When Protection Makes You Weaker

A recent best-selling book suggests that people were Born to Run, yet data suggest that between a third and half of runners get hurt running every year. Why is this? Journalist Chris McDougall wondered why he was getting hurt when humans have been running for two million years. His book is a well-told tale of people who run barefoot without getting hurt and of researchers who discover a paradox: supporting your foot can make it weaker, not stronger. The wrong kind of support changes how your foot, ankle and calf muscles develop and can leave you more prone to injury. This paradox of protection is not confined to runners.

McDougall presents the stories that led to science and science that has led to a resurgence of barefoot or minimal shoe running. He visits the Tarahumara, an impoverished clan of long distance runners living in the remote Copper Canyons of Mexico. McDougall romanticizes their lives, describing men and women of all ages routinely running for dozens of miles in sandals over hot, steep mountains.

Scientists have studied the Tarahumara for years because their isolation makes them good subjects. As roads arrive, the Tarahumara embrace modernity: their diet goes from corn meal to Fritos. Pickup trucks replace long runs. These people are not idiots. As always, epidemiologists have documented the diabetes, cancer, and heart disease that result. McDougall looks past this, focusing instead on the propensity of the canyon-dwelling Tarahumara and some of their more crazed gringo brethren to race ridiculous distances wearing heuraches cut from old tires.

Back home, McDougall consults a Stanford track coach who refuses to let his athletes wear expensive running shoes and discovers data suggesting that both the extent and severity of injuries go up with the price of shoes. He interviews Daniel Lieberman, a Harvard biomechanics professor, who explains precisely how the support a of a running shoe makes most runners over stride and heel strike, which delivers a much sharper blow than a barefoot runner who lands mid foot. A good video of Lieberman explaining his research is below. The peer reviewed work is here in Nature.

Lots of testing and learning is still being done both by individuals and by researchers, but nobody these days takes for granted that running shoes are always helpful. Shoe companies are trying to shift their designs and their message to promote “minimalist” shoes, some of which are now best-sellers.

Is this just a fad? Sure — any sports shoe can become a fad if well marketed. On the other hand, humans have run barefoot for two million years but have worn running shoes for only about 30. I would not bet against barefoot running, given the injury rates that shod runners experience.

Protection deceives because it can weaken. As a runner, I want lots of cushioning. I want to avoid pronation, which must be awful because it sounds so bad. It would be simple to sell me orthotics — hey, my knees hurt sometimes. Although some people surely do fine in running shoes, for many people, highly protective shoes are like a cast. They reduce your mobility and your foot gets continually weaker as a result.

Economists know that protection often makes competitors weaker. They believe instinctively that competition strengthens counterparties, be they muscles, individuals, teams, companies, or regions. I have argued that even organizations designed to protect need to compete to remain strong and that those who favor stronger labor unions need to force unions to compete. Economists left and right argue that trade protection weakens both parties, although this knowledge never stops companies, communities, or workers who are hurt by trade from seeking it. Doubtless some similar principal applies to parenting: too much protection weakens your kids. Fine, now buckle your damned seat belt.

To evaluate social programs or parenting, we need the equivalent of the Tarahumara — a group isolated from extraneous influences that can test whether social protections produce more benefits than costs. Fortunately, an impressive young economist has shown that many of our protective programs are testable. Esther Duflo is an MIT professor, a MacArthur genius grant winner, and the winner of the 2010 John Bates Clark Medal for the best economist under the age of forty. Watch her fascinating TED talk on how she tests programs to fight malaria, educate kids, and immunize children. This is barefoot economics at its best.

Testing of this sort requires an appetite for failure. Politicians, business people, and scientists each approach tests differently, depending on how failure affects them.
Politicians pay a huge price for failure. This forces them to simplify problems and promise sound bite solutions. If they do not do this, they won’t be elected and they won’t be politicians. Politicians cannot say “wow, this is a tough problem. Let’s try a bunch of things, fail at most of them, and learn what works.” Most politicians suffer from what Tim Hartford calls the “God Complex”. Hartford writes the Undercover Economist column for the Financial Times. He has published a terrific book called Adapt: Why Success Always Starts with Failure. You can get a flavor of his thinking at his fantastic TED talk. The God Complex is the equivalent of intelligent design: certainty that complex systems can best be managed centrally and that complex questions can be answered without the painful process of trial and error. Parents, CEOs, physicians, gods, and anyone else who pays a high price for failure are especially vulnerable.

Business people embrace trial and error mainly because markets force them to. Hartford notes that ten percent of all businesses fail every year. A market economy can be looked at as a huge, ongoing experiment that evolves, like every complex system, because of variation and selection. The best leaders of complex systems acknowledge that leading edge problems don’t have obvious solutions and encourage a structured process of trial and error. Hartford’s book discusses the value of lots of small, low cost trials that are decoupled so that they don’t spill over and of carefully documenting and interpreting results. An important and highly recommended read.

Scientists love failure (although failures are much less published, which is a problem). It’s how they learn. They understand that humans have evolved as complex systems through millions of years of variation and selection. They reason either deductively from data or inductively to ask have we evolved to run? Evolutionary biologists have long noted that the unique way we sweat for thermoregulation, our hairlessness, our odd bipedal design (more energy efficient than any quadruped), our unusual ability to breath multiple times per step, and our highly engineered feet, ankles, and hips all suggest anatomy designed to run.
But until the 1980s, researchers were stymied by one big problem: we are slow. Why on earth would running matter, when every mammal worth eating can outrun us?

It fell to David Carrier, a graduate student at the University of Utah, to notice something that had escaped other scientists: we are built for endurance, not for speed. The case for humans designed for endurance running is now widely accepted. This is partly because we have discovered a story that backs the data. Hunter-gatherers in the central Kalahari Desert in Southern Africa still practice persistence hunting: they run their prey to death (there is one other group that practices persistence hunting — or at least remembers it. Our pals the Tarahumara). Running down a large mammal takes as little as an hour or as long as 8 hours, but if a human can keep a mammal galloping so that it cannot catch its breath, cool down, or rejoin its herd, it will collapse of exhaustion before the human does. It appears that before we invented spears, humans survived by high-endurance, persistence hunting. Barefoot.

The BBC managed to film a group of men in the Kalahari hunting a kudu this way. Despite the drums and the breathless narration, it is a stunning film. Notice that the runners are shod in cheap shoes that do not let them heel strike. They look a lot like the sneakers we all wore as kids.