Fig. 3.

Center of mass (COM) and hips vertical displacement at slow-, intermediate-, and fast-walking speed. Ensemble-average vertical displacement of the COM of the 10 subjects (red curve) over a stride during walking at −9° (top), +9° (bottom), and on the level (middle). Each blue line represents the mean curve of the vertical displacement of the hips (see methods) of a subject. In each condition, r corresponds to the average Pearson’s correlation coefficient between the COM and the hips vertical displacement.