Physiological responses to incremental exercise in patients with chronic fatigue syndrome

Purpose: The purpose of this investigation was to characterize the physiolo gical response profiles of patients with chronic fatigue syndrome (CFS), to an incremental exercise test, performed to the limit of tolerance. Methods : Fifteen patients (12 women and three men) who fulfilled the case definiti on for chronic fatigue syndrome, and 15 healthy, sedentary, age- and sex-ma tched controls, performed an incremental progressive all-out treadmill test (cardiopulmonary exercise test). Results: As a group, the CFS patients dem onstrated significantly lower cardiovascular as well as ventilatory values at peak exercise, compared with the control group. At similar relative subm aximal exercise levels (% peak (V)over dotO(2)), the CFS patients portrayed response patterns (trending phenomenon) characterized, in most parameters, by similar intercepts, but either lower ((V)over dotCO(2), HR, O-2pulse, ( V)over dot(E), V-T, PETCO2) or higher (B-f, (V)over dotE/(V)over dotCO(2)) trending kinetics in the CFS compared wit the control group. It was found t hat the primary exercise-related physiological difference between the CFS a nd the control group was their significantly lower heart rate at any equal relative and at maximal work level. Assuming maximal effort by all (indicat ed by RER, PETCO2, and subjective exhaustion), these results could indicate either cardiac or peripheral insufficiency embedded in the pathology of CF S patients. Conclusion: We conclude that indexes from cardiopulmonary exerc ise testing may be used as objective discriminatory indicators for evaluati on of patients complaining of chronic fatigue syndrome.