Estimation of Ankle Joint Impedance Based on Mechanical Response During Treadmill Belt Deceleration

The accurate estimation of ankle joint impedance during walking is crucial for understanding human gait dynamics. However, conventional methods often rely on large experimental setups or invasive techniques, which limit their practicality and accessibility. This study aimed to develop and validate a compact method for applying perturbations to the ankle joint using treadmill belt deceleration. External torque was applied to the ankle joint by rapidly decelerating the treadmill belt without prior notice to the participant. A differential model was employed to estimate the joint impedance for two participants, with the stiffness and viscosity normalized by body weight. Only models with stable poles (pole magnitude < 1) were considered. The resulting impedance estimates aligned with the expected gait-phase trends, confirming the consistency and physiological relevance of the method. This approach enables experiments to be conducted in more compact settings than those in previous studies involving large walkways. The results are comparable with previous findings, demonstrating the validity of the proposed method, which offers a practical solution for conducting gait and balance studies in constrained spaces.