Sam Hobert has suffered for his flip-flops.
A few years ago, the 19-year-old broke a toe after his foot slammed into a rock while hiking in New Hampshire in his favorite summer footwear. A few weeks ago, the George Washington University freshman was nursing blisters, courtesy of a new pair of flip-flops.
"It's looks over comfort," he said. "But I'm regretting it a little bit, I'm not going to lie."
It's spring, and flip-flops - or thongs - are back, much to the frustration of podiatrists. Wearing flip-flops can cause problems ranging from stubbed toes and cuts to overuse injuries such as foot stress fractures.
In warmer weather, Howard Osterman, a podiatrist who has practiced in Washington, D.C., for 20 years, says he sees at least one patient with a flip-flop injury most days.
Osterman treats a lot of tourists whose flip-flops aren't up to the rigors of eight-hour days tromping across the Mall.
The No. 1 problem he sees from the lightweight footwear are overuse injuries such as stress fractures of the metatarsals, the five long bones that reach out to the toes. A stress fracture happens after constant, repetitive stress to a bone and is generally treated with rest, more-supportive shoes and perhaps a walking boot.
The lack of arch support can cause plantar fasciitis - inflammation of the thick band of tissue along the bottom of the foot that causes a stabbing pain, especially in the heel. People with flatter arches are more prone to such overuse injuries because they need more support for their muscles and ligaments, Osterman says.
Flip-flops also leave the feet unprotected and exposed, causing cold toes, sunburn, cuts and bruises.
Few studies have looked at the pros and cons of flip-flops.
In 2008, Justin Shroyer, a biomechanics graduate student at Auburn University in Alabama, studied 39 college-age men and women to see how they walked in flip-flops compared with sneakers. Shroyer, now an assistant professor at the University of Louisiana at Lafayette, found that the flip-flop wearers took shorter steps. He hypothesized that this was because they were trying to get their feet on the ground faster to prevent the shoe from flying off. Also, flip-flop wearers didn't bring their toes up as much during the leg's swing phase because they tended to grip the sandals with their toes.
"Your toe flexors are fighting what you're naturally trying to do," Shroyer said. "It's kind of an antagonistic push-pull, tug-of-war going on, and it's not happening in running shoes or bare feet."
Researchers theorized that the altered gait could result in pain from the foot up into the hips and lower back.
A 2010 study by Rush University Medical Center in Chicago found that flip-flops and sneakers with flexible soles were easier on knees than clogs or special stability shoes. The researchers analyzed the gaits of 31 people with osteoarthritis of the knee while they wore the various types of footwear.
Osterman doesn't suggest avoiding flip-flops entirely, but he says they should be worn in moderation - for a few hours on the beach or at the movies, for example.
Shoppers should look for flip-flops with a stable sole, he says. Brands such as Reef, Rainbow, FitFlops, Teva and Merrell make models that throw more of the weight into the heel and out of the forefoot, he says.