Spring-like gait mechanics observed during walking in both young and older adults.

A spring loaded inverted pendulum model successfully demonstrated the oscillatory behavior of the center of mass (CoM) and corresponding ground reaction forces (GRFs) of young healthy subjects. This study questioned whether spring-like leg walking dynamics are consistently observed in the walking of older adults that exhibit different gait characteristics, such as slower gait speed, from the young. Eight young and eight older adult subjects participated in overground walking experiments performed at four different gait speeds, ranging from their self-selected speed to a maximum walking speed. To calculate the effective leg stiffness, the damped compliant leg model with a curved foot was used. The model parameters of leg stiffness and damping constant were optimized to achieve the best fit between model and human GRFs data. We observed that the GRFs data from both age groups were reasonably well fitted by spring-like leg dynamics throughout the broad range of gait speeds. The leg stiffness and damping constant consistently increased as a function of the walking speed in both age groups, but slightly greater variations of the model parameters were observed for the older adults' trials. The results imply that human walking dynamics and the variation with respect to age can be well captured by spring-like leg dynamics.