Effects of a task failure exercise on the peroneus longus and brevis during perturbed gait.

Ankle inversion injuries represent the most common trauma sustained by athletes. Muscle fatigue from activity may contribute to a delay in the response of the ankle proprioceptors and dynamic restraints during unexpected inversion. The purpose of this investigation was to determine changes in peroneal average EMG, peak EMG, and time to peak EMG following a task failure exercise. Thirty-two subjects (age 20+/-1.43 yrs; 21 male, 11 female) with no lower extremity injuries reported for data collection. Data were collected from each subject's dominant leg using surface electromyography (EMG). EMG electrodes were applied over the peroneus longus (PL) and brevis (PB) using a standard protocol Subjects walked at a fixed pace on a 6.1 m runway with one section that could be unexpectedly dropped into 30 degrees of inversion upon foot contact. Trials with perturbed and unperturbed gait were randomized to reduce prediction of the unexpected inversion. Once 3 trials of perturbed gait were recorded, subjects completed an isotonic activity that isolated the peroneals. The task was completed to failure. Immediately following the task failure exercise, subjects walked on the perturbation runway once again until 3 trials of perturbed gait were recorded. Analysis revealed no significant differences with regard to average muscle activity between pre- and post-task failure exercise for the PL (F1,31 = 0.133; p = 0.718) or for the PB (F1,31 = 0.795; p = 0.380). There was also no significant difference in peak muscle activity pre- to post-task failure for the PL (F1,31 = 0.032; p = 0.859) or the PB (F1,31 = 0.156; p = 0.695). Finally, there was no significant difference in time-to-peak muscle activity pre- to post-task failure for the PL (F1,31 = 0.830; p = 0.369) or the PB (F1,31 = 1.037; p = 0.316). We concluded that the task failure exercise did not contribute to changes in peroneal activity during perturbed gait. These results indicate that peroneal fatigue does not play a significant role in the incidence of inversion ankle sprains.