Transcranial direct current stimulation of primary motor cortex modulates post-contraction potentiation

Surface electromyographic activity (sEMG) of the biceps brachii (BB) during weak elbow flexion has been reported to immediately increase after strong even while exerting consistent force; this phenomenon is called “post-contraction potentiation” (PCP). To determine whether central nervous system involved in PCP, we investigated effect transcranial direct current stimulation (tDCS) and magnetic (TMS) primary motor cortex (M1) PCP. Initially, participants were instructed perform successive muscle contraction tasks with different forces: 2% (Test 1); then 25%, 50%, or 100% (conditioning [CC]); again 2) maximum voluntary (MVC). In subsequent experiments, CC intensity was set at 50% MVC, tDCS (anodal, cathodal, sham) applied M1 before task. last experiment, TMS evaluate excitability corticospinal tract Tests 1 2. The MVC generated but didn’t 25% MVC. Anodal significantly decreased magnitude cathodal showed an compared sham tDCS. BB motor-evoked potential amplitude Test 2 lower that 1. These findings suggest changes resultant activation pattern unit play a role generating