Figure 5.

Horizontal and vertical COM displacements in four types of perturbation. Representative responses of the horizontal trajectory (top) and the vertical trajectory (bottom) of the body’s COM during four types of perturbation. A positive value indicates that the COM displaces toward the anterior or upward direction, while a negative value indicates that the COM displaces toward the posterior or downward direction. The black dots indicate the initial peak or the first reversal of the COM displacement tracing, and the gray dots indicate the second reversal or the returned baseline. The arrows in the bottom figure indicate the reversal vertical COM displacements in BT and UR.