2022, Vol. 26 ›› Issue (20): 3273-3280

Effect of anodal transcranial direct current stimulation on muscle strength and endurance: a Meta-analysis

Hao Zhixin1, Wu Yixin2, Wang Xin3, Xia Zhongliang4   

Abstract: OBJECTIVE: Transcranial direct current stimulation has shown positive effects in clinical medicine, but its application in sports biomechanics is still at its infant stage. Some scholars still question the effect of this technique on enhancing muscle strength and improving sports performance. This study systematically reviewed the effect of anodal transcranial direct current stimulation on muscle strength and its mechanism.
METHODS: PubMed, Web of Science, Google Scholar, and Scopus databases were searched for randomized controlled trials regarding the effect of anodal transcranial direct current stimulation on muscle strength according to inclusion and exclusion criteria. Cochrane Handbook for Systematic Reviews of Interventions was used to evaluate the quality of the included literatures. RevMan 5.3 software was used for statistical analysis, and effect size was uniformly represented by ES.
RESULTS: The total effect size of anodal transcranial direct current stimulation on muscle strength level was ES=0.38, 95% confidence interval (Cl) [0.20, 0.57] (P < 0.05). The effect sizes of anodal transcranial direct current stimulation on different brain regions were that ESdorsolateral prefrontal cortex (0.88) > ESmotor cortex (0.32) > EStemporal cortex (0.29). The effect sizes of different current intensities on anodal transcranial direct current stimulation were ES1.5 mA (0.57) > ES2 mA (0.35). The effect sizes of anodal transcranial direct current stimulation on different subjects were ESathlete (0.64) > EShealthy person (0.29). The effect sizes of anodal transcranial direct current stimulation on different task types were ESendurance task (0.45) > ESpower task (0.35).
CONCLUSION: Transcranial direct current stimulation could enhance the muscle strength of athletes and the muscle endurance performance of healthy individuals and athletes by changing the excitability of cerebral cortex and regulating the perception of effort. The study did not find the positive effect of anodal transcranial direct current stimulation on the maximum strength of healthy individuals. Application strategy of anodal transcranial direct current stimulation parameters: To enhance muscle strength, the motor cortex was selected and equipped with unilateral or bilateral electrodes, followed by anodal transcranial direct current stimulation, 2 mA, 10-20 minutes, a polar plate of 25-35 cm2. To enhance muscle endurance, the dorsolateral prefrontal cortex and motor cortex were selected and equipped with unilateral electrode alone or combined with other cortex electrodes, followed by anodal transcranial direct current stimulation, 1.5 mA, 10-20 minutes, a polar plate of 25-35 cm2. Transcranial direct current stimulation can be used as a neuroregulatory technology in sports biomechanics; however, further explorations on the neurophysiological mechanism of transcranial direct current stimulation are warranted.
Key words: transcranial direct current stimulation, muscle strength, muscle endurance, sport performance, Meta-analysis