On a rural road out the back of Pauatahanui the most unlikely shoe company pin-up stretches his legs. You won't know his name; you haven't seen him on TV. And he's not wearing shoes.

Brendon Keenan's bare feet lightly strike the stone-studded tarmac. His soles are so tough there's no flinching as he bounces over pine needles and sharp stones flicked out from gravel driveways. The veins and muscles on his calves stand out like vines climbing a tree trunk. The nail on his right big toe is bruised black - legacy of some rogue obstruction. He doesn't remember it happening.

Keenan, 37, is part of a growing barefoot- running movement based on the idea that the body is precision-engineered to run and that the modern running shoe - with its motion- controlled, super-cushioning stability - actually counteracts centuries of evolution, encouraging runners to thwack the ground with their heels, increasing the impact force on the body and, presumably, making it more susceptible to injury.

CHRIS SKELTON/Fairfax NZ Brendon Keenan, who runs 180km per week, is part of a growing running movement that eschews padded running shoes.

Keenan is at the extreme end, running 180 kilometres a week exclusively barefoot or in minimalist shoes. Locals might have seen the senior sergeant barefooting the 16km around Pauatahanui Inlet to work at Porirua's police college, and back again. Or dodging roots in Belmont Regional Park in his sponsored Vibram FiveFingers - those goofy-looking mesh slippers increasingly seen on running trails, at the bus stop and even in the office.

The barefoot brotherhood is a broad church, spanning novice plodders, elite athletes, scientists, NZ Post executives, Weta creatives. Many are as zealous as any evangelical missionary. They preach the teachings of chief prophet Christopher McDougall, whose 2009 book Born to Run is the catalyst for many barefoot conversions, including Keenan's. McDougall's portrait of the reclusive Tarahumara Indians, who regularly run ultramarathon distances unshod yet seem immune to injury, is a compelling argument for a return-to-natural movement.

But does the science stack up? Here's the theory: humans have been endurance running for millennia and our bodies are designed for the task. Run barefoot and you're most likely to strike the ground with your foot's front or middle.

Until the 1970s, runners wore lightweight sneakers with little cushioning. It was Bata Bullets, flimsy plimsolls or barefoot - think Zola Budd, Abebe Bikila, New Zealand's Lorraine Moller. That all changed with Nike's heavily cushioned running shoe. Ever since, shoe companies have been pushing fatter heels, air cushions, greater stability.

Studies, chiefly by Harvard human evolutionary biology professor Daniel Lieberman, have shown these super-structured shoes actually counteract the body's natural running style, encouraging runners to stride out and hit the heel instead of the forefoot.

In a paper in Nature in 2010, Lieberman found that landing on the heel creates a collision-force of 1.5 to 3 times the body's weight, which could contribute to stress fractures and plantar fasciitis. Barefoot runners landing on the forefoot or midfoot generated lower impacts, even on hard surfaces.

When studying a group of barefoot- running Americans, he found 75 per cent landed on their forefoot or midfoot without shoes. That dropped to half when the same group ran shod, suggesting the shoe was influencing running technique.

"Evidence that barefoot and minimally shod runners avoid RFS [rear foot strike] with high-impact collisions may have public health implications. An average runner hits the ground 600 times per kilometre, making them prone to repetitive stress injuries. The incidence of such injuries has remained considerable [up to 79 per cent by some estimates] for 30 years despite technological advancements that provide more cushioning and motion control in shoes designed for heel-toe running," Lieberman concluded.

The theory makes logical sense and barefoot converts say it also works in practice. But throwing off your shoes and kicking out for a 10km run also has health implications (see Lori Smallwood's story overleaf).

Keenan has only been running two years, after signing up to a half marathon with a colleague. After reading Born to Run, he began running 4km to 6km barefoot on grass - more than most experts would recommend.

He switched from heel-striking to landing on the forefoot. Initially it was a harder workout for the feet and calves because every muscle had to be strengthened. But Keenan can now run comfortably barefoot for two hours. "I started on softer surfaces but after a while whether I was running on grass or concrete it became like one surface."

When Keenan won last year's Taranaki Round the Mountain 160km ultramarathon, veterans complimented him on his running efficiency. He ran that race in Asics shoes, as the distance was an unknown, but says his body is now so conditioned to land on his forefoot that his technique doesn't change in shoes. He has more ultramarathons lined up and hopes to one day run for New Zealand.

Marine ecologist Tara Ross-Watt, 43, who has a history of injury, was hooked by the argument that barefoot running reduced the strain on the body. "Even trying to run on the front of my feet in regular shoes I could feel a difference, there wasn't so much impact. It was just obvious."

He switched to FiveFingers last June and describes his conversion as a rebirth. "A very painful rebirth. You are retraining your body to run in a totally different way. This was one time when I have not felt comfortable pushing through pain."

In the early stages his calves screamed. Having previously run 8km to work and 10km to 12km for pleasure, he trimmed his training to 3km to 4km circuits close to home. He's still having intermittent calf trouble, but has no intention of returning to cushioned shoes. "You feel so much more of the ground. It's like walking with your eyes fully open instead of squinting."

Weta animation manager Jarom Sidwell was an early convert, and has been running, living and working in FiveFingers for six years. He wears them everywhere, including to a friend's wedding, because he's always liked the barefoot feeling. As well as transforming his gait, he jokes that the wacky-looking shoes have transformed his social life.

"They're such a conversation piece: 'What are those? Oh gross, get away'. People stare at you. In the line at the grocery store, you give your toes a little wiggle and freak them out."

Is the multibillion-dollar running shoe industry just an extraordinarily successful marketing rort?

In 2008, Australian researcher Craig Richards looked for evidence that 40 years of running shoe development had reduced running injuries. He found none. But even Lieberman admits that, as yet, there's no hard evidence that barefoot running reduces injuries either. And the burgeoning industry surrounding the barefoot-running movement (McDougall estimates it's worth US$1.7 billion or about NZ$2.1b) quickly muddies the waters.

Richards runs a website designing and selling barefoot and minimalist shoes. Podiatrists, who stand to lose if everyone ditches their orthotics, say custom-orthotics in lighter shoes give the same barefoot feeling.

Shoe retailer The Front Runner says minimalist shoes make up less than 5 per cent of its total running shoe sales but the numbers are growing. Kiwis bought 10,200 pairs of FiveFingers last year. US FiveFinger sales have quadrupled since 2009. Major shoe manufacturers are also jumping on the barefoot bandwagon.

Despite facing criticism for the cushioned shoe revolution, Nike also spearheaded the minimalist movement. It released the flex-sole, minimalist Nike Free in 2005, in response to the observation of Stanford athletics coach Vin Lananna that his runners ran better when training barefoot.

Kiwi Nike designer Andreas Harlow, who was global director of running shoe design from 2007-2009, argues that shoe design reflects the zeitgeist, and the heavily engineered runners of the 1980s and 1990s mirrored those decades of excess. Now, it's all about organics, yoga and getting back to nature.

Hindsight is always clear. I don't think there was an underlying deception going on," Harlow says. "If our top athletes at the time were telling us 'Hey, I'm out running 100 to 110 miles a week, I need something to protect me from injury', we're going to make a shoe that fits their needs. We still operate like that. Do some of those things end up being harmful? Yeah, they possibly do. But at the same time we are also making products some people found tremendously successful."



Minimalist shoes are no quick-cure pill, Harlow says. Nonetheless, he believes natural-movement running is here to stay. The Free is now one of the company's top-selling running shoes.



Biomechanics expert, runner and manager of Auckland University of Technology running clinic Kelly Sheerin says there's nothing new about barefoot running, especially in New Zealand, where kids routinely trot around without shoes. A young John Walker ran five miles barefoot to school and back, and no-one batted an eyelid when he won an Auckland championship title running barefoot on gravel.



Sheerin agrees that landing on your forefoot reduces impact on the body and running barefoot can help achieve that. Heel striking produces an impact transient spike as the foot hits the ground, which then rockets up through the body. However, the benefits of barefoot running remain inconclusive.



"The same claims are being made by the barefoot community that have been made by the big shoe manufacturers for years. There's just no proof.



"It's more about running technique, than 'are you in running shoes or not?' For some people it's solving all their problems but others who were previously injury free are actually developing injuries. That's where things break down. We don't know, practically and scientifically, who are the ones who are going to benefit and who are the ones it's going to harm."



Sheerin believes there's still a place for supportive running shoes, especially for beginners. He advises pure barefoot running ("I don't think you need to spend $250 on a pair of barefoot shoes just to run on grass") a couple of times a week as part of a broader training package.



Wellington physiotherapist Gayle Snyders covers both ends of the debate. She's a barefoot advocate, selling FiveFinger shoes, but also treats the injuries from over-enthusiastic conversions. She cuts an unusual figure in purple work dress and matching purple and black FiveFingers. She sells 10 to 15 pairs a week, at between $130 and $260, to everyone from outdoor buffs to 50 to 60-year-olds who grew up running in flimsy shoes.



She advocates barefoot training to strengthen muscles and teach the body a better running technique. But she advises they're no cure all, and can be harmful if you don't transition gradually. "If you pop a pair on and go for a 5km run you will not walk the next day, your calves will be screaming at you."



She doesn't recommend barefoot for injured runners, those with different leg lengths, or those who find it uncomfortable or difficult to land on their forefoot.



Podiatrist Bruce Baxter gives similar advice. He first noticed the surge in barefoot running about 18 months ago.



"My practice is right on the riverbank in Christchurch. I was seeing all these middle-aged men. It was bloody funny because you could still see their sock marks. You see them picking their way across the road then they get on to the grass. They kind of run funny, like it hurts. Over the weeks you start to see them get a little bit more comfortable with it."



Baxter concedes that many podiatrists reject the barefoot movement, because it threatens their orthotics business. But he takes a different view. Barefoot running promotes landing underneath your centre of gravity, and that's good running technique. But Baxter argues you can also change your running posture without ditching the shoes, by a combination of video analysis and simple drills.



Unlike Sheerin, he's confident he can isolate those who can comfortably run barefoot, and those who shouldn't. "You only need to look at people running a half marathon to see every person has a different idiosyncratic movement and some people are far safer than others biomechanically to be running unsupported."



The last word goes to one of New Zealand's most successful endurance runners, Lisa Tamati, who has run 65,000km in the past 13 years. She strongly believes the body was made to run barefoot, and runs up to 10km without shoes.



But she's hesitant to completely reject what works for her. "Because of the mileage I do I would get bloody sore feet if I had to run barefoot. People do, I'm just not tough enough."

Though she buys the theory, she's skeptical of the surrounding commercial boon. "I think it is exaggerated what the shoe industry does with cushioning. On the other hand, it's all a marketing ploy as well for barefoot running."



THE GOOD



Contemplating a hefty bill for new shoes after the 2007 Coast to Coast adventure race, veteran Josh Stevenson thought to himself: "Why do we need shoes?"



He was "looking for another challenge, so flippantly thought: 'I'll do the Coast barefoot'."



He didn't tell anyone, reckoning they'd think he was mad, especially since he wore orthotics. There was little training information, so Stevenson devised his own 18-month schedule. For a month he only walked, in different shoes without orthotics. He gradually moved from running 5km in shoes, to minimalist Nike Frees, to ditching shoes for the last 500 metres, to FiveFingers and eventually no shoes. He believes his speed, energy efficiency and technique improved by 40 to 50 per cent."Running barefoot forces you to go from a heel strike and striding out to landing your foot under your hip. Because you run with a better running technique and less impact, you use less energy and you're lighter on your feet."



There were downsides - broken glass to watch out for and blistering on hot days. And the Coast to Coast did hurt. But podiatrist Bruce Baxter was astonished how well his feet survived. "They didn't look knocked around at all."

THE BAD



Motivated by reading to Run, Lori Smallwood was busting to join the "cult".



A runner for 12 years, Smallwood had signed up for two marathons, in Wellington and the Gold Coast, to celebrate turning 40 last year. She was struggling with a knee injury and liked the idea of a more natural way of running that was easier on the joints.



It was too late to switch to barefoot for the marathons, but afterwards, in August, she bought a pair of FiveFingers and began the transition. She started on a gym treadmill, five minutes at a time, gradually increasing to 20 or 30 minutes within a month. It felt strange - like running naked - but immediately improved her running posture. "My spine shot straight up and I was keeping my core tucked in."



During the first months her calves ached, but she quickly felt comfortable and, within about six weeks, ramped up to 60-minute runs. Then one day something jabbed. She took a break and the pain retreated. Then she ran from her home in Owhiro Bay.



"I went right around the corner to Island Bay and it just went 'crick' and I could hardly walk. I had to limp home."



The result - a stress reaction between her foot's fourth metatarsal and cuboid. Two weeks of strapping and a month in a moonboot later she's finally ready to get back to barefoot running. Slowly. "I ramped up too quickly. But I'm not put off. It just makes biological sense."