Ohashi, Kyoko, Yamamoto, Yoshiharu, Natelson, Benjamin H · Physiology & behavior · 2002 · DOI
This study looked at whether exhausting exercise disrupts the body's internal daily rhythm in people with ME/CFS. Researchers measured activity patterns in ME/CFS patients and healthy controls before and after a strenuous treadmill test. They found that ME/CFS patients' activity rhythms became abnormally lengthened (longer than 24 hours) after exercise, while healthy people's rhythms stayed normal—suggesting the body loses its ability to keep time after strenuous activity in ME/CFS.
This study provides mechanistic insight into why ME/CFS patients experience dramatic symptom worsening after exertion by linking post-exertional exacerbation to measurable disruption of the body's circadian timing system. Understanding this biological mechanism could inform treatment strategies targeting circadian regulation and help validate post-exertional exacerbation as a physiological phenomenon rather than a psychological one.
This small, short-term observational study does not prove that circadian dysregulation causes post-exertional exacerbation—only that the two occur together after exercise. The study cannot establish whether the circadian disruption is a primary cause, a consequence of symptom worsening, or both. Results are limited to the specific exercise protocol tested and may not generalize to other types or intensities of exertion.
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 →
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