The Running Shoe Debate: How Barefoot Runners are Shaping the Shoe Industry

A group of running rebels are shedding their shoes and reporting years of injury-free miles. Some ultramarathoners, biomechanics experts and doctors think that's probably a good thing. Others go so far as to say running shoes are in fact causing injuries. Meanwhile, running shoe companies continue to precisely measure runners, and pound and flex shoes in their high-tech labs. Could shoes—and shoe companies—be covering hundreds of thousands of perfectly able bare feet? If shoes are doing damage, just what are the companies measuring?

By Tyghe Trimble
Published on: April 22, 2009

The Boston Marathon, one of the world's most competitive 26.2-mile races, had the best runners from Kenya, Ethiopia, the U.S. and around the globe churning out 5-minute miles on Monday for over two hours. While all eyes were on the front-runners—notably the United States' Ryan Hall (third) and Kara Goucher (third among female racers)—way back in the pack there was one person, Rick Roeber, who stole headlines with his unique running style. One glance at Roeber's feet and you can see what all the fuss is about: he isn't wearing shoes. And a number of people—ultramarathoners, biomechanics experts and doctors included—think that's probably the best way to run. Some go so far as to say running shoes are in fact causing injuries.

While entry into the Boston Marathon is a feat in itself—Roeber needed to have about an 8-minute-mile pace over 26 miles to qualify—attempting the race barefoot is something most runners would find an absurd, even obscene, gesture. Runners are hooked on shoes. For good reason, it would appear: Ranging from 5 mm to 22 mm thick and made mostly of polymer, running shoes are engineered to support feet for mile after mile of rough asphalt and rocky terrain. They protect vulnerable soles from glass and debris, provide padding and, shoe companies claim, help correct problematic twists and turns of our ankles and legs caused by excessive pronation.

But to barefoot advocates such as Chris McDougall, author of Born to Run (Knopf, hitting bookstores in May), Roeber is one of the few in Monday's race not drinking the shoe industry's Kool-Aid. In his book, McDougall follows the Tahumara, a Mexican tribe of ultrarunners who race from 50 to 200 miles straight without shoes, yet remain healthy and injury-free. Science doesn't support the shoe industry's claim that "humans are born broken," McDougall tells PM, and that running shoes exist to fix our stride. Humans have been barefoot for nearly 2 million years, but have had running shoes for only a little more than 40—when Nike-founder Bill Bowerman cobbled together the modern-day running shoe with glues, plastic and a waffle iron in his basement. Shoes cause runners to lose musculature in their feet, McDougall argues, and takes away the natural cushion in their stride.

Could shoes—and shoe companies—be part of a $25 billion snake oil industry, covering hundreds of thousands of perfectly able bare feet? Or is barefoot running dangerous for marathoners and weekend joggers alike? That's the debate now brewing in the running community. The answer depends in part on a classic chicken and egg question: Do we run the way we do because of running shoes, or do running shoes support the way we now run?


Taking it in Stride
In a back room at the $2 million New Balance running shoe research and development lab in Lawrence, Mass., the MTS 858 Mini Bionix II—a giant hydraulic piston with the cast of a foot attached—loudly pounds into the heel of a light blue, cushioned running shoe. This stress-testing machine, made by the same company that builds earthquake simulators, can apply 5620 pounds of force to a shoe 30 times every second (although researchers at New Balance tend to be gentler on the footwear). Down the hall, a glass plate sitting in the middle of a polished wooden floor conceals a camera that measures the impact of the shoe on the ground. Cameras also capture the light reflected by tiny silver dots worn by a runner on a treadmill, tracking hundreds of points on the body during each stride. Across the room, an outline of feet projected onto the wall conveys the treadmill runner's footstrike in real time. Meanwhile, a computer records streams of data relaying angle and force, to be interpreted and analyzed by researchers later. This is high-tech biomechanics, all in the service of designing the perfect running shoe.

Some researchers and runners think this ideal shoe will be cushioned and wide, with high-tech gels, plastics and perhaps even moving parts to better absorb shock. To others, the perfect shoe looks more like a sock, with only a thin cover to protect feet from glass and other ground hazards. The two design camps split cleanly between catering to different strides: While the barefoot runner's gait tends to strike on the forefoot, a significant amount of shoe technology is aimed toward a heel-to-toe motion. A study from 1980, which was repeatedly cited by shoe experts at the New Balance labs, reveals how much more prevalent heel-to-toe running is. Analyzing the form of 753 runners, biomechanical researcher Benno Nigg found that 80 percent of runners (videotaped in two races) ran with a heel-to-toe motion; 45 percent of the faster runners (those with a 5-minute, 18-second-mile pace or better) ran heel-to-toe-step; rest ran with what he calls a midfoot strike, in which the heel and forefoot strike the ground simultaneously.

Shoe companies design shoes for the vast majority-the 80 percent of heel-to-toe runners—and their goal is to prevent excessive rolling movement of the foot. "There are people who will pronate a lot but will not get injured," says Keith Williams, a senior lecturer at the University of California, Davis, who has consulted in the footwear industry for 30 years. "Then there are those who will pronate a little and get injured." To play it safe, shoe companies bulk up the heel, the arch and extend the sides of shoes, which stabilizes the foot as it rolls from heel to toe.

While there are as many ways to do this as there are shoes for sale, Sean Murphy, manager of advanced product engineering at New Balance, says shoe companies often fall back on what he calls the 22-12 solution-placing 22 millimeters of material under the heel of the shoe and 12 millimeters under the forefoot. "Shoe companies have been stuck in the paradigm of the 22-12 for years," Murphy says, and people buy them in part because it's the feel they've grown accustomed to. "We're just now building products for people who tend to run more on their forefoot, like many ultramarathoners."

But according to McDougall, all shoes with cushioned heels, however spare, encourage heel-to-toe running, which he says leads to excessive pronation. "Take the heel off the shoe and those problems will be solved," McDougall says. In other words: Run barefoot. He points to a 2008 paper in the British Journal of Sports Medicine, in which the author, a researcher at the University of Newcastle in Australia, "revealed that there are no evidence-based studies-not one-that demonstrate that running shoes make you less prone to injury."

Murphy agrees. "The studies on injuries just aren't there," he says. However, there is also a dearth of studies demonstrating that running shoes make runners more prone to injury.


The More Perfect Shoe
With or without shoes, humans are evolved to run. In a 2004 study published in Nature, Dennis Bramble and Daniel Lieberman provide clear physiological evidence of this: Humans are efficient sweaters, for one. We also have tall bodies with ample surface area to cool ourselves, large buttocks with muscles critical for stabilization in running, and long legs that include Achilles tendons-ideal for storing and releasing mechanical energy. These features, the authors argue, allowed us to be superior scavengers and even hunters (by tracking sprinting animals).

The problem modern-day runners face, according to Hugh Herr, Popular Mechanics 2005 Breakthrough Award winner and head of the biomechatronic group at MIT, isn't presented by our bodies but by the evolution of running surfaces. Humans that ran to scavenge or hunt for their food weren't pounding concrete. Herr is in a unique position to weigh in on shoe technology. He defended the double-prosthetic sprinter, Oscar Pistorius, in his appeal to the International Association of Athletics Federations board last year against charges that his Cheetah prosthetics provided a mechanical advantage. Herr also invented the iWalk Powerfoot One, the most advanced robotic ankle in existence.

Bare feet just aren't meant to support running on modern day hard-top surfaces, Herr says. In his research, Herr focused on two problems with both shod and barefoot running-pronation angle and impact force. While barefoot running is best for a natural, stress-free pronation angle, Herr says, it is not ideal for coping with roads and sidewalks that can lead to stress-impact injuries. Shoes, on the other hand, excel at diminishing the force of impact on hard ground. But they do so at the cost of the natural stride-all the padding added to the shoe exaggerates the foot's rotation. "It's hard to design a shoe with pronation as small as what exists naturally," Herr says. "When you're barefoot, you have the advantage of the heel being very thin [and thus diminishing rotation]."



Herr's solution to the problem of shoe design is to start from scratch and fundamentally redesign the running shoe. His first-stage prototype looks nothing like any shoe for sale today. Called the SpringBuck, Herr's shoe is form fitting, taking advantage of the barefoot runner's naturally low pronation, while a spring-like heel diminishes the impact of feet on hard surfaces. This shoe even shows a metabolic reduction for the runner, Herr says, thanks to the optimized stride. Though no doubt radical to barefoot advocates and shoe labs alike, a running shoe that rethinks humans' relationship with their environment may fill the vacuum of science on the great shoe debate and finally provide a one-size-fits-all solution.

Herr's solution to the problem of shoe design is to start from scratch and fundamentally redesign the running shoe. His first-stage prototype looks nothing like any shoe for sale today. Called the SpringBuck, Herr's shoe is form fitting, taking advantage of the barefoot runner's naturally low pronation, while a spring-like heel diminishes the impact of feet on hard surfaces. This shoe even shows a metabolic reduction for the runner, Herr says, thanks to the optimized stride. Though no doubt radical to barefoot advocates and shoe labs alike, a running shoe that rethinks humans' relationship with their environment may fill the vacuum of science on the great shoe debate and finally provide a one-size-fits-all solution.