Chu, Lily, Valencia, Ian J, Garvert, Donn W et al. · PloS one · 2018 · DOI
This study asked 150 ME/CFS patients to describe what happens when they experience post-exertional malaise (PEM)—the characteristic crash that follows physical activity, mental effort, or emotional stress. Researchers found that 90% of patients experienced PEM from all three types of triggers, with fatigue being the most common symptom, but also cognitive problems, sleep issues, headaches, and muscle pain. Most patients' PEM lasted at least 24 hours, though the timing and severity varied from person to person.
This study is important because PEM is central to ME/CFS diagnosis, yet patients' actual experiences had rarely been systematically documented. By characterizing the specific symptoms and time patterns of PEM as patients experience them in daily life, the research provides evidence that could improve clinical recognition and inform the design of future mechanistic studies that require accurate PEM phenotyping.
This study does not prove the biological mechanism underlying PEM or establish why certain patients show delayed onset while others do not. It is descriptive and observational—it documents what patients report but does not use biomarkers, controls, or objective measures to validate symptom changes or identify underlying pathophysiology.
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
Chu, Lily, Valencia, Ian J, Garvert, Donn W, & Montoya, Jose G (2018). Deconstructing post-exertional malaise in myalgic encephalomyelitis/ chronic fatigue syndrome: A patient-centered, cross-sectional survey.. PloS one. https://doi.org/10.1371/journal.pone.0197811
BibTeX
@article{mecfsatlas-chu-2018-deconstructing-post,
author = {Chu, Lily and Valencia, Ian J and Garvert, Donn W and Montoya, Jose G},
title = {Deconstructing post-exertional malaise in myalgic encephalomyelitis/ chronic fatigue syndrome: A patient-centered, cross-sectional survey.},
journal = {PloS one},
year = {2018},
doi = {10.1371/journal.pone.0197811},
note = {PubMed: 29856774},
url = {https://www.mecfsatlas.com/evidence/chu-2018-deconstructing-post},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-27. https://www.mecfsatlas.com/evidence/chu-2018-deconstructing-post
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