Is physical deconditioning a perpetuating factor in chronic fatigue syndrome? A controlled study on maximal exercise performance and relations with fatigue, impairment and physical activity

Background. Chronic fatigue syndrome (CFS) patients often complain that phy sical exertion produces an increase of complaints, leading to a greater nee d for rest and more time spent in bed. It has been suggested that this is d ue to a bad physical fitness and that physical deconditioning is a perpetua ting factor in CFS. Until now, studies on physical deconditioning in CFS ha ve shown inconsistent results. Methods. Twenty CFS patients and 20 matched neighbourhood controls performe d a maximal exercise test with incremental load. Heart rate, blood pressure , respiratory tidal volume, O-2 saturation, O-2 consumption, CO2 production , and blood-gas values of arterialized capillary blood were measured. Physi cal fitness was quantified as the difference between the actual and predict ed ratios of maximal workload versus increase of heart rate. Fatigue, impai rment and physical activity were assessed to study its relationship with ph ysical fitness. Results. There were no statistically significant differences in physical fi tness between CFS patients and their controls. Nine CFS patients had a bett er fitness than their control. A negative relationship between physical fit ness and fatigue was found in both groups. For CFS patients a negative corr elation between fitness and impairment and a positive correlation between f itness and physical activity was found as well. Finally, it was found that more CFS patients than controls did not achieve a physiological limitation at maximal exercise. Conclusions. Physical deconditioning does not seem a perpetuating factor in CFS.