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

To investigate whether transcranial magnetic stimulation (TMS) has an effec t 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 th e quadriceps femoris muscles of six volunteers before and within 1 min afte r TMS. VA improved by 5% (P = 0.019) and MVC by 17% (P = 0.002), whereas th ese 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 af ter stimulation. (C) 2000 John Wiley & Sons, Inc.