EFFECTS OF EXERCISE ON COGNITIVE AND MOTOR FUNCTION IN CHRONIC-FATIGUE-SYNDROME AND DEPRESSION

Objectives-Patients with chronic fatigue syndrome complain of physical and mental fatigue that is worsened by exertion. It was predicted tha t the cognitive and motor responses to vigorous exercise in patients w ith chronic fatigue syndrome would differ from those in depressed and healthy controls. Methods-Ten patients with chronic fatigue syndrome, 10 with depressive illness, and 10 healthy controls completed cognitiv e and muscle strength testing before and after a treadmill exercise te st. Measures of cardiovascular functioning and perceived effort, fatig ue, and mood were taken during each stage of testing. Results-Depresse d patients performed worst on cognitive tests at baseline. During the treadmill test, patients with chronic fatigue syndrome had higher rati ngs of perceived effort and fatigue than both control groups, whereas patients with depression reported lower mood. After exertion, patients with chronic fatigue syndrome showed a greater decrease than healthy controls on everyday tests of focused (p=0.02) and sustained (p=0.001) attention, as well as greater deterioration than depressed patients o n the focused attention task (p=0.03). No between group differences we re found in cardiovascular or symptom measures taken during the cognit ive testing. Conclusions-Patients with chronic fatigue syndrome show a specific sensitivity to the effects of exertion on effortful cognitiv e functioning. This occurs despite subjective and objective evidence o f effort allocation in chronic fatigue syndrome, suggesting that patie nts have reduced working memory capacity, or a greater demand to monit or cognitive processes, or both. Further insight into the pathophysiol ogy of the core complaints in chronic fatigue syndrome is likely to be realised by studying the effects of exercise on other aspects of ever yday functioning.