Fig. 2
COP displacement and its segments. Preparation: the time before the target turns on; Planning: the time required for the CNS to plan for the movement; APA: a COP movement for counteracting the expected mechanical effects of the perturbations due to the reaching movement; Reaching: from the end of the APA until reaching the targets; Returning: from the end of the reaching until returning to the initial level. \({t}_{r}, {t}_{APA}, {t}_{f},\mathrm{ and} {t}_{b}\) are reaction time, APA time, reaching time, and returning time, respectively, ‘APA size’ is the maximum displacement of the COP during the APA, and ‘Leanmax’ is the distance between the COP signal in the upright position and its maximum value after hitting the target