When NHL star Mike Cammalleri slipped them on for the first time, the feeling was "primitive and powerful."
He began darting around the artificial turf at the Montreal Canadiens' training facility in Brossard, Que., testing their worth.
He was convinced they could make him stronger.
Now the recently traded Calgary Flame has become the face of the adidas Adipure Trainer, billed as the first minimalist shoe designed for working out. It's the latest entry into the booming market for footwear with a less-is-more kick.
Mr. Cammalleri was an early convert. About a year after that initial test run, "If I'm training, I'm wearing them," said the 29-year-old, known for his rigorous workout regimen.
There are signs the shoes are verging on ubiquity.
For runners, the trend away from tricked-out, uber-supportive shoes and toward minimal footwear has taken off in the past few years, turning a fringe product into a roughly $2-billion annual cash cow. The New Balance Minimus, Nike Free, Reebok RealFlex and Vibram FiveFingers are among the slew of stripped-down shoes – flexible enough to be rolled, scrunched and squeezed at will – praised for triggering small, neglected foot muscles.
Now shoe companies are targeting the gym, hoping the success of minimalist running shoes, Footwear readers' 2011 trend of the year, will translate to the workout crowd.
But as the buzz builds and the industry pitches the shoes as a muscle-building fix for many foot and ankle injuries, there is some debate as to whether it's a biomechanical paradigm shift in shoe design or a cleverly engineered cash grab.
Proponents of the footwear often compare ultra-supportive shoes with wearing a cast that prohibits muscle growth, while skeptics say there hasn't been enough research.
Mark Verstegen, who trains some of the world's top athletes as the president of Phoenix-based Athletes' Performance, helped design adidas's new shoe. "The shoe offers an almost sock-like environment that gives great mobility so you can turn on all the muscles and joints in the legs," he said.
Mr. Verstegen holds a master's degree in sport sciences and said he's long believed in barefoot workouts. He credits the 2009 book Born to Run by Christopher McDougall for pushing the barefoot-minimalist movement into the mainstream.
The research has been playing catch-up ever since.
Scott Landry, an assistant professor of kinesiology at Acadia University in Nova Scotia who has studied minimalist footwear, has published articles that generally laud the shoes' ability to strengthen smaller foot muscles.
Shoes with a lot of stability were first designed in the 1970s to reduce injury, but the belief is that injuries haven't decreased, Dr. Landry said.
He wears minimalist shoes in the gym and explained how students in his anatomy and biomechanics class constantly ask him about the new footwear. "I always caution them, don't make the sudden jump, introduce exercise gradually, " Dr. Landry said. "… If you've got a deformity in the foot, you might need an orthotic."
Dr. Landry, Mr. Verstegen and Brad Gibbs, president of the Pedorthic Association of Canada, all stressed the need to take it slow.
"My immediate concern would be the lack of stability if you're doing lateral or side-to-side motion – I think that's where a minimalist shoe could be a danger," Mr. Gibbs said. He suggested testing the shoes for "10 to 20 per cent" of your workouts initially.
"If you are starting to develop a small discomfort … go back to your old or conventional footwear." he said, adding, "Don't try to work through an injury."
Mr. Verstegen adamantly opposes a full-throttle switch. "You wouldn't do any other aspect of your life that way – you need the progressions."
But even a measured approach has its doubters. Michael Mesic, a doctor of podiatric medicine at the Canadian Foot Clinic & Orthotic Centre in St. Catharines, Ont., is skeptical of the shift away from supportive footwear.
"Most of the hype is generated by shoe companies – they're creating a new market," Dr. Mesic said. "… There is that subset of the population with great mechanics who don't need that extra support, but the average person needs support."
And yet John Shier, a 36-year-old software engineer from Burlington, Ont., said that after years of suffering from plantar fasciitis, shin splints and knee pain, and throwing hundreds of dollars at orthotics, he hasn't had "a single physical problem" since buying Vibram FiveFingers four years ago.
When he works out, whether doing squats or dead-lifts, Mr. Shier dons the shoes or opts to go unshod. "I found that wearing cross-trainers, with the amount of cushioning and height off the ground, I didn't feel that stable."
There's plenty of anecdotal evidence that echoes Mr. Shier's experience, Dr. Landry said.
That's not to say all the reviews have been gushing.
Mauricio Morales, a barefoot proponent who operates the blog BarefootCanada.org, has some qualms with the footwear. "My feet become clammy and stinky very quickly," he said.
While "Barefoot Moe," as he's known on his blog, said he wears minimalist shoes in the winter and occasionally to work out, he finds the cost "outrageous." The new shoe from adidas will sell for $100, and most other brand-name minimalist footwear falls in that range.
As for Mr. Cammalleri, he just finished an upper-body workout, he said, but sporting the shoes, "my knees and feet muscles are being triggered."
The man championing the new minimalist kicks expects the NHL to catch on quickly.
"You'll probably see a lot more guys using them in the off-season."