Dynamic Stability of the Center of Mass in the Anteroposterior Direction during Fast Walking

The purpose of this study was to assess the difference in dynamic stability between young and older adults during normal and fast walking. Position and velocity of the center of mass (COM) were calculated in normal and fast walking in young and older adults. Boundaries of the region of stability were determined based on the COM position and velocity, and the margin to the forward boundary was calculated as the stability margin. Although no significant difference was detected in the stability margin, the COM for the older adults was significantly more anteriorly positioned during fast walking, which seems to result from their significantly shorter step length. These results suggest that older adults are dynamically unstable during fast walking as young are, although they walk with a shorter step.