Fig. 3. Strain in triceps did not change as a function of speed during phase 3 but the strain rate was faster (more negative) at higher speeds. Values are means ± S.E.M. from the four horses used in the study. In the vastus, strain increased with speed during phases 3 and 5, the two concentric phases, but not during phase 4. Also during both concentric phases in the vastus the strain rate was faster at higher speeds.