Keller, Betsy, Receno, Candace N, Franconi, Carl J et al. · Journal of translational medicine · 2024 · DOI
This study tested 84 people with ME/CFS and 71 healthy controls on an exercise bike on two days, 24 hours apart. People with ME/CFS performed worse on the second day of testing—their oxygen use, heart rate, and exercise capacity all declined—while healthy people stayed about the same. This objective decline mirrors the real-world experience of post-exertional malaise, where ME/CFS patients feel worse after physical activity.
This is the largest two-day CPET study to date providing objective, reproducible evidence that ME/CFS involves impaired recovery from exertion—a core diagnostic feature. The findings validate the use of sequential CPET protocols in clinical assessment and research, offering measurable biomarkers of disease severity that could guide treatment decisions and track response to interventions.
This study demonstrates correlation between exertional stress and physiological decline but does not definitively prove the underlying mechanism (autonomic dysfunction, mitochondrial impairment, or other factors). It does not establish causation or identify which specific physiological abnormality is primary. The study also cannot determine whether the observed post-exertional declines would predict clinical symptom severity or response to specific treatments in individual patients.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
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