Discussion
MP
Here we compared, for the first time, the effect of anodal-tDCS over M1 and DLPFC areas on repeated all-out anaerobic performance, psychophysiological responses, and cognitive function. The main findings of this study were that tDCS did not affect repeated anaerobic performance, HR, felt arousal, CRT, and EMG activity of VM and RF muscles. However, tDCS targeting the left DLPFC significantly decreased RPE, increased EMG activity of VL muscle, and improved the affective valence and CWST score.So far, few studies have explored the efficacy of tDCS for anaerobic performance, in particular, anaerobic performance with repeated nature (repetitions ranging from <10 to 90 s in duration) which is quite similar to the performance in many sports [In the present study, anaerobic performance gradually decreased over time but, contrary to our main hypothesis, anodal tDCS over the M1 or left DLPFC had no significant effect on repeated all-out performance (i.e., PP, MP, and FI). It has been postulated that voluntaryly recruiting all motoneuron pools at their highest firing frequency is crucial for reaching peak performance in short all-out activities [Recent findings have highlighted the role of the PFC and particularly, the DLPFC area in regulating different aspects of exercise performance [Our results demonstrated that after performing the third bout of the Wingate test, the affective valence was higher in the DLPFC tDCS compared to the sham which shows a possible moderating effect of the DLPFC stimulation for perceived pleasure [The results also showed that there was no difference in the EMG amplitude of the VM and RF muscles under 3 different stimulation conditions but, conversely, the EMG amplitude of the VL muscle was higher during the second and third bouts of the Wingate test under the DLPFC condition compared to the sham condition. Previous studies have reported conflicting results concerning the causative effect of tDCS on muscle EMG as most of the studies did not find any effect of tDCS on the muscle EMG [It has also been shown that the effect of acute physical activity on cognitive function depends primarily on exercise modalities and the cognitive task performed and accordingly, inconsistent results have been reported in the previous studies [Despite taking all necessary details into account to provide optimum control over the study procedure, caution must be taken when considering the findings of the present study because they are not free from the effects of limiting factors. In this study, we were not able to use TMS for hot spotting the lower limb representation in the M1 which might have affected the response of this region to tDCS. In addition, we were not able to use neurophysiological/neuroimaging measures that could provide more information concerning any changes induced in brain activity. The inclusion of a complete control condition (without any intervention, even sham) would help to rule out a placebo effect, as expectations and placebo effects might be induced in tDCS studies [