Influence of repetitive hand movements on intracortical inhibition.

Repetitive movements have been reported to induce task-specific changes of intracortical inhibition and facilitation, but the mechanism operating shortly after hand movement is unclear. Transcranial magnetic single and paired stimuli (2 ms) were applied to 15 healthy subjects at rest and 1 s after repetitive (every 6 s) active and passive hand extensions. Motor evoked potentials (MEPs) were recorded from hand extensors (agonists) and flexors (antagonists). A strong overall inhibitory effect was observed after applying paired stimuli. In agonists only, active movements produced significantly larger MEPs. Inhibition, however, did not differ between active or passive movements and rest. This suggests that MEP increases produced by active movements in agonists are not caused by disinhibition, but are rather due to excitation (facilitation). This finding may also have implications for future studies evaluating the preferential activation of target muscles in physiotherapy.