The acute effects of motor cortex transcranial direct current stimulation on athletic performance in healthy adults: A systematic review and meta-analysis

This systematic review and meta-analysis assesses independently the acute
effects of anodal and cathodal motor cortex transcranial direct current stimula-
tion (tDCS) on athletic performance in healthy adults. Besides, it evaluates the
unique and conjoint effects of potential moderators (i.e., stimulation parame-
ters, exercise type, subjects’ training status and risk of bias). Online database
search was performed from inception until March 18th 2024 (PROSPERO:
CRD42023355461). Forty-three controlled trials were included in the system-
atic review, 40 in the anodal tDCS meta-analysis (68 effects), and 9 (11 effects)
in the cathodal tDCS meta-analysis. Performance enhancement between pre-
and post-stimulation was the main outcome measure considered. The anodal
tDCS effects on physical performance were small to moderate (g = .29, 95%CI
[.18, .40], PI = -.64 to 1.23, I 2 = 64.0%). Exercise type, training status and use
of commercial tDCS were significant moderators of the results. The cathodal
tDCS effects were null (g = .04, 95%CI [-.05, .12], PI = -.14 to .23, I2 = 0%),
with a small to moderate heterogeneity entirely due to sampling error, thus
impairing further moderator analysis. These findings hold significant implica-
tions for the field of brain stimulation and physical performance, as they not
only demonstrate a small to moderate effect of acute tDCS but also identify
specific categories of individuals, devices and activities that are more suscepti-
ble to improvements. By addressing the multidimensional factors influencing
the mechanisms of tDCS, we also provide suggestions for future research.