As versatile as they are comfortable, the rubbery sandals are worn by the young and old, the fashion conscious and fashion oblivious. People don them with suits, three-piece and swim varieties. And, yes, the thwap-thwap of flip-flops echoes through the halls of the Capitol, occasionally.
Too bad, then, that podiatrists and researchers say flip-flops hurt our feet and lead to lower-leg injuries.
Researchers at Auburn University, studying the bio-mechanics of flip-flop use compared against that of athletic shoes, found that the distinct change of gait among sandal-wearers puts strain on the arch, ankle, even the hips and lower back.
"There's a larger angle in your ankle in flip-flops," says Justin Shroyer, the lead researcher, "That could be because people are gripping with their toes so the flip-flop won't fly off. … So you've got this battle going on between muscles on top and on bottom, what your foot does in tennis shoes as opposed to flip-flops."
That confirms an earlier study by the American College of Foot and Ankle Surgeons, showing a rise in flip-flop related heel pain among patients ages 15 to 25.
Podiatrists took these findings and, well, ran with them. They say flip-flops – and even more stable forms of sandals – should be worn only for short durations, not as a primary footwear. Unlike more stable shoes, flip-flops do not absorb the impact of steps, forcing the arch, heel calf or back to bear the brunt of the force.
So, it's perfectly fine to waddle from the pool to the car in flip-flops, not so great to wear them to work for eight hours.
"It's like walking on gravel," says Tracey Vlahovic, associate professor of podiatric medicine and orthopedics at Temple University. "Think about how many steps you take in a day and how much jarring that is. Over time, that has to affect you in some way."
Yet no one, not even the most tightly wound podiatrist, is suggesting a ban on flip-flops – or even a warning label. Even Auburn's Shroyer admits he wears flip-flips "frequently" during Alabama's sweltering summers.
They merely want the public to be aware of potential problems and perhaps buy a higher-quality sandal (with arch-support molding and harder tread) than the 10-buck flimsy drug-store model.
Americans spent $7.4 billion on sandals in the past year, down from $8.1 billion in 2007. It ranks third behind dress shoes and athletic wear, according to the NPD group, which tracks consumer spending.
Tracy Basso, a Davis podiatrist and past president of the California Podiatric Medical Association, says he has treated flip-flop wearers for pain conditions such as plantar fasciitis – inflammation of the tissue along the bottom of the foot that connects the heel bone to the toes.
"I especially see it with pronated feet – semi-flat feet," says Basso, who also own Shoes & Feet, a retail store in Natomas. "The arch is falling, the foot rolls in. That's a patient that would have problems with flip-flops and needs support."
Basso says that, occasionally, he has had patients need specially molded orthotics to wear with flip-flops. Usually, though, a patient whose foot problems necessitate orthotics usually will eschew flimsy sandals altogether.
"But unless you have predisposing foot problems, I don't have strong reservations about sandals," Basso says. "But to the degree that a family has within their budget to buy a better or more supportive sandal, I'd do it. But they tend to be expensive."
High-end brands, such as Teva, Merrell and Bite, can cost $36 to $104. The advantages of those flip-flops, says Basso, is that you can safely wear them for prolonged periods.
"The support is there, just like an athletic shoe," he says. "Those cheapie sandals don't protect in any meaningful way. Might as well go barefoot."
Even Basso, who says he has five kids who wear flip-flops, knows that most people don't follow the podiatric advice. In fact, many podiatrists say people actually think flip-flops are good for the feet because they are not binding and let them breathe.
"When they have heel pain, they'll reach for the shoe that's easiest to put on and off," Temple University's Vlahovic says. "Usually, that's a flip-flop. I'll have patients come in wearing a flat slipper or flip-flop and, in reality, it's not helping with support."
Flip-flop wearers encountered one recent sunny afternoon in midtown Sacramento know the risks and simply don't care.
"I bought these for $3 on the beach in Florida a few years ago," says 48-year-old east Sacramento resident Bryan Lopez, pointing to his rubber-thonged flip- flops with barely a quarter-inch of sole. "They are crap, but they're cheap and easy to throw on. They really do make my feet ache. I do own a pair of (higher-priced) Echo sandals at home, but I find I wear these a lot."
Some seem personally attached to their low-support, "casual" flip-flops. And the thought of forking over big bucks for them seems antithetical to the laid-back gestalt of summer.
"They only hurt when you walk around all day," says Stephanie Kolb of Woodland, who had, indeed, been walking around all day in flip-flops. Kay Brown, her friend also shod in sandals, added, "I wish I had some arches in mine. I can feel it."
Then there are flip-flop wearers in denial, such as Sacramento's Taylor Eichelberg.
"These are fine," he says, looking down at a thinly soled pair. "I got these in Mexico. I've never had any foot problems."
It could be, Basso says, that people such as Eichelberg are genetically immune to flip-flop ravages.
"I often blame the foot as opposed to the shoe," he says. "Some people just have feet that shouldn't be in flip-flops."
Dr. Tracy Basso is a California College of Podiatric Medicine (CCPM) alum.