Figure 2: Grand-averaged (z-score of the) MEP amplitudes of FDI during observation of a fixation cross (Fixation), preparation (0% MVC) and execution (100% MVC) of right-foot dorsiflexion (FD), teeth clenching (TC) and simultaneous right-foot dorsiflexion and teeth clenching (FD & TC).

During both 0% and 100% MVC, the excitability of the FDI muscle increased for FD, TC and FD & TC from the level during observation of the fixation cross (Fixation). Furthermore, execution and preparation of simultaneous movements (FD & TC) resulted in higher excitability than FD as well as TC. The error bars represent standard errors. *p < 0.05.