Keep on running. Ultramarathons do take a toll on a runner’s body, breaking down cartilage and even shrinking the brain, but athletes seem to bounce back from both, with joints repairing before the race has even finished.

For many, marathons represent the ultimate fitness challenge. But a minority go much further, taking part in ultramarathons like the Trans Europe Foot Race, covering 4500 kilometres from the south of Italy to Norway in 64 days.

This race equates to around 100 marathons, with no rest days, prompting researchers to wonder what such long periods of intense exercise would do to the body.


Uwe Schütz at the University Hospital of Ulm in Germany and his colleagues have spent the last six years finding out. In 2009, they followed a group of 44 runners as they ran the nine-week race across Europe. The team took a portable MRI scanner with them, and periodically scanned the legs, feet, heart, brains and cardiovascular systems of the athletes, as well as taking blood and urine samples.

Scanning feet and leg joints every 900 kilometres, Schütz and his team measured the amount of water that was released from the shock-absorbing cartilage between the bones – a sign of whether cartilage is breaking down. They found that the runners’ cartilage seemed to degrade during the first 2500 km of the race.

But after that distance – around 60 marathons – the cartilage seemed to recover, says Schütz, who presented the findings at the Radiological Society of North America annual meeting in Chicago this week. “It was thought that cartilage could only regenerate during rest,” he says. “We have shown for the first time that it can regenerate during running.”

Brain size

A runner’s joints aren’t the only parts of their body affected. Earlier analyses of the same runners revealed that their brains seemed to temporarily shrink in size by 6 per cent over the course of the race.

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.

Others have suggested that athletes’ brains may reorganise themselves to divert energy to regions involved in motivation. “It is hard to explain what’s going on,” says Schütz. “But we do see total recovery after six months.”

Schütz says people who run normal marathons won’t experience the same degradation.

Aerobic exercise is generally beneficial for the brain, helping to stave off depression and dementia.

(Image credit: Helmut Dietz)