Ultramarathons Linked to Red Blood Cell Damage, Study Finds

Extreme endurance races may harm red blood cells, reducing their flexibility and speeding up their breakdown, according to research published in Blood Red Cells & Iron, a journal of the American Society of Hematology.

Researchers analyzed blood samples from 23 runners before and after two demanding events: the 40 km Martigny-Combes à Chamonix race and the 171 km Ultra Trail de Mont Blanc. The team found that prolonged running caused both mechanical and molecular damage to red blood cells, driven by inflammation and oxidative stress. The longer the race, the greater the signs of cellular injury and accelerated aging.

Lead author of the University of Colorado Anschutz Medical Campus said the long-term health effects remain unclear. Co-author noted the findings may also inform improvements in blood storage and transfusion practices.

21-02-2026