient India, integrates physical, men-tal, emotional, and spiritual dimensions to improve theholistic health. The benefits of yoga include: increased mus-cle strength and endurance,1—6 muscle power,7 anaerobicpower,8 flexibility,1,3,5 balance and coordination,1,4 and painattenuation.9,10 However, yoga is not without its detrac-tors. Critics have argued that several poses may go beyondsome practitioners’ capabilities and produce negative con-sequences, such as muscle strains and ligament rupture.11
Yoga postures comprise basic elements such as standing,sitting, forward and backbends, twists, inversions and lying.Each pose is expected to activate specific muscles. To ourknowledge, only one study12 has examined muscle utiliza-tion patterns during specific yoga poses and no studies havequantified variations in muscle activity as practitioners’ skilllevels evolve with practice. As yoga becomes more populararound the globe, understanding these factors may reduce
injuries, provide guidelines for improved progression andcuing, and allow the design of pose sequences which cantarget needs related to specific sports, special populationsand rehabilitation programs.
The purpose of this study was to quantify differencesin muscle activity during different yoga poses by novices(NOV), advanced practitioners (ADV) and instructors (INST).Results can help yoga instructors choose appropriate pos-tures based on students’ skill and fitness levels, allowpractitioners to modify their practice to match their needsand capacities, and provide critical data for prevention andrehabilitation programs designed to treat the needs of ath-letes, the general community, and special populations.
Methods
Participants
Thirty-six Baptiste yoga practitioners using Vinyasa styleparticipated in the study (9 men, 27 women; mean age ± SD,31.6 ± 12.6 years). Subjects were recruited through flyersand personal contacts at yoga studios and wellness centers.To be included in the study an individual must fall into oneof three categories: NOV having practiced for 3—12 months;ADV who had practiced more than 3 years; or INST whopossessed a yoga instructor certification. Additionally, sub-jects must have participated in yoga training for 1—1.5 h atleast once per week for at least three months, must nothave participated regularly in any other exercise program,and must have been capable of completing the study’s yogasequence without assistance. Individuals with musculoskele-tal and neurological impairments or unresolved injurieswere excluded from study participation. Participants wereinformed of experimental procedures and completed a writ-ten consent approved by the University’s Subcommittee forthe Use and Protection of Human Subjects. Participants’characteristics are presented in Table 1. A power analysisusing an effect size of 0.25, ˛ of 5% and power of 95%,yielded a minimal sample size of 27.
Procedures
Participants arrived at the laboratory and completed theconsent form and health questionnaire. They then warmed-up using surya namaskar (sun salutation) A three times andsurya namaskar B twice at a self-determined pace. Next,electrodes were placed on the skin over the muscles ofinterest on participants’ dominant side (32 right-handed/4left-handed). Fourteen muscles were randomly evaluated ontwo separate days. Surface electromyography (EMG) datawere normalized across subjects and collection days, usingEMG results from 3 s maximal voluntary contractions (MVC)targeting each muscle. Following preparation and normal-ization, each subject performed 11 Sun salutation poses(Fig. 1) maintaining each for 15 s. The pose sequences wererandomized for each subject using a random number gener-ator (Microsoft Excel, 2010; Microsoft Corp. Redmond, WA).Each pose was digitally recorded and evaluated by an inde-pendent group of yoga instructors blinded to the subjects’skill level assignments, to confirm each subject’s skill levelclassification. Subjects were asked to avoid doing intensive
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Table 1 Demographics characteristics of the participants by skill levels (mean ± SD).
Fig. 1 The poses of sun salutation sequence. (a) Chair; (b) downward facing dog; (c) halfway lift; (d) forward fold; (e) highplank; (f) low plank; (g) mountain pose with arms up; (h) mountain pose with arms down; (i) upward facing dog; (j) Non-dominantside warrior 1 pose; (k) Dominant side warrior 1 pose. For detailed descriptions of each pose see the Yoga Journal Website athttp://www.yogajournal.com/poses/finder/browse index.
exercise 24 h before the tests. During the test, they weretold to exert their maximal effort and perform each pose tothe best of their abilities.
EMG measurement procedures
The location of the electrodes for each muscle was deter-mined using anatomical landmarks.13 The skin surface ateach site was shaved, rubbed with light abrasive paper, andcleansed with alcohol to remove dead surface tissues andoil that might reduce conductivity. Disposable bipolar elec-trodes (Noraxon USA, Scottsdale, AZ) were then positionedparallel to the underlying muscle fibers, as determined bythe muscles’ pennations.
Raw EMG signals were recorded using a wireless EMGtelemetry system (BTS Bioengineering, Milano, Italy), andthe quality of each muscles’ signal was examined visuallythroughout the data collection. The gain was set at 2.000with band-pass filtering set between 1 and 500 Hz.13 Signalswere sampled at a speed of 1.000 Hz, digitized using a 16-bit A/D converter, amplified (gain = 2000, CMRR > 110 dB at50—60 Hz), and stored on a laboratory computer.
EMG data analysis
EMG signals from each muscle were analyzed using ded-icated Labview Softwarec (National Instruments, Austin,TX). The root mean square of the EMG signal (rmsEMG)
Skill levels of the practitioners 665
Table 2 Significant main effects of pose in muscles without pose × skill level interaction in NrmsEMG.
collected from the third to thirteenth second of the 15 spose period was used as a measure of average muscle activ-ity for each muscle during that pose. Data were normalized(NrmsEMG) using the rmsEMG values collected during themiddle 3 s of each 5 s MVC. MVCs were repeated three timesfor each muscle, with an intervening 30 s passive recovery.14
The activities for obtaining the MVC for each muscle wereestablished in previous studies: biceps brachii (BB),15 tricepsbrachii (Tri),15 anterior deltoid (DeltANT), 16 medial deltoid(DeltMED), 15 pectoralis major sternal head (PECS),17 uppertrapezium (TRAPUP),18 middle trapezium (TRAPMID),18 erec-tor spinae (ES),15 upper rectus abdominis (RAMUP),19 recutsfemoris (RF),20 vastus medialis (VM),20 biceps femoris (RF),21
gastrocnemius lateralis (GastrocLAT),22 and tibialis anterior(TA).22
Statistical analyses
Data were assessed using a 3 (skill level) × 11 (pose)repeated-measures ANOVA for each muscle of the 11 poses.These analyses were designed to examine how differencesin skill level and pose affected muscle utilization pat-terns. When significant main effects or interactions weredetected, Bonferroni post hoc tests were used to determinethe sources. Threshold significance was set at p < 0.05.
Results
Group demographics
No significant differences were detected across groups forany demographic characteristic with the exception of thetime practicing yoga.
Main effect of pose
Significant main effects of pose were detected for all14 muscles except the TRAPMID (Table 2), three showed
significant main effects by skill level, and five showed sig-nificant pose by skill level interactions.
Upper body musclesThe TRAPUP post hoc analysis revealed significantly higherNrmsEMG values for Chr, DogDWN and WarDOM compared toFFold and HLift (p < .003). Post hoc analyses for the BBshowed significantly higher NrmsEMG values for Chr than allother poses except PlnkHI, PlnkLOW and DogUP (p < .043). TheTri showed significantly higher values for PlnkLOW than allother poses except Chr, WarNON-DOM and WarDOM (p < .001) andfor PlnkHI and DogUP compared to HLift and MntDWN (p < .021).
Core musclesPost hoc analysis for the ES showed significantly higher Nrm-sEMG values for Chr, HLift, DogUP, WarNON-DOM and WarDOM
than DogDWN, FFold and MntUP (p < .016).
Lower body musclesThe RF showed significantly higher NrmsEMG values for Chr,DogDWN, PlnkHI and WarDOM compared to FFold (p < .022), andfor DogUP and WarDOM compared to HLift (p < .039). PlnkLOW
and WarNON-DOM showed significantly higher NrmsEMG val-ues than all other poses except PlnkHI, DogUP and WarDOM
(p < .001). The BF produced significantly higher values forChr, PlnkHI, PlnkLOW, DogUP, WarNON-DOM and WarDOM than FFold(p < .032). Finally, the TA showed significantly higher Nrm-sEMG for Chr, DogDWN, PlnkHI, PlnkLOW and WarDOM comparedto FFold and MntDWN (p < .047), and for WarNON-DOM comparedto all other poses except Chr, DogDWN and WarDOM (p < .043).
Main effect of skill level
A significant main effect of group was detected only inVM (p = .027; Fig. 2). Post hoc anlysis revealed significantlyhigher NrmsEMG for INST compared to NOV.
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Fig. 2 Main effect of skill level for muscles where no skilllevel × pose interaction was detected. *Instructor significantlydifferent than novice (p < .049).
Pose by skill level interactions
The 3 (skill level) × 11 (pose) ANOVA showed significantskill level × pose interactions for the PECS (p = .030), DeltANT
Upper body musclesPost hoc analyses revealed significant differences amongskill levels for each pose. For the PECS (Fig. 3a), NOV gen-erated higher NrmsEMG INST in the Chr. For the DeltANT
(Fig. 3b), the values for INST were higher than NOV for FFoldand WarDOM. For the DeltMED (Fig. 3c), Chr and FFold producedhigher NrmsEMG for INST than ADV and NOV, and for DogDWN,WarNON-DOM and WarDOM values were higher for INST than forNOV.
Core musclesFor the RAMUP (Fig. 4a), although there was a significantinteraction, post hoc comparisons revealed no significantdifferences.
Lower body musclesFor the GastrocLAT (Fig. 4b), HLift and WarDOM producedhigher NrmsEMG for INST than NOV and ADV.
Discussion
The principle finding of this study was that different mus-cle groups can be targeted using specific yoga poses andactivation levels are affected by skill levels.
Effect of pose
The targeting of the TRAPUP by Chr, MntUP and WarDOM
can be attributed to the flexing and external rotation ofthe shoulder and retraction of the scapula during theseposes. The most effective exercise for targeting the TRAPUP
is the shoulder shrug.18 Our results indicate activity lev-els of the TRAPUP during Chr, MntUP and WarDOM poses(84.2—97.6% MVC) rivaled that reported for the shrug using
Fig. 3 Significant interaction bewteen pose and skill level forthe (a) pectoralis major sternal head; (b) anterior deltoid; (c)medial deltoid. *Instructor significantly different than novice.**Instructor significantly different than advanced and novice(p < .05).
external loading (119% MVC). The increased NrmsEMG dur-ing these poses without external loading allows improvedperformance while reducing injury potential during trainingprogression.16
The TRAPMID, DogUP, where the shoulders retract with cer-vical extension, may be an effective strengthening exercisegiven its activation level (92.3% ± 44.6% MVC). Supportingthe weight of the upper body and against the tonus of the
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Fig. 4 Significant interaction bewteen pose and skill levelfor the (a) rectus abdominis upper fibers; (b) gastrocnemiuslateralis. **Instructor significantly different than advanced andnovice (p < .05).
chest and abdominal muscles requires considerable activa-tion of the TRAPMID.23 This pose offers an alternative toresistance training and is especially important for personswhose jobs require prolonged computer use or individualswhose postures are negatively affected by neuromuscularinjury.24
The PlnkLOW pose can effectively target Tri, since the Trilifts the chest from the floor and stabilizes the elbows. Otherposes where the arms supported a high percentage of bodyweight (PlnkHI, DogUP) the Tri activity levels were also higherthan other poses. Our results showing an activity level of74.1% MVC, compare favorably to those reported for the dan-gerous one-arm (78.7% MVC) and plyometric clapping (88.6%MVC) push-ups.25
Activation levels of the ES were low for all poses witha relatively higher activity for the poses requiring trunkextension (Chr, HLift, DogUP) compared to neutral positionor forward flexion (DogDWN, FFold and MntUP).12 The RAMUP
activity was similar to ES, most likely due its co-contractionduring stabilization of the spine.26
For the RF, PlnkHI, PlnkLOW, DogUP and WarNON-DOM wereeffective activators and BF activation patterns, though low,mirrored those seen for the RF. This suggests a co-activationof knee extensors and flexors, as subjects held these posesand may offer a less stressful alternative for addressing ante-rior cruciate ligament (ACL) deficiencies while reducing therisk of ligamentous damage.27—30
The Chr and WarNON-DOM targeted the TA, the dorsiflexorassociated with fall probability in older adults.31,32 It is also amajor muscle targeted during ankle rehabilitation followinginjury and is typically strengthened in programs designed toreduce ankle sprains and other injuries related to poor anklestability. In the Chr, the dominant knee and hip are flexed asthe toes lifted. This strengthens the TA and reduces the pres-sure on the metatarsals. Strengthening the TA and increasingdynamic range during dorsiflexion allows uniform weight dis-tribution over the hallux during weight bearing.33 Reductionin plantar pressure is currently a therapeutic goal for reduc-ing pain and tissue damage.34,35 Because the dominant sideknee is fully extended with the foot flat on the floor, the co-contraction of the ankle musculature during this pose mayalso improve ankle stability.
Effect of skill level
Significant differences in VM activation were seen by skilllevels (Fig. 2). Higher activation for INST versus ADV andNOV; therefore, ADV and NOV should concentrate on engag-ing this muscle during all sun salutation poses. Attention tothe VM during these poses will increase the training effecton the lower body musculature. Cuing students to contractthese muscles during support poses such as the PlnkLOW,PlnkHI, DogUP, and DogDWN, will provide more balanced forcedistribution between the core and lower body. Adddition-ally, weakness of the VM and strength imbalances betweenthe VM and vastus lateralis (VL) are underlying mechanismfor patellofemoral pain.36 The Chr and PlnkLOW can targetthe VM and potentially help correct VM/VL imbalances.37
VM activation patterns during the PlnkHI and PlnkLOW werealso affected by skill level. INST and ADV demonstratedincreased VM activities indicating better force distributionacross upper, core and lower body musculature during arm-support poses.
Pose and skill level interactions
The interactions seen between pose and skill level for thePEC provide guidelines for using selected poses to target spe-cific muscle groups at different skill levels. The analyses alsoexpose neuromuscular inadequacies or ineffective recruit-ment strategies in less experienced practitioners, allowingguidelines for targeted cuing as practitioners’ skill and fit-ness levels increase.
For the Chr, NOV produced higher activity than INSTfor the PEC, indicating that NOV PEC are weaker or havelower localized endurance than INST since increases in meanamplitude are common marker of increased recruitment dueto lower specific muscle force or fatigue during submaxi-mal isometric contractions.38,39 Yoga teachers can use thisinformation to correct NOV posture during this pose.
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The DeltANT NrmsEMG (Fig. 3b) for INST during the WarDOM
and FFold were significantly higher than for NOV. For theWarDOM pose, reflects INST tendency to incorporate moreshoulder flexion, abduction and external rotation than NOV.For the FFold, INST activate the DeltANT draw the torsodeeper and increase flexibility in the lower back and ham-string, as the trunk bends deeply forward accomplished inpart by the DeltANT bringing the arms forward in coordina-tion with the core and lower body musculature .12,23 The Chrand FFold were effective activators of the DeltMED (Fig. 3c);however, only for INST and ADV. This selective benefit forINST and ADV also held true for the DogDWN, WarNON-DOM andWarDOM. The DeltMED is a synergist for DeltANT during posesrequiring shoulder flexion and horizontal abduction, such asChr, FFold, WarNON-DOM and WarDOM. The high NrmsEMG of theDeltMED for INST during the DogDWN is likely due to its functionas a stabilizer. The low activation levels for NOV may indi-cate an inability to effectively activate this muscle whichmay lead to shoulder injuries if these poses are offered attoo high a volume early in yogic training.
The trunk muscles are crucial for transferring force fromthe lower to upper body and reducing lower back pain.For training the RAMUP (Fig. 4a), the PlnkHI is the mosteffective pose, however, activation levels are modest (27%MVC). The trend toward NOV producing greater activity thanADV and INST during post hoc analysis for the Chr, may beattributed to greater lumbar flexion rather than extensionin the NOV compared with INST.12 Based on these findings,yoga instructors can provide specific cues for practitionersto concentrate on lower back extension.
For the GastrocLAT (Fig. 4b), INST generated higher Nrm-sEMG in the HLift and WarDOM than NOV and ADV. This isneeded for ankle stabilization during forward bends andlunges. In the WarDOM, the dominant front knee is bent;the foot is flat with ankle joint at 90◦. The greater activ-ity by INST allows enhanced forward position and deeperknee flexion.
In Chr, FFold, PlnkLOW, HLift, DogDWN, WarNON-DOM andWarDOM which produced significant pose x skill interactions,INST generated higher NrmsEMG than NOV, and the DeltMED
and GastrocLAT than NOV and ADV. This indicates that theseposes present greater neuromuscular challenges for lessskilled or conditioned practitioners compared to other posesin the sun salutation sequences. This implies that programmodifications allowing longer adaptation periods for theseposes than less challenging poses. Yoga teachers may mod-ify the poses sequences, placing a series of lower intensityposes between these poses allowing greater recovery so stu-dents can achieve proper performance.
Our results provide information that muscle activationlevels vary during different poses and are affected by prac-titioners’ skill levels. Although subjects were asked to exertmaximal efforts during each pose, this could not be guaran-teed. Differences in skill level may have affected joint angleand muscle length and therefore muscle activation levels.40
Cresswell et al41 suggest that decreases in NrmsEMG maybe due to a reduced central drive to the shortened musclevia impaired neuromuscular transmission, or via reduc-tion in neuromuscular facilitation of the motoneuron pool.For example, increased knee flexion and decreased mus-cle length could increase NrmsEMG in the gastrocenimus.41
Both kinetics and kinematics should be employed in future
studies to examine the biomechanics underlying our elec-tromyographic analyses. We also suggest that EMG frequencyanalyses using wavelets be used to assess fiber recruitmentpatterns and fatigue levels across sequences among yogapractitioners with different skill and fitness levels.
Conclusion
Understanding the differences in muscle utilization pat-terns across skill levels can help instructors focus students’attention on proper alignment during specific poses andhelp the instructor to understand the muscle weaknessprofiles that may be delaying students’ progress and increas-ing injury potential. Additionally, intervention programs forprevention and rehabilitation of musculoskeletal injuries,improving neuromuscular performance specific to differentsports or disease states, and improving strength, postureand balance in specific populations such as older individu-als or persons with chronic joint instability can be designedbased on our findings. Finally it is our hope that these resultswill provide information which allows more effective pro-gram design enabling greater progress and more effectiveinterventions across fitness levels for populations rangingfrom athletes to persons with specific disabilities or diseasestates.
Conflict of interest
The authors confirm that there are no known conflicts ofinterest.
Acknowledgement
The authors would like to thank Jonathan Siegel and NicoleMorales for their help with data collection.
References
1. Cowen VS. Functional fitness improvements after a worksite-based yoga initiative. J Bodyw Mov Ther 2010;14:50—4.
2. Dash M, Telles S. Improvement in hand grip strength in nor-mal volunteers and rheumatoid arthritis patients following yogatraining. Indian J Physiol Pharmacol 2001;45:355—60.
3. Gharote ML, Ganguly SK. Effects of a nine-week yogic trainingprogramme on some aspects of physical fitness of physicallyconditioned young males. Indian J Med Sci 1979;33:258—63.
4. Telles S, Hanumanthaiah B, Nagarathna R, Nagendra HR.Improvement in static motor performance following yogic train-ing of school children. Percept Mot Skills 1993;76:1264—6.
5. Tran MD, Holly RG, Lashbrook J, Amsterdam EA. Effects of Hathayoga practice on the health-related aspects of physical fitness.Prev Cardiol 2001;4:165—70.
6. Cowen VS, Adams TB. Physical and perceptual benefits of yogaasana practice: results of a pilot study. J Bodyw MovTher2005;9:211—9.
7. Gauchard GC, Jeandel C, Tessier A, Perrin PP. Beneficial effectof proprioceptive physical activities on balance control inelderly human subjects. Neurosci Lett 1999;273:81—4.
8. Bera TK, Rajapurkar MV. Body composition, cardiovascularendurance and anaerobic power of yogic practitioner. IndianJ Physiol Pharmacol 1993;37:225—8.
Skill levels of the practitioners 669
9. Williams K, Abildso C, Steinberg L, Doyle E, Epstein B, Smith D,Hobbs G, Gross R, Kelley G, Cooper L. Evaluation of the effec-tiveness and efficacy of Iyengar yoga therapy on chronic lowback pain. Spine (Phila Pa 1976) 2009;34:2066—76.
10. Kolasinski SL, Garfinkel M, Tsai AG, Matz W, Van Dyke A, Schu-macher HR. Iyengar yoga for treating symptoms of osteoarthritisof the knees: a pilot study. J Altern Complement Med2005;11:689—93.
11. Broad WJ. How yoga can wreck your body. In: The New YorkTimes. 2012.
12. Ni M, Mooney K, Harriell K, Balachandran A, Signorile JF. Coremuscle function during specific yoga poses. Complement TherMed 2014 [published Online First: 24 February 2014].
13. Konrad P. The abc of EMG. A practical introduction to kinesio-logical electromyography; 2005. p. 1.
14. Ekstrom R, Donatelli R, Carp K. Electromyographic analysis ofcore trunk, hip, and thigh muscles during 9 rehabilitation exer-cises. J Orthop Sports Phys Ther 2007;37:754—62.
15. Kendall F, McCreary E, Provance P, et al. Muscles, testing andfunction with posture and pain. Philadelphia, PA: LippincottWilliams & Wilkins; 2005.
16. Hintermeister RA, Lange GW, Schultheis JM, Bey MJ, HawkinsRJ. Electromyographic activity and applied load during shoulderrehabilitation exercises using elastic resistance. Am J SportsMed 1998;26:210—20.
17. Barnett C, Kippers V, Turner P. Effects of variations of the benchpress exercise on the EMG activity of five shoulder muscles. JStrength Cond Res 1995;9:222—7.
18. Ekstrom RA, Donatelli RA, Soderberg GL. Surface electromyo-graphic analysis of exercises for the trapezius and serratusanterior muscles. J Orthop Sports Phys Ther 2003;33:247—58.
19. Lehman GJ, McGill SM. Quantification of the differences in elec-tromyographic activity magnitude between the upper and lowerportions of the rectus abdominis muscle during selected trunkexercises. Phys Ther 2001;81:1096—101.
20. Boudreau SN, Dwyer MK, Mattacola CG, Lattermann C, Uhl TL,McKeon JM. Hip-muscle activation during the lunge, single-leg squat, and step-up-and-over exercises. J Sport Rehabil2009;18:91—103.
21. Clark BC, Collier SR, Manini TM, Ploutz-Snyder LL. Sexdifferences in muscle fatigability and activation patternsof the human quadriceps femoris. Eur J Appl Physiol2005;94:196—206.
22. Murley GS, Buldt AK, Trump PJ, et al. Tibialis posterior EMGactivity during barefoot walking in people with neutral footposture. J Electromyogr Kinesiol 2009;19:69—77.
23. Long R. Anatomy for vinyasa flow and standing poses. 1st ed.Plattsburgh, NY: Bandha Yoga Publications; 2010.
24. Cook CJ, Kothiyal K. Influence of mouse position on muscularactivity in the neck, shoulder and arm in computer users. ApplErgon 1998;29:439—43.
25. Freeman S. Quantifying muscle patterns and spine load dur-ing various forms of the push-up. Med Sci Sports Exerc2006;38:570—7.
26. Stokes IA, Gardner-Morse M. Spinal stiffness increases with axialload: another stabilizing consequence of muscle action. J Elec-tromyogr Kinesiol 2003;13:397—402.
27. Baratta R, Solomonow M, Zhou BH, Letson D, Chuinard R,D’Ambrosia R. Muscular coactivation. The role of the antago-nist musculature in maintaining knee stability. Am J Sports Med1988;16:113—22.
28. Chimera NJ, Swanik KA, Swanik CB, Straub SJ. Effects ofplyometric training on muscle-activation strategies and perfor-mance in female athletes. J Athl Train 2004;39:24—31.
29. Hewett TE, Lindenfeld TN, Riccobene JV, Noyes FR. The effectof neuromuscular training on the incidence of knee injuryin female athletes. A prospective study. Am J Sports Med1999;27:699—706.
30. Beard DJ, Dodd CA, Trundle HR, Simpson AH. Propriocep-tion enhancement for anterior cruciate ligament deficiency. Aprospective randomised trial of two physiotherapy regimes. JBone Joint Surg Br 1994;76:654—9.
31. Macgilchrist C, Paul L, Ellis BM, Howe TE, Kennon B, Godwin J.Lower-limb risk factors for falls in people with diabetes melli-tus. Diabet Med 2010;27:162—8.
32. Whipple R, Wolfson L, Amerman P. The relationship of knee andankle weakness to falls in nursing home residents: an isokineticstudy. J Am Geriatr Soc 1987;35:13—20.
33. Morag E, Cavanagh PR. Structural and functional predictorsof regional peak pressures under the foot during walking. JBiomech 1999;32(4):359—70.
34. San Tsung BY, Zhang M, Mak AFT, Wong MW. Effectiveness ofinsoles on plantar pressure redistribution. J Rehabil Res Dev2004;41:767—74.
35. Duckworth T, Boulton AJ, Betts RP, Franks CI, Ward JD. Plantarpressure measurements and the prevention of ulceration in thediabetic foot. J Bone Joint Surg Br 1985;67:79—85.
36. Cowan SM, Bennell KL, Hodges PW, Crossley KM, McConnellJ. Delayed onset of electromyographic activity of vastusmedialis obliquus relative to vastus lateralis in subjectswith patellofemoral pain syndrome. Arch Phys Med Rehabil2001;82:183—9.
37. Powers CM, Landel R, Perry J. Timing and intensity of vastusmuscle activity during functional activities in subjects with andwithout patellofemoral pain. Phys Ther 1996;76:946—55, dis-cussion 956—967.
38. Fallentin N, Jørgensen K, Simonsen EB. Motor unit recruitmentduring prolonged isometric contractions. Eur J Appl PhysiolOccup Physiol 1993;67:335—41.
39. Edwards RH. ‘‘Human muscle function and fatigue’’. Humanmuscle fatigue: physiological mechanisms. London, UK: PitmanMedical; 1981. p. 1—18.
40. Inbar G, Allin J, Kranz H. Surface EMG spectral changes withmuscle length. Med Biol Eng Comput 1987;25:683—9.
41. Cresswell AG, Löscher W, Thorstensson A. Influence ofgastrocnemius muscle length on triceps surae torque devel-opment and electromyographic activity in man. Exp Brain Res1995;105:283—90.
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