Abstract

Background: The purpose of this study was to investigate the differences in the kinematics of the ankle joint and the activity of the lower leg muscles in subjects with functional ankle instability (FAI) during a double-leg heel rise.
Methods: Ten male athletes with FAI (age=19.9 ± 1.4 years; height=1.71 ± 0.04 m, weight=66.5 ± 3.6 kg) and ten male control athletes (age=20.1 ± 1.1 years; height=1.74 ± 0.03 m, weight=67.1 ± 4.5 kg) performed the heel rise on a force plate. The kinematic data and the electromyography (EMG) activity of the tibialis anterior (TA), gastrocnemius lateralis (GL), peroneus longus (PL), peroneus brevis (PB) and tibialis posterior (TP) muscles during the heel rise were recorded. Ankle movement was divided into two phases, a heel rise phase and a pause phase, and the data collected for each motion was compared between the two groups.
Results: During the pause phase, subjects with FAI tended to present a more abducted position and a less inverted position compared with that of the controls, which was accompanied by decreased peroneus brevis activity during the same period. An altered movement of the ankle joint due to deficits of muscle function was observed in subjects with FAI. The kinematic and kinetic differences observed in subjects with FAI may lead to recurrent ankle sprain.

Keywords: Functional ankle instability; Electromyography; Motion analysis