What Happens to Long-Distance Runners' Bodies

Long-distance runners showed temporarily decreased cartilage and gray matter


There's a lot going on inside long-distance runners' bodies.

The chief findings of a new study highlight two major occurrences in these athletes: damage to cartilage and reductions in brain gray matter — and the subsequent regeneration of these body parts.

"The fact that ultra-distance running places stress on the body has been well-documented," said study author Uwe Schütz, MD, a radiologist and specialist in orthopedics and trauma surgery in the Department of Diagnostic and Interventional Radiology at the University Hospital of Ulm in Germany, in a press release. "Our research provides detailed information on how the various organ systems change and adapt in response to that stress."

Dr. Schütz and colleagues conducted their study on 44 ultra-runners taking part in a race that covered nearly 2,800 miles over 64 days in 2009. These researchers used a mobile MRI scanner and various other tests to document the changes in the athletes' bodies.

Between the first 1,000 to 1,500 miles of the race, the runners began to show damage to almost all of the cartilage in their knees, ankles and feet. But that wasn't the end of that story.

"Interestingly, further testing indicated that ankle and foot cartilage have the ability to regenerate under ongoing endurance running," Dr. Schütz said. "The ability of cartilage to recover in the presence of loading impact has not been previously shown in humans. In general, we found no distance limit in running for the human joint cartilage in the lower extremities."

In other words, the runners' cartilage began to repair itself during the two-month race. And these researchers found no evidence of long-term physical damage to these runners.

"The human foot is made for running," Dr. Schütz said.

These researchers didn't just look at the joints and feet of these runners — they also examined their brains. And they found something that, initially, sounds scary: By the end of the race, the 44 runners showed a roughly 6 percent reduction in total gray matter.

Gray matter is thought to play a part in sensory perception, muscle function, emotions, memory and speech, among other functions.

But there's good news: Eight months after the race had ended, the athletes' gray matter appeared to have returned to normal levels.

This study was presented Nov. 30 at the annual meeting of the Radiological Society of North America. Research presented at conferences may not have been peer-reviewed.

Information on funding sources and conflicts of interest was not available at the time of publication.