Figure 3.

Angular excursion of the trunk and ankle in four types of perturbation. Representative trials of the angular excursion of the trunk (top) and the ankle (bottom) during four types of perturbation. A positive value indicates flexion or dorsiflexion, and a negative value indicates extension or plantarflexion. The black dots indicate the initial peak or the first reversal of the angular displacement tracing, and the gray dots indicate the second reversal or the returned baseline. The vertical dotted lines from left to right indicate the onset of the platform movement, the initial joint movements and the reversal movement as well as the end of the reversal movements (second reversal or the returned baseline). The initial movement phase begins from the onset of the initial movement to the onset of the reversal movement. The reversal movement phase begins from the onset of the reversal movement to the end of the reversal movement. The gray arrows indicate the main ankle movement in the reversal movement phase in DR and UR.