Discussion
cortico-subcortical motor networksIn
CORTEX
In this randomized, cross-over, sham-controlled study, we investigated the impact of bilateral anodal tDCS (2 mA, 20 min) over the premotor and cerebellar cortices on peak performance and physiological parameters in a sample of professional gymnastic athletes. The results showed that in general premotor and/or cerebellar tDCS improved performance parameters (e.g., power speed, static and dynamic strength) as compared to sham, and EMG parameters showed an enhancement of MVIC in right and left upper limb muscles. These results support our hypothesis about the important role of premotor and cerebellar cortices in improving performance parameters in professional gymnastic athletes.With respect to task performance, bilateral anodal premotor stimulation furthermore significantly improved power speed, strength/coordination, as well as static and dynamic strength, and bilateral anodal cerebellar stimulation improved strength/coordination as compared to sham tDCS. Moreover, bilateral anodal premotor stimulation significantly improved power speed in the broad jump test, as compared to bilateral anodal cerebellar stimulation. Comparisons between pre-to post-intervention conditions in all tasks showed no significant differences in the sham stimulation condition, but significant performance enhancements in the premotor and cerebellar stimulation conditions in all tasks except Rating of Perceived Exertion (for physical activity intensity). However, neither type of tDCS had a significant effect on endurance scores, static or dynamic flexibility and physical activity intensity factors. In general, consistent with these findings, in sports, bilateral M1 tDCS-induced improvements in athletic performance with regard to cycling endurance performanceFor a mechanistic explanation of these effects, it has been shown that anodal tDCS over M1 enhances functional connectivity of the cortico-cortical, and cortico-subcortical motor networksIn accordance with our behavioral results, for the EMG parameters, bilateral premotor stimulation improved the MVIC index in all upper limb muscles (bilateral deltoid, biceps, triceps, trapezius, and pectoralis muscles), as compared to sham stimulation, while bilateral cerebellar anodal stimulation improved MVIC as compared to sham only in some of these muscles (right deltoid, left biceps, right trapezius and left pectoralis muscles). Furthermore, for some of the tested muscles, real stimulation over the premotor cortex had larger effects as compared to cerebellar stimulation, suggesting a superiority of premotor over cerebellar tDCS (Fig. Target region and stimulation intensity are two important factors which determine stimulation efficacyComparing tDCS over the premotor cortex and cerebellum, previous studies have demonstrated a role of both areas in motor learningOur study has several implications. First of all, we showed that the use of bilateral anodal stimulation with 2 mA intensity was well tolerated and elicited no serious side effects. Second, we showed that bilateral anodal tDCS over the premotor cortex and cerebellar tDCS is effective for improving peak performance parameters in gymnastic athletes.