The Effects of Direct Current Stimulation on Exercise Performance, Pacing and Perception in Temperate and Hot Environments

Background: Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulatory technique and has previously been shown to enhance submaximal exercise by reducing rating of perceived exertion (RPE). The present study examined the effects of tDCS on high-intensity self-paced exercise in temperate conditions and fixed followed by maximal exercise in the heat; it was hypothesised performance and RPE would be altered. Methods: Two separate studies were undertaken in which exercise was preceded by 20-minutes of sham tDCS (SHAM), or anodal tDCS (TDCS). Study 1: six males completed a 20-km cycling time trial, on two occasions. Power output (PO), RPE, O2 pulse, and heart rate (HR) were measured throughout. Study 2: eight males completed fixed intensity cycling exercise at 55% of a pre-determined maximal power output (PMax) for 25-minutes before undertaking a time to exhaustion test (TTE; 75% PMax) in hot conditions (33°C), on two occasions. Test duration, heart rate, thermal and perceptual responses were measured. Study specific and combined statistical analyses was undertaken and effect sizes established. Results: Study 1: mean PO was not improved with the tDCS (197 ± 20 W) compared to SHAM (197 ± 12 W) and there were no differences in pacing profile HR, O2 pulse or RPE (p >.05). Study 2: TTE duration (SHAM 314 ± 334 s cf 237 ± 362 s tDCS), thermal, heart rate and perceptual responses were unchanged by tDCS compared to SHAM (p> .05). When combined, performance in the SHAM trial tended to better than the tDCS. Conclusion: tDCS did not influence cycling performance (study 1) exercise tolerance (study 2) or perception (studies 1&2). tDCS does not appear to facilitate high intensity exercise performance or exercise performance in the heat.