JEB -- Daley et al. 209 (1): 171 Figure IG8

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Fig. 8. The COM mechanics occur along a continuum related to how well the limb supported body weight BW and whether it produced or absorbed net energy. Different symbols represent different `energy mode' categories. The GRF impulse magnitude and direction (|J| and ${phi}$ ) distinguish the different response patterns, as illustrated by their relationship with two energy ratios. (A) The vertical energy ratio ( ${Delta}$ E_Kv: ${Delta}$ E_P) strongly correlates with |J|, and indicates the level of BW support (0 indicates full BW support, 1.0 indicates free fall). We categorized trials in which the E_V ratio $≥$ 0.5 as `E_Kv' mode (dotted line). (B) The perturbation energy ratio ( ${Delta}$ E_com: ${Delta}$ E_V) correlates with ${phi}$ , and distinguishes energy redistribution vs actuation by the limb. A value of zero indicates that the ${Delta}$ E_V was converted to E_Kh ( ${Delta}$ E_V $->$ ${Delta}$ E_Kh), with no net muscular work, consistent with spring-like limb function. A value of 1.0 indicates that all of ${Delta}$ E_V is absorbed, a value >1.0 indicates deceleration (- ${Delta}$ E_Kh) and a value <0 indicates acceleration (+ ${Delta}$ E_Kh). We categorized trials in which the perturbation energy ratio $≥$ 0.5 as `E_com' mode (dotted line).