Postexertional Symptom Exacerbation after Submaximal Exercise in Individuals with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Postacute Sequelae of COVID-19. — CFSMEATLAS
Postexertional Symptom Exacerbation after Submaximal Exercise in Individuals with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Postacute Sequelae of COVID-19.
Berardi, Giovanni, Janowski, Adam, McNally, Samuel et al. · Medicine and science in sports and exercise · 2026 · DOI
Quick Summary
This study looked at what happens when people with ME/CFS or long COVID do moderate exercise. Researchers asked 60 patients and 30 healthy people to exercise for 25 minutes, then tracked their symptoms for a week. Most patients with ME/CFS experienced worsening fatigue, mental fog, and other symptoms in the days after exercise, but the severity and which symptoms got worse varied from person to person.
Why It Matters
Understanding PESE variability is crucial for tailoring exercise recommendations in ME/CFS and long COVID. This study provides evidence that symptom response to exercise is heterogeneous, suggesting that one-size-fits-all exercise prescriptions may not be appropriate and that careful individual assessment is necessary to avoid harm.
Observed Findings
Physical fatigue was reported by 77% of all patients (46/60), while anxiety was reported by only 60% (18/30), showing variable symptom involvement
PESE changes were greatest in the 72-hour window post-exercise rather than extending across all 7 days
27% of ME/CFS patients (8/30) and 40% of PASC patients (12/30) showed minimal to no increase in PESE symptoms
20-23% of patients across both groups showed clinically significant increases (>3/10 points) on aggregate symptom scores
ME/CFS participants showed greater PESE magnitude than PASC participants
Inferred Conclusions
PESE response to submaximal exercise is heterogeneous, with some patients showing minimal symptoms while others show clinically relevant exacerbations
An aggregate symptom score capturing physical fatigue, mental fatigue, physical function, and flu-like symptoms better characterizes PESE than individual symptoms
Intensity modifications may be necessary for some individuals with ME/CFS and PASC to minimize PESE, while others tolerate submaximal exercise without exacerbation
The 72-hour post-exercise period is critical for PESE manifestation in this patient population
Remaining Questions
Which clinical, immunological, or genetic factors predict which patients will experience severe PESE versus minimal symptoms?
What This Study Does Not Prove
This study does not establish whether submaximal exercise is universally safe or harmful for ME/CFS patients—only that responses vary significantly. It does not identify which biological mechanisms cause PESE or predict which individual patients will experience severe exacerbations. The 7-day timeframe may not capture delayed or prolonged exacerbations lasting weeks or longer.