Schematic of the experimental approach used to calculate the COM. (A) Frontal view of the platform placed on three force transducers. (B) Dorsal view of the tortoise on the platform. Positions of the supporting force transducers (a., b., c.) and the COM are indicated. (C) The platform was tilted to allow measurement of the vertical position of the COM. Gray lines indicate the tilted platform. (D) Dorsal view showing the position of the tilted platform in gray. (E) Detail of the displacement of the COM: a. indicates the total horizontal displacement of the COM, b. shows the horizontal displacement due to the vertical position of the COM relative to the platform.