During Mike DeFrancisco’s freshman year of college, his feet started to hurt. It started as a minor pain in the heel and then began to radiate out through the arches.
He went to see a podiatrist, who then diagnosed him with plantar fasciitis and heel spurs. "One of the first questions my doctor asked was how often I wore sandals," said DeFrancisco. "And when I told him, he said that my problems most likely stemmed from the shoes I had been wearing."
His footwear of choice? DeFrancisco had been wearing flip-flops almost every single day for six years.
While most people vary their footwear much more frequently, warmer days do mean that more and more New Yorkers are hitting the streets in their Havaianas. And with the familiar sound of rubber smacking concrete comes a familiar concern: Can wearing flip-flops cause damage to your feet?
"The problem is that they give absolutely no support," said Dr. Marlene Reid, a spokesperson for the American Podiatric Medical Association. "It’s like running around barefoot, but worse, because sometimes your toes have to scrunch down to keep the shoes on."
One study, published in 2008 in the Journal of the American Podiatric Medical Association, found that flipflops significantly increased pressure on the bottom of the foot, as compared to sneakers. This pressure, the researchers wrote, "has been correlated to an increased risk of foot deformity."
The pressure is heightened when you factor in the non-pliant city streets New Yorkers tread on. "The flip-flop is so thin that it offers little shock absorption," said Dr. Krista Archer, a Manhattan podiatric surgeon affiliated with Lenox Hill Hospital.
In 2010, Dr. Justin Shroyer, a researcher at Auburn University in Alabama, published a study in the Journal of the American Podiatric Medical Association that looked at how flip-flops affect the way in which a person moves while walking or running.
His study found that flip-flops, as compared to sneakers, shortened the wearer’s stride and increased a measurement called "ankle angle" as the individual swung their leg through mid-stride.
According to Dr. Shroyer, the shortened stride matters because it leads to an overall increase in the number of steps an individual takes, increasing pressure on the foot.
The increased ankle angle is an indication that the struggle to keep the flip-flop on the foot (by curling the toes down) could be causing strain. "Your body is trying to pull your foot up to swing the leg through, but in inadvertently trying to keep the flipflop on, it’s pulling the foot down," said Dr. Shroyer. "So the muscle that’s pulling the foot up has to work harder. Because it’s working more and it’s such a repetitive motion, it’s a chronic effect that leads to lower leg pain and ankle pain."
And no, it is not normal (or healthy) for the bottoms of your feet to be coated in a black film after a full day walking the summer streets. "City streets are gross and there’s no protection against dirt and grime!" said Dr. Reid.
While wearing sneakers every day would technically be the best idea, experts concede that for most people, and especially in a fashion-focused city, that is not a practical alternative.
Other footwear options are at least somewhat kinder.
"The good thing about a ballet flat or a flat sandal with a buckle is that your toes aren’t working hard to keep the shoe on," said Dr. Archer.
If you’re going to wear flip-flops, you can minimize the harm by choosing a style that the American Podiatric Medical Association has given their "seal of approval" to. A full list, available on their website (apma.org), includes brands like Fit Flop and Chaco, which offer better support.
"There are some that have a built-in arch, and some that have a deeper setting for the heel," said Dr. Reid. "Those are better."
In the end, your best bet is to save the flip-flops for sandy surfaces or the occasional picnic in Sheep Meadow.
If it’s too late to save your soles, don’t try to walk away from the problem. "If you have pain, don’t ignore it, and don’t keep wearing shoes that are causing the pain," warned Dr. Archer. "If you switch to better shoes and it still hurts, see a doctor."