The document explores the relationship between neuromuscular inhibition and hamstring strain injuries, suggesting that inhibition may lead to persistent eccentric weakness and increased re-injury risk after recovery. It discusses how athletes with a history of hamstring strains often experience deficits in muscle activation and strength, affecting rehabilitation outcomes. Evidence indicates that targeted rehabilitation strategies focusing on eccentric strength and muscle activation can enhance recovery and reduce the likelihood of re-injury.

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. Ryan Timmins, Morgan Williams, Matt Bourne, Dave Opar

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. 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. 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. Is rehabilitation sabotaged by neuromuscular inhibition?
6

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. ‘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. Our model…
•Athletes with Hx of unilateral strain injury
–At least one grade 2-3 strain
–‘Conventional’ rehabilitation
–Returned to full training & competition

10. Evidence for inhibition
8-12% deficits
18-20% deficits
23(3):696-703

11. Reduced voluntary activation
Inhibition limited to eccentric actions
Twitch interpolation during maximal isokinetic contractions
Buhmann et al unpublished

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Bourne et al unpublished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. 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Bourne et al unpublished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. Timmins et al (2014) Med Sci Sports Exerc. [Epub ahead of print]

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. 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. Rehabilitation
Retraining
Competing
Intensity of eccentric
SM, ST & BFlh contractions
Time
With BF inhibition…
17

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
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