Transcranial direct current stimulation and sporting performance: A systematic review and meta‐analysis of transcranial direct current stimulation effects on physical endurance, muscular strength and visuomotor skills

Abstract

Transcranial direct current stimulation (tDCS) is a non‐invasive brain stimulation technique that has been linked with a range of physiological and cognitive enhancements relevant to sporting performance. As a number of positive and null findings have been reported in the literature, the present meta‐analysis sought to synthesise results across endurance, strength and visuomotor skill domains to investigate if tDCS improves any aspect of sporting performance. Online database searches in August 2020 identified 43 full‐text studies which examined the acute effects of tDCS compared to sham/control conditions on physical endurance, muscular strength, and visuomotor skills in healthy adults. Meta‐analysis indicated a small overall effect favouring tDCS stimulation over sham/control (standardized mean difference (SMD) = 0.25, CI95%[.14;.36]). Effects on strength (SMD = 0.31, CI95%[.10;.51]) and visuomotor (SMD = 0.29, CI95%[.00;.57]) tasks were larger than endurance performance (SMD = 0.18, CI95%[.00;.37]). Meta‐regressions indicated effect sizes were not related to stimulation parameters, but other factors such as genetics, gender, and experience may modulate tDCS effects. The results suggest tDCS has the potential to be used as an ergogenic aid in conjunction with a specified training regime.

A Single Anodal Transcranial Direct Current Stimulation Session to Enhance Sport-Specific Performance in Trained Individuals? A Systematic Review and Meta-Analysis

“…Furthermore, a separate meta-analysis was conducted with studies clustered in subgroups according to different sports performance domains (i.e., endurance, strength, visuomotor skill). Here, studies were divided into these groups depending on the most prominent performance domain in each respective sport studied (e.g., cycling – endurance; bodybuilding – strength; pistol-shooting – visuomotor skill) [12]. According to Cochrane guidelines, pooled standardized mean differences of subgroup analyses and the overall effect were estimated using Cohen’s effect size: small (≤ 0.2), moderate (≤ 0.5) large (≤ 0.8), and very large (> 0.8).…”

“…As noted above, reviews and meta-analyses already exist that highlight the potential of tDCS to enhance performance in the motor domain [11][12][13]. However, none of these studies have focused on sport task specificity in athletes.…”

“…Particularly in the context of motor functions, there is a growing interest to evaluate the potential of tDCS in high-performance populations, i.e., athletes. This is evident, among other things, in the recent increase in reviews and meta-analyses evaluating the enhancement of motor skills by tDCS in healthy individuals (for further reading please refer to [11][12][13]). Initial positive findings led to the now-common term Neurodoping [9].…”

Reduced isometric knee extensor force following anodal transcranial direct current stimulation of the ipsilateral motor cortex

“…Similarly, a multivariate metaregression revealed that women demonstrated greater magnitude responses to tDCS, which might be attributed to sex differences in the precise cortical anatomical locations, cognitive task strategies, as well as hormonal differences affecting brain stimulation [62]. Furthermore, the heterogeneity and genetic diversity of overall (both sexes) muscle strength, endurance, and corticospinal excitability findings is likely a result of variation in protocols [43].…”

“…Meta-analyses of the overall literature tend to suggest small magnitude improvements in muscle strength [43][44][45][46] and endurance [45][46][47]. The small magnitude benefits might have been affected by low quality studies and selective publication bias [45].…”