De Becker, P, Roeykens, J, Reynders, M et al. · Archives of internal medicine · 2000 · DOI
This study measured how much exercise women with ME/CFS could tolerate compared to healthy women without the condition. Patients with ME/CFS were able to exercise at only about half the capacity of healthy controls—they couldn't reach high heart rates and couldn't sustain heavy workloads. The findings show that ME/CFS significantly limits physical ability in ways that can be objectively measured.
This study provides objective physiological evidence that ME/CFS involves genuine exercise intolerance, not deconditioning alone, which validates patient experiences of functional impairment. Understanding the mechanistic basis—potentially autonomic dysfunction—helps guide more appropriate treatment approaches and distinguishes ME/CFS from simple sedentary behavior.
This study does not prove that autonomic dysfunction is the primary cause of reduced exercise capacity, only that it may be a limiting factor. It does not establish whether these findings are unique to ME/CFS or common to other post-viral or chronic conditions. The cross-sectional design cannot determine whether exercise capacity is a cause or consequence of the disease.
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 →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
De Becker, P, Roeykens, J, Reynders, M, McGregor, N, & De Meirleir, K (2000). Exercise capacity in chronic fatigue syndrome.. Archives of internal medicine. https://doi.org/10.1001/archinte.160.21.3270
BibTeX
@article{mecfsatlas-de-becker-2000-exercise-capacity,
author = {De Becker, P and Roeykens, J and Reynders, M and McGregor, N and De Meirleir, K},
title = {Exercise capacity in chronic fatigue syndrome.},
journal = {Archives of internal medicine},
year = {2000},
doi = {10.1001/archinte.160.21.3270},
note = {PubMed: 11088089},
url = {https://www.mecfsatlas.com/evidence/de-becker-2000-exercise-capacity},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/de-becker-2000-exercise-capacity
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