Cartilage in the ankle and feet of of humans can regenerate even while a person is running, according to a new study which tracked runners for 4,500 kilometres through Europe over a span of 64 days.
"The fact that ultra-distance running places stress on the body has been well documented," said Uwe Schutz, from the University Hospital of Ulm in Germany.
"Our research provides detailed information on how the various organ systems change and adapt in response to that stress," said Schutz.
The Trans Europe Foot Race (TEFR) took place from April 19 to June 21, 2009.
It entailed running 4,487 km starting in southern Italy and ending in the North Cape in Norway without any day of rest. Forty-four of the runners (66 per cent) participated in the study.
A 1.5 Tesla MRI scanner mounted on a mobile unit was used to scan each participant every three to four days, resulting in 15 to 17 MRI exams over the course of the race.
The runners were also randomly assigned to additional examinations, and protocols were created for daily urine, blood and other tests.
The results showed that with exception to the patellar joint, nearly all cartilage segments of knee, ankle and hind-foot joints showed a significant degradation within the first 1,500 to 2,500 kilometres of the race.
"Interestingly, further testing indicated that ankle and foot cartilage have the ability to regenerate under ongoing endurance running," Schutz 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," Schutz said.
MRI study of the soft tissues and bones of the ultra-runners' feet showed a significant increase of the diameter of the Achilles tendon.
"We found no relevant damage to bone or soft tissues in the 44 runners. The human foot is made for running," Schutz said.
The researchers also looked at how ultramarathon running affects brain volume. Baseline comparison of TEFR participants and controls showed no significant differences in grey matter volume.
At the end of the race, MRI of the brain showed about a 6.1 per cent loss of grey matter volume in the runners. After eight months, grey matter volume had returned to normal levels.
Although the finding on grey matter volume loss while running is astonishing, it is not cause for alarm, Schutz said.
"Despite substantial changes to brain composition during the catabolic stress of an ultramarathon, we found the differences to be reversible and adaptive," he said.
