This Is Why You Cross Your Legs

And why you may want to stop—immediately.

If you're from a western culture, there's a good chance that, upon sitting, you cross your legs in some way or another. Maybe you're the type to instinctively overlap them at your feet. Or maybe you're a diehard yogi, and regularly sit Sukhasana (colloquially, "criss-cross applesauce"). Or maybe you're a devout figure-four (ankle rested on the opposite knee) or European-style (knee on top of and flush against the opposite knee) sitter—the two most common postures. There's also a good chance that you haven't given a single thought as to why you sit the way you do.

"Your body is designed to move," says posture expert Dr. Steven Weiniger, author of Stand Taller Live Longer: An Anti-Aging Strategy. "When you cross your legs, you're trying to improve the mechanics of the lower back and take the strain off." Put another way: you're trying to mitigate discomfort in all its forms. Weiniger breaks discomfort into two broad categories, low-grade (your leg's asleep) and high-grade ("Oh, my god, I'm in agony!"). Shifting into a cross-legged position is your mind subconsciously preventing your body from ending up in high-grade discomfort.

But more than just in the name of boosting comfort, crossing your legs is a learned behavior—particularly regarding which side you do it. As a study in the Journal of Physical Therapy Science revealed, people who cross their right leg over their left more than double those who cross the other way around. "That's the way they are, and that's the way their body has molded," says Weiniger. "It's not just the the hips—its the whole body muscle system. Think of a shirt that you twisted a bit, and how that now has crease lines on it. It's doing the same thing but on multiple layers of muscles."

At the same time, consciously crossing your legs can be a total a power move. Just look to the Oval Office. You'll find extensive documentation of U.S. presidents—including John F. Kennedy, Richard NixonRonald Reagan, George Bush Sr. and Jr.Bill ClintonBarack Obama—sitting European-style, whether during interviews, meetings, or post-service conferences. In a certain way, this makes sense: crossing your legs takes up more space than sitting regularly—and taking up more space is seen as dominant. "If you run into a coyote or—or something like that—in the woods," says Weiniger, "in general you want to make yourself look bigger not smaller," to project dominance.

But the question remains: Should we all be crossing our legs so much?

According to research in Blood Pressure Monitoring, regularly assuming a crossed-leg position—be it figure-four, European-style, or any variation—can cause your BP levels to spike by more than 6 percent. It's also horrible for your posture; crossing your legs puts undue pressure on your peroneal nerve, or the part of your nervous system responsible for sensation from the knees down, and can also stretch out your piriformis, or the muscle that helps your hips rotate. (Making matters worse: the piriformis muscle, says Weiniger, is right above the sciatic nerve, and when that gets pinched or compromised in any way, serious high-grade discomfort is imminent.) Finally, per Johns Hopkins Medicine, keeping your legs crossed while sitting can purportedly cause varicose, or "spider," veins (though some experts believe that it's the act of sitting itself, crossed-legs or not, that causes the condition).

For his part, Weiniger recommends simply being mindful of how much time you spend sitting cross legged. "It's easy for someone like to me say, 'Hey, every X amount of time, you need to move,'" says Weiniger. "But everybody's body is different." In other words, if you set a timer to uncross your legs every ten minutes, but you're feeling low-grade discomfort at the eight-minute mark, feel free to shift your legs.

Or consider the standing desk. Trust me: it'll work wonders on your back—and help you burn nearly 100 calories per day.

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Ari Notis
Ari is an editor specializing in news and lifestyle. Read more