Wallman, Karen E, Morton, Alan R, Goodman, Carmel et al. · Research in sports medicine (Print) · 2005 · DOI
Researchers tested whether measurements of fatigue, mood, thinking ability, and physical performance in ME/CFS patients were reliable when checked weekly over four weeks. Most measurements were reliable and consistent, but fatigue ratings—both mental and physical—varied too much week-to-week to be fully trusted. Interestingly, how well people performed during exercise didn't match up well with their reported depression or mood, suggesting the problem may be in how the brain processes fatigue rather than actual muscle weakness.
Understanding which measurements are reliable is crucial for ME/CFS research, as unreliable measures can obscure true findings and slow progress toward better treatments. The finding that fatigue ratings fluctuate significantly highlights why subjective fatigue alone may not be the best way to track disease or treatment response. The weak link between exercise performance and mood suggests ME/CFS fatigue involves brain processing rather than simple deconditioning, supporting research into central nervous system dysfunction.
This study does not prove that fatigue is entirely psychological or that depression causes ME/CFS symptoms; the weak correlation may reflect that exercise performance and mood measure different biological systems. The small sample size (31 per group) limits generalizability, and the study was not designed to identify what *causes* the central fatigue mechanism, only to document its characteristics. Reliability findings from 2005 may not apply to modern assessment tools.
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
Wallman, Karen E, Morton, Alan R, Goodman, Carmel, & Grove, Robert (2005). Reliability of physiological, psychological, and cognitive variables in chronic fatigue syndrome.. Research in sports medicine (Print). https://doi.org/10.1080/15438620500222562
BibTeX
@article{mecfsatlas-wallman-2005-reliability-physiological,
author = {Wallman, Karen E and Morton, Alan R and Goodman, Carmel and Grove, Robert},
title = {Reliability of physiological, psychological, and cognitive variables in chronic fatigue syndrome.},
journal = {Research in sports medicine (Print)},
year = {2005},
doi = {10.1080/15438620500222562},
note = {PubMed: 16392538},
url = {https://www.mecfsatlas.com/evidence/wallman-2005-reliability-physiological},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-28. https://www.mecfsatlas.com/evidence/wallman-2005-reliability-physiological
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