Ickmans, Kelly, Clarys, Peter, Nijs, Jo et al. · Journal of rehabilitation research and development · 2013 · DOI
This study looked at whether people with ME/CFS who have better thinking skills (like memory and reaction time) also tend to be more physically fit or active. Researchers tested 31 women with ME/CFS and 13 healthy women on thinking tasks and physical fitness measures. They found that physical fitness—especially heart and muscle function—was linked to thinking speed, but daily activity levels were not.
Cognitive dysfunction ('brain fog') and exercise intolerance are hallmark features of ME/CFS, yet few studies examine their mechanistic relationship. This study provides evidence that physical deconditioning may contribute to cognitive slowing, potentially informing rehabilitation approaches and suggesting that improving cardiovascular and muscular fitness might benefit cognition in this population.
This study cannot establish causation—it is unclear whether better fitness improves cognition, whether cognitive impairment prevents fitness improvement, or whether both stem from a common underlying mechanism. The small sample (31 CFS patients) limits generalizability to all ME/CFS populations, and the cross-sectional design cannot track changes over time. Additionally, the lack of association with daily activity levels does not rule out structured exercise interventions having cognitive benefits.
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
Ickmans, Kelly, Clarys, Peter, Nijs, Jo, Meeus, Mira, Aerenhouts, Dirk, Zinzen, Evert, et al. (2013). Association between cognitive performance, physical fitness, and physical activity level in women with chronic fatigue syndrome.. Journal of rehabilitation research and development. https://doi.org/10.1682/JRRD.2012.08.0156
BibTeX
@article{mecfsatlas-ickmans-2013-association-between,
author = {Ickmans, Kelly and Clarys, Peter and Nijs, Jo and Meeus, Mira and Aerenhouts, Dirk and Zinzen, Evert and Aelbrecht, Senne and Meersdom, Geert and Lambrecht, Luc and Pattyn, Nathalie},
title = {Association between cognitive performance, physical fitness, and physical activity level in women with chronic fatigue syndrome.},
journal = {Journal of rehabilitation research and development},
year = {2013},
doi = {10.1682/JRRD.2012.08.0156},
note = {PubMed: 24203542},
url = {https://www.mecfsatlas.com/evidence/ickmans-2013-association-between},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/ickmans-2013-association-between
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