Author Christopher McDougall runs barefoot down Cherry Hill Road near his home in Peach Bottom, Pennsylvania. McDougall believes the human body is built to run long distances without shoes.

PHILADELPHIA — Imagine running 100 miles — barefoot. Christopher McDougall believes that's what the human body is built to do.

In his best-selling new book, "Born to Run," McDougall argues that the humans evolved for persistence hunting — basically, chasing down game animals for hours until they keel over from overheating or exhaustion.

"We didn't evolve as weight lifters, yoga gurus, or swimmers — we evolved as long-distance runners," he said after an early-morning barefoot jog along paved Kelly Drive.

Can't imagine yourself outlasting an antelope on the open savannah? Neither could McDougall before he began working on the book. In fact, he wasn't sure if he would ever be able to run again.

Born and reared in Philadelphia, the 47-year-old freelance writer and former war correspondent had moved to Lancaster County, Pa., to enjoy a quieter life with his wife and two daughters. He'd taken up running on local dirt roads, two or three miles every other day.

But five years of what should have been healthy exercise had left him with a catalogue of ailments — torn hamstrings, aching arches, sprained ankles, strained Achilles tendons and, finally, dislocation of the small, wedge-shaped cuboid bone, which felt like "an ice pick driving straight up through the sole of my foot."

Like many runners, he saw pain as an unavoidable part of the sport. At least, that is, until he began reading up on the Tarahumara. Members of the reclusive tribe live in the Copper Canyons of north-central Mexico, where they routinely run hundreds of miles through the harsh, rocky desert in flimsy sandals made from strips of tire rubber.

What really got McDougall, though, was that they do it smiling.

As he learned more about the Tarahumara and other long-distance runners from around the world, McDougall gradually became convinced that these amazing athletes were not just interesting aberrations. They were living — and running — as nature intended.

Several intriguing lines of evidence, laid out in a 2004 Nature paper by University of Utah biologist Dennis Bramble and Harvard University biological anthropologist Daniel Lieberman, support McDougall's argument. Unlike other animals, they wrote, humans can dissipate excess heat on the run by sweating. And our breathing rhythm is independent of our stride, allowing us to breathe faster and get more oxygen into our bloodstream during exertion.

Other anatomical features — short toes, the Achilles tendon, a head-stabilizing ligament absent in other primates — also appear to be adaptations for running.

The "running man hypothesis" also helps explain a seeming paradox: Although young men leave women and older runners in the dust in short races and even marathons, when it comes to ultramarathons — competitions that typically are 30 to 100 miles long — the playing field becomes surprisingly level.

Since primitive humans hunted in packs, different individuals would have needed to maintain the same pace over a long distance in order to stay together, said McDougall. So it makes sense that everyone — old, young, male and female — would have similar long-distance running ability.

For natural-born runners, though, we hurt ourselves pretty often. According to a 2007 review paper published in the British Journal of Sports Medicine, up to 80 percent of runners suffer an injury each year. And, despite major advances in running-shoe technology over the last three decades, injury rates have held steady or even increased.

McDougall now thinks that modern running shoes may actually be the problem.

Their raised heels encourage people to run with a higher-impact, heel-first strike, and their cushioned soles make such a strike less painful — but not less damaging.

And, by preventing the foot's arch from bearing weight, support features in the shoe may weaken it over time and increase the likelihood of injury.

In contrast, feet that are in direct contact with the ground get constant sensory feedback. They adjust to reduce impact. Except for falls, running injuries are almost unheard of among the Tarahumara.

"In bare feet, you can't over-pronate, overtrain, or overstride," McDougall said. "The bare foot is the best coach of all."

Nike spokesman Derek Kent acknowledged that running barefoot could help strengthen the feet and improve performance. This insight, he said, led to the development of the Nike Free, a lighter, less supportive shoe with grooves in the sole that "allow for a more natural range of motion." Wearing the shoe, he said, protected the foot from cuts, abrasions, and other hazards.

Asked about McDougall's assertion that traditional running shoes weakened the feet and predisposed people to injury, Kent said he had no information.

Podiatrist Howard Palamarchuk, director of sports medicine at Temple University's Gait Study Center, said he believed that running shoes might not always be beneficial. "We encase our feet in a box, and those muscles never develop," Palamarchuk said.

But he added: "As a medical practitioner who specializes in the foot, I'd say there are some people who should not even attempt to run barefoot."

These include diabetics and others who do not have full feeling in their feet (peripheral neuropathy), as well as people with certain conditions — including club foot, very high arches, or legs that differ in length — that prevent their feet from absorbing shock well.

Stephen Pribut, the former president of the American Association of Podiatric Sports Medicine, concurred. "Too much structure (in running shoes), for many people, is not a good thing," he said. "But I don't think everyone is made to run barefoot."

Like McDougall, Pribut believes that humans evolved not just to walk, but to run.

That's not to say, however, that the average Philadelphian could step out the front door tomorrow and lope down to Harrisburg.

In addition to rigorous physical training and a change in footwear, McDougall said, most modern runners would need an attitude adjustment.

"You can't look at running as punishment for eating cheesecake," he said.

"Running a long distance barefoot or with minimal shoes is all about paying attention," added "Barefoot" Ted McDonald, a barefoot ultramarathoner in Seattle who coaches others in the technique. "It's all about being mindful of what you're doing. You can't be a robot."

Before losing his shoes entirely, McDougall four years ago began experimenting with minimal footwear, including the glove-like Vibram FiveFingers. It was a gradual transition; for the last three months, he has run only barefoot.

His feet are still "supple as a well-worn baseball mitt," he said, "not calloused, not cracked, not tough, not dry." And, except for the occasional stubbed toe or minor cut, he's been injury-free.

Now that he's not getting hurt all the time, McDougall is finally able to reap the benefits of running. He has lost 30 pounds, worked his way up to 50-mile runs, and lowered his stress level.

He attributes the last benefit to a simple fact of barefoot running: If you tense up, your feet hurt more.

And, like the elusive Tarahumara, he runs smiling.

———

BEFORE YOU TRY RUNNING BAREFOOT

Preparation:

If done properly, running barefoot can be a fun, safe addition to people's fitness programs, says sports podiatrist Stephen Pribut.

His suggestions:

Start slowly — five or 10 minutes a day at a pace slow enough for you to carry on a conversation.

Increase speed and distance as your feet get stronger.

If you have foot problems, consult a podiatrist first.

Diabetics and others without full feeling in their feet or with conditions that prevent shock absorption should not attempt to run barefoot.

Technique:

Always pay attention to what your feet are telling you, says "Born to Run" author Christopher McDougall. Try to relax and adapt your technique, or stop, rather than pushing through any pain or discomfort. His tips:

Keep your feet and legs relaxed, with knees slightly bent. This will reduce the impact on your body and make stepping on sharp surfaces less painful.

Step straight down, rather than forward, and land gently on the ball of your foot rather than the heel.

Kick your feet back toward your buttocks instead of pushing off from the ground.

Keep your back straight and your hips slightly forward — and look ahead, not down.

IF YOU'RE NOT QUITE READY

If you're not prepared to completely kick the shoe habit — or if your running surface is too hot, cold, rough, or otherwise hazardous for comfort — runners say several minimalist footwear options are available. For example:

Popular products that resemble booties include the Vibram FiveFingers and the Feelmax line.

The Nike Free, more like a sneaker, "exposes your feet to the brilliance of barefoot-like running," the company's Web site says.

Some people run in socks or Tarahumara-inspired sandals (http://barefootted.com/shop/).

ON A PERSONAL NOTE

While reporting this story, Inquirer staff writer Karen Knee, 28, went on a four-mile barefoot run — about as far as she normally goes in shoes — on city streets. Her thoughts four days later:

"It was fun to feel the ground beneath my feet and the wind on my toes, and I liked the sense of lightness provided by the barefoot running style."

"To my surprise, I had no cuts, blisters, or other problems — although my calf muscles and quads were quite sore for a few days afterward!"

"I went on two barefoot jogs in my South Philly neighborhood, and plan to keep trying it out."