OBJECTIVES: Patients with chronic fatigue syndrome complain of
physical and mental fatigue that is worsened by exertion. It
was predicted that the cognitive and motor responses to
vigorous exercise in patients with 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
cognitive and muscle strength testing before and after a
treadmill exercise test. Measures of cardiovascular
functioning and perceived effort, fatigue, and mood were taken
during each stage of testing.
RESULTS: Depressed patients
performed worst on cognitive tests at baseline. During the
treadmill test, patients with chronic fatigue syndrome had
higher ratings 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 on the focused attention task (p=0.03). No between
group differences were found in cardiovascular or symptom
measures taken during the cognitive testing.
Patients with chronic fatigue syndrome show a specific
sensitivity to the effects of exertion on effortful cognitive
functioning. This occurs despite subjective and objective
evidence of effort allocation in chronic fatigue syndrome,
suggesting that patients have reduced working memory capacity,
or a greater demand to monitor cognitive processes, or both.
Further insight into the pathophysiology of the core
complaints in chronic fatigue syndrome is likely to be
realised by studying the effects of exercise on other aspects
of everyday functioning.