Effect of anodal transcranial direct current stimulation on full-effort stepping exercise performance

Abstract

We investigated the effect of anodal transcranial direct current stimulation (anodal tDCS) on the performance of full-effort box stepping exercises in athletes and non-athletes. Twenty-one subjects (athletes: five men and six women, non-athletes: four men and six women) participated in this study. tDCS was applied through two electrodes placed on the vertex (anode) and the forehead (cathode). A 2-mA anodal stimulation was applied for 15 minutes, while sham stimulation was applied on different days with similar electrodes. Participants were asked to apply a maximal effort while stepping up and down a 10-cm tall box for 20 s following termination of the tDCS. The 20 s box stepping was repeated three times with 15 s of rest. The number of total steps was significantly increased following anodal tDCS compared to sham tDCS. The degree of increase in performance was more prominent in non-athletes than in athletes. In non-athletes, a differential pattern of fatigue in performance between stimulus conditions was observed. In contrast, this significant performance modulation between stimulus conditions was not detected in athletes. Our findings of improved stepping performance following anodal tDCS depended on the training level of the subject group; this implies modulation of descending command from CNS to active muscles by tDCS. It is suggested that the degree of neural modulation for controlling complex and full-effort leg movements due to tDCS is higher in non-athletes than in athletes.