Ultramarathon Running Could Rapidly Age and Breakdown Red Blood Cells

Running can be a great way to keep the body moving and stay fit. But extreme endurance running, or ultramarathoning, can also have adverse effects on the body, including damage to red blood cells that can impair their function.

A new study in Red blood cells and iron joins a growing body of research that reveals these forms of ultra exercise may be doing the body more harm than good.

“Based on these data, we have no indication as to whether or not people should participate in these types of events; what we can say is that when they do, persistent stress damages the most abundant cell in the body,” said Travis Nemkov, lead author of the study and associate professor in the Department of Biochemistry and Molecular Genetics at the University of Colorado Anschutz, in a press release.

Learn more: When running a marathon, the brain can start to eat itself

Ultramarathon running and impact on red blood cells

Previous studies, such as the one published in Annals of Translational Medicine in 2019 examines how ultramarathon runners can experience red blood cell breakdown during a race, which can cause anemia. Although this study noted cellular degradation, the research team wasn’t sure what the actual cause was.

Fast forward to 2026, and the Red blood cells and iron Study results show that runners participating in ultramarathons experience their red blood cells becoming less flexible, which can reduce the cells’ ability to efficiently transport nutrients, oxygen and waste throughout the body.

“Participating in events like these can cause general inflammation in the body and damage red blood cells,” Nemkov said.

The results also helped the research team create the most detailed and complex molecular map of the impact of long-distance endurance running on red blood cells.

“Red blood cells are remarkably resilient, but they are also extremely sensitive to mechanical and oxidative stress,” study co-author Angelo D’Alessandro, Ph.D, said in a press release.

Blood collection from ultramarathon runners

For the study, the research team examined blood samples from 23 runners participating in either the Martigny-Combes to Chamonix race (25 miles) or the Mont Blanc Ultra Trail (106 miles). The team collected the runner’s blood just before and after races and analyzed the samples for red blood cell health markers.

The team then analyzed red blood cells and proteins, metabolites and lipids. The results indicated consistent evidence of damage caused by physical and molecular factors. According to the study, physical damage to cells was most likely caused by running-induced fluid pressure throughout the body, while molecular damage was likely caused by inflammation or oxidative stress.

The damage to these cells – which accelerates their aging and causes them to break down – begins to take effect during the 25-mile race and is only amplified in runners who participated in the 106-mile race, meaning that the longer the race, the more damage the red blood cells suffer.

“At some point between marathon and ultra-marathon distances, the damage really starts to be felt,” Nemkov said in a press release. “We’ve seen this damage, but we don’t know how long it takes for the body to repair this damage, whether this damage has a long-term impact, and whether that impact is good or bad.”

Preserving blood for the future

Although these forms of exercise can be harmful to red blood cells, the research team hopes that these findings could fuel further studies aimed at improving athletic performance or even reducing the impact of endurance exercise on red blood cells. These findings could even help improve blood bank storage, which is only viable for about 6 weeks.

“This study shows that extreme endurance exercise pushes red blood cells toward accelerated aging through mechanisms that mirror what we observe during blood storage. Understanding these common pathways gives us a unique opportunity to learn how to better protect blood cell function in athletes and in transfusion medicine,” D’Alessandro concluded.

The team noted that the study had a limited number of participants, lacked racial diversity, and collected blood samples at just two points in the race rather than multiple points. Future studies should incorporate a more diverse group of athletes and more blood samples.

This article does not offer medical advice and should be used for informational purposes only.

Learn more: This ancient practice can lower blood pressure in the same way as certain medications

Article sources

Our Discovermagazine.com editors use peer-reviewed research and high-quality sources for our articles, and our editors review the articles for scientific accuracy and editorial standards. See the sources used below for this article: