Protection That Makes You Weaker

I have taken up running and, like boomers everywhere, I worry about hurting myself. Data suggest that between a third and half of runners get hurt running every year, making running a surprisingly high risk exercise. Why is this? Journalist Chris McDougall wondered why he was getting hurt when humans have been running for two million years. His best-selling book, Born to Run, is a well-told tale of people who run barefoot without getting hurt and of researchers who discover a paradox: support can make you weaker, not stronger. The more support a running shoe gives you, the more it weakens your foot, ankle, and calf muscles and the more prone you become to injury. McDougall presents the stories that led to the science and the 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 very 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 and long runs to pickup trucks and Hohos. 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? Of course any 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 turns out to be deceptive. It seems completely normal to me that as a runner, I would prefer a protective shoe. 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, of course, know that protection often makes competitors weaker. They believe instinctively that competition strengthens counterparties, be they muscles, individuals, teams, companies, or regions. I have even argued that those who want stronger labor unions need to force unions to compete. Economists left and right can show 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 thatmany 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 isbarefoot 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.

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.

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