Running extreme distances may strain more than just muscles and joints. New research suggests ultramarathons can alter red blood cells in ways that make them less flexible and more prone to breakdown, ...

Extreme endurance running damages red blood cells in ways that may affect their ability to function properly, according to a study published in the American Society of Hematology's journal Blood Red ...

Long-distance trail running and extreme cardio activity led to red blood cell damage, per a new study. Here, doctors explain ...

Learn more about the impact ultramarathon running has on red blood cells and how it may do more harm than good for the body.