FIG. 3.

One-week postoperative EMG activity of selected lower-limb muscles and knee flexion force during voluntary efforts in the presence of varying VSS intensities: none (A), 1 mA (B), and 3.8 mA (C). Amplitude scales for EMG signals are provided on the far right. The lowest row depicts the associated knee flexion force (N) over a 2-second period. The unstimulated group shows the weakest activity and force, whereas the 1-mA and 3.8-mA stimulation groups show strong and consistent muscle activation, with the 1-mA group showing larger variability in force. We also observed a simultaneous burst of activity from the SOL during MH activation in both stimulation groups. Note that the scale of observed electrical activity has a magnitude of 0.01 mV, which is much smaller than the typical electrical activity (> 1 mV) observed in concerted muscular events.¹⁷