This Study Says Ultramarathoners Have Tinier Brains

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Ultra Marathon Runers Compete Below Sea Level In Jordan
Photo: Salah Malkawi/Getty Images

Many weird things can happen to the brain and body during an ultramarathon, including partial loss of vision and terrifying hallucinations, but this has to be the weirdest: A group of German scientists claim that ultramarathoners’ brains literally shrink over the course of the race, reports New Scientist.

Ultramarathons are imprecise things to define. A marathon is always and only 26.2 miles, but an ultra can mean anything over that distance. So a 30-mile race is technically an ultramarathon, but so is something like the Trans Europe Foot Race, a 2,800-mile, 64-day race, in which runners travel from Southern Italy all the way to Norway. The latter is what those German researchers, led by Uwe Schütz of the University Hospital of Ulm, zeroed in on for their study, which they presented at the annual meeting of the Radiological Society of North America earlier this week.

In 2009, they followed 44 runners in that race, using a “portable MRI scanner” to examine various parts of their bodies throughout the race, including their brains. As the days wore on, a funny thing happened: Their brain volume shrank, by 6 percent on average. New Scientist explains what might be happening here:

The loss may simply be the result of extreme fatigue and undernourishment, but Schütz thinks it could be caused by lack of stimulation. One of the four brain regions that seems to be particularly affected is known to be involved in visual processing. That area may have been massively under-stimulated by 64 days of viewing little other than roads, he says.

Their brains returned to normal within six months of finishing the race, Schütz added. Phew?