Ultramarathons can be bad for your blood

While exercise is important for a long and healthy life, ultramarathons can accelerate the aging of the cells in our blood. Athletes who ran 170 kilometers over mountainous terrain accumulated more age-related red blood cell damage than those who ran a shorter distance.

Long-distance running has been linked to health problems before, such as temporary suppression of the immune system and anemia. But it’s only now that we understand what it does to red blood cells – which transport oxygen around the body – especially when it’s done outdoors in mountainous terrain.

Angelo D’Alessandro at the University of Colorado, Anschutz and his colleagues analyzed blood samples from 11 adults with an average age of 36 in the hours before and after they ran a 40-kilometer trail race. They did the same for a separate group of 12 people of about the same age competing in a 170-kilometer ultramarathon over similar terrain.

The researchers found that competing in both races caused the runners’ red blood cells to accumulate more damage from molecules known as reactive oxygen species, which are produced at higher levels when those cells need to deliver more oxygen to the body.

But such damage, which naturally accumulates as red blood cells age, was significantly higher in ultramarathon runners. “Anecdotally, the blood after an ultramarathon looks like the blood of someone who just got hit by a car,” says D’Alessandro. “Red blood cells accumulate damage and age.”

Running an ultramarathon, but not a shorter race, also seemed to cause their red blood cells to shift more quickly from a disc shape to a more spherical shape, which is typically seen as they age. The shape of the disc allows them to bend and push through tiny blood vessels in the spleen, where old red blood cells are destroyed. “This spherical shape means they get stuck in the spleen and are engulfed by immune cells,” says a team member Travis Nemkovalso at the University of Colorado Anschutz.

This damage is likely caused by exercise that increases inflammation and particularly strenuous activity that pushes red blood cells harder around the body, he says.

Additionally, only ultra-marathon runners experienced a roughly 10 percent drop in red blood cell counts after the race, but that’s not necessarily a health problem. This change is too small to cause anemia, and the body can probably recover from it quickly, Nemkov says.

Scientists are now studying the red blood cells of ultramarathon runners the day after they finish the race to better understand how long these effects last. They also want future work to investigate whether these changes affect runners’ performance. “It could just be how the damage signals look to make the body more resistant to endurance running, or it could have a negative impact,” Němkov says.

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