title: Reduced biceps femoris myoelectrical activity influences eccentric knee flexor weakness after repeat sprint running.
abstract: The aim of this study was to determine whether declines in knee flexor strength following overground repeat sprints were related to changes in hamstrings myoelectrical activity. Seventeen recreationally active men completed maximal isokinetic concentric and eccentric knee flexor strength assessments at 180°/s before and after repeat sprint running. Myoelectrical activity of the biceps femoris (BF) and medial hamstrings (MHs) was measured during all isokinetic contractions. Repeated measures mixed model [fixed factors = time (pre- and post-repeat sprint) and leg (dominant and nondominant), random factor = participants] design was fitted with the restricted maximal likelihood method. Repeat sprint running resulted in significant declines in eccentric, and concentric, knee flexor strength (eccentric = 26 ± 4 Nm, 15% P < 0.001; concentric 11 ± 2 Nm, 10% P < 0.001). Eccentric BF myoelectrical activity was significantly reduced (10%; P = 0.035). Concentric BF and all MH myoelectrical activity were not altered. The declines in maximal eccentric torque were associated with the change in eccentric BF myoelectrical activity (P = 0.013). Following repeat sprint running, there were preferential declines in the myoelectrical activity of the BF, which explained declines in eccentric knee flexor strength.
authors.affiliation: School of Exercise and Nutrition Sciences and Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia.|School of Exercise Science, Australian Catholic University, Victoria, Australia.
authors.forename: R G
authors.initials: RG
authors.lastname: Timmins
authors.affiliation: School of Exercise Science, Australian Catholic University, Victoria, Australia.
authors.forename: D A
authors.initials: DA
authors.lastname: Opar
authors.affiliation: Division of Sport and Science, University of South Wales, Pontypridd, Wales, UK.
authors.forename: M D
authors.initials: MD
authors.lastname: Williams
authors.affiliation: Department of Mechanical Engineering, University of Melbourne, Victoria, Australia.
authors.forename: A G
authors.initials: AG
authors.lastname: Schache
authors.affiliation: School of Exercise and Nutrition Sciences and Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia.
authors.forename: N M
authors.initials: NM
authors.lastname: Dear
authors.affiliation: School of Exercise and Nutrition Sciences and Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia.
authors.forename: A J
authors.initials: AJ
authors.lastname: Shield
mesh_terms: D000328:Adult; D004576:Electromyography; D005080:Exercise Test; D006801:Humans; D008297:Male; D009119:Muscle Contraction; D018908:Muscle Weakness / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000502:physiology*; D011897:Random Allocation; D012420:Running / Q000502:physiology*; D013848:Thigh; D019415:Torque; D055815:Young Adult
keywords: Fatigue; eccentric; hamstring injury; isokinetic dynamometry; repeat sprint; surface electromyography