Fig 7 -

Comparison of Unified Actuated Spring-mass model (top) including work and force-rate costs against human data (bottom). Shown are (A) CoM trajectories, (B) vertical ground reaction forces, (C) leg mechanical power, and (D) vertical acceleration vs. displacement. Initial force transients are highlighted (red impulse arrow for model, red line for human). In (C), spring (orange shaded area) and actuator work (blue shaded area) contributions are shown. Gait parameters v and f are 3.9 m s -1 and 3 Hz, respectively. Stiffness and force-rate coefficient in the model are selected to approximately match stance time duration: k * is 35.6 kN m -1 and ε* is 0.5∙10 −3 .