Fig. 1

Representative examples of CoM and ankle trajectories for the three requested speeds of trial execution: slow, preferred, and fast. The COM trajectory and its velocity (color code), together with the right and left ankle trajectory (dashed) for a representative control subject a and a subject with PD b. Solid black line represents the path reference traced on the floor with direction of walking indicated by arrows and numbers. The box insert for the fast trajectory shows a zoomed 90° turn trajectory in which the subject with PD has the COM outside the base of support longer than the control subject