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Tuesday, February 09, 2010

Running barefoot is better, researchers find

Scientific American: January 29, 2010 By Katherine Harmon

Mother Nature has outpaced science once again: the bare human foot is better for running than one cushioned by sneakers. What about those $125 high-tech running shoes with 648 custom combinations? Toss ‘em, according to a new study published online January 27 in the journal Nature

“Most people today think barefoot running is dangerous and hurts,” Daniel Lieberman, a professor of human evolutionary biology at Harvard University, said in a prepared statement. “But actually you can run barefoot on the world’s hardest surfaces without the slightest discomfort and pain … It might be less injurious than the way some people run in shoes.”


Lieberman and his group used 3-D infrared tracking to record and study the running and strike style of three groups of runners: people who had always run barefoot, people who had always run with shoes, and people who had switched from shoe to shoeless.

They found that when runners lace up their shmancy sneakers and take off, about 75 to 80 percent land heel-first. Barefoot runners—as Homo sapiens had evolved to be—usually land toward the middle or front of the food. “People who don’t wear shoes when they run have an astonishingly different strike,” Lieberman said.

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Comparing the footfall of two Kenyan runners from the study: The runner on the left has worn shoes most of his life and lands on his heel, whereas the runner on the right has primarily run barefoot and lands on the ball of her foot.

Without shoes, landing on the heel is painful and can translate into a collision force some 1.5 to 3 times body weight. “Barefoot runners point their toes more at landing”, which helps to lessen the impact by “decreasing the effective mass of the foot that comes to a sudden stop when you land,” Madhusudhan Venkadesan, an applied mathematics and human evolutionary biology postdoctoral researcher at Harvard who also worked on the study, said in a prepared statement. But as cushioned kicks have hit the streets and treadmills, that initial pain has disappeared, and runners have changed their stride, leading to a way of high-impact running that human physiology wasn’t evolved for—one that the researchers posit can lead to a host of foot and leg injuries.
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Gary comments:
Barefoot running is fast becoming the in thing. While I am a fan of going barefoot I have serious reservations about the message in this article.

There is enormous benefit for children going barefoot for most of the time until at least puberty. My sister, Lorraine, attributes some of her marathon running success to her having very strong feet from a barefoot childhood in rural New Zealand. The same for me! But I am not about to urge all my readers to go and run their next marathon barefoot.

Despite the Professorial input, this study displays an ignorance of basic biomechanics and lack of understanding of the practical challenges of running on modern surfaces.

The average Kenyan male runner is very thin and wiry and probably less than 50kg weight. Allometric scaling (Read about it here) means that a 50kg runner can run barefoot with much less risk of injury than an 80kg runner. Allometry tells us that a 30kg child running on pavement only needs leather slippers when running; whereas an 80kg runner is best served wearing shoes with substantial shock absorption.

Kenyan runners typically have enormously strong feet hardened by physically robust childhoods and being mostly barefoot - very different to the feet of the Western raised person.

The foot is designed for negotiating rough natural terrain that constantly changes in texture. The monotonous environs of hard concrete pavement throw enormous and unrelenting stresses on the foot that it simply was never designed for.

There is a big difference between running a few Km in a lab setting and training daily on a paved road.

There are two types of running: Ball of the foot first. Toey runners tend to be very good up to about 3-5 km races; but much further and they tend to be excessively injury prone. Running landing on the ball of the foot is the most natural way to negotiate rough terrain. It is also the natural way to sprint; but not to run a marathon on hard pavement. Artificial surfaces that have no give demand artificial solutions to reduce the sudden shock wave of foot impact - Shoes. And heel first landing.

Why heel first is best
When the forefoot hits the ground first, the impact shock is absorbed over a small area of the foot within a brief space of time. It is that sharp shock wave that causes the damage such as stress fracture and shin splints. Nature has the answer - heel strike!

Please refer to the graphic of the foot while reading what follows.
When the heel hits the ground two shock absorbing mechanisms simultaneously kick into gear (There are other mechanisms but we will not complicate matters any more than they need to be).

The sole of the foot is a quarter moon shape. This is an ingenious mechanism to spread the shock wave over time and over a distance longer than the length of the foot. The heel strikes the ground then the sole of the foot prescribes a circular motion, rolling smoothly forward over the ground to finally push off at the pad of the big toe. The orange arrow shows how this happens and explains why a healthy foot causes wear on the outer portion of the heel of the shoe.

The other action happening is the arch of the foot is compressed like the leaf springs of a car suspension as depicted by the lilac arrows. This action absorbs shock wave energy which is stored in the elastic tissues. This stored energy is released as the foot pushes off the ball of the foot and the big toe. Ingenious!

When a runner lands forefoot first, the leaf spring kicks into gear, but the shock-spreading heel roll is absent. Great for sprinting but not for running a marathon on pavement, even with shoes.

While forefoot running may be best for short, fast sprints or a lithe Kenyan loping across the African Savannah, it is a sure recipe for injury for the larger and less "barefoot conditioned" city raised athlete.
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