Transcranial direct current stimulation (tDCS) and cycling performance on the 3-minute aerobic test (3mAT): placebo and nocebo effects

Abstract

Transcranial direct current stimulation (tDCS) has been used extensively but research on its efficacy within the sport and exercise science realm has been inconsistent. There may be placebo and nocebo effects present with its use. Our objective was to determine if subjects can be influenced to believe that tDCS will improve cycling performance. Subjects were separated into a belief group (B; 5 women, 6 men) and a disbelief group (DB; 9 women, 3 men). The B group was told that the stimulation would improve performance on a subsequent cycling test. In the DB group, subjects were told that it was not effective and would hinder performance. The cycling test was a 3-minute aerobic test (3mAT) where subjects maintained the highest power output possible for three minutes, after completing a full 20 min warmup. During the warmup, they were given either no stimulation (control) or 2 mA bilateral stimulation over the M1 region. There was a very slight increase in maximal minute power for the B group (0.22%) and a small decrease for the DB group (-1.00%); however, these differences were not significant. No significant differences were found for any of the cycling variables. In conclustion, tDCS was unable to improve performance on the 3mAT. These findings, in conjunction with others, suggest that the acute effect of tDCS is still questionable when aiming to enhance endurance performance.