Figure 4.

Mechanical cost of transport CoT_mech as a function of dimensionless speed in bipedal and quadrupedal mammals (reviewed by Lee et al., 2013). Cool colors represent gaits that target orthogonal constraint as a strategy to reduce CoT_mech, which is equivalent to stride collision angleΦ. Warm colors represent SLIP-like “bouncing” gaits, having two- to five-times greater CoT_mech at a given dimensionless speed. An apparent boundary zone (gray shading) suggests a discrete separation between SLIP-like gaits and those targeting orthogonal constraint.