The influence of ankle sprain injury on muscle activation during hip extension.

The likely influence of a localised injury in a distal joint on the function of proximal muscles is an important consideration in assessment and treatment of musculoskeletal injuries. However, little experimental evidence in humans exists in this area. Accordingly, a controlled study was carried out, in which the function of muscles at the hip was compared between subjects who had suffered previous severe unilateral ankle sprain and matched control subjects. The pattern of activation of the gluteus maximus, the hamstring muscles and the ipsilateral and contralateral erector spinae muscles was monitored through the use of surface electromyography during hip extension from prone lying. Analyses revealed that the pattern of muscle activation in subjects with previous injury differed markedly from normal control subjects, and that changes appeared to occur on both the uninjured and the injured sides of the body. A significant difference between the two groups was the delay in onset of activation of the gluteus maximus in previously injured subjects. The existence of remote changes in muscle function following injury found in this study emphasise the importance of extending assessment beyond the side and site of injury.