Long before anyone ever ran a 10K or a marathon, humans were running down wild animals.
Meat, not medals, was the reward for the hunters who scampered barefoot through the wilds.
"We evolved to run," says Dr. Irene Davis, director of the Spaulding National Running Center and a professor in the department of physical medicine and rehabilitation at Harvard Medical School in Boston. "Running is in our genes."
Davis, an expert on running biomechanics, says our feet, legs and lungs are structured to run long distances. We succeeded in persistence hunting by chasing prey to overheated exhaustion while our more efficient cooling systems kept us going, she says. Our feet are equipped with a flexible, longitudinal arch for bearing body force. We have long Achilles tendons to store and return energy. The padded ball on the forefoot gives us a natural landing spot. Those features, combined with slow-twitch muscles and body design, made us natural distance runners for two million years without the aid of cushioned running shoes, Davis says.
"We ran without anything at all," she says.
It's why Mexico's indigenous Raramuri people -- or the ancient Greek athletes, 1960 Olympic marathon champ Abebe Bikila or boys and girls in Kenya or Ethiopia -- have been marvelous distance runners while barefoot. They're fine without shoes or wearing thin sandals (which provide protection for the sole without changing the gait).
"That's the way we were adapted to run," Davis says.
Studies on shoeless running by Davis and Daniel Lieberman, a professor of human evolutionary biology at Harvard, have received much attention. And, the human ability to run barefoot was central to the popular 2009 book "Born to Run" by Christopher McDougall, which focuses on the Raramuri (also known as the Tarahumara). In that book, former Stanford track and cross country coach Vin Lananna, now associate athletic director at Oregon and USA Track & Field president, told McDougall he often employed barefoot runs for his athletes and that such training made them faster and less prone to injury.
Davis believes runners such as the Raramuri can thrive running barefoot for long distances -- and stay injury-free -- for a number of reasons:
With shoes, most runners land heel first. The vast majority of habitual barefoot runners land on the ball of the foot. It's less jarring, with the calf absorbing much of the load. The shock with a heel strike can be twice as significant, Davis says, and can strain joints, ligaments and muscles throughout the body. "It's my belief that forefoot-striking is as fundamental to running as rear-foot striking is to walking," Davis says, noting that runners who don't wear shoes perfect a "softer foot strike" on the ball of the foot.
Barefoot runners can have better balance. With nothing between the foot and the ground, runners such as the Raramuri get a better feel for the surface and can make adjustments. Plus, shoes with posterior and lateral flares that make the soles wider than the foot tend to alter running mechanics. "The minute you start adding these flares between the foot and the ground, you increase the torque to the ankle, foot, knee and hips," Davis says.
Awareness. Barefoot runners pay more attention to the surface. "You don't just put on earphones and zone out and slam your heel into the ground," Davis says. "You're being careful of what you're running over." And, shoeless runners -- who also develop tougher soles -- will reflexively put less weight on their foot when they step on something uncomfortable.