From New York’s sweltering sidewalks to Brazil's sandy beaches, there's no sandal that signals summer quite like the flip-flop. But are these no-fuss flats as harmless as they seem? Studies show that despite their easy-breezy appeal, extended flip flop use can cause a range of physical ailments, ranging from plantar fasciitis and muscle soreness, to lower back pain. Not exactly what we signed up for, right?

Foot Action — Why It Matters

With the average American taking 5,117 steps a day — and experts recommending we take close to 5,000 more — our footwear is hardly an inconsequential choice [1]. A 2012 survey found 78 percent of American adults over the age of 21  report having had some sort of foot pain or issue at some point in their lives, and more than half reported having such issues at the time of the survey. And while there’s no single shoe that’s a perfect across the board, flip flops may be the riskiest pick of them all — excluding Gaga’s armadillo hoof stilettos, of course (and just imagine how that armadillo feels).

In one study, researchers compared the effects of wearing flip-flops and athletic shoes on 39 male and female college students. The flip-flop wearers took shorter steps and struck their heel to the ground with less vertical force than when in sneakers, causing their gaits to sway away from their natural rhythm. The reason? Most flip-flop wearers tend to clench their toes around the thong portion of the sandal to keep them from flying off. But toe curls aren’t quite what the doctor ordered and can instead lead to repetitive stress on the ankle and foot.

Where Flip Flops Fall Flat — The Answer/Debate

Even though thong-like sandals provide some cushioning benefit over bare feet alone, studies show they’re responsible for throwing human gait kinetics out of whack. The body is forced to compensate, and what starts as stress on the arch, heel, and the rest of the foot can eventually manifest as soreness in the legs, hips, and lower back.

Among the most treated flip-flop induced injuries is plantar faciitis, an inflammation of the connective tissue along the bottom of the foot that affects close to two million Americans each year (including a few members of the Greatist team itself!). This acute heel pain is most often sparked by all-day wear, with overweight or sedentary wearers even more susceptible since their arches are already under strain. Roughly 20 percent of sufferers develop a chronic condition, making plantar faciitis even worse.

But it’s not all doom and gloom on the flip-flop front. Here are a few tips to keep in mind when picking a pair to rock for the warm weather:

• Time it right. Replace flip-flops every three to four months, and only wear them for short periods of time.
• Opt for leather. The plastic ones may come in every color under the sun, but a soft, high-quality pair of leather flip-flops is less likely to cause irritation, including blisters.
• Find the right fit. Make sure the heel and toes don't hang off the edges of the sandal and that when you bend the sandal from end to end it bends where the ball of the foot hits  — not at the arch!
• Wear selectively. Beach walking, pool deck trolling, and a quick run to the grocery store? Yes. Soccer game, lawn mowing, and a five-mile hike? Not so much.
• Make it official. Look for sandals approved by the American Podiatric Medical Association. They have a whole handy-dandy list of the approved shoes (of all types), so search around and see if there's something you dig!
• And whatever you do: Please, don't wear them with socks.

Originally published June 2011. Updated August 2012.

Do flip flops give your feet summer troubles? And what do you do about it? Commiserate with us in the comments below! 

Photo by Jordan Shakeshaft