The effect of manipulation of the center of pressure of the foot during gait on the activation patterns of the lower limb musculature

Background: Therapeutic devices that manipulate the center of pressure (COP) of the foot can induce kinetic and kinematic changes in gait. Appropriate changes in joint moments and muscle activation during gait have been proven to be beneficial for patients with neuromuscular and orthopedic disorders. The purpose of this study was to investigate the effect of different COP positions during gait on the activity of the lower limb musculature of healthy subjects. Methods: A novel foot-worn biomechanical device that allows controlled manipulation of the COP during gait was used. Twelve healthy males underwent EMG analyses of the key muscles of the leg while wearing the device. The trials were carried out at six COP positions relative to neutral configuration: anterior, posterior, medial, lateral, dorsi flexion and plantar flexion. Results: The EMG activity of the lateral gastrocnemius varied significantly with COP during terminal stance (p=0.023) and preswing (p=0.020), the tibialis anterior during load response (p=0.019) and midstance (p=0.004), the biceps femoris during terminal stance (p=0.009) and the vastus lateralis during initial contact (p=0.010). Conclusion: There are significant changes in the muscle activity of the lower limb in response to manipulation of the COP of the foot during gait.