Fig. 1. Vertical, horizontal, and lateral force tracings from a typical walking trial (corresponding to Fig. 3A). Tortoise mass=171 kg. Data were filtered using a fourth order low-pass filter at 20 Hz. At 5.73 s, the animal placed its left front foot on the force platform, followed by the right front at 7.43 s. Full support on the force platform occurred with the lifting of the right hind foot at 11 s. The step analyzed in Fig. 3A occurred with right front contact at 13.33 s to left front contact at 15.28 s. Only the hind feet remained on the platform by 19 s and the last hind foot lifted from the platform at 24.5 s.