The influence of aerobic fitness and fibromyalgia on cardiorespiratory and perceptual responses to exercise in patients with chronic fatigue syndrome Arthritis Rheum. 2006 Sep 28;54(10):3351-3362 [Epub ahead of print] Dane B. Cook [1 *], Paul R. Nagelkirk [2], Ashok Poluri [3], John Mores [3], Benjamin H. Natelson [3] [1] University of Wisconsin, Madison [2] University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Newark [3] Ball State University, Muncie, Indiana [*] Correspondence to Dane B. Cook, University of Wisconsin, Madison, Department of Kinesiology, Room 2033-Unit II Gym, 2000 Observatory Drive, Madison, WI 53706 email: Dane B. Cook Funded by: NIH; Grant Number: AI-32247 NLM Citation: PMID: 17009309 OBJECTIVE: To investigate cardiorespiratory and perceptual responses to exercise in patients with chronic fatigue syndrome (CFS), accounting for comorbid fibromyalgia (FM) and controlling for aerobic fitness. METHODS: Twenty-nine patients with CFS only, 23 patients with CFS plus FM, and 32 controls completed an incremental bicycle test to exhaustion. Cardiorespiratory and perceptual responses were measured. Results were determined for the entire sample and for 18 subjects from each group matched for peak oxygen consumption. RESULTS: In the overall sample, there were no significant differences in cardiorespiratory parameters between the CFS only group and the controls. However, the CFS plus FM group exhibited lower ventilation, lower end-tidal CO(2), and higher ventilatory equivalent of carbon dioxide compared with controls, and slower increases in heart rate compared with both patients with CFS only and controls. Peak oxygen consumption, ventilation, and workload were lower in the CFS plus FM group. Subjects in both the CFS only group and the CFS plus FM group rated exercise as more effortful than did controls. Patients with CFS plus FM rated exercise as significantly more painful than did patients with CFS only or controls. In the subgroups matched for aerobic fitness, there were no significant differences among the groups for any measured cardiorespiratory response, but perceptual differences in the CFS plus FM group remained. CONCLUSION: With matching for aerobic fitness, cardiorespiratory responses to exercise in patients with CFS only and CFS plus FM are not different from those in sedentary healthy subjects. While CFS patients with comorbid FM perceive exercise as more effortful and painful than do controls, those with CFS alone do not. These results suggest that aerobic fitness and a concurrent diagnosis of FM are likely explanations for currently conflicting data and challenge ideas implicating metabolic disease in the pathogenesis of CFS.