Modulation of prefrontal functional connectivity by tDCS over the left DLPFC predicts performance enhancement in...

While transcranial direct current stimulation (tDCS) has been proposed as a method to enhance physical performance in athletes, the underlying neural mechanisms and the reasons for the widely reported individual variability in its effects remain unclear. This study investigated whether prefrontal hemodynamic responses, measured by functional near-infrared spectroscopy (fNIRS), are associated with the effects of anodal tDCS over the left dorsolateral prefrontal cortex (DLPFC) on swimming performance.

In a double-blind, sham-controlled, crossover design, eight trained male swimmers performed 100 m freestyle trials after receiving anodal tDCS or sham stimulation. We recorded prefrontal cortical activation and functional connectivity using fNIRS during a resting-state period and a subsequent stimulation period.

While tDCS administered prior to the 100 m freestyle swim led to a numerical improvement in performance compared with the sham condition, the overall effect was not statistically significant. The fNIRS analyses revealed that tDCS significantly reduced functional connectivity, especially in the stimulated left prefrontal cortex. Greater reductions in functional connectivity were associated with larger performance improvements. Exploratory analyses further suggested that baseline functional connectivity may be related to the neural response to tDCS, with higher baseline connectivity associated with greater reductions during stimulation.

Anodal tDCS over the left DLPFC may be associated with decreased prefrontal functional connectivity and changes in physical performance. Baseline functional connectivity may be relevant to individual responsiveness to tDCS, although further research is required.