Acute effect of transcranial direct current stimulation (tDCS) on postural control of trained athletes: a randomized controlled trial

Transcranial direct current stimulation (tDCS) is used to modulate the brain function in targeted brain areas, and can acutely modulate motor control, such as postural control. While the acute effect of tDCS is well documented on patients, little is still known whether tDCS can alter the motor control of healthy populations with an already high level of motor skills. This study aimed to assess the acute effect of tDCS on postural control of trained athletes. Eighteen parkour practitioners, known for their good balance abilities, were tested on three occasions in the laboratory for each stimulation condition (2 mA ; 20 minutes) - primary motor cortex (M1), prefrontal cortex (dlPFC) and sham (placebo). Postural control was evaluated PRE and POST each stimulation by measuring Center of Pressure (CoP) displacements on a force platform during static conditions (bipedal and unipedal stance). Following M1 stimulation, significant decreases were observed in CoP area in unipedal (P=0.003) and bipedal (P<0.001) stances. As well, the CoP total length was significantly reduced in bipodal (P=0.005) as well as in unipedal stance (P<0.001), only after M1 stimulation. Relative pre-post changes observed after M1 stimulation were negatively correlated to experience in parkour only after unipedal stance (r=0.715, P<0.001), meaning that the more participants were trained the less tDCS was effective. No significant changes were noticed after sham and dlPFC stimulation. These results suggested that the modulation of gait performance in athletes following an acute intervention of tDCS is specific to the targeted brain region, and that more complex postures (such as unipedal stance) were more sensitive to the effect of tDCS according to the level of practice.