You’ll hear them coming before you see them — the flap, flap, flap of rubber-clad feet on concrete. These rebels of the “barefoot” running movement are trying something traditional runners find crazy: They’re wearing shoes.

Their shoes aren’t like any you’ve seen before. Skin-tight booties swaddle feet in lightweight leather or nylon and stretchy mesh sleeves hug each individual toe. Molded rubber bottoms grip the ground, but they don’t cushion the foot: The thin, flexible soles are only a few millimeters thick — roughly the same as two stacked quarters.

The shoes, with brand names such as Vibram Five Fingers and FutGlove, mimic the feel of running barefoot, while protecting feet from sticks, stones and rough, bumpy roads. Instead of using padded foam heels as shock absorbers — as with traditional running shoes — they rely on a runner’s own foot to soften the impact of each step. Instead of controlling foot movement with stiff shoe structures, they trust a runner’s form to dictate proper stride.

Stephanie Lain, a runner from Santa Cruz, Calif., has been wearing “barefoot” shoes since 2009. She said she’d never go back to ordinary running shoes.

“I love being able to stretch out my toes,” she said. “I feel like a cat.”

In a sport plagued by injuries — shin splints, hip pain and sore ankles, knees and feet — the idea behind this new breed of footwear is simple: Remove the shoes and return to a more natural, and less injurious, way of running.

Vibram Five Fingers debuted in 2005 and were the first barefoot shoe on the market. But in the past year Tim Schenone, owner of the Running Revolution in Santa Cruz and Campbell, Calif., has seen interest in Five Fingers plateau.

It could be the unusual fit, he said, but it’s probably the style. “A lot of people are resistant to wearing them,” he said. “They look like frog feet.”

But at the same time, less conspicuous “minimalist” styles — lightweight shoes with thin soles and smaller heel-to-toe drops — are gaining ground. This year, Schenone’s customers are gravitating toward normal-looking running shoes that disguise their barefoot styling, such as New Balance’s Minimus shoes or Brooks’ PureProject collection. Schenone said demand for the new products is strong, especially in Santa Cruz, where he sells twice as many minimal-style shoes than in Campbell.

Jeff Moreno, a physical therapist at Precision Physical Therapy and Fitness in Santa Cruz, thinks a runner’s technique is more important than their shoes, though he admits that people can use minimalist shoes to work on form and position.

“Putting someone in a deconstructed shoe can be a very beneficial thing,” he said. “It tells your body that a large impact is going to occur.”

Runners will naturally shorten their stride and take softer, quicker steps, gently padding along on the balls of their feet. But Moreno encourages his patients to make the transition to barefoot-style shoes slowly, noting that new shoes don’t guarantee good form.

Russ Coillot, owner of Fleet Feet, a specialty running store in Aptos, Calif., said he agrees. He said if your feet are flapping against the ground, you’re probably doing it wrong. True barefoot runners don’t plod — they pitter-patter.

A movement toward minimalism may be booming in Santa Cruz, but the barefoot running philosophy is nothing new to the running world. It has been in and out of vogue for decades.

In the 1980s, South African runner Zola Budd raced to barefoot fame when she competed in the Olympics without shoes. The movement was rebooted in 2009 when Christopher McDougall published “Born to Run,” a book about an elite tribe of Mexican barefoot runners. A year later, Harvard researchers reported in the scientific journal Nature that bare feet take less of a pounding during a run than their shoe-cushioned counterparts.

The news exploded through the running world, prompting new runners to flock to the sport. Many podiatrists, however, disputed the findings. If constraining feet in running shoes is bad, they argued, why do custom-made orthotics help so many people?

Alvie Hurray, a Santa Cruz podiatrist, thinks some runners can get away with running barefoot or in minimal shoes. After all, he said, “There are people who can jump out of a tree and not break a leg.” But he worries about the potential for injuries.

On both sides, the evidence is still largely anecdotal: Minimalist runners swear that tossing out their thick-soled shoes reduces injuries, while podiatrists argue that tailoring shoes and orthotics to fit people’s feet is the best way not to get hurt.

Until recently, little data existed to support either claim, though running shoe stores routinely analyze a person’s foot shape and gait before fitting them into shoes.

In the past few years, the U.S. Army, Air Force and Marine Corps all studied the effectiveness of assigning basic combat training running shoes based on foot shape. People with flat feet were put into sturdy, supportive shoes, and people with high arches were put into shoes with foam-padded insoles. All three branches of the military found that using foot shape to assign shoes was no better than randomly assigning them: Injury rates were the same in both groups.

Fleet Feet’s Coillot admits that fitting a customer in running shoes is more of an art than a science. And the Running Revolution’s Schenone agrees. He thinks there’s a place for barefoot and minimalist running. But, he said, it’s not for everyone.

“A lot of people just want to go out and run a mile or two with their dogs,” he said. “They don’t always want to feel the road.”

Despite the worries of many doctors, the rise of the minimal shoe hasn’t seemed to increase the number of running-related injuries.

In fact, Mark Brenis, a Santa Cruz podiatrist, hasn’t seen any injuries related to running barefoot or in minimal shoes. Though he doesn’t think shoes are needed to “correct” the motion of the foot, he does think they’re good for protection.

“Personally, my feeling is to go towards wearing shoes,” he said. But if runners want to forgo even the most minimal of shoes and bare their soles to the road, he’s not that worried.

“Have you ever seen the bottom of a barefoot runner’s foot?” Brenis asked. “Their skin is like leather.”