Lower Extremity Muscle Activation During Functional Exercises in Patients With and Without Chronic Ankle Instability

Objective: To determine whether individuals with chronic ankle instability (CAI) exhibit altered neuromuscular control as demonstrated by surface electromyography (EMG) amplitudes compared with healthy controls during single-limb eyes-closed balance, Star Excursion Balance Test, forward lunge, and lateral hop exercises. Design: A cross-sectional laboratory study. Setting: A research laboratory. Participants: Fifteen young adults with CAI and 15 healthy controls. Interventions: The subjects performed functional exercises while surface EMG signals were recorded from the tibialis anterior, peroneus longus, lateral gastrocnemius, rectus femoris, biceps femoris, and gluteus medius. Main Outcome Measurements: Surface EMG amplitudes (root mean square area) for each muscle, muscles of the shank (distal 3 muscles), muscles of the thigh (proximal 3 muscles), and total muscle activity (all 6 muscles) of the lower extremity were analyzed and compared between the groups. Results: Individuals with CAI demonstrated significantly less EMG activity in the muscles of the lower extremity during all 4 functional exercises. Effect sizes for significant differences between groups ranged from -0.75 to -1.08, none of which had 95% confidence intervals that crossed zero, which indicates moderate to large decreases in muscle activity in patients with CAI compared with healthy controls. Conclusions: Patients with CAI demonstrated decreased muscle activity of ankle, knee, and hip musculature during common functional rehabilitative tasks. Clinicians may benefit from implementing functional exercises for patients with CAI that target both distal and proximal muscles of the lower extremity.