Extreme Endurance Exercise Linked to Accelerated Red Blood Cell Aging: Study

A new study published in Blood Red Cells & Iron, a journal of the American Society of Hematology, suggests that extreme endurance running may damage red blood cells in ways that affect their normal function.

Researchers from the University of Colorado Anschutz Medical Campus analyzed blood samples from 23 athletes who participated in two major races: the 40-kilometer Martigny-Combes à Chamonix race and the 171-kilometer Ultra-Trail du Mont-Blanc. Blood was collected immediately before and after the races to examine changes in thousands of proteins, lipids, metabolites, and trace elements.

The findings showed that red blood cells became less flexible after both races, particularly the longer ultramarathon. Since red blood cells must bend and squeeze through tiny blood vessels to deliver oxygen and remove waste, reduced flexibility could impair their efficiency. The study found evidence of both mechanical damage — caused by changes in blood flow and pressure during prolonged running — and molecular damage linked to inflammation and oxidative stress.

The researchers observed that these changes resembled accelerated aging of red blood cells and were more pronounced after the 171-kilometer race. This suggests that as race distance increases, red blood cell damage may intensify, potentially increasing the risk of anemia.

While the long-term consequences remain unclear, the authors caution that extreme endurance exercise may place sustained stress on the body’s most abundant cells. However, they do not advise against participation, noting that more research is needed.

Future studies aim to better understand recovery timelines and explore how these findings might improve athlete recovery strategies and even blood storage practices in transfusion medicine.

REFERENCE: Nemkov, T., et al. (2026) Long-Distance Trail Running Induces Inflammatory-Associated Protein, Lipid, and Purine Oxidation in Red Blood Cells. Blood Red Cells & Iron. DOI: 10.1016/j.brci.2026.100055. https://ashpublications.org/bloodrci/article/doi/10.1016/j.brci.2026.100055/566321/Long-Distance-Trail-Running-Induces-Inflammatory