Thomas et al. (2026)
- Authors: Callum Thomas, Ruth E. Ashton, Rebecca Owen, Ethan McNeil-Angopa, Jack Carr, Thomas Bewick, Mark A. Faghy
- Institutes: University of Derby, Derby, UK, University Hospitals of Derby and Burton NHS Foundation Trust, Derby, UK
- Publisher: Physiological Reports
- Link: DOI
Summary
This research provides objective evidence of physiological dysfunction at the muscle level in Long COVID, moving beyond subjective symptom reports. By demonstrating that oxygen delivery worsens with repeated exertion, it validates patient experiences of post-exertional malaise and suggests that peripheral hypoxia is a critical driver of the condition.
What was researched?
This study examined peripheral tissue hypoxia and muscle oxygenation during repeated submaximal exercise to understand the physiological basis of symptoms in adults with Long COVID.
Why was it researched?
Researchers aimed to identify mechanisms behind post-exertional symptom exacerbation (PESE) and reduced exercise capacity, focusing on whether oxygen delivery to muscles is impaired.
How was it researched?
The study compared 46 participants with Long COVID to 10 healthy controls using a two-day submaximal cardiopulmonary exercise test (CPET) protocol. Near-infrared spectroscopy (NIRS) was used to continuously monitor oxygen saturation levels in the gastrocnemius muscle before, during, and after the sessions.
What has been found?
Long COVID patients showed significantly impaired physical function on the second day of testing compared to the first. Results indicated that muscle tissue saturation remained elevated for a shorter duration during exercise in the Long COVID group, a response that worsened on day two and was followed by rapid normalization.
Discussion
These findings suggest that impaired muscle oxygenation and recovery during repeated exertion are key features of Long COVID. The worsening of these responses on the second day highlights the importance of multi-day testing to capture exertional intolerance accurately.
Conclusion & Future Work
The study concludes that peripheral oxygen delivery is dysfunctional in Long COVID patients. This impairment likely contributes to the persistence of symptoms and the phenomenon of post-exertional malaise.