Gait Biomechanics with Portable EMG Biofeedback at Increasing Muscle-Activation Goals: Walking Speed, Propulsion, Braking, and Step Length

Portable electromyography biofeedback (EMG-BFB) may support gait rehabilitation, but whole-gait responses across increasing portable auditory feedback goals are unclear. Twenty-four adults completed baseline treadmill walking and four counterbalanced right medial gastrocnemius activation-goal conditions set at 20%, 40%, 60%, and 80% above baseline; 23 contributed primary biomechanical data. Treadmill speed was adjusted within each condition to support achievement of the activation goal. Outcomes included walking speed, ground-reaction forces, force-time metrics, step length, temporal measures, and asymmetry. Repeated-measures MANOVA, outcome-specific repeated-measures ANOVAs, dose-response coefficients, bootstrap intervals, and leave-one-participant-out analyses were used. The combined gait-biomechanics outcomes differed significantly across activation-goal conditions (p < 0.001), with large condition effects for walking speed, propulsion, braking magnitude, and step length. From baseline to the highest goal, treadmill speed increased from 1.07 to 1.44 m/s, mean propulsion by 0.086 N/BW, braking magnitude by 0.109 N/BW, and mean step length by 0.150 m. Exploratory speed-adjusted models retained anterior–posterior and vertical loading-response associations but not peak propulsion; activation goal and achieved speed were strongly collinear. Unilateral feedback was not associated with systematic step-length or step-time asymmetry. Portable auditory EMG-BFB at increasing activation goals was accompanied by coordinated changes across gait mechanics.