Effect of ankle braces on lower extremity muscle activation during functional exercises in participants with chronic ankle instability.

backgroundAnkle bracing and rehabilitation are common methods to reduce the rate of recurrent ankle sprain in participants with chronic ankle instability (CAI). CAI participants utilize less muscle activity when performing functional exercises compared to healthy controls. The effect of ankle braces on muscle activity during functional exercises in participants with CAI has not been previously studied. PURPOSE: To determine the effect of bracing on motor output as demonstrated by surface EMG amplitudes in participants with CAI during single limb, eyes closed balance, star excursion balance, forward lunge, and lateral hop exercises.

methodsA descriptive laboratory study was performed. Fifteen young adults with CAI performed functional exercises with and without ankle braces while surface EMG signals were recorded from the tibialis anterior, peroneus longus, lateral gastrocnemius, rectus femoris, biceps femoris, and gluteus medius. The main outcome measures were normalized surface EMG amplitudes (root mean square area) for each muscle, muscles of the shank (distal three muscles), muscles of the thigh (proximal three muscles), and total muscle activity (all six muscles) of the lower extremity. A paired t-test was performed for each dependent variable to compare conditions. The level of significance was set a priori at p ≤ 0.05 for all analyses.

resultsDuring the forward lunge, bracing significantly reduced muscle activity pre-initial contact in the lateral gastrocnemius and post-initial contact in the peroneus longus. During the star excursion balance anterior reach the peroneus longus, lateral gastrocnemius, rectus femoris, and gluteus medius had significantly less muscle activity during braced trials. Bracing significantly reduced thigh and total muscle activity during the anterior reach and gluteus medius activity during the posterolateral reach. There were no differences between braced and unbraced conditions during the single limb eyes closed balance, star excursion balance posteromedial reach, or during lateral hop exercises.

conclusionsClinicians should be aware of the decreased muscle activity that occurs during common rehabilitation exercises when patients with CAI complete those activities while wearing ankle braces. LEVEL OF EVIDENCE: Level III.