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Is neuromuscular inhibition a risk factor for hamstring strain? 
Tony Shield 
School of Exercise & Nutrition Sciences 
Ins...
Ryan Timmins, Morgan Williams, Matt Bourne, Dave Opar
Running & knee flexor strength 
Greig (2008) 
Eccentric strength loss with little or no concentric decline. 
Suggests poss...
doi: 10.1111/sms.12171 
The decline in Bfem sEMG ‘explains’ changes in eccentric knee flexor strength (r2=0.69, p<0.001) 
...
Prior hamstring injury  Persistent eccentric weakness 
From Croisier & Crielaard 2000 
Evident months to years after grad...
Is rehabilitation sabotaged by neuromuscular inhibition? 
6
Hamstring strain injury 
Pain 
Avoid long m lengths 
 Activity 
NMI 
Atrophy 
 Fascicle lengths 
 Opt. m length 
 Stre...
‘Recovered hamstring’ 
Resume long m lengths 
 Activity 
NMI 
Atrophy 
 Fascicle lengths 
 Opt. m length 
 Strength 
E...
Our model… 
•Athletes with Hx of unilateral strain injury 
–At least one grade 2-3 strain 
–‘Conventional’ rehabilitation ...
Evidence for inhibition 
8-12% deficits 
18-20% deficits 
23(3):696-703
Reduced voluntary activation 
Inhibition limited to eccentric actions 
Twitch interpolation during maximal isokinetic cont...
Reduced muscle use (MRI) 
0 
10 
20 
30 
40 
Inj BFlh 
Uninj BFlh 
%  T2 relaxation 
Limb 
9 elite to sub-elite track ath...
p<0.05 
* 
ST > BFlh, BFsh, SM 
p<0.05 
10 recreational to sub-elite 
athletes, ~9.8 mo post injury 
Reduced muscle use (M...
Timmins et al (2014) Med Sci Sports Exerc. [Epub ahead of print]
Hamstring strain injury 
Pain 
Avoid long m lengths 
 Activity 
NMI 
Atrophy 
 Fascicle lengths 
 Opt. m length 
 Stre...
Return to play w/out inhibition 
Rehabilitation 
Retraining 
Competing 
Intensity of eccentric hamstring contractions 
Tim...
Rehabilitation 
Retraining 
Competing 
Intensity of eccentric 
SM, ST & BFlh contractions 
Time 
With BF inhibition… 
17
•Croisier JL, & Crielaard JM. (2000) Isokin Exerc Sci, 8:175-180. 
•Fyfe JJ, Opar DA, Williams MD, Shield AJ. (2013) J Ele...
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Anthony Shield - is nmi a risk factor for hamstring strain injury

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Anthony Shield
Senior lecturer, School of Exercise and Nutrition Science Institute of Health and Biomedical Innovation Queensland University of Technology, Brisbane, Australia.
-
Is neuromuscular inhibition a risk factor for hamstring strain?
(6th MuscleTech Network Workshop)
13th and 14th October, Barcelona

Published in: Health & Medicine

Anthony Shield - is nmi a risk factor for hamstring strain injury

  1. 1. Is neuromuscular inhibition a risk factor for hamstring strain? Tony Shield School of Exercise & Nutrition Sciences Institute of Health & Biomedical Innovation Queensland University of Technology
  2. 2. Ryan Timmins, Morgan Williams, Matt Bourne, Dave Opar
  3. 3. Running & knee flexor strength Greig (2008) Eccentric strength loss with little or no concentric decline. Suggests possibility of inhibition Concentric Torque Eccentric Torque
  4. 4. doi: 10.1111/sms.12171 The decline in Bfem sEMG ‘explains’ changes in eccentric knee flexor strength (r2=0.69, p<0.001) 1830m sprints
  5. 5. Prior hamstring injury  Persistent eccentric weakness From Croisier & Crielaard 2000 Evident months to years after grade 2+ injury Jönhagen et al 1994, Lee et al 2009 Opar et al 2013
  6. 6. Is rehabilitation sabotaged by neuromuscular inhibition? 6
  7. 7. Hamstring strain injury Pain Avoid long m lengths  Activity NMI Atrophy  Fascicle lengths  Opt. m length  Strength Ecc>Con, Long>Short  Prop. m damage  Re-injury risk
  8. 8. ‘Recovered hamstring’ Resume long m lengths  Activity NMI Atrophy  Fascicle lengths  Opt. m length  Strength Ecc>Con, Long>Short  Prop. m damage  Re-injury risk BFlh
  9. 9. Our model… •Athletes with Hx of unilateral strain injury –At least one grade 2-3 strain –‘Conventional’ rehabilitation –Returned to full training & competition
  10. 10. Evidence for inhibition 8-12% deficits 18-20% deficits 23(3):696-703
  11. 11. Reduced voluntary activation Inhibition limited to eccentric actions Twitch interpolation during maximal isokinetic contractions Buhmann et al unpublished
  12. 12. Reduced muscle use (MRI) 0 10 20 30 40 Inj BFlh Uninj BFlh %  T2 relaxation Limb 9 elite to sub-elite track athletes ~8.5 mo post injury 1040m sprints p<0.05 Bourne et al unpublished
  13. 13. p<0.05 * ST > BFlh, BFsh, SM p<0.05 10 recreational to sub-elite athletes, ~9.8 mo post injury Reduced muscle use (MRI) 610 Nordics Bourne et al unpublished
  14. 14. Timmins et al (2014) Med Sci Sports Exerc. [Epub ahead of print]
  15. 15. Hamstring strain injury Pain Avoid long m lengths  Activity NMI Atrophy  Fascicle lengths  Opt. m length  Strength Ecc>Con, Long>Short  Prop. m damage  Re-injury risk Opar et al Sole et al Timmins et al Silder et al Sole et al Opar et al Jönhagen et al Lee et al
  16. 16. Return to play w/out inhibition Rehabilitation Retraining Competing Intensity of eccentric hamstring contractions Time 16  Eccentric strength  Voluntary activation  Muscle size  Fascicle lengths Altered collagen expression?  Damage resistance
  17. 17. Rehabilitation Retraining Competing Intensity of eccentric SM, ST & BFlh contractions Time With BF inhibition… 17
  18. 18. •Croisier JL, & Crielaard JM. (2000) Isokin Exerc Sci, 8:175-180. •Fyfe JJ, Opar DA, Williams MD, Shield AJ. (2013) J Electromyog Kinesiol, 23(3): 523-530. •Greig, M. (2008) Am J Sports Med, 36(7):1403-1409. •Jönhagen, S, Nemeth, G, & Eriksson, E. (1994) Am J Sports Med, 22(2):262-266. •Lee MJ, Reid SL, Elliott BC, Lloyd DG. (2009) Med Sci Sports Exerc, 41(10):1942- 1951. •Opar DA, Williams MD, Timmins RG, Dear NM, Shield, AJ. (2013) J Electromyog Kinesiol, 23(3):696-703. •Opar DA, Williams MD, Timmins RG, Dear NM, Shield, AJ. (2013) Am J Sports Med, 41(1):116-125. •Silder A, Heiderscheit BC, Thelen DG, Enright T, Tuite, MJ. (2008) Skeletal •Radiology 37(12):1101-1109. •Sole G, Milosavljevic S, Nicholson HD, Sullivan SJ. (2011) JOSPT, 41(5):354-363. •Timmins RG, Opar DA, Williams MD, Schache AG, Dear NM, Shield AJ. (2014) Scand J Med Sci Sport. Jan 15. doi: 10.1111/sms.12171 •Timmins RG, Shield AJ, Williams MD, Lorenzen C, Opar DA. (2014) Med Sci Sports Exerc, Sep 9. [Epub ahead of print] References 18

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