Fig. 5

Types of trends observed in biomechanical descriptors. Our analysis showed four types of relationships between preference-normalized VSPA stiffness and different biomechanical descriptors: no trend, linear trend, quadratic trend with vertex far from the preferred stiffness, and quadratic trend with vertex at or near the preferred stiffness. Light lines show second-order fits to the inter-subject mean value of the plotted descriptor at each stiffness and speed (plotted points). All stiffness values are normalized to each subject’s preferred stiffness at each speed. Grey shading indicates the 95% CI for the stiffness value corresponding to the descriptor’s vertex, shown only when that CI includes the preferred stiffness. Error bars indicate SEM