Ultramarathons could be bad for your blood

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

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

Angelo D’Alessandro of the University of Colorado Anschutz and colleagues analyzed blood samples from 11 adults with an average age of 36, hours before and after running a 25-mile trail race. They did the same for a separate group of 12 people of the same age who competed in a 170-kilometer ultramarathon over similar terrain.

The researchers found that competing in either race seemed to cause runners’ red blood cells to accumulate more damage from molecules called reactive oxygen species, which are produced at higher levels when these cells need to deliver more oxygen into the body.

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

Running the ultramarathon, but not the shorter race, also appears 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 squeeze into the tiny blood vessels of the spleen, where old red blood cells are destroyed. “This spherical shape means they get stuck in the spleen and eaten by immune cells,” says team member Travis Nemkov, also at the University of Colorado Anschutz.

This damage is likely due to increased inflammation through exercise and particularly strenuous activity that pushes red blood cells more forcefully through the body, he says.

Additionally, only ultramarathon runners experienced about a 10 percent drop in their red blood cell counts after the race, but this is not necessarily a problem for their health. This change is too small to cause anemia and the body can probably recover quickly, Nemkov says.

Researchers are now studying ultramarathon runners’ red blood cells a day after completing a race, to better understand how long these effects last. They also want future work to examine whether these changes affect runners’ performance. “It could just be what the damage signals look like to make the body more resilient to endurance running, or it could have a negative impact,” says Nemkov.