Linsey Corbin has finished 15 Ironmans and logged thousands of miles running through the mountainous terrain near her Montana home.
When she hits the flat, grassy ground, she kicks off her traditional running shoes and frees up her toes.
"I don't think I could sustain the proper running mileage and type of mileage that I need to do as a professional triathlete with only barefoot running," Corbin said.
She's not alone. While American runners sprinted to stores to pick up barefoot shoes a year ago, the trend appears to be hitting a cool-down.
According to Matt Powell, an athletic-shoe analyst for SportsOneSource, sales of true minimalist and barefoot running shoes in the United States have accounted for about 4 percent of all running shoes sold year to date, a decline of about 5 percent from the same period last year.
"Minimalist and barefoot peaked last year," Powell said. "Most true runners are returning to shoes that offer more cushioning and stability, but that are still lightweight."
Or alternating between the two.
"Doing a small amount of running barefoot allows the body to work naturally, strengthening weaknesses developed from a lifetime in restrictive footwear," said Neely Spence Gracey, an eight-time NCAA Division II national champion and professional runner with the Hansons-Brooks Distance Project in Michigan. "That being said, I emphasize small amount because we are so unaccustomed to this lack of support that it can cause serious injuries."
Back to the beginning
While there have long been shoes of the minimalist variety, the barefoot rage picked up steam with the release of Christopher McDougall's book "Born to Run: A Hidden Tribe, Superathletes, and the Greatest Race the World Has Never Seen" in 2009. Chronicling the training practices of the Tarahumara Native Americans in Mexico, some of the world's greatest distance runners, he searches for a solution for his own persistent running injuries. Upon adopting minimalist/barefoot training, modeled after the tribe's approach, he discovers an answer to his running ailments.
The popularity of the Vibram FiveFingers, which had been around since 2005, soared soon after. The story was compelling, and the product, which looked more like gloves for the feet, was interesting. But more important, it promised to solve an issue 50 percent of runners encounter on an annual basis -- injuries.
Some runners found that these shoes, originally fashioned for kayaking, sailing and canoeing, solved long-standing running ailments. The reduction in injuries was thought to be a result of the change in running style -- namely striking on the forefoot or midfoot rather than the heels -- that the minimalist footwear encouraged.
John Durant, a barefoot convert and author of the forthcoming book "The Paleo Manifesto: Living Wild in the Man-made World," was one of these runners. After a series of knee injuries, he decided to try something different.
"I experimented with barefoot running," he said. "The knee problem went away, and I've never looked back."
Barefoot believers were further encouraged by a 2010 study by Daniel Lieberman that was published in Nature. Lieberman studied unshod Kenyans from the Kalenjin tribe and observed that they tended to run on their forefeet and hit the ground with less impact.
The barefoot movement had hit the trifecta with a unique product, a bestselling book singing its praises and, now, research backing up the practice.
Since that study, an assumption has been largely held that there is an inextricable link between running barefoot and forefoot striking. But new research, including one study of another Kenyan tribe, the Daasanach, showed that many of those perpetually barefoot adults ran on their heels -- much like the majority of runners you'll spot in your local 5K. This was evidenced in a 2012 study of about 2,000 runners at the Milwaukee Lakefront Marathon, where 94 percent hit with their heels.
Herein lies the problem. While the barefoot movement has been highly successful in igniting a conversation about running technique that was long overdue, the message became oversimplified. The research bears out the fact that a runner does not arm herself against running injuries simply by running barefoot.
"The media has a tremendous impact on what people do," said Dr. Stephen Pribut, a sports podiatrist on the advisory board of Runner's World Magazine. "There's a great schism, and 'My way or the highway' is perhaps not a good philosophy."
Road to compromise
To be sure, there is no silver bullet to wipe out runners' injuries. Technique matters. Biomechanics matter. The approach to training and mileage matters.
To date, there remains no across-the-board recommendation for dosage when it comes to barefoot running. Some have jumped right in, going cold turkey without problems. Others go for a few short jaunts and end up with a stress fracture.
Initially shedding his shoes with zeal, even Durant encountered a few issues.
"It takes time for the skin to adjust, and the same is true of muscles, tendons, ligaments and bones," he said. "It's important to start slowly and gradually."
A recent study published in Medicine & Science in Sports & Exercise looked at the transition issues. Researchers organized experienced runners who wore traditional running shoes into two groups. After MRI scans of their feet and lower legs, one group continued to run as usual and the other was given Vibram FiveFingers and instructed how to follow the company's suggested protocol for gradually easing into this type of footwear. At the end of 10 weeks, the two groups received MRIs again, revealing that only one runner from the group that wore regular shoes had any sign of injury, but half of those in the "barefoot" group showed signs of edema, fluid accumulation that can indicate bone-stress injuries, and two of them developed full-blown stress fractures.
These results don't invalidate the use of barefoot footwear but rather highlight the importance of approaching new training regimens with caution. Indeed, Vibram's transitional protocol has since been revised.
Other research has shown barefoot running can improve running economy, and there is plenty of anecdotal evidence demonstrating that some runners do truly benefit from at least a small amount of unshod running.
"I think running barefoot for drills and strides is great for building muscular proprioception and strength in the lower-leg region," Corbin said. "It's also great for helping you focus on form and technique."
"There is not a muscle or bone in the body that doesn't grow stronger through appropriate use," he said, while emphasizing that barefoot proponents aren't suggesting there's not still a place for running shoes. "One of the primary benefits of barefoot running is learning better form, whether you decide to run in shoes or not -- using a gentle foot strike instead of the plodding heel strike that so many joggers use."
So we may just have to be happy with shades of gray. Some people will benefit from going barefoot full time, some find it best to go minimalist a couple times a week, and others are best suited to steer clear completely.
"We are genetically diverse and carry different characteristics," Pribut said. "One solution that works for some people won't for others."
For Gracey, the compromise means about 6 miles per week barefoot on a soft surface.
"The other 70-plus miles need to be in protective shoes with my orthotics," she said. "To keep my feet happy and healthy."