Stevens, Staci, Snell, Chris, Stevens, Jared et al. · Frontiers in pediatrics · 2018 · DOI
This study explains how doctors can properly test ME/CFS patients using a special exercise test called CPET (cardiopulmonary exercise test) done on two consecutive days. The first test measures how much exercise a patient can do, while the second test 24 hours later shows how much the patient's performance has dropped due to post-exertional malaise (PEM)—the symptom flare that happens after exertion. This two-day approach objectively demonstrates one of the key features of ME/CFS: the inability to recover normal function after exercise.
This study establishes a standardized, reproducible methodology for objectively documenting exertion intolerance and post-exertional malaise in ME/CFS—a cardinal feature often dismissed in clinical and research settings. Having validated protocols helps researchers compare findings across studies and gives clinicians a tool to confirm ME/CFS diagnosis. This objective measurement is crucial because it demonstrates that ME/CFS involves real physiological dysfunction rather than deconditioning or psychological factors.
This is a methodological paper describing how to perform the 2-day CPET protocol; it does not prove what causes the abnormal CPET response in ME/CFS or identify the underlying biological mechanisms. The paper does not establish whether the 2-day CPET protocol is diagnostic or predictive of ME/CFS severity, nor does it provide data on sensitivity/specificity in distinguishing ME/CFS from other conditions. Results are specific to the populations studied and may not generalize to all ME/CFS patients or all fatiguing illnesses.
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
Stevens, Staci, Snell, Chris, Stevens, Jared, Keller, Betsy, & VanNess, J Mark (2018). Cardiopulmonary Exercise Test Methodology for Assessing Exertion Intolerance in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.. Frontiers in pediatrics. https://doi.org/10.3389/fped.2018.00242
BibTeX
@article{mecfsatlas-stevens-2018-cardiopulmonary-exercise,
author = {Stevens, Staci and Snell, Chris and Stevens, Jared and Keller, Betsy and VanNess, J Mark},
title = {Cardiopulmonary Exercise Test Methodology for Assessing Exertion Intolerance in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.},
journal = {Frontiers in pediatrics},
year = {2018},
doi = {10.3389/fped.2018.00242},
note = {PubMed: 30234078},
url = {https://www.mecfsatlas.com/evidence/stevens-2018-cardiopulmonary-exercise},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-29. https://www.mecfsatlas.com/evidence/stevens-2018-cardiopulmonary-exercise
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