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Fig. 8. Segmental angular displacements and instantaneous velocities during single representative cycles by a hanuman galloping at 3.2 m s^–1 (left column) and a bonnet galloping at 2.1 m s^–1 (right column). (A) The segmental displacement graphs depict changes in head-to-space (H-S), trunk-to-space (T-S) and head-to-trunk (H-T) angles. Earth horizontal is indicated by 0° (broken horizontal line), and negative values indicate a nose-down angle of the head axis and a shoulders-down angle of the trunk axis. Positive values, seen in T-S, indicate a shoulders-up angle. The horizontal lines depict the support phases of the left hind limb (LH), left forelimb (LF), right forelimb (RF) and right hind limb (RH). The remaining graphs depict instantaneous angular velocity changes of (B) the head relative to space, (C) the trunk relative to space and (D) the head relative to the trunk. In B, the head-to-space velocity graphs, the solid horizontal lines indicate 350 deg. s^–1, which, at least in humans, is the saturation velocity for the vestibulo-ocular (VOR) reflex (Pulaski et al., 1981). Note that head angular velocities remain below 350 deg. s^–1 throughout the cycle duration and that the pitch velocities of the head-to-space angular displacements are similar to those during walking. The pitch velocities of the trunk, however, increase to or surpass the levels of the head.

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