Measurement of Kinematics and Electromyography during a Tilted Landing Task in Patients with Functional Ankle Instability

Functional ankle instability (FAI) is a condition that the ankle with normal range of motion, but gets sprained easily due to poor control. Many studies found that decreased stabilizing mechanism existed in open and closed loop feedback during pre- and post-landing. However, little is known about the detailed neuromuscular functions in subjects with FAI. The purpose of this study was to determine the patterns of kinematics and electromyography of ankle during a tilted landing task. Twelve subjects with unilateral FAI and 12 age-matched healthy controls were recruited in this study. Researchers measured the 3D ankle kinematics (average and peak joint angle) and electromyography (the peroneus longus, tibialis anterior, gastrocnemius, and soleus muscle) during the titled ground landing task for the periods of 100 ms pre- and 200 ms post-initial contact (IC). The results were as follows: Patients with FAI had significantly higher gastrocnemius activity and the plantar flexion in the affected side compared to the sound side during pre-landing. The peroneus longus activity in the affected side was significantly lower than the sound side during post-landing. However, no differences were found among affected side of FAI patients and both sides of control. These findings conclude that open-loop and closed-loop neuromuscular controls in patients with FAI may be disadvantageous during tilted landing task, but they could develop a compensation action to imitate the tilted landing of the healthy controls.