If you’re wearing high heels, you may want to sit down for this one. Really. According to new research, those stilettos may not only have you teetering down the street (or taking an ego-shattering spill as many a model has done), they could be wrecking your leg muscles and tendons, leaving you open to injury.

Published in last week’s Journal of Applied Physiology, three Australian scientists became curious about the impact of high heels after watching a woman who looked obviously “uncomfortable” and “unstable” in hers. And even though heel-wearers have been complaining about foot pain and fatigue for years, there was little scientific evidence to explain why.

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To find out, the researchers recruited nine women who had worn heels at least 40 hours a week for a minimum of two years, and 10 women who rarely, if ever, wore heels.

After observing both groups walk, the researches found that those who regularly wore heels walked differently than those who didn’t. The heel wearers moved with shorter, more forceful strides, and their feet were perpetually in a plantar-flexed or toe-pointed position (think Barbie feet)—even after they kicked off their shoes to walk barefoot.

They also noted that heel-wearers tended to use their calf muscles more when walking, while those who rarely wore heels used more of their Achilles tendon.

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And that’s a big problem, according to one of the researchers, Dr. Neil Cronin, who is now a researcher at the University of Jyvaskyla in Finland. Apparently using the calf muscle versus the tendons requires more energy to cover the same distance (imagine how useful that information could be for runners).

“The efficiency of the muscle-tendon system is higher when the muscle operates at an approximately constant length,” Cronin tells YouBeauty, “whilst the tendon acts as a kind of biological spring, lengthening to store energy during the early part of the step cycle and then recoiling to return most of this energy during the latter part of the step cycle (similar to an elastic band). This pattern of muscle-tendon interaction is efficient because both the muscle and the tendon are well adapted to those specific roles. It seems that in women who have worn high heels for a long time, this efficient pattern is disturbed, meaning that more energy is required to move a given distance.”

Not only do heel-wearers have a less efficient gait, but they are also at an increased risk of straining the calf muscle, which is three times higher when sporting our beloved pumps regularly.

This same risk continues even after ditching our heels. In other words, toggling from heels to sneakers when hitting the gym after work could be a dangerous thing. Our calf muscles and tendons are “set” into a shorter, heel-wearing state, and putting them into flat shoes forces additional strain on them.

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So what’s a stiletto/wedge/pump-loving girl to do?

Aside from switching to shorter heels or flats, Cronin advises that we wear them just once or twice a week. And when our feet are squished, we mean, adorned in heels, we should try to remove them as much as possible, like when we’re sitting at our desk.

Oh, and if you’ve worn heels for years and are now afraid of permanent damage to your calves and feet, Cronin says don’t be.

“We know that the muscles and tendons can respond to changes in the way they are loaded over long periods of time (which is what happens when they wear heels for a long time). As long as there is no permanent structural damage, the changes due to wearing heels for a long time may be reversible.”

When in doubt though, take your cues from Oprah: She carries her heels onto the stage, slips them on only when sitting, and then takes them off again to walk off stage. Chances are, she doesn’t have short calf muscles!

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