Inbar, O, Dlin, R, Rotstein, A et al. · Medicine and science in sports and exercise · 2001 · DOI
Researchers compared how the bodies of 15 people with ME/CFS responded to a gradually increasing exercise test on a treadmill, compared to 15 healthy people. People with ME/CFS showed lower heart rates and weaker cardiovascular responses during exercise, even when they appeared to be pushing themselves as hard as they could. This suggests their bodies may have trouble with either heart function or muscle oxygen use during physical exertion.
This study provides objective physiological evidence that ME/CFS involves measurable exercise intolerance—not deconditioning or psychological factors—by documenting distinctive cardiopulmonary abnormalities during standardized testing. Establishing reliable biomarkers for exercise response could improve diagnostic accuracy and help researchers distinguish ME/CFS from other fatigue disorders.
This study does not identify the underlying cause of the abnormal exercise response—whether the problem originates in the heart, lungs, blood vessels, or muscles. It also cannot establish whether these physiological changes are primary features of ME/CFS or secondary consequences of the illness, nor does it determine whether exercise response patterns would predict post-exertional malaise or recovery trajectories.
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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