Metabolic rate, cardiac response, and aerobic capacity in fibromyalgia: a case-control study

Objectives: Several studies report reduced aerobic capacity in patients with fibromyalgia (FM). The purpose of our study was to investigate whether a reduction in aerobic capacity in these patients is accompanied by alterations in metabolic rate and heart rate (HR) response. Method: Twelve women with FM and 12 healthy controls (HCs) matched on sex and age, and with similar leisure time physical activity, participated in the study. All subjects performed an incremental submaximal cycle ergometer test to anaerobic threshold [AT; i.e. blood lactate concentration (bLa) >= 4 mmol/L], followed by a stepwise test to exhaustion to estimate maximal oxygen consumption (VO2max). Results: Oxygen consumption and workload were lower among patients than HCs both at AT and at termination of the VO2max test (p < 0.011 for all comparisons). Two patients (18%) and nine HCs (75%) reached VO2max criteria. The relationship between metabolic rate and workload did not differ between groups at exercise below AT. At exercise above AT, the metabolic rate increased disproportionally to workload in the patients. Although the patients had a higher anaerobic contribution to the total metabolic rate at the end of the submaximal test, the anaerobic contribution at the end of the maximal test did not differ between groups. HR responses were largely similar between groups. Conclusions: The current study indicates that patients with FM have similar metabolic and cardiovascular responses to submaximal exercise as HCs. However, these patients have reduced ability to reach VO2max and a possible deficit in the metabolic system when exercising above the AT.