Figure 4.

Mediolateral marker positions and paretic limb gluteus medius (GM) activity over the course of a stride are illustrated for typical walking trials. Each line represents the average of five strides (from paretic heel-strike to next paretic heel-strike). High-activity strides were those with the greatest paretic limb GM activity during the first half of swing (shaded area), and low-activity strides were those with the lowest paretic limb GM activity during this period. (a) For the low fall risk participant, the center of mass (CoM) displacement (x_CoM) from the nonparetic stance foot was larger during high-activity strides, which ended with the paretic limb being placed more laterally (increased foot placement distance). (b) For the higher fall risk participant, the CoM moved more quickly toward the stance foot (indicated by steeper slope of CoM velocity [v_CoM]) for the first half of swing during high-activity strides. The presence of increased paretic limb GM activity did not cause the paretic limb to be placed more laterally. EMG = electromyography.