The Influence of Bihemispheric Transcranial Direct Current Stimulation on Muscle Fatigue

Unilateral transcranial direct current stimulation (tDCS) using two electrodes placed over the primary motor cortex (M1) and the contralateral supraorbital (SO) region (M1-SO montage) has been shown to decrease the progression of muscle fatigue. The primary purpose was to determine the impact of bihemispheric tDCS (bi-tDCS) applied over the left and right M1s (bi-tDCS) on the time to task failure (TTF) of a precision-grip task. The study implemented a double-blind, randomized, SHAM-controlled, within-subjects design. A total of 20 participants performed two experimental sessions (bi-tDCS and SHAM conditions) separated by a one-week washout. During each experimental session, a fatiguing isometric contraction of the right hand was performed with a precision grip during concurrent application of either bi-tDCS or SHAM stimulation of the two M1s. The fatiguing contraction required participants to match a target force equal to 15% of their maximum voluntary contraction (MVC) force until TTF. The main findings were that there were no statistically significant differences in TTF (P = 0.730) and percentage decline in MVC force (P = 0.733) between the bi-tDCS and SHAM conditions. Furthermore, there were no significant differences in force error, standard deviation of force, or EMG activity between the two conditions. These results indicate that bi-tDCS does not delay the progression of fatigue during a precision grip task in healthy adults in the task conditions of the current study.