The acute effects of hip abductors fatigue on postural balance

The aim of this study was to investigate the effects of unilateral hip abductor fatigue on body sway in ipsilateral and contralateral single legged stance. Acute effects repeated measurements design. Thirteen recreationally active middle aged subjects participated in the study. All subjects performed two 30s repetitions of unilateral stance on each leg. The first measurement was obtained at baseline, the second followed a control protocol of active hip abduction in supine position without additional resistance and the third measurement was conducted as aforementioned second protocol, only against elastic resistance. The center of pressure (CoP) movement characteristics during single-leg quiet stance (i.e. body sway) were analyzed by calculating the average velocity of the CoP movement and direction specific (medial-lateral and anterior-posterior) average velocity, amplitude and frequency of the CoP movement. The results of this study indicate that fatigue significantly affected body sway in both single leg stances (p 0.05) and in both medial-lateral and anterior-posterior direction. However, medial-lateral body sway tended to be increased more than in anterior-posterior direction. A significant crossover effect of increased body sway on the opposing limb suggests that in addition to local muscle fatigue, changes in central nervous system might have taken place. The above findings are of greater importance as they allow a more thorough insight into the mechanisms responsible for controlling balance that could have an important implication on designing training programs.