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

Abstract

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 that 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). In 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. In study 2, eight males completed fixed intensity cycling exercise at 55% of a pre-determined maximal power output (P_Max) for 25-minutes before undertaking a time to exhaustion test (TTE; 75% P_Max) in hot conditions (33 °C), on two occasions. Test duration, heart rate, thermal and perceptual responses were measured. Study specific and combined statistical analyses were undertaken and effect sizes established.

Results: In 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). In 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 and 2). tDCS does not appear to facilitate high intensity exercise performance or exercise performance in the heat.

Keywords: Anodal stimulation; Environmental temperature; Fixed and self-paced exercise.