"The fact of the matter is we have very poor data on what causes people to get injured," says Lieberman. "It's research that should have been done a long time ago." That research is soon under way: Brooks Sports Inc. recently announced two major studies on running motion and injuries, one to be conducted by Hamill. At least one large study from the American College of Sports Medicine has shown that runners who use shorter strides and land more gently – as barefooters tend to do – are less prone to stress fractures. And other research suggests that heavily cushioned running shoes tempt runners to pound harder.
So what does this all mean for everyday runners? As McDougall can attest, barefooting certainly can improve your stride. But most experts agree that people should ease into it over a period of months or even years to allow the muscles and ligaments time to adapt.
One fact remains undisputed even by most barefooters: Shoes help you run fast. "Barefoot technique gets you to think, gets you to become aware of what your body is doing in space," says Jurek. "That's the first element of getting better at any sport. But if you want to win a race, you're gonna wear shoes."