Mancini, Donna M, Cook, Dane B, Brunjes, Danielle L et al. · Frontiers in physiology · 2026 · DOI
Researchers asked whether doing two exercise tests on consecutive days could reliably detect post-exertional malaise (PEM) in ME/CFS patients. They found that oxygen consumption and other key exercise measures did not change between Day 1 and Day 2 in either ME/CFS patients or healthy controls. However, ME/CFS patients reported much greater fatigue during exercise and had lower maximum heart rates. One study's findings do not establish whether this two-day test method is truly useful for measuring PEM in clinical practice.
This study directly addresses a growing clinical practice: using sequential CPETs to diagnose PEM and measure disability in ME/CFS. The finding that standard CPET metrics do not decline between test days challenges the validity of this protocol and may help clinicians and researchers reconsider how to objectively assess PEM and exercise-related worsening.
This single cross-sectional study does not establish whether alternative CPET protocols, outcome measures, or subgroup definitions might yet reveal PEM-related changes. It does not confirm a mechanism for PEM or explain why ME/CFS patients experience greater perceived exertion. It does not determine whether other biomarkers (metabolic, inflammatory, cardiac) show declines on Day 2.
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
Mancini, Donna M, Cook, Dane B, Brunjes, Danielle L, Soto, Tiffany, Blate, Michelle, Quan, Patrick, et al. (2026). Cardiopulmonary exercise test results do not change over two sequential days in patients with chronic fatigue syndrome.. Frontiers in physiology. https://doi.org/10.3389/fphys.2026.1816082
BibTeX
@article{mecfsatlas-mancini-2026-cardiopulmonary-exercise,
author = {Mancini, Donna M and Cook, Dane B and Brunjes, Danielle L and Soto, Tiffany and Blate, Michelle and Quan, Patrick and Yamazaki, Tadahiro and Norweg, Anna and Natelson, Benjamin H},
title = {Cardiopulmonary exercise test results do not change over two sequential days in patients with chronic fatigue syndrome.},
journal = {Frontiers in physiology},
year = {2026},
doi = {10.3389/fphys.2026.1816082},
note = {PubMed: 42212259},
url = {https://www.mecfsatlas.com/evidence/mancini-2026-cardiopulmonary-exercise},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/mancini-2026-cardiopulmonary-exercise
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