Fig. 1

Schematic illustrations of the setup and data analysis. A Sinusoidal speed changes at different periods (120, 60, and 30 s). Shaded areas are the analyzed sections. B Definitions of elevation angles at the thigh, shank, and foot. C The calculation procedure of the best-fit loop of the elevation angles of thigh, shank, and foot is plotted in a squared 3D space as a “plane” (shaded in yellow). This plane was simultaneously rotated around the z and y axes (shaded in blue). The z angle, at which the smallest standard deviation was obtained, is regarded as the “thickness” of the spatiotemporal intersegmental coordination (shaded in red)