Norweg, Anna, Yao, Lanqiu, Barbuto, Scott et al. · Respiratory physiology & neurobiology · 2023 · DOI
This study looked at why people with long COVID struggle with exercise. Researchers tested 59 patients using a standard exercise test and found that their bodies were not extracting and using oxygen efficiently during activity. The patients also showed an unusual heart rate response during exercise. These findings suggest that problems with how the body produces and uses energy may be a key reason why long COVID patients experience fatigue and feel worse after exertion.
Exercise intolerance and post-exertional malaise are hallmark symptoms of both long COVID and ME/CFS. This study provides physiological evidence that oxygen extraction defects—not simply deconditioning—may underlie exercise intolerance, which could redirect treatment strategies away from graded exercise programs toward interventions targeting cellular energy metabolism. Understanding these mechanisms is crucial for developing safe, effective therapies.
This study does not prove causation or establish the specific biochemical mechanisms causing impaired oxygen extraction. The small sample size (n=59) from a single center and retrospective design limit generalizability. The authors cannot determine whether oxygen extraction impairment is primary or secondary to other physiological disturbances, nor can they rule out that early exercise termination reflects central (neurological) rather than peripheral (muscular) limitations.
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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