On her training runs through the streets of San Diego, Emilie Reas is reminded about once every mile by passersby that she is missing her shoes. In her most recent marathon, she counted more than 40 comments spectators and runners made about her bare feet - about one per kilometer.

Reas, 35, a neuroscientist at the University of California-San Diego, has been running for more than 20 years - since high school - and most of that time was spent in shoes.

But on Saturday, she'll toe the Grandma's Marathon start line just outside of Two Harbors and run 26.2 miles down Highway 61 to the finish line in Canal Park barefoot - across hot pavement, cobblestone and debris.

She shed her shoes in 2013 after reading that barefoot running could help prevent injuries. Research suggests she may be right.

Barefoot runners are more likely to land on their forefeet than shod runners, who tend to land on their heels, according to Larry Birnbaum, chair of the exercise physiology department at the College of St. Scholastica. He also teaches a biomechanics class at CSS. The difference in stride could result in less injury. Birnbaum said a study of college cross-country runners found that forefoot strikers experienced much lower rates of stress injury than heel strikers.

A runner's stride could change simply by reducing the amount of material under a runner's foot. Using an orthotic designed to measure the force under the foot, Jena Ogston, an associate professor of physical therapy at CSS, looked at how the impact differed when runners wore big, cushioned shoes and thin, minimalist shoes, which some say partially mimic barefoot running. The findings, she said, show that cushioned shoes could take the impact off during the foot plant, but when people wore minimalist shoes, they landed more on their forefoot.

"It's interesting: you throw them in a minimalist shoe and you don't tell them anything and then they end up running a little bit differently," Ogston said.

Reas began the transition by walking barefoot at any opportunity. Although her first barefoot walk resulted in sore feet after just the first two blocks, she now only experiences pain if she were to step on a thorn or get stung by a bee, she said. She does still prefer roads and sidewalks to trails.

"My feet just became really strong - the skin, the bones, the tendons - everything," Reas said.

Runners can't expect that to happen overnight. Reas, Birnbaum and Ogston all stressed the importance of transitioning into either barefoot or minimalist running slowly.

Forefoot running leads to more load on the Achilles tendon and on the midfoot - which can result in more stress fractures in the feet, Ogston said. To prevent this, Ogston recommends a slow transition into a minimal shoe and to supplement it with lower leg and foot strengthening exercises. Birnbaum agrees.

"All the research I have read on making the transition says you have to progress slowly," Birnbaum said. "You can't just jump from being fully shod to barefoot or minimally shod because you're going to have problems."

But Ogston also expressed caution for runners looking to make the transition, especially if they are generally injury free when running in shoes.

"If it's not broken, probably no need to go off and change it," Ogston said. She added that when barefoot and minimalist running became popular 5 to 8 years ago, there was a wave of injuries when runners attempted to transition away from shoes too quickly.

Many attribute Christopher McDougall's 2009 book "Born to Run" with spurring the barefoot running movement. The book examines the Tarahumara, a tribe of Native Mexicans know for their ability to run incredibly long distances. McDougall, an American journalist, used the Tarahumara's methods - one of which is running in thin sandals - to find ways to finally run injury free. The book inspired Reas to try it, too.

"I'm a very stereotypical barefoot runner," Reas said. " 'Born to Run' is the book that first got me interested in it."

After the rise in popularity, researchers began to look at it closer, too, and more studies have been released in subsequent years, according to Birnbaum.

But the popularity of the movement has shrunk in the past few years; shoe companies are not marketing minimalist shoes nearly as heavily.

"I think we're all coming back a little bit. It swung one way and now we're coming back to the middle a little bit more," Ogston said.