Exercise capacity in CFS

De Becker, P., Roeykens, J., Reynders, M., McGregor, N., De Meirleir K. Exercise capacity in chronic fatigue syndrome.  Archives of Internal Medicine, 2000, 160, 3270-3277.

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

They compared 427 women with CFS (CDC criteria '88 or '94) and 204 matched sedentary control subjects who all performed a maximal test with graded increase on a bicycle ergometer. Gas exchange ratio was continuously measured. In a second stage, they 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%.

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." 

"The decrease in physical capacity in patients with CFS appears to be associated with disease severity and is consistent with the reduction seen in many other chronic illnesses."


This is a very interesting article although it might have been more illuminating if the researchers had compared and contrasted subgroups (e.g. post infection versus gradual onset), and if they had repeated the test 24 hours later (to assess post-exertional exercise capacity).


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