Age-related changes in leg control at minimum toe clearance during walking

The variability of the minimum toe clearance (MTC) has been considered as a risk parameter for stumbling and falling, especially in elderly people. This study evaluates the hypothesis that MTC variability increases with age because the inter-joint synergy – suppressing the variability of the toe position relative to the hip position – deteriorates. We recorded the leg joint trajectories of six young and six old subjects during level walking, and the strength of joint synergies at the instant of MTC was evaluated based on uncontrolled manifold analysis. The results indicated that the variance of toe height from the ground was larger in the older group, although the joint synergies observed in both age groups exhibited no statistical difference. This fact suggested that the increase in the variability of the MTC might not result from the functional decline of inter-joint synergy but from the instability of the hip height.