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Elevated Perceived Exertion in People with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Fibromyalgia: A Meta-analysis

Supplemental digital content is available in the text. ABSTRACT Purpose Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and fibromyalgia (FM) are two debilitating illnesses primarily characterized by chronic symptoms of fatigue and musculoskeletal pain, respectively. Some investigators have observed an elevated sense of effort in these patient groups; however, this effect has not been substantiated via quantitative review. As such, we conducted a meta-analysis of RPE responses to aerobic exercise in ME/CFS and FM compared with healthy adults. Methods Case–control studies involving adults with ME/CFS or FM that measured RPE and heart rate responses to acute aerobic exercise were included. Data sources included PubMed, Scopus/Embase, CINAHL, CENTRAL, and Google Scholar. Risk of bias was assessed by evaluating each study’s description of participant characteristics, matching procedures, and administration of RPE scales. Hedges’ d effect sizes for RPE were calculated and aggregated using random-effects models, and potential moderators were explored with meta-regression analysis. Results Forty-one effects were extracted from 37 studies involving 1016 patients and 686 healthy controls. We observed a large (Hedges’ d = 0.85, 95% confidence interval = 0.62–1.08) effect indicating higher RPE in patients than controls. The mean effect size was significantly moderated (P < 0.001, R2 = 0.38) by whether RPE data were analyzed at a peak or submaximal intensity (b = 0.60, z = 4.6, P < 0.001) and the type of patient group that was studied (b = 0.25, z = 2.08, P = 0.04). Conclusions People with ME/CFS and FM perceive aerobic exercise as more effortful than healthy adults, but the exact causes are unclear. The large magnitude of this effect merits further exploration of underlying mechanisms that could provide insight into the pathophysiology of ME/CFS and FM or the broader debate about the nature of central and/or peripheral signals that influence RPE.