Differences in abductor hallucis activity during running in individuals with chronic ankle instability and copers.

BACKGROUND: Assessment of neuromuscular dysfunction following a lateral ankle sprain during running typically focuses on the activities of the extrinsic foot muscles. Although the interaction between intrinsic and extrinsic foot muscles has been reported, there are no studies on the activities of intrinsic foot muscles in individuals with chronic ankle instability and ankle sprain copers.

RESEARCH QUESTION: Do copers and individuals with chronic ankle instability (CAI) have different abductor hallucis activity?

METHODS: This study included 11 controls, 11 copers, and 16 CAI participants. A wireless surface electromyography system was applied to the abductor hallucis, peroneus longus, tibialis anterior, and medial gastrocnemius muscles. Running was performed on a treadmill (speed of 3.5 m/s). The stance phase is divided into four functional phases. The muscle activities during these phases were calculated using the root mean square standardized by the root mean square during static standing with a double-leg stance.

RESULTS: Abductor hallucis activity was significantly lower during most phases in the coper and control groups than in the CAI group (P < 0.05). There were no differences in the extrinsic foot muscles among the groups (P > 0.05).

SIGNIFICANCE: Simultaneous investigations of muscle activity in the abductor hallucis and extrinsic foot muscles identified neuromuscular dysfunction after ankle sprains. Increased activity of the abductor hallucis may be associated with recurrent ankle sprains.