Fig. 1. Box plots of percentage changes in motor evoked potential (MEP) amplitudes of control after the application of tetanic stimulation of the tibial nerves. MEPs were recorded from the abductor hallucis muscle. Control MEPs were measured without tetanic stimulation. Tetanic stimulation (50 Hz, 50 mA) with a duration of 1, 3, or 5 s was applied on the tibial nerve 1, 3, or 5 s (interval) before transcranial electrical stimulation. * P < 0.05 versus control value without tetanic stimulation (100%).