Barefoot running has been getting a lot of press in recent months, with the publication of Christopher McDougall's book Born to Run, which describes the Tarahumara native American tribe who run hundreds of miles over varied terrain... without shoes. Inspired by McDougall's story, many people are testing the hypothesis that the footwear purchased to help them to run safely over large distances is in fact the source of their chronic pain. Now, two new studies seem to begin confirming what these tough-soled folk have long suspected: running shoes, as currently designed, can cause chronic pain and injury. But both studies' authors preach extreme caution before going foot-commando.
Harvard biologist Daniel Lieberman (who is also a runner) wondered if running barefoot might be good for us, since we obviously evolved as a running species without, until recently, the benefit of Nikes. He theorized that running shoes, by changing our stride, cause secondary problems in the leg and foot. Runners running barefoot land on the front or middle of the foot, while shod runners land heel-first. Lieberman's research, published in this month's edition of Nature, observed the physical stresses on the feet associated with the different types of running. He gathered several groups of runners, ranging from lifelong barefoot runners from the US and Kenya to people who have run their entire lives in shoes. He used a forceplate (more on that below) to measure foot impact in tests performed on both indoor and outdoor tracks. HIs finding: that shod runners hit the ground with more than three times the force of barefoot runners.
"It's really about how you hit the ground," said Lieberman. "When you hit the ground, some of your body comes to a dead stop." For a shod runner, he says, "it is literally like someone hitting you on the heel with a hammer." But, he said, "the way in which barefoot runners run is more or less collision-free." The most dangerous moment for the foot is when it contacts the ground, and in particular is at its heaviest for people who land heel-first—which is most shod runners. And the effect remains if you remove the shoes: a habitually shod runner who tries to run barefoot will hit the ground with seven times the impact of a habitual barefoot runner.
Lieberman's conclusions converge with those of Dr. Casey Kerrigan, who conducted research on shoes and joint injury while a professor of physical medicine and rehabilitation at the University of Virginia. Her earlier research demonstrated that high-heeled shoes can cause women to experience increased knee pressure at particularly vulnerable points in the joint. She associated this with osteoarthritis of the knee, which afflicts millions of Americans. For her more recent study, Kerrigan observed that running shoes similarly elevate the heels above their natural angle. She set out to investigate whether they caused similar joint disturbance. The short answer: yep.
Kerrigan's study, performed before she left the University of Virginia and published in the December edition of PM&R: The journal of injury, function and rehabilitation, observed 31 men and 37 women who were already regular runners. They were put on treadmills in the lab, running either barefoot or in a standard running shoe. Cameras tracked them as they ran, observing markers affixed to their knees, hips and ankles. The treadmills were also outfitted with forceplates, which Kerrigan calls a "glorified bathroom scale." The forceplate picks up the magnitude and direction of the subject's bodyweight movement, and allows the researchers to measure the degree of torque, or twisting motion, involved in each step. Such motion puts uneven pressure on the joints; if it does so at weak points, it can cause joint deterioration. And that is exactly what Kerrigan found in the runners wearing sneakers. In fact, her team observed a 38 percent increase in torque at the sites in the knee where osteoarthritis is most likely to occur. This outpaced, she said, the effect she found for women wearing high heels.
So, should you ditch your running shoes and go au naturel? Both scientists warn us to be very cautious with barefoot running. In fact, Kerrigan is opposed to it entirely. "I'm concerned, I don't think this study should promote running barefoot," she said. "I think people should run in what they feel most comfortable running in... and whether that's in a pair of running shoes or in a minimum kind of running shoe, that's just fine." Her reticence comes, she says, from the fact that we are not running across the Serengeti—most of us are running across the intersection of Main and Broadway. Sidewalks, in other words, don't have enough "compliance," or give. "We've evolved to run on compliant surfaces, not on asphalt or concrete," she said. "You run on something hard, your body has to work that much harder to help absorb those forces, and that can lead to stresses and strain, wear and tear, really throughout the whole body." On the other hand, Kerrigan is in the process of developing her own patented shoe to address the problems she discovered in running shoes. She has an interest in keeping us shod.
For Lieberman, a devoted barefoot runner, the key is moderation and good sense. If you make sudden changes, he says, "you have a high probability of injuring yourself." Instead, aim for changing no more than 10 percent of your running pattern per week. And, he says, exercise a bit of common sense about where and when you run. "We did not evolve to run barefoot in New England in the winter," he said.
If going barefoot scares you (and why wouldn't it?), there are techniques for stride modification that may help with running pain—for example, Chi Running. And, of course, you can always buy a pair of these funny things.