Effects of Weight-Bearing Posture During Heel Raise on Lower Extremity Muscle Activation in Adults with Chronic Ankle Instability

Purpose: Muscle weakness of the lower extremity is one of the causes of chronic ankle instability, and the heel raise exercise has been proposed as a means of increasing ankle stability.This study sought to investigate the most effective weight-bearing posture for adults with chronic ankle instability during the heel raise exercise.Methods: Thirteen patients with chronic ankle instability participated in this study.Each subject performed the heel raise exercise in three postures: neutral weight-bearing posture, medial weight-bearing posture, and lateral weight-bearing posture.The participants performed 10 heel raises per posture.This routine was carried out for 3 days except on the first day for the measurement of % maximum voluntary isometric contraction (MVIC).The Cumberland Ankle Instability Tool (CAIT) was used for the data analysis. Results:The muscle activity assessed according to the weight-bearing posture was significant in the tibialis anterior, the peroneus longus, and the medial gastrocnemius, but not in the lateral gastrocnemius.In addition, there was a significant difference in the activity of all four muscles when compared in the lateral and neutral weight-bearing posture.However, in the comparison of neutral and medial weight-bearing posture, there was no significant difference in activity among the four muscles. Conclusion:For patients with chronic ankle instability, the heel raise exercise in the lateral weight-bearing posture increases the risk of ankle injury by inducing inversion and is ineffective in improving muscle strength.Therefore, we suggest using the neutral and medial weight-bearing postures during the heel raise exercise for the highest improvement in effective muscle strength.