By Gretchen Reynolds, NY Times, March 6, 2013
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, Utah, who studies impact injuries in sports, and suggested she undertake one.
The resulting study, published last month in Medicine and Science in Sports and Exercise, is likely to add fuel to the continuing 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 barefoot enthusiasts believe)? Or does barefoot running simply contribute to the development of a different set of injuries in some runners?
To find out, Dr. Ridge began by recruiting 36 adult, experienced runners, male and female, who, until then, had run between 15 and 30 miles a week while wearing normal running shoes. She sent them to Dr. Brown for baseline M.R.I. scans of their feet and lower legs to check for current injuries or problems.
Those who believe in barefoot running often point out that humans ran and walked without shoes for millennia 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 who treat runners, indicates that some people who take up barefoot running develop entirely new aches and injuries.
Dr. Ridge’s shod volunteers all started the study with normal feet and lower legs, according to their M.R.I. scans, which were read by multiple radiologists.
She then randomly assigned half of the group to continue running as they had: same mileage, same shoes.
The other half were given a pair of Vibram Five Fingers barefoot-style shoes and asked to begin sprinkling 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 Web site recommended at the time of the 2011 study.
After 10 weeks, both groups of runners received a follow-up M.R.I. There was no evidence of injuries to or changes in the tissues of the lower leg, like the Achilles’ tendon, among any of the runners. But more than half of the runners wearing the minimalist shoes now 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 0 to 4, with 0 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,” Dr. Ridge said, and three had signs of more-extensive level 3 bone edema, “which constitutes an actual injury,” Dr. Ridge said.
Two even had full stress fractures or level 4 edema, one in her heel bone and one in his metatarsal, the bones that connect the ankle and toes.
Almost all of the runners in the minimalist shoe group were spontaneously running fewer miles at the end of the 10 weeks than they had been at the start, “probably,” Dr. Ridge said, “because their feet hurt.”
The results don’t mean that everyone who chooses to switch to minimal or no footwear will court foot injury, Dr. 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-style running may have been natural for our ancestors, Dr. Ridge points out, but it’s a new experience for most of our feet.
Your mileage may most certainly vary…