Davenport et al. (2026)
- Authors: Todd Davenport, Staci Stevens, Jared Stevens, Mark Van Ness
- Institutes: Department of Physical Therapy, University of the Pacific, Stockton, CA, USA, Workwell Foundation, Ripon, CA, USA
- Publisher: Research Square (Preprint)
- Link: DOI
Summary
This research provides objective evidence that Long COVID and ME/CFS are physiologically indistinguishable in how they process energy and recover from exertion. By demonstrating that the ‘energy crash’ is a measurable metabolic failure rather than a result of deconditioning, the study validates the lived experience of patients in both groups. These findings suggest that the two conditions share a common underlying pathology, potentially allowing for unified diagnostic and therapeutic approaches.
What was researched?
The study compared physiological responses during exercise in patients with ME/CFS and Long COVID to determine if they share a common bioenergetic basis for post-exertional malaise (PEM). Researchers specifically investigated whether both groups exhibit a similar failure to reproduce performance on consecutive days.
Why was it researched?
Since both conditions are characterized by PEM, the authors hypothesized they share metabolic dysfunctions. Establishing these commonalities is critical for validating Long COVID’s relationship to ME/CFS and identifying objective markers for disability.
How was it researched?
This retrospective study used a two-day cardiopulmonary exercise test (CPET) protocol, requiring participants to perform maximal exercise 24 hours apart. The cohort included 84 patients with ME/CFS, 79 with Long COVID, and 71 healthy controls, with data analyzed across sexes using repeated measures ANOVA.
What has been found?
Both ME/CFS and Long COVID groups demonstrated significant reductions in oxygen consumption and workload at the anaerobic threshold on the second day compared to controls. No significant differences were observed between the two patient groups, indicating nearly identical metabolic impairment. Furthermore, hemodynamic and ventilatory measures were normal, suggesting the dysfunction is cellular rather than related to heart or lung health.
Discussion
The results indicate that the functional limitations in both conditions are driven by bioenergetic failure and inadequate recovery. While females in the study exhibited more pronounced abnormalities, the overall consistency across cohorts supports the utility of two-day CPET as a reliable objective marker for PEM.
Conclusion & Future Work
ME/CFS and Long COVID involve a functionally significant bioenergetic failure that is unexplained by standard heart or lung testing. The study confirms that two-day CPET is a vital tool for objectively measuring the systemic recovery failure characteristic of these diseases.