Measures of plantar pressure and influences of fatigue on muscle activation in subjects with and without chronic ankle instability

Although much research has been conducted on those with chronic ankle instability (CAI), more research is necessary in understanding how activation of both proximal and distal lower extremity muscles influence the positioning of the ankle during a functional task. This study measured peak pressures on the plantar foot and the influences of fatigue on four lower extremity muscles during a lateral hop in those with and without CAI. The results revealed no significant differences in peak pressure between groups for the plantar pressure areas. The muscle measurements demonstrated higher peroneus longus and gluteus maximus activity just prior to landing the lateral hop. There were no statistically significant outcomes for fatigue. Both the muscle activation and the plantar pressure results suggest a pre programmed, feed-forward mechanism adapted by those with CAI. Altered neuromuscular activity in those with CAI has been documented in previous research. These results continue to support this theory, now demonstrated during a functional task which indicates those with CAI are finding methods to land a jump without injury in controlled situations.