Associations between heart rate and physical activity in people with post-COVID-19 condition accounting for myalgic encephalomyelitis/chronic fatigue syndrome symptoms. — CFSMEATLAS
Associations between heart rate and physical activity in people with post-COVID-19 condition accounting for myalgic encephalomyelitis/chronic fatigue syndrome symptoms.
Adodo, Rachel, Sarmento Da Nobrega, Antonio, Villar, Rodrigo et al. · Journal of rehabilitation medicine · 2026 · DOI
Quick Summary
This study looked at how heart rate and physical activity are related in people with long COVID who also have ME/CFS-like symptoms. Researchers found that people experienced more episodes of rapid heartbeat (over 100 beats per minute) when they were resting or doing very little, but surprisingly had fewer of these episodes during moderate-to-vigorous exercise. This suggests that the relationship between activity and heart rate in long COVID may be more complex than previously thought.
Why It Matters
Understanding heart rate responses to activity in post-COVID and ME/CFS populations is critical for developing safe rehabilitation protocols, as inappropriate exercise recommendations can worsen symptoms. This finding challenges assumptions about post-exertional malaise and heart rate patterns, potentially informing more nuanced clinical guidelines for activity management in these conditions.
Observed Findings
Average daily heart rate increased progressively from sedentary to light to moderate-vigorous physical activity levels.
Percentage of time in tachycardia (HR >100 bpm) was significantly lower during moderate-to-vigorous physical activity compared with sedentary periods.
This tachycardia pattern remained significant even after statistical adjustment for ME/CFS symptom severity.
Participants wore monitoring devices an average of 11-12.5 hours per day over 4 days.
Inferred Conclusions
Tachycardia in post-COVID condition may be more prominent during periods of low physical activity rather than during activity itself.
The relationship between physical activity intensity and tachycardia in PCC is not simply linear and may involve different physiological mechanisms than expected.
ME/CFS symptom severity does not fully explain the observed tachycardia patterns during rest versus activity.
Remaining Questions
What physiological mechanisms explain why tachycardia is more prevalent during rest than during moderate-to-vigorous activity in this population?
Do heart rate and tachycardia patterns differ in the hours or days following activity (post-exertional effects)?
How do findings generalize to larger, more diverse populations with longer monitoring periods and different severity levels of PCC/ME/CFS?
What This Study Does Not Prove
This study cannot establish cause-and-effect relationships or explain why tachycardia occurs more during rest than activity. The small sample size and short duration limit generalizability, and the findings do not prove that moderate exercise is safe or beneficial for all people with PCC/ME/CFS, nor do they address post-exertional malaise that may occur after activity cessation.