Lien, Katarina, Johansen, Bjørn, Veierød, Marit B et al. · Physiological reports · 2019 · DOI
This study looked at how the bodies of ME/CFS patients handle repeated exercise tests done 24 hours apart. Researchers measured how much oxygen patients used and tracked a substance called lactate in their blood during exercise. They found that ME/CFS patients performed worse on the second test and had higher lactate levels, opposite to what happened in healthy people, whose bodies actually recovered better the second time.
This study provides objective physiological evidence that post-exertional malaise in ME/CFS involves abnormal lactate metabolism, suggesting that the body's inability to clear metabolic byproducts after exercise may contribute to delayed recovery. These findings support the biological basis of exercise intolerance in ME/CFS and could help guide rehabilitation approaches and validate patient experiences of worsening symptoms after exertion.
This study does not establish the mechanisms causing abnormal lactate accumulation, nor does it prove that lactate itself causes post-exertional malaise symptoms. The small sample size (18 patients) and female-only population limit generalizability. Correlation between lactate changes and symptom severity was not directly measured, so causality remains unclear.
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
Lien, Katarina, Johansen, Bjørn, Veierød, Marit B, Haslestad, Annicke S, Bøhn, Siv K, Melsom, Morten N, et al. (2019). Abnormal blood lactate accumulation during repeated exercise testing in myalgic encephalomyelitis/chronic fatigue syndrome.. Physiological reports. https://doi.org/10.14814/phy2.14138
BibTeX
@article{mecfsatlas-lien-2019-abnormal-blood,
author = {Lien, Katarina and Johansen, Bjørn and Veierød, Marit B and Haslestad, Annicke S and Bøhn, Siv K and Melsom, Morten N and Kardel, Kristin R and Iversen, Per O},
title = {Abnormal blood lactate accumulation during repeated exercise testing in myalgic encephalomyelitis/chronic fatigue syndrome.},
journal = {Physiological reports},
year = {2019},
doi = {10.14814/phy2.14138},
note = {PubMed: 31161646},
url = {https://www.mecfsatlas.com/evidence/lien-2019-abnormal-blood},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-25. https://www.mecfsatlas.com/evidence/lien-2019-abnormal-blood
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