Cardiorespiratory Parameters Do Not Account For Elevated Perceived Exertion In Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Abstract

Our prior meta-analysis of 37 case-control studies found that people with Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome (ME/CFS) perceive aerobic exercise as more effortful than otherwise healthy people (HP). Whether elevated perceived exertion (RPE) is disease specific or a secondary consequence of between-group differences in aerobic fitness or other cardiorespiratory parameters is not well studied. PURPOSE: Determine the influence of cardiorespiratory parameters on elevated RPE in people with ME/CFS. METHODS: We examined peak RPE responses during ramped cycle ergometry in 178 people with ME/CFS (age = 49.3 ± 13.2; BMI = 27.3 ± 6.9; % female = 65) and 169 HP (age = 42.5 ± 13.2; BMI = 26 ± 5.1; % female = 68). Subgroup analyses were conducted for 198 participants (99 ME/CFS; 99 HP) matched for age (±5 years) and peak oxygen consumption (VO2peak) (~1 ml/kg/min-1). Independent samples t-tests and Hedges’ d (d) effect sizes were used to test for between-group differences in RPE at peak exercise. A series of one-way analysis of covariance (ANCOVA) models with group (ME/CFS, HP) as the between-subjects factor tested whether peak cardiorespiratory parameters influenced between-group differences in RPE. These covariates included ventilatory equivalents for carbon dioxide and oxygen, heart rate, power, respiratory rate, and tidal volume. RESULTS: Mean ± SD peak RPE was 19.1(1) and 18.3(1.9) for ME/CFS and HP, respectively. Peak RPE was significantly higher in people with ME/CFS before (p < 0.001, d = 0.53; 95%CI: 0.32, 0.75) and after (p < 0.001, d = 0.56; 95%CI: 0.27, 0.84) matching for aerobic fitness. ANCOVA models revealed that between-group differences in RPE remained significant after including cardiorespiratory parameters as covariates in the model (all p < 0.05). CONCLUSIONS: People with ME/CFS perceive aerobic exercise as more effortful than HP, but these differences are not influenced by aerobic fitness or other cardiorespiratory factors. These findings extend those of our prior meta-analysis and also signify the importance of incorporating physiological measures beyond indirect calorimetry when studying mechanisms of elevated RPE in ME/CFS. Supported by Centers for Disease Control Contract AAD3581 to the University of Wisconsin-Madison.