Fig. 2. Work performed on COM as a function of foot radius of curvature , from various dynamic walking models. Models are powered by push-off to walk on level ground: the `Simplest Model' (SM) with point mass pelvis and feet (Kuo, 2001), the `Anthropomorphic Model' (AM) with human-like mass distribution (Kuo, 2001), the `Forward-foot Model' (FM) with feet facing forward from the legs, and the `Kneed Model' (KM) with knees and forward feet (after McGeer, 1990b). All simulations generally predict decreasing step-to-step transitions with increasing arc foot radius, roughly in proportion to (1–)² as in Eqn 7. However, FM and KM have a slight upward trend for larger values of , due to different foot geometry and introduction of knees. The SM is used as a prediction for experimental results. Over the range of arc radii studied experimentally, all other models match the trend of Eqn 7 reasonably well, with r² ranging 0.940–0.998.