Can exercise limits prevent post-exertional malaise in chronic fatigue syndrome? An uncontrolled clinical trial.

OBJECTIVE: It was hypothesized that the use of exercise limits prevents symptom increases and worsening of their health status following a walking exercise in people with chronic fatigue syndrome. DESIGN: An uncontrolled clinical trial (semi-experimental design). SETTING: Outpatient clinic of a university department. SUBJECTS: Twenty-four patients with chronic fatigue syndrome. INTERVENTIONS: Subjects undertook a walking test with the two concurrent exercise limits. Each subject walked at an intensity where the maximum heart rate was determined by heart rate corresponding to the respiratory exchange ratio = 1.0 derived from a previous submaximal exercise test and for a duration calculated from how long each patient felt they were able to walk. MAIN OUTCOME MEASURES: The Short Form 36 Health Survey or SF-36, the Chronic Fatigue Syndrome Symptom List, and the Chronic Fatigue Syndrome -Activities and Participation Questionnaire were filled in prior to, immediately after and 24 hours after exercise. RESULTS: The fatigue increase observed immediately post-exercise (P= 0.006) returned to pre-exercise levels 24 hours post-exercise. The increase in pain observed immediately post-exercise was retained at 24 hours post-exercise (P=0.03). Fourteen of the 24 subjects experienced a clinically meaningful change in bodily pain (change of SF-36 bodily pain score > or =10); 6 indicated that the exercise bout had slightly worsened their health status, and 2 had a clinically meaningful decrease in vitality (change of SF-36 vitality score > or =20). There was no change in activity limitations/participation restrictions. CONCLUSION: It was shown that the use of exercise limits (limiting both the intensity and duration of exercise) prevents important health status changes following a walking exercise in people with chronic fatigue syndrome, but was unable to prevent short-term symptom increases.