Flip-flops might make you feel like you’re on vacation, but they’re actually making your feet work overtime.
When you wear the thonged sandals, you have to slightly “clench” your toes to keep them on, says Doug Kechijian, D.P.T., doctor of physical therapy at Peak Performance in New York City. And that’s not a natural position for your feet.
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See for yourself: Take your shoes off. Take a step, paying attention to how your midfoot and toes bend at the end as your heel leaves the floor.
Now slightly “clench” your toes, curling them down toward the pads of your feet. Take another step. It doesn’t feel the same, does it? Your foot will be stiffer, and the step won’t “flow” like the first step.
This constant tension alters your gait, eventually causing muscular issues in your feet and calves. That can lead to the painful condition plantar fasciitis–also called “jogger’s heel”–when you run. You’ll feel a sharp shooting pain in the bottom of your heels with each step. In extreme cases, flip-flops may even be the cause of other lower-body issues like knee pain.
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But let’s face it: Flip-flops are a summertime staple. So wear them–but put a cap on the distance you travel in the sandals. It’s truly the dose that makes the poison, says Kechijian.
“If you have to walk more than, say, 10 blocks, you probably want to wear regular shoes,” says Kechijian. “But if you’re just walking down to the beach or hanging out at a barbecue, flip-flops aren’t going to cause any real problems.”
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Another option is to find a sandal that stays on easily and doesn’t put your foot to work like flip-flops do. “Something that completely wraps your feet in straps is a better option,” says Kechijian. A good option is Birkenstock Milanos. ($90; Birkenstock.com)
Just make sure that the toe area of those sandals bends. If the zone where your toes sit is too stiff–and Kechijian says many sandals have this problem–that can also negatively impact your gait.
