Subjects will have a baseline screening visit, electromyography (EMG) and nerve stimulation, sensory threshold testing, and measurements of brain excitability using motor evoked potentials (MEPs) from transcranial magnetic stimulation (TMS). They will then undergo rapid TMS repetitively paired with stimulation of a nerve in the arm. Outcome variables will again be measured immediately after (T0), 30 minutes (T30) after, and 60 minutes (T60) after the end of brain stimulation.