Exercise Triggers Dangerous Microclot Fragmentation in Long COVID Patients Says New Study
Nikhil Prasad Fact checked by:Thailand Medical News Team May 28, 2025 2 days, 44 minutes ago
Medical News: Alarming Changes in Blood Detected After Physical Exertion
A groundbreaking new study has uncovered troubling evidence that exercise may worsen biological disturbances in individuals suffering from Long COVID by triggering the fragmentation of dangerous blood microclots. These tiny clots, which are increasingly recognized as a hallmark of Long COVID pathology, were found to break apart and contribute to increased inflammation and vascular damage following even moderate physical activity.
Exercise Triggers Dangerous Microclot Fragmentation in Long COVID Patients Says New Study
The research was conducted by a multidisciplinary team from the University of Derby, Stellenbosch University, Coventry University, University of Liverpool, and University Hospitals of Derby and Burton NHS Foundation Trust. This
Medical News report highlights the key findings and their significance for millions worldwide still grappling with persistent symptoms long after their initial COVID-19 infection.
The Study and Its Approach
Researchers recruited 46 individuals with Long COVID who were considered low risk for post-exertional malaise (PEM), a known complication where symptoms flare after physical effort. Participants underwent two days of submaximal cardiopulmonary exercise testing (CPET), designed to assess heart and lung function without reaching maximum exertion.
Blood samples were taken before and after each session to examine inflammatory biomarkers and the size and quantity of microclots present. Using advanced imaging flow cytometry and cytokine profiling, the study team investigated how exercise influenced the dynamics of microclots and inflammatory responses.
Shocking Biological Responses to Exercise
Results revealed a disturbing trend. After physical exertion, large microclots (100–3000 µm²) fragmented into smaller clots (<30 µm²), which did not disappear from the bloodstream but instead increased in quantity. These smaller microclots correlated with elevated levels of pro-inflammatory cytokines like IL-6 and interferon-gamma inducible protein 10 (IP-10), indicating a surge in systemic inflammation following exercise.
Contrary to the popular belief that exercise helps clear harmful clots, the findings showed that in Long COVID patients, exercise altered clot size but failed to eliminate them. In fact, the breakdown of larger microclots may have released trapped inflammatory substances, triggering an immune response that further inflamed the vascular system.
Implications for Rehabilitation Programs
Researchers warn that these results challenge current rehabilitation strategies for Long COVID, many of which rely on exercise to aid recovery. While graded exercise therapy might benefit healthy individuals, it could have dangerous effects for Long COVID sufferers with underlying microclot pathology.
The study also found that many patients experienced reduced oxygen del
ivery and utilization (as measured by lower VO₂ and oxygen pulse) after the second day of exercise, likely due to impaired microvascular function caused by the redistribution of microclot sizes.
A Closer Look at the Immune Response
The study’s cytokine analysis revealed that certain pro-inflammatory signals increased significantly after exercise, while anti-inflammatory cytokines like IL-10 and IL-13 did not show meaningful changes. This imbalance suggests a failure of the body’s compensatory mechanisms to control the inflammation induced by microclot fragmentation.
Moreover, vascular injury markers like epidermal growth factor (EGF) dropped post-exercise, implying potential damage to blood vessels. These biological changes were observed alongside worsening functional capacity and increased symptoms in some participants.
Conclusions and Caution for Long COVID Patients
This study is the first to provide strong biological evidence that moderate exercise may aggravate rather than alleviate Long COVID symptoms by promoting microclot fragmentation and inflammatory responses. The findings call into question one-size-fits-all exercise recommendations for Long COVID patients and stress the importance of tailored rehabilitation programs based on individual vascular health and clotting profiles.
The researchers conclude that while exercise is generally beneficial for health, it may pose serious risks for those with Long COVID due to the persistence and behavior of microclots in their bloodstream. As such, rehabilitation approaches should be designed with caution, integrating screening for post-exertional symptom exacerbation and novel treatments to target microclot clearance and repair endothelial damage.
The study findings were published on a preprint server and are currently being peer reviewed.
https://www.researchsquare.com/article/rs-6717727/v1
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