When Dr. Douglas Brown, a radiologist in Orem, Utah, noticed an uptick recently in the number of barefoot runners he was seeing with heel and foot problems, he wondered if there might be a connection between their unshod training and their sore feet. But he couldn’t find any scientific studies that had examined the issue.
So he approached Sarah Ridge, a professor of exercise science at Brigham Young University in Provo, who studies impact injuries in sports, and suggested she undertake one.
The resulting study, published last month in Medicine & Science in Sports & Exercise, will probably add fuel to the debate about the benefits of running barefoot or wearing minimalist “barefoot” shoes. Does the barefoot style reduce a runner’s risk of pain and injury (as enthusiasts believe)? Or does barefoot running simply contribute to the development of a different set of injuries in some runners?
To find out, Ridge began by recruiting 36 experienced runners, men and women, who until then had run 15 to 30 miles a week while wearing normal running shoes. She sent them to Brown for baseline MRI scans of their feet and lower legs to check for any injuries or problems.
Those who believe in barefoot running often point out that humans ran and walked without shoes for millenniums before footwear was invented. They argue that being unshod is normal for humans and should reverse past injuries related to modern running shoes and prevent future ones.
But anecdotal evidence, including from physicians, indicates that some people who take up barefoot running develop entirely new aches and injuries.
Ridge’s volunteers all started the study with normal feet and lower legs, according to their MRI scans, which were read by multiple radiologists.
Half of the group members were randomly assigned to continue running as they had: same mileage, same shoes.
The other runners were given a pair of Vibram Five Fingers barefoot-style shoes and asked to begin incorporating some barefoot-like mileage into their runs, but gradually. They were told to wear the minimalist shoes for one mile during the first week of the study, two miles the second, three the third, and then as much as they liked, which is what the Vibram website recommended at the time of the 2011 study.
After 10 weeks, both groups of runners got a follow-up MRI. There was no evidence of injuries to or changes in the tissues of the lower leg, like the Achilles’ tendon, in any of the runners. But more than half of the runners wearing the minimalist shoes showed early signs of bone injuries in their feet.
Specifically, most had developed bone marrow edema, an accumulation of fluid, similar to what happens during bruising, in their foot bones. The radiologists graded the edema on a scale of zero to 4, with zero representing no edema and 1 the slight bone damage caused by simply moving around on and loading the foot. This amount of edema is considered healthy, a sign that the bone is responding to training and growing stronger.
Most of the runners in the control group, who were wearing their normal shoes, had edema levels of 1 throughout their feet.
But a majority of the runners in the minimalist-shoe group had developed at least a level 2 edema, “which indicates early bone injury,” Ridge said, and three had signs of more-extensive level 3 bone edema, “which constitutes an actual injury.”
Two even had full stress fractures or level 4 edema, one in her heel bone and one in his metatarsal, one of the long foot bones.
Almost all of the runners in the minimalist shoe group were spontaneously running fewer miles at the end of the 10 weeks, “probably,” Ridge said, “because their feet hurt.”
Why some of the barefoot-style runners developed serious foot problems and others did not is not yet clear, but Ridge is now analyzing additional data about the volunteers, which includes information about each runner’s mileage, running form, body weight and other variables.
“What we hope to see is whether there are some runners who, because of their biomechanics or other factors,” seem to be predisposed to foot injuries during the transition to barefoot-style running and “perhaps shouldn’t” make the switch at all from normal running shoes, she said.
She hopes to have findings ready to publish by this summer.
The results don’t mean that everyone who chooses to switch to minimal or no footwear will court foot injury, Ridge said.
“But I would tell anyone who wants to try” kicking off their normal shoes, “to be extremely cautious during the transition period.” In her study, substituting a mere mile per week of normal running at the start with one in minimal shoes “was probably too much,” she says. So go slow.
Barefoot running may have been natural for our ancestors, Ridge points out, but it’s a new experience for most of us.