Fig. 7. Leg kinematics (leg length versus leg angle) during treadmill running at 3 m s^-1. For the undisturbed condition, the mean ± S.D. of 35 running steps for one male subject (78 kg) are shown (A). The leg length l_LEG was measured as the distance between hip and toe marker. The leg angle is defined as the projection angle with respect to the ground (Fig. 1). Swing-leg retraction is present between the onset angle _R (length l_R) and the angle of attack ₀ (length l₀) as shown magnified in (B). For the disturbed swing phase, the leg operation of the same experimental subject is plotted. Although only a single subject is depicted here, similar results were observed in all experimental subjects (see Table 1).