Knee flexor strength and biceps femoris activation deficits following hamstring strain injury

Opar, David A., Dear, Nuala, Timmins, Ryan, Williams, Morgan, & Shield, Anthony (2012) Knee flexor strength and biceps femoris activation deficits following hamstring strain injury. In ISEK 2012 : XIX Biennial Conference of the International Society of Electrophysiology and Kinesiology, 19-21 July, 2012, Brisbane, Qld.

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Background: Hamstring strain injuries (HSI) are prevalent in sport and re-injury rates have been high for many years. Maladaptation following HSI are implicated in injury recurrence however nervous system function following HSI has received little attention. Aim: To determine if recreational athletes with a history of unilateral HSI, who have returned to training and competition, will exhibit lower levels of voluntary activation (VA) and median power frequency (MPF) in the previously injured limb compared to the uninjured limb at long muscle lengths. Methods: Twenty-eight recreational athletes were recruited. Of these, 13 athletes had a history of unilateral HSI and 15 had no history of HSI. Following familiarisation, all athletes undertook isokinetic dynamometry testing and surface electromyography assessment of the biceps femoris long head and medial hamstrings during concentric and eccentric contractions at ± 180 and ± 60deg/s. Results: The previously injured limb was weaker at all contraction speeds compared to the uninjured limb (+180deg/s mean difference(MD) = 9.3Nm, p = 0.0036; +60deg/s MD = 14.0Nm, p = 0.0013; -60deg/s MD = 18.3Nm, p = 0.0007; -180deg/s MD = 20.5Nm, p = 0.0007) whilst VA was only lower in the biceps femoris long head during eccentric contractions (-60deg/s MD = 0.13, p = 0.0025; -180deg/s MD = 0.13, p = 0.0003). There were no between limb differences in medial hamstring VA or MPF from either biceps femoris long head or medial hamstrings in the injured group. The uninjured group showed no between limb differences with any of the tested variables. Conclusion: Previously injured hamstrings were weaker than the contralateral uninjured hamstring at all tested speeds and contraction modes. During eccentric contractions biceps femoris long head VA was lower in the previously injured limb suggesting neural control of biceps femoris long head may be altered following HSI. Current rehabilitation practices have been unsuccessful in restoring strength and VA following HSI. Restoration of these markers should be considered when determining the success of rehabilitation from HSI. Further investigations are required to elucidate the full impact of lower levels of biceps femoris long head VA following HSI on rehabilitation outcomes and re-injury risk.

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ID Code: 54836
Item Type: Conference Item (Presentation)
Refereed: Yes
Subjects: Australian and New Zealand Standard Research Classification > MEDICAL AND HEALTH SCIENCES (110000) > HUMAN MOVEMENT AND SPORTS SCIENCE (110600)
Divisions: Current > QUT Faculties and Divisions > Faculty of Health
Current > Institutes > Institute of Health and Biomedical Innovation
Current > Schools > School of Exercise & Nutrition Sciences
Copyright Owner: Copyright 2012 please consult the authors
Deposited On: 19 Nov 2012 03:12
Last Modified: 19 Nov 2012 03:12

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