RESUMO
OBJECTIVES: This study aimed to evaluate the effect of anodal transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex (DLPFC) in addition to visuomotor training (VMT) on choice reaction time (CRT) and cognitive function in amateur soccer players. DESIGN: Single-center, randomized, placebo-controlled, double-blind, parallel-group study. SETTING: Neuroscience and Motor Control Laboratory. PARTICIPANTS: Thirty Brazilian male amateur soccer players, aged 18-30 years. MAIN OUTCOME MEASURES: Participants were allocated to the intervention or control groups. Both groups performed VMT, but the intervention group additionally underwent anodal tDCS over the left dorsolateral prefrontal cortex (DLPFC; F3). The cathodal electrode was positioned in the right supraorbital region (Fp2). The tDCS was applied at 2 mA for 20 min for five consecutive sessions (24 h intervals). The VMT protocol was delivered during the application of tDCS and was composed of kicking a ball for 10 min (between the fifth and fifteenth minutes of the 20 min of tDCS application). The primary outcome was assessed based on changes in CRT during reaching (non-trained limb) and kicking (trained limb) tasks. Secondary outcomes were overall cognitive function measured by the Trail Making Test part A (TMT-A) and part B (TMT-B), and Digit Span Test forward (DSF) and backward (DSB) scores. All outcomes were evaluated before and after the intervention. RESULTS: In the primary outcomes, compared with the control group, the anodal tDCS combined with VMT group had greater reduction in CRT for the rectus femoris (p = 0.007) adjusted for age and baseline performance (F (1,26) = 22,23; p < 0,001) and for the triceps (p = 0.039) adjusted for training frequency (days/week) and baseline performance (F (1,26) = 5,70; p = 0,016). No differences were observed in the CRT of other muscles (anterior deltoid [p = 0.181], brachial biceps [p = 0.130], and vastus medialis [p = 0.074]). And, there were no differences between the groups in terms of cognitive function (TMT-A [p = 0.062]; TMT-B [p = 0.320]; DSF [p = 0.102]; DSB [p = 0.345]). CONCLUSION: Anodal tDCS over the left DLPFC in addition to visuomotor training of a functional task can be an efficient tool for athletes to decrease the CRT of the rectus femoris (trained limb) and triceps (non-trained limb); however, there were no differences between the groups in the others muscles (anterior deltoid, brachial biceps, and vastus medialis), and in terms of cognitive function.