Effects of transcranial magnetic stimulation on results of the twitch interpolation technique.

To investigate whether transcranial magnetic stimulation (TMS) has an effect on isometric muscle force elicited by maximal voluntary contractions (MVC) and the ability to activate a muscle voluntarily (VA, as a percentage of full muscle activation), a twitch-interpolation technique was applied on the quadriceps femoris muscles of six volunteers before and within 1 min after TMS. VA improved by 5% (P = 0.019) and MVC by 17% (P = 0.002), whereas these parameters were unchanged in a control experiment. The results suggest that TMS has an effect on the central motor drive, at least within 1 min after stimulation.