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Knee flexor strength and bicep femoris electromyographical activity is lower in previously strained hamstrings

Opar, David .A., WIlliams, Morgan , Timmins, Ryan, Dear, Nuala, & Shield, Anthony (2012) Knee flexor strength and bicep femoris electromyographical activity is lower in previously strained hamstrings. Journal of Electromyography and Kinesiology, 23(3), pp. 696-703.

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    The aim of this study was to determine if athletes with a history of hamstring strain injury display lower levels of surface EMG (sEMG) activity and median power frequency in the previously injured hamstring muscle during maximal voluntary contractions. Recreational athletes were recruited, 13 with a history of unilateral hamstring strain injury and 15 without prior injury. All athletes undertook isokinetic dynamometry testing of the knee flexors and sEMG assessment of the biceps femoris long head (BF) and medial hamstrings (MH) during concentric and eccentric contractions at ± 180 and ± 600.s-1. The knee flexors on the previously injured limb were weaker at all contraction speeds compared to the uninjured limb (+1800.s-1 p = 0.0036; +600.s-1 p = 0.0013; -600.s-1 p = 0.0007; -1800.s-1 p = 0.0007) whilst sEMG activity was only lower in the BF during eccentric contractions (-600.s-1 p = 0.0025; -1800.s-1 p = 0.0003). There were no between limb differences in MH sEMG activity or median power frequency from either BF or MH in the injured group. The uninjured group showed no between limb differences in any of the tested variables. Secondary analysis comparing the between limb difference in the injured and the uninjured groups, confirmed that previously injured hamstrings were mostly weaker (+1800.s-1 p = 0.2208; +600.s-1 p = 0.0379; -600.s-1 p = 0.0312; -1800.s-1 p = 0.0110) and that deficits in sEMG were confined to the BF during eccentric contractions (-600.s-1 p = 0.0542; -1800.s-1 p = 0.0473) Previously injured hamstrings were weaker and BF sEMG activity was lower than the contralateral uninjured hamstring. This has implications for hamstring strain injury prevention and rehabilitation which should consider altered neural function following hamstring strain injury.

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    ID Code: 54691
    Item Type: Journal Article
    Keywords: muscle, , surface electromyography, maladaptation, strain injury
    DOI: 10.1016/j.jelekin.2012.11.004
    ISSN: 1050-6411
    Subjects: Australian and New Zealand Standard Research Classification > MEDICAL AND HEALTH SCIENCES (110000) > HUMAN MOVEMENT AND SPORTS SCIENCE (110600) > Human Movement and Sports Science not elsewhere classified (110699)
    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 Elsevier
    Copyright Statement: This is the author’s version of a work that was accepted for publication in Journal of Electromyography and Kinesiology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Electromyography and Kinesiology, Volume 23, Issue 3 (2013). DOI: 10.1016/j.jelekin.2012.11.004.
    Deposited On: 15 Nov 2012 08:25
    Last Modified: 04 Sep 2013 19:55

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