PHYSICAL FATIGABILITY AND EXERCISE CAPACITY IN CHRONIC FATIGUE SYNDROME - ASSOCIATION WITH DISABILITY, SOMATIZATION AND PSYCHOPATHOLOGY

Physical fatigability and avoidance of physically demanding tasks in c hronic fatigue syndrome (CFS) were assessed by the achievement or nona chievement of 85% of age-predicted maximal heart rate (target heart ra te, THR) during incremental exercise. The association with functional status impairment, somatization, and psychopathology was examined. A s tatistically significant association was demonstrated between this phy sical fatigability variable and impairment, and a trend was found for an association with somatization. No association was demonstrated with psychopathology. These results are in accordance with the cognitive-b ehavioral model of CFS, suggesting a major contribution of avoidance b ehavior to functional status impairment; however, neither anxiety nor depression seem to be involved in the avoidance behavior. Aerobic work capacity was compared between CFS and healthy controls achieving THR. Physical deconditioning with early involvement of anaerobic metabolis m was demonstrated in this CFS subgroup. Half of the CFS patients who did not achieve THR did not reach the anaerobic threshold. This findin g argues against an association in CFS between avoidance of physically demanding tasks and early anaerobic metabolism during effort. (C) 199 7 Elsevier Science Inc.