Purpose: The potential mechanisms of hamstring strain injuries in athletes are not well understood. The study, therefore, is aimed at understanding hamstring mechanics by studying loading conditions during maximum-effort overground sprinting.
Methods: Three-dimensional kinematics and ground reaction force data were collected from 8 elite male sprinters sprinting at their maximum effort. Maximal isometric torques of hip and knee were also collected. Data from the sprinting gait cycle was analysed via an intersegmental dynamics approach and the different joint torque components were calculated.
Results: During the initial stance phase, the ground reaction force passed anteriorly to the knee and hip, producing an extension torque at the knee and a flexion torque at the hip joint. Thus, the active muscle torque functioned to produce flexion torque at the knee and extension torque at the hip. The maximal muscle torque at the knee joint was 1.4 times the maximal isometric knee flexion torque. During late swing phase, the muscle torque counterbalanced the motion-dependent torque and acted to flex the knee joint and extend the hip joint. The loading conditions on hamstring muscles were similar to those of the initial stance phase.
Conclusion: During both initial stance and late swing phases, the large passive torques at both the knee and hip joints acted to lengthen hamstring muscles. The active muscle torques generated mainly by the hamstrings functioned to counteract those passive effects. As a result, during sprinting or high speed locomotion, the hamstring muscles may be more susceptible to a high risk of strain injury during these two phases.
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(C) 2014 American College of Sports Medicine