Figure 1

Trailing-limb push-off affects both sagittal plane and frontal plane dynamics. Ankle push-off generates a force (F) commonly understood to affect motions in the sagittal plane (left) but which also affects motions in the frontal plane (right). In general, the combination of push-off and gravity, with finite mediolateral displacement between the center of pressure and the center of mass (r) results in a mediolateral force at the foot (F _y ), thereby contributing to mediolateral acceleration of the body (a _y ). Neglecting rotational inertia about the center of mass, the effect on lateral acceleration is proportional to push-off force as \(\Delta \textmd {\textit {a}}_{\textmd {\textit {y}}} = \frac {1}{m} \cdot \frac {\textmd {\textit {r}}}{L} \cdot \Delta \textmd {\textit {F}}\), where L is leg length.