Fig. 5. Segmental angular displacements and instantaneous velocities during single representative cycles of rotary gallops at treadmill speeds of 2.57 m s^–1 (left column) and 3.03 m s^–1 (right column). Note that in left gallop cycle (A), both the head and trunk are rotating through more than 20° in the pitch plane, but that the head has just surpassed this threshold. Note also that in the right gallop cycle (B), head rotation in the pitch plane exceeds 20° by several degrees, but that trunk rotations have dropped to below 20°. In both cycles, however, head rotations do not occur in any other plane. The (A,B) 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° (dashed horizontal line), and negative values indicate a nose-down angle of the head axis and a shoulders-down angle of the trunk axis. 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 (C,D) the head relative to space, (E,F) the trunk relative to space, and (G,H) the head relative to the trunk. In (C,D) the head-to-space velocity graphs, the solid horizontal lines indicate 350° s^–1 that, at least in humans, is the saturation velocity for the vestibulo–ocular (VOR) reflex (Pulaski et al., 1981).