Effect of hip and ankle muscle fatigue on unipedal postural control.

Fatigue and deficits in postural control may predispose musculoskeletal injury. The purpose of this study was to examine the effects of fatigue at the hip and ankle during frontal plane movements on postural control during single-leg stance. Thirteen healthy volunteers completed two testing sessions 1 week apart consisting of isokinetic fatigue of the frontal plane movers of either the ankle or hip with measures of static unipedal postural control taken before and after fatigue. Postural control was assessed during three 30-s trials of unilateral stance with eyes open before and after the fatigue protocol at each testing session. Mean center of pressure (COP) excursion velocity in the sagittal and frontal planes was compared between pre- and post-fatigue across the two joints. Fatigue of the hip musculature led to postural control impairments in the frontal and sagittal planes, while fatigue of the ankle musculature did not significantly impair postural control in either plane. Our results suggest that there is a greater effect of localized fatigue of the frontal plane movers of the hip compared to the ankle on maintenance of a postural control in single-leg stance.