van Campen, C Linda M C, Visser, Frans C · Healthcare (Basel, Switzerland) · 2021 · DOI
This study compared how men with ME/CFS respond to exercise testing on two consecutive days versus men with chronic fatigue that doesn't meet ME/CFS criteria. When ME/CFS patients exercised on the second day, they performed worse and couldn't reach the same levels they achieved on day one. Men with chronic fatigue (but not ME/CFS) actually improved on day two, similar to healthy people.
This study provides objective physiological evidence that ME/CFS produces a characteristic abnormal response to exercise (post-exertional malaise) that distinguishes it from other forms of chronic fatigue. The two-day CPET protocol may serve as a useful biomarker to help clinicians differentiate between ME/CFS and other fatigue conditions, improving diagnostic accuracy and potentially guiding treatment decisions.
This study does not prove that the two-day CPET can be used routinely in clinical practice—it was conducted in a research setting with relatively small numbers. It does not establish why ME/CFS patients show this deterioration pattern, only that they do. Results are limited to males and may not apply to female ME/CFS patients, who represent the majority of the ME/CFS population.
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
van Campen, C Linda M C & Visser, Frans C (2021). Comparing Idiopathic Chronic Fatigue and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) in Males: Response to Two-Day Cardiopulmonary Exercise Testing Protocol.. Healthcare (Basel, Switzerland). https://doi.org/10.3390/healthcare9060683
BibTeX
@article{mecfsatlas-van-campen-2021-comparing-idiopathic,
author = {van Campen, C Linda M C and Visser, Frans C},
title = {Comparing Idiopathic Chronic Fatigue and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) in Males: Response to Two-Day Cardiopulmonary Exercise Testing Protocol.},
journal = {Healthcare (Basel, Switzerland)},
year = {2021},
doi = {10.3390/healthcare9060683},
note = {PubMed: 34198946},
url = {https://www.mecfsatlas.com/evidence/van-campen-2021-comparing-idiopathic},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-29. https://www.mecfsatlas.com/evidence/van-campen-2021-comparing-idiopathic
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