Is Transcranial Electrical Stimulation A Doping?

Transcranial electrical stimulation(tES) can modulate cortical excitability, strengthen brain network connectivity and synchronize brain oscillations, and they have been used in sports science to enhance athletes' performance. For ethical considerations,some researchers have appealed to the World Anti-Doping Agency(WADA) to discuss the potential effect of tES on competitive sports. In this paper, we systematically reviewed literatures referring to tES techniques in the past 20 years, and the criteria of substances and methods prohibited by WADA in the World Anti-Doping Code. And we also analyzed whether tES meet the “2/3rule”(performance enhancement, health risk, and violation of “spirit of sport”), to discuss whether it belongs to doping. It is concluded that: 1) tES can be used to improve sports performance in humans, including increasing muscle strength, promoting endurance performance, enhancing balance ability, and facilitating skill acquisition as well as cognitive performance. However, there are limited studies focus on athletes and the tDCS is the major stimulation in previous studies; 2) tES is safe and can be tolerated by humans, and it will not lead to severe and irreversible damage to human health; 3) Wearable tES device is easily accessible, and athletes should combine this technique with hard training to improve performance efficiently, which is consistent with the spirit of sport. Altogether, tES doesn't meet the criteria of 2/3 and doesn't violate the rules of the World Anti-Doping Code. It is suggested that WADA should introduce policies and guidelines for coaches and athletes to apply tES rationally.