Fig. 3

Oscillations and shifts in medial-lateral （upper）, anterior-posterior （middle） and vertical （lower） directions for all subjects. The ordinate represented shifts of COP in mm for medial-lateral and anterior-posterior directions, and in Kg for a vertical direction. The abscissa represented a time course in sec; standing upright for the early 5 sec, knees flexion for the middle 9.5 sec, and knees extension for the last 5 sec.