Effect of hip flexion angle on hamstring optimum length after a single set of concentric contractions.

The eccentric contraction mode was proposed to be the primary stimulus for optimum angle (angle at which peak torque occurs) shift. However, the training range of motion (or muscle excursion range) could be a stimulus as important. The aim of this study was to assess the influence of the training range of motion stimulus on the hamstring optimum length. It was hypothesised that performing a single set of concentric contractions beyond optimal length (seated at 80° of hip flexion) would lead to an immediate shift of the optimum angle to longer muscle length while performing it below (supine at 0° of hip flexion) would not provide any shift. Eleven male participants were assessed on an isokinetic dynamometer. In both positions, the test consisted of 30 consecutive knee flexions at 4.19 rad · s⁻¹. The optimum angle was significantly shifted by ∼15° in the direction of longer muscle length after the contractions at 80° of hip flexion, while a non-significant shift of 3° was found at 0°. The hamstring fatigability was not influenced by the hip position. It was concluded that the training range of motion seems to be a relevant stimulus for shifting the optimum angle to longer muscle length. Moreover, fatigue appears as a mechanism partly responsible for the observed shift.