The Ergogenic Effects of Transcranial Direct Current Stimulation on Exercise Performance

Abstract

The physical limits of the human performance have been the object of study for a considerable time. Most of the research has focused on the locomotor muscles, lungs, and heart. As a consequence, much of the contemporary literature has ignored the importance of the brain in the regulation of exercise performance. With the introduction and development of new non-invasive devices, the knowledge regarding the behavior of the central nervous system during exercise has advanced. A first step has been provided from studies involving neuroimaging techniques where the role of specific brain areas have been identified during isolated muscle or whole-body exercise. Furthermore, a new interesting approach has been provided by studies involving non-invasive techniques to manipulate specific brain areas. These techniques most commonly involve the use of an electrical or magnetic field crossing the brain. In this regard, there has been emerging literature demonstrating the possibility to influence exercise outcomes in healthy people following stimulation of specific brain areas. Specifically, transcranial direct current stimulation (tDCS) has been recently used prior to exercise in order to improve exercise performance under a wide range of exercise types. In this review article, we discuss the evidence provided from experimental studies involving tDCS. The aim of this review is to provide a critical analysis of the experimental studies investigating the application of tDCS prior to exercise and how it influences brain function and performance. Finally, we provide a critical opinion of the usage of tDCS for exercise enhancement. This will consequently progress the current knowledge base regarding the effect of tDCS on exercise and provides both a methodological and theoretical foundation on which future research can be based.

Anodal transcranial direct current stimulation does not influence the neural adjustments associated with fatiguing contractions in a hand muscle

“…Together, these results suggest that the numerous changes occurring within the corticospinal pathway during C2 were not influenced by a-tDCS, likely explaining the absence of change in time to task failure of C2. This is in contrast with previous work which investigated elbow flexor muscles (Abdelmoula et al 2016;Cogiamanian et al 2007), questioning thereby the existence of a muscle-dependent effect of a-tDCS (Angius et al 2017). However, it should be emphasized the lack of consensus on a-tDCS effects on time to task failure of fatiguing contractions performed with elbow flexor muscles (Angius et al 2017).…”

“…This is in contrast with previous work which investigated elbow flexor muscles (Abdelmoula et al 2016;Cogiamanian et al 2007), questioning thereby the existence of a muscle-dependent effect of a-tDCS (Angius et al 2017). However, it should be emphasized the lack of consensus on a-tDCS effects on time to task failure of fatiguing contractions performed with elbow flexor muscles (Angius et al 2017). These divergent results may reflect differences in the initial activation state of the targeted network (Antal et al 2007), task difficulty and individual cognitive performance differences (Hsu et al 2016), as well as the absence of a standardized and reliable protocol to assess a-tDCS effect on corticospinal excitability (Madhavan et al 2016).…”

Bilateral extracephalic transcranial direct current stimulation improves endurance performance in healthy individuals

“…A similar inconsistency in endurance performance outcomes has been also reported in cycling studies [16–19]. The inconsistent effects of tDCS on endurance performance found in previous experimental studies might be partly caused by the different electrode montages adopted [20]. For example, Angius et al, [21] did not find any improvement in TTF during cycling exercise when anodal tDCS was delivered over M1 with the cathode over the right dorsolateral prefrontal cortex [21].…”

Testing the role of cognitive inhibition in physical endurance using high-definition transcranial direct current stimulation over the prefrontal cortex

“…However, it should be noted that similar null results have been reported by previous studies that attempted to influence physical endurance by modulating cortical excitability using tDCS (Kan et al, 2013;Muthalib et al, 2013;Radel et al, 2017;Williams et al, 2013). Despite these results, recent reviews have indicated that the net effect resulting from all these previous studies was nonetheless positive, and of a moderate amplitude (Angius et al, 2017;Radel et al, 2017). That said, the reliability of many previous studies is questionable due to a lack of double-blinding of experimental conditions and small sample sizes.…”

“…A causal role of the PMC on endurance has been directly tested using transcranial direct current stimulation (tDCS), which can modulate the neuronal excitability of this region. The heterogeneity of the results means that there is no strong evidence that an increase in PMC excitability results in a higher capacity to endure physical effort (see Angius et al, 2017 for a review). Neuroimaging studies have highlighted the contribution of other cortical regions in the maintenance of physical effort.…”