Motor cortex tDCS does not improve strength performance in healthy subjects

Rafael Montenegro,Flávia Porto,Renato Massaferri,Paulo Farinatti,Alexandre Okano,Felipe Cunha,Jonas Gurgel

doi:10.1590/s1980-65742015000200009

Abstract

The influence of transcranial direct current stimulation (tDCS) upon maximal strength performance in exercises recruiting large muscle mass has not been established in healthy populations. The purpose of this study was to investigate whether anodal tDCS was able to increase the performance during maximal strength exercise (MSEX) in healthy subjects. Fourteen volunteers (age: 26 ± 4 yrs) performed two MSEX after anodal or sham tDCS (2mA; 20min prior MSEX), involving knee extensors and flexors in concentric isokinetic muscle actions of the dominant limb (3 sets of 10 repetitions). The electrical muscle activity (sEMG) of four recruited muscles was recorded during MSEX. Anodal tDCS was not able to improve force production (i.e., total work and peak torque), fatigue resistance, or electromyographic activity during MSEX when compared to sham condition. In conclusion, anodal tDCS applied upon the contralateral motor cortex was not capable of increasing the strength performance of knee extensors and flexors in young healthy subjects.

Highlights

Transcranial direct current stimulation is a non-invasive technique that can be used to alter cortical activity and has been widely used in the treatment of several neurological disorders (Nitsche et al, 2008; Nitsche & Paulus, 2011)
The main purpose of the present study was to investigate the potential effects of 20 min of anodal Transcranial direct current stimulation (tDCS) applied over the left motor cortex, upon the maximal isokinetic strength performance in healthy young men
Our findings indicated that anodal tDCS was not able to increase neither force production, nor fatigue resistance during maximal isokinetic exercise when compared to sham condition

Summary

Introduction

Transcranial direct current stimulation (tDCS) is a non-invasive technique that can be used to alter cortical activity and has been widely used in the treatment of several neurological disorders (Nitsche et al, 2008; Nitsche & Paulus, 2011). Anodal tDCS has been shown to induce changes in the cell membrane resting potential, favoring depolarization and increasing spontaneous neuronal firing rate, whereas opposite effects are provoked by cathodal tDCS (Nitsche & Paulus, 2000). These changes in neuronal excitability may persist for an hour or more if applied for 9 min or longer using 0,3-2mA of the current intensity (Nitsche & Paulus, 2001). We have recently demonstrated that tDCS applied over the temporal or prefrontal cortex can induce changes in cardiac autonomic modulation at rest in athletes (Montenegro et al, 2011), as well as to increase peak cycling performance (Okano et al, 2013), and energy expenditure during post-exercise recovery (Montenegro, Okano, Cunha, Fontes, & Farinatti Pde, 2013)

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