Priming anodal transcranial direct current stimulation attenuates short interval intracortical inhibition and increases time to task failure of a constant workload cycling exercise

Abstract

Transcranial direct current stimulation (tDCS), a non-invasive neuromodulatory technique has been shown to increase the excitability of targeted brain area and influence endurance exercise performance. However, tDCS-mediated interaction between corticospinal excitability, GABAA mediated intracortical inhibition and endurance exercise performance remains understudied. In two separate sessions, twelve subjects performed fatigue cycling exercise (80% peak power output) sustained to task failure in a double-blinded design, following either ten minutes of anodal tDCS (atDCS) or sham. Corticospinal excitability and short interval intracortical inhibition (SICI) were measured at baseline, post neuromodulation and post-exercise using paired-pulse transcranial magnetic stimulation (TMS) in a resting hand muscle. There was a greater a decrease in SICI (P < 0.05) post fatigue cycling with atDCS priming compared to sham. Time to task failure (TTF) was significantly increased following atDCS compared to sham (P < 0.05). These findings suggest that atDCS applied over the motor cortex can augment cycling exercise performance; and this outcome may be mediated via a decrease in the excitability of GABAA inhibitory interneurons.