DECREASED POSTEXERCISE FACILITATION OF MOTOR EVOKED-POTENTIALS IN PATIENTS WITH CHRONIC FATIGUE SYNDROME OR DEPRESSION

We studied the effects of exercise on motor evoked potentials (MEPs) e licited by transcranial magnetic stimulation (TMS) in 18 normal (contr ol) subjects, 12 patients with chronic fatigue syndrome, and 10 depres sed patients. Subjects performed repeated sets of isometric exercise o f the extensor carpi radialis muscle until they were unable to maintai n half maximal force. MEPs were recorded before and after each exercis e set and for up to 30 minutes after the last set. The mean amplitude of MEPs recorded from the resting muscle immediately after each exerci se set was 218% of the mean pre-exercise MEP amplitude in normal subje cts, 126% in chronic fatigue patients, and 155% in depressed patients, indicating postexercise MEP facilitation in all three groups. The inc reases in the patient groups, however, were significantly lower than n ormal. The mean amplitudes of MEPs recorded within the first few minut es after the last exercise sets in all three groups were approximately half their mean pre-exercise MEP amplitudes. This postexercise MEP de pression was similar in all groups. We conclude that postexercise cort ical excitability is significantly reduced in patients with chronic fa tigue syndrome and in depressed patients compared with that of normal subjects.