Center of Mass Work Components May Offer Estimates for Preferred Walking Speeds for Any Walking Conditions

It is suggested that preferred walking speeds coincide with the minimum metabolic energy expenditure. Since the positive step work performed on the center of mass (COM) broadly represents walking energetics, at the preferred walking speed, the positive step work must also be minimized. Positive step work is exerted at the beginning of the step (push-off) and during the stance phase (rebound), each followed by associated mechanical energy dissipation. A simple walking model suggests that the best walking economy is achieved when the entire step’s active work is provided by the push-off, making the rebound merely the release of stored mechanical energy in tendons to swing the limbs. Accordingly, we propose a criterion where the preferred walking speed is when the rebound work does not energize COM motion and is completely absorbed by subsequent negative work (preload). We developed preferred walking speed trajectories for different terrain amplitudes, considering the influence of age and state of lookahead. We estimated that with normal lookahead, the preferred walking speed for young adults would be 1.22 m · s ^-1 . As walking conditions became more challenging (e.g., due to age, restricted lookahead, etc.), our estimated preferred walking speeds also declined.