Hickey, J. T, Hickey, P. F, Maniar, N., Timmins, R. G, Williams, M. D, Pitcher, C. A & Opar, DA. (2018). A novel apparatus to measure knee flexor strength during various hamstring exercises: A reliability and retrospective injury study [accepted manuscript]. Journal of Orthopaedic & Sports Physical Therapy,48(2), 72-80. United States of America: American Physical Therapy Association. Retrieved from https://doi.org/10.2519/jospt.2018.7634
Study Design: Reliability and case-control injury study.
Objectives: To establish test re-test reliability of a novel apparatus measuring knee flexor strength during various hamstring exercises; to investigate whether these measures detect between-leg differences in males with and without history of unilateral hamstring strain injury (HSI).
Background: Knee flexor strength is a key variable when dealing with HSI and methodologies of objective measurement are often limited to single exercises.
Methods: Twenty males without and ten males with previous unilateral HSI participated. Isometric knee flexor strength and peak rate of force development (RFD) at 0/0, 45/45 and 90/90 degrees of hip/knee flexion were measured, as well as force impulse during bilateral and unilateral variations of an eccentric slider and hamstring bridge, using a novel apparatus. Intraclass correlation coefficient (ICC), typical error (TE) and typical error as a co-efficient of variation (%TE) were calculated for all measures. The magnitude of between-leg differences within each group were calculated using estimates of effect sizes reported as Cohen’s d with a ± 90% confidence interval (CI).
Results: Moderate to high test re-test reliability was observed for isometric knee flexor strength (ICC = 0.87 to 0.92) and peak RFD (ICC = 0.87 to 0.95) across three positions and mean force impulse during the eccentric slider (ICC = 0.83 to 0.90). In those with prior HSI, large deficits were seen in the previously injured leg compared to the contralateral uninjured leg for mean force impulse during the unilateral eccentric slider (d = -1.09, 90% CI = -0.20 to -1.97), isometric strength at 0/0 (d = -1.06, 90% CI = -0.18 to -1.93) and 45/45 (d = -0.88, 90% CI = -0.02 to -1.74) and peak RFD at 45/45 (d = -0.88, 90% CI = -0.02 to -1.74).
Conclusions: The novel apparatus provides a reliable measure of isometric knee flexor strength, peak RFD and force impulse during an eccentric slider, with deficits seen in previously injured hamstrings for these measures.
School of Exercise Science
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