Development of Center of Pressure Guided Wearable Haptic Feedback System to Improve Propulsion With Rigid Ankle Foot Orthosis: A Proof-of-Concept Study in Healthy Individuals

Rigid ankle foot orthosis (RAFO) is a commonly prescribed rehabilitation treatment to immobilize the ankle during recovery after an ankle injury. However, its use affects propulsion, which impacts gait speed, toe clearance, and metabolic cost of walking. Propulsion mechanics generate propulsive force that depends on two critical components, i.e., trailing limb angle (TLA) and ankle moment during push-off. This study aimed to investigate the immediate training effect of center of pressure (CoP) biofeedback on propulsion mechanism in healthy adults wearing RAFO during unconstrained overground walking. We hypothesized that shifting the CoP at heel strike in the target limb (limb with RAFO) will prompt adjustments in foot placement relative to the body’s center of mass (CoM), thereby altering TLA and propulsive force during push-off. A wearable haptic biofeedback system was developed to provide CoP shift information, and six healthy subjects, simulating an immobile ankle with RAFO, participated in the study. Subjects walked under three conditions: without RAFO, with RAFO but without feedback, and with RAFO while receiving feedback (anterior or posterior CoP shift). Results revealed that walking with RAFO with posterior CoP shift feedback significantly increased peak propulsive force (PPF) (by ~13%) and peak TLA (by ~17%) compared to walking with RAFO but without feedback in the target limb. Conversely, anterior CoP shift feedback produced opposite effects. Interestingly, feedback does not affect the ankle moment. The findings suggest the potential incorporation of a CoP-guided biofeedback training system in the clinical rehabilitation of individuals with an immobile ankle wearing RAFO.