Transcranial direct current stimulation improves cycling performance in healthy individuals

Central motor command originating from motor and premotors areas have been shown to correlate with the intensity of perception of effort (RPE) (1). Recently, non-invasive brain stimulation techniques able to change excitability of targeted area have been shown to improve exercise capacity on single joint exercise (2) and to alter perception of effort (3). In the present study we monitored whether stimulation of both motor cortexes can alter perception of effort and exercise capacity of whole body cycling exercise. Twelve healthy volunteers were recruited and underwent a placebo (SHAM), anodal tDCS (ANODAL) and cathodal tDCS (CATHODAL) condition in a double-blind, randomised and counterbalanced experimental design. tDCS stimulation was delivered for 10 min at 2.0 mA by using two extracephalic montages with the active electrode placed over the motor cortex and the reference electrode over the shoulder. Neuromuscular assessment was performed before and after tDCS stimulation to monitor central and peripheral parameters. This consisted on a maximal voluntary contraction (MVC) of knee extensor muscles with superimposed doublet followed by a resting potentiated doublet. Then, four brief submaximal contractions at 10% MVC with superimposed transcranial magnetic stimulation and one at 10% MVC with superimposed femoral nerve stimulation were executed. Volunteers then underwent a cycling time to exhaustion (TTE) at 70% of peak power output previously assessed. Heart rate (HR), ratings of perceived exertion (RPE) and leg muscle pain (PAIN) were monitored during the TTE while blood lactate (BLa-) was measured immediately after the TTE. TTE was significantly longer in the ANODAL (P=0.003) compared to the CATHODAL and SHAM conditions (13.24 ± 4.34 min; 11.1 ± 4.28 min; 10.75 ± 3.03 min). A significant reduction of RPE (P<0.001) and higher increase of BLa- (P<0.001) were found in the ANODAL condition. No differences were found for HR (P=0.80) and PAIN between conditions (P=0.27) (Fig. 1). MVC, voluntary activation level (VAL) and doublet were not affected by tDCS stimulation. However, an increase in cortical excitability was found following ANODAL tDCS as demonstrated by the increased motor evoked potential (MEParea/Mwave ratio) response (Fig 2). None of the monitored parameters were significantly affected in the SHAM and CATHODAL conditions. This experiments demonstrated that ANODAL tDCS stimulation improves constant cycling performance. Moreover, the increased excitability of the motor cortex might facilitate the central command required and consequently reduced the perception of effort during exercise. These findings further demonstrate that the motor cortex plays an important role in the generation of perception of effort.