Anodal transcranial direct current stimulation (a-tDCS) has been shown to improve time to fatigue (TTF) in incremental- and constant load cycling tests, by increasing the cortical excitability, while also modulating heartrate (HR) and rate of perceived exertion (RPE) at submaximal intensities. The purpose of this study was to: Examine the effect of a-tDCS on performance during a 250 kJ time trial cycling test and examine the effect of a-tDCS on a 120 s. RPE-production test, with a subjective intensity at 13 on the RPE scale.
Twenty subjects underwent the 250 kJ time trial and the RPE-production test four times in a randomized order (familiarization, control, sham and a-tDCS). To assess physiological parameters, HR and Vo2 were measured, and RPE was obtained after every 25 kJ during the 250 kJ time trial. 11 subjects received transcranial magnetic stimulation (TMS) at sham and a-tDCS trials to examine Motor evoked potentials (MEP).
MEPs increased significantly after receiving 13 min of a-tDCS (tDCS_Pre (452 ± 374 μV) and tDCS_Post (676 ± 642 μV) (p = 0.038)). No significant difference was found in completion time of the 250 kJ time trial, the RPE-production test, in RPE or Vo2. One significant difference was found in HR at 200 kJ (p = 0.043) between the control (169 ± 12 bpm) and the sham (172 ± 12 bpm) condition (p = 0.023).
In conclusion, MEPs was significantly increased after a-tDCS. No differences in accumulated energy was observed in the RPE-production test in this study. a-tDCS appears to have no effect on completion time in a self-paced time trial test. Similarities in completion time, HR, Vo2, RPE-production and RPE suggest that, 13min of a-tDCS was insufficient in modulating the central mechanisms involved in these factors.