Fig. 2. Stride frequency increased with speed at the trot (open symbols and solid line) on both the level (circle) and incline (triangle and broken line) but was independent of speed at the gallop (solid symbols) on the level (circle) and incline (triangle and broken line). The transition speeds are denoted for incline and level running by a gray bar. The left side of the bar represents the fastest speed at which the horses would trot (the maximum sustained trotting speed) for a 1-min period, and the right side of the bar represents the lowest speed at which the horses would gallop for a 1-min period (the minimum sustained galloping speed). The energetically optimal transition speed (EOTS) is denoted by an asterisk with the gray bar. Values are means ± 1 S.D.