Fig. 3. Vertical force component, vertical COM oscillations and energy and power fluctuations during a complete stride of a slow (0.94 m s^-1; left), moderate (1.55 m s^-1; middle) and fast (2.08 m s^-1; right) bipedal sequence. Black horizontal bars on the top graphs indicate the stance phase of each foot; hatched vertical bars indicate the double support phases. For abbreviations, see Table 1.