His group recently published a study examining runners on Harvard’s cross-country team. They looked at foot strike, whether they landed first with the heel (rearfoot strike) or ball of the foot (forefoot strike), and correlated it with injury rates. (These runners all wore shoes, some more minimalist than others, but it obviously touches on the idea of running barefoot. Barefoot running forces you to run in a more forefoot strike style, because your heel doesn't like to land first when it's unprotected by a shoe. Shoes absorb the impact and let you run in a more rearfoot strike style.) Runners with a rearfoot strike had about 2.5 times more injuries than those with a forefoot strike. They also examined the type of injury and put different injuries into two broad categories: injuries that are more likely for a rearfoot striker and injuries that are more likely for a forefoot striker. Because the impact forces are distributed differently depending on which part of your foot hits first, rearfoot strikers are predicted to have more knee and hip injuries, while forefoot strikers are predicted to have more ankle injuries.The rearfoot striking Harvard runners did have more “rearfoot striking injuries,” but the forefoot striking runners didn’t have increased “forefoot striking injuries.” (So people that forefoot strike may not need to worry about increased ankle injuries based on their foot strike.)
One major caveat of this study is that it was done in collegiate athletes, an advanced group of runners. These athletes had been running for years, had low BMIs, and were young, factors that all affect injury. I worry that extrapolating this to your typical everyday runner may be extrapolating a little too much. Also, although this study will give something for barefoot running proponents to celebrate, they weren't actually studying footwear, but running style. Even Lieberman is cautious: “Running style is probably a more important determinant of injury than footwear (with the caveat that footwear probably influences running style.)”
My humble (and unscientific) opinion: I don't run barefoot, but I am not anti-barefoot running. (Although I do think Vibrams are weird and a little creepy.) I do own a pair of minimalist shoes. (In the olden days we called them "racing flats.") I do think Lieberman’s main hypothesis, that we evolved running barefoot and therefore that's what our body is best at, is a good one. But I think it’s important to note that we’re not the same people we were when we were running across the plains chasing antelope. We are far more sedentary and weigh much more; being out of shape and carrying extra weight means extra pounding when we run.
I think the emphasis should be placed on good form and not on specific shoes. Collegiate athletes and professional runners have most likely been running for years, starting on a cross country team where drills and correct running technique were emphasized, where a coach watched them and gave them critiques to fix their bad habits before it was too late. I think before everyday runners read Born to Run and immediately jump on the barefoot bandwagon (side note opinion: Born to Run is not nearly as much a Barefoot Bible as people make it out to be) they should work on learning how to run correctly. Running barefoot and wearing minimalist shoes can be part of that process, but easing into it is key, especially if they are new to running or carrying a few extra pounds. Vibram is being sued by someone who got injured wearing their shoes, but Vibram will probably win that lawsuit because they specifically warn you to ease into their shoes over the course of an entire year.
In related news, Iain Hunter, a biomechanist, compiled photographs of the foot strikes of competitors from last week’s Olympic Trials 10k, see below. It’s a pretty even mix, including some heel strikers that you might not expect at that level. Hunter doesn't agree that people should worry about changing their form, but that the body figures out the most economical way for that individual to run. (Short description of Hunter and the photos here.)
*Potential Bias: Daniel Lieberman got a “gift” from Vibram.