Altered postural sway following fatiguing foot muscle exercises

This study investigated the acute effects of fatiguing foot muscle exercises on the maximum muscle strength of the foot and postural control ability. Eighteen healthy young individuals performed fatiguing foot muscle strength exercises, and their toe flexor and ankle plantar flexor strength and postural control ability were measured before and after the exercises. Postural control ability was evaluated using the path of the center of pressure (COP) during three balance tasks: double-leg standing with eyes open; double-leg standing with eyes closed; and single-leg standing with eyes open. After the exercises, the muscle strength of both the toe and ankle plantar flexor significantly decreased. Under all of the conditions, most COP variables did not significantly differ before and after the exercises; however, the total length and mean velocity in the single-leg standing with eyes open significantly decreased after the exercises. Postural sway velocities in the anteroposterior direction of double-leg standing with eyes closed and in both anteroposterior and mediolateral directions of single-leg standing with eyes open significantly decreased after the exercises. The associations between relative changes in muscle strength after the exercise and relative changes in COP variables after the exercise were not found. These results indicate that postural control while standing could be maintained even though foot muscle strength is decreased after fatiguing foot muscle exercises.