Under normal conditions, motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation increase in amplitude if the subject exercises the examined muscle immediately before recording. The authors examined the effect of nonfatiguing exercise on the amplitude of MEPs on 42 psychiatric, medicated inpatients (14 with depression, 14 with schizophrenia, and 14 with mania) compared with 14 healthy control subjects. For each subject, a total of 50 baseline and 50 postexercise MEPs were recorded. The mean (+/- standard deviation) postexercise MEP facilitation, expressed as a percentage of mean baseline values, was significantly lower (p

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