Figure 4.

Effects of flexed, neutral, and extended wrist postures on phase portraits and muscle activity. Upper panels: typical phase portraits as obtained for unpaced wrist cycling in the three postures for a single participant. The black circle indicates a harmonic oscillation. Lower panels: for each wrist posture, normalized EMG amplitudes for FCR (gray) and ECR (black) muscles, determined for 16 phases of the movement cycle, were averaged over participants and acoustic pacing conditions; error bars represent the corresponding standard error