They found that, for the first 2,500 kilometers, runners’ cartilage—the shock-absorbing material found between bones—degraded. But after that, the cartilage actually started to recover.
“It was thought that cartilage could only regenerate during rest,” lead researcher Uwe Schütz told New Scientist. “We have shown for the first time that it can regenerate during running.” The researchers revealed their results at the annual meeting of the Radiological Society of North America.
Extraordinarily, they also found that a runner’s brain shrinks as much as 6% by the end of the race.
What’s amazing is how little we still know about how our bodies actually function.