Figure 4

A) Average tibialis anterior (TA) electromyographic (EMG) activity from left (LTA) and right (RTA) legs during tracking (black line) and no-tracking (gray line) conditions (n = 7 subjects). The vertical dashed line indicates the onset of perturbation. B) Average onset latencies and standard errors of left and right TA EMG activity. C) Average magnitudes and standard errors for left and right TA EMG activity. Integrated EMG activity is computed for three time windows (initial 50 ms, 50–100 ms, and 100–150 ms). Magnitude is expressed as a percentage difference between tracking and no-tracking conditions (positive values indicate greater relative activity in the tracking condition). * denotes statistically significant differences between tasks (p < 0.05).