Zhang, Tianmai M, Sharp, Sydney P, Scott, John D et al. · JMIR formative research · 2025 · DOI
Researchers gave 82 people with long COVID or ME/CFS Fitbit devices to track their physical activity, heart rate, and sleep for up to a year, while also asking them to report how they felt. They found that people who were less physically active reported worse fatigue, breathing problems, and physical function, and their symptoms worsened over time compared to those who remained more active. This suggests that activity levels may be related to symptom severity in long COVID, though the study couldn't prove that low activity causes worse symptoms.
Most long COVID and ME/CFS research relies on patient self-reports of symptoms, but this study combined objective wearable device data with validated symptom questionnaires, providing rare physiological insight into activity-symptom relationships in a vulnerable low-income population. Understanding how activity patterns relate to symptom trajectories could inform personalized treatment approaches and help prevent symptom worsening in this debilitating condition.
This study cannot establish that low physical activity causes worse symptoms—the relationship may be reversed (worse symptoms force lower activity) or both may be driven by underlying disease severity. High attrition and missing data prevent generalization to the broader long COVID/ME/CFS population. The exploratory design and lack of a control group mean findings are hypothesis-generating only and require confirmation in larger, controlled trials.
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
Zhang, Tianmai M, Sharp, Sydney P, Scott, John D, Taren, Douglas, Samaniego, Jane C, Unger, Elizabeth R, et al. (2025). Characterization of Post-Viral Infection Behaviors Among Patients With Long COVID: Prospective, Observational, Longitudinal Cohort Analyses of Fitbit Data and Patient-Reported Outcomes.. JMIR formative research. https://doi.org/10.2196/77644
BibTeX
@article{mecfsatlas-zhang-2025-characterization-post,
author = {Zhang, Tianmai M and Sharp, Sydney P and Scott, John D and Taren, Douglas and Samaniego, Jane C and Unger, Elizabeth R and Bertolli, Jeanne and Lin, Jin-Mann S and Ramers, Christian B and Godino, Job G},
title = {Characterization of Post-Viral Infection Behaviors Among Patients With Long COVID: Prospective, Observational, Longitudinal Cohort Analyses of Fitbit Data and Patient-Reported Outcomes.},
journal = {JMIR formative research},
year = {2025},
doi = {10.2196/77644},
note = {PubMed: 41474983},
url = {https://www.mecfsatlas.com/evidence/zhang-2025-characterization-post},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/zhang-2025-characterization-post
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