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Arch Intern Med. 2000 Nov 27;160(21):3270-7.

Exercise capacity in chronic fatigue syndrome.

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Human Performance Laboratory and Department of Internal Medicine, Faculty of Physical Education and Physical Therapy, Vrije Universiteit Brussel, LK-Third Floor, Pleinlaan 2, 1050 Brussels, Belgium.

Erratum in

  • Arch Intern Med 2001 Sep 10;161(16):2051-2.



Patients with chronic fatigue syndrome (CFS) suffer from various symptoms, including debilitating fatigue, muscle pain, and muscle weakness. Patients with CFS can experience marked functional impairment. In this study, we evaluated the exercise capacity in a large cohort of female patients with CFS.


Patients with CFS and matched sedentary control subjects performed a maximal test with graded increase on a bicycle ergometer. Gas exchange ratio was continuously measured. In a second stage, we examined only those persons who achieved a maximal effort as defined by 2 end points: a respiratory quotient of at least 1.0 and an age-predicted target heart rate of at least 85%. Data were assessed using univariate and multivariate statistical methods.


The resting heart rate of the patient group was higher, but the maximal heart rate at exhaustion was lower, relative to the control subjects. The maximal workload and maximal oxygen uptake attained by the patients with CFS were almost half those achieved by the control subjects. Analyzing only those persons who performed a maximal exercise test, similar findings were observed.


When compared with healthy sedentary women, female patients with CFS show a significantly decreased exercise capacity. This could affect their physical abilities to a moderate or severe extent. Reaching the age-predicted target heart rate seemed to be a limiting factor of the patients with CFS in achieving maximal effort, which could be due to autonomic disturbances. Arch Intern Med. 2000;160:3270-3277.

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