Acute and chronic effects of transcranial direct current stimulation (tDCS) on swimming performance and cognitive function of elite swimmers

Transcranial direct current stimulation (tDCS) is one of the latest strategies used to improve the performance of elite athletes. The aim of this study was to investigate the effects of short- and long-term unihemispheric concurrent dual-site anodal tDCS of the primary motor cortex (M1) and dorsolateral prefrontal cortex (DLPFC) on swimming performance and maximal strength (1-RM), as well as physiological (blood lactate levels- BL and heart rate- HR), cognitive (reaction times- RTs and distance of perceived fatigue- DPF) and psychological (mental toughness- MT) variables. Nineteen elite male swimmers participated in a randomized and sham-controlled study over 25 days. Freestyle swimming (100 m) test times were recorded in the morning and evening as pre-intervention tests of swimming performance. The swimmers then received acute and multi-session tDCS (2 mA for 20 min; once daily; 3 days per week) in addition to their routine training. Two days after the 10th tDCS session, the participants repeated the swimming performance tests (morning and evening). In addition, 1-RM, RT and MT were assessed as pre-post intervention tests in a rested state the day before and after the swimming tests. After 10 sessions of tDCS, morning and evening swimming performance improved (p < 0.05) and evening BL and DPF, and MT scores were higher than pre-intervention values compared with sham. Mean and best RTs decreased (p < 0.05) in tDCS compared with sham. No significant differences were found for HR and 1-RM scores. We conclude that multi-session tDCS, but not single session, improves swimming performance more than sham-treatment, as well as affects physiological, psychological, and cognitive function variables.