Affiliations: [a] University of Portsmouth, Sport and Exercise Science
Department, Portsmouth, Hampshire, UK | [b] University of Canberra, Faculty of Health,
Australia
Note: [] Address for correspondence: Dr. Louise Wood, University of
Portsmouth, Sport and Exercise Science Department, Spinnaker Building,
Cambridge Road, Portsmouth, Hampshire PO1 2ER, UK. Tel.: +44 2392 845163;
E-mail: louise.wood@port.ac.uk
Abstract: The objective of this study was twofold: first to assess the effect
of fatigue on two muscle strength ratios: the conventional ratio –
H_{con}/Q_{con} and dynamic
control ratio(DCR) – H_{ecc}/Q_{con}
and second to assess the coactivation of hamstrings and
quadriceps during isokinetic knee flexion/extension. Eight recreational
football players (mean ± SD age: 22 ±
2.3 yr; body mass: 85 ± 3.30~kg) volunteered
to participate in this study. Peak concentric and eccentric torque of the
hamstrings and quadriceps were measured at 120°/s pre
and post fatigue using an isokinetic dynamometer. The fatiguing protocol
consisted of 50 maximal concentric knee flexion/extension repetitions. Using
surface EMG, peak RMS of the biceps femoris and vastus lateralis were measured
in order to calculate muscle coactivation during extension and flexion of the
knee. Paired samples t-tests concluded that there was a significant increase in
both the conventional ratio (0.75 vs. 1.02) and the DCR (0.88 vs. 1.08)
following fatigue. A significant increase in hamstring coactivation during
concentric quadriceps muscle actions following fatigue was also observed (18.6
vs. 21.3%. These data contribute to the literature aiding the future
development of the DCR and its use in injury prevention and rehabilitation
strategies.
