Effects of transcranial magnetic stimulation with maximum voluntary muscle contraction for serial 4 days on motor function in elder persons

Our previous study suggested that transcranial magnetic stimulation (TMS) during the maximum voluntary muscle contraction (MVC) has a potential to facilitate motor neuron function in humans. Objective: To evaluate the effects of TMS with MVC for serial 4 days to facilitate motor neuron function in elder persons, motor evoked potentials (MEPs) and the maximum pinching muscle force were recorded sequentially. Methods: Four MEPs in the first digital interossei (FDI) muscle elicited by TMS during MVC for pinching a strain-gauge transducer with MVC for 2 seconds were recorded before and at an each 15 minutes interval until 1 hour after 4 MVC (test condition). In a control condition, sham TMS was employed except that real TMS was delivered to record MEPs before and 1 hour after the onset of TMS with MVC. Results: MEP amplitudes or areas in FDI muscle and pinching muscle force were significantly increased by TMS with MVC. Pinching muscle force tended to be significantly larger before starting TMS with MVC from the day 2 to the day 4 in the test condition in comparison with the control condition. Changes of MEP sizes did not significantly difer between the groups. Conclusion: Although TMS with MVC for serial days may raise muscle power of the bottom, we need further studies to confirm this effect of TMS with MVC.