Fig. 3

Calculation method for COP parameters (left-side hemiplegia). The gray solid line represents the COP trajectory, with vertical segments indicating the single-support phase and diagonal segments representing the double-support phase. In the left panel, the red arrow shows the COP width on the paretic side, defined as the horizontal distance from the COP trajectory intersection to the midpoint of two consecutive gait events (toe-off to heel-strike of the same foot). The blue arrow indicates the COP width on the non-paretic side. In the right panel, the red arrow shows the COP length on the paretic side, defined as the vertical distance between two consecutive gait events (heel-strike to toe-off of the opposite foot). The blue arrow represents the COP length on the non-paretic side. LHS left heel-strike, LTO left toe-off; RHS: right heel-strike, RTO right toe-off, LSSP single-support phase of the left leg, RSSP single-support phase of the right leg