A softer ride for barefoot runners
People who run long distances without shoes cushion the blow with their gait.
Barefoot endurance runners may have a more cushioned ride than most people who run in shoes, according to a biomechanical analysis.
Barefoot long-distance running has been a small but growing trend in the athletics community, driven in part by popular books and articles that maintain that runners might get fewer injuries if they ran the way humans evolved to — without supportive, cushioned running shoes. But although the idea is seductive, with running shoe companies recently marketing 'minimal' footwear, there has been little evidence to support the claims.
Now, evolutionary biologist Daniel Lieberman at Harvard University in Cambridge, Massachusetts, has found crucial differences in the way that barefoot and shod runners land, with dramatic consequences for how the body takes the impact (see Nature's video).
"The first time we had a long-distance barefoot runner come to the lab and run across the force-plate, I was amazed," says Lieberman. Whereas most runners hit the ground with a sudden collision force as the body abruptly decelerates, says Lieberman, this barefoot runner made no such impact.
Lieberman found that long-distance runners who usually wear shoes, in both the United States and in Kenya, tend to land directly on their heels, abruptly bearing the full force of the impact. The force of the collision, even with a cushioned sole, was the equivalent to up to three times their bodyweight. The force could be linked to common running injuries such as stress fractures and plantar fasciitis, although this has yet to be demonstrated.
Americans and Kenyans accustomed to running barefoot, however, tend to strike the ground with the ball of their feet before touching down the heel — a fore-foot strike — allowing the tendons and muscles in the foot and lower leg to act as shock absorbers, bringing the impact force down to 60% of their bodyweight. The team's research is published in Nature1.
"The ankle is a very compliant, springy joint, and barefoot runners use it a lot," says Lieberman. "It isn't available to you when you rear-foot strike. Then you're relying solely on the spring on the heel of the shoe."
By not taking advantage of the structure and function of the foot, says biologist Dennis Bramble at the University of Utah in Salt Lake City, runners may be risking injury. "Ignoring how we evolved and what our bodies were made to do is risky business," he adds.
Together with Bramble, Lieberman has proposed that features of the human body such as longer legs, shorter toes and a highly arched foot are linked to long-distance running and enabled early hominins to chase and eventually exhaust prey2.
But just because human ancestors landed on the balls of their feet when they ran, that doesn't mean it's ideal for today's runners who grew up with shoes. There's no evidence showing that running shoes prevent injuries. But nor is there much evidence that people who run barefoot get fewer injuries than those who run in shoes.
- Lieberman, D. E. et al. Nature 463, 531-536 (2010).
- Bramble, D. M. & Lieberman, D. E. Nature 432, 345-352 (2004).