Postexercise facilitation of motor evoked potentials following transcranial magnetic stimulation: a study in normal subjects.

Abstract

The size of the motor evoked potential (MEP) elicited by transcranial magnetic stimulation increases soon after a nonexhaustive voluntary contraction of the target muscle (postexercise facilitation). Our aim was to determine whether the duration or intensity of voluntary muscle contraction influenced postexercise facilitation in normal subjects. We recorded the MEP from the thenar muscles following contractions of different durations (5, 15, and 30 s) and intensities (10%, 25%, and 50% of maximal voluntary contraction). We found that every combination of the tested intensities and durations of physical effort could induce postexercise MEP facilitation. Although the degree of postexercise MEP facilitation was comparable across the different durations and intensities, the maximal facilitation was observed with the shortest and strongest muscle contraction. Our study thus defines the optimal setting to study postexercise facilitation for clinical purposes.