Fig. 5. Predicted and measured running gait parameter selection for all subjects. Solid circles indicate measured parameter selection under specific constraint conditions; (A) red circles, v-constrained; (B) blue circles, f-constrained; (C) green circles, d-constrained. Thick black lines indicate least-squares linear regression of the behavioral data, as determined using each constrained parameter as the independent variable. The broken black lines give 95% confidence intervals of the regression. Contours lines indicate equivalent cost of transport with the region of least cost surrounded by the inner contour and cost increasing outward from that. The bold red lines indicate the optimal predicted behavior (zero slope/minimum cost), the orange area represents the region of C_min + 0.001 ml O₂ kg^-1 m^-1, and the yellow area that of C_min + 0.005 ml O₂ kg^-1 m^-1.