Assessment of kinematic asymmetry for reduction of hamstring injury risk

Context: Kinematic asymmetry is believed to be associated with elevated risk for muscle injury, but little is known about the links between hamstring injuries and asymmetry of sprinting mechanics. Objective: To evaluate the value of kinematic analysis of sprinting for the detection of injury-related asymmetry in athletes with a history of hamstring strain. Participants: Six sub-elite male sprinters, including two who sustained a hamstring strain injury. Outcome Measures: Absolute differences between left and right symmetry indices and symmetry angles were both calculated for ground contact time and selected angular displacements. Measurements were acquired at foot strike, during the stance phase, and at toe-off. Results: At toe-off, injured athletes exhibited greater knee flexion and less hip extension for the injured extremity compared to the uninjured extremity. Symmetry indices for these variables markedly exceeded an established 15% threshold for clinically relevant asymmetry. Each of the uninjured athletes exhibited a high degree of symmetry for all parameters, with mean values for symmetry indices significantly lower than the 15% threshold (P < 0.05). Conclusions: Kinematic analysis of sprinting asymmetry appears to be valuable for identification of elevated risk for hamstring injury.