5 Reasons It's Important to Have a Strong Butt—Besides Looking Good

Do you know what protects your back? "The 'two A's,'" says Sara Lewis, celeb trainer (who's trained clients like Ryan Gosling, Kim and Khloë Kardashian, Christina Ricci, Nikki Reed, Sofía Vergara, and Jaimie Alexander, just to name a few) and creator of XO Fitness in Los Angeles. And what are the two A's? "Your abs and your ass. You can't succeed at one without winning with the others."

In case you didn't know, all the muscles in your body work together—that's why you can't spot reduce or strengthen just one muscle at a time, says Lewis. And three areas that work together a lot are your core, your butt, and your lower back. Butt-targeting moves like squats and donkey kicks require you to engage your core, meaning you're earning your core strength and abs through all those booty-builders—and strength in both those areas means you're protecting your back. (And that's key when it comes to this one trick for preventing back pain when strength-training.)

Going right back to that whole "all the muscles in your body work together" thing—a strong butt means your whole hip system is highly functioning, says Lewis.

"Your hip flexors (the front side of the hip), your hip extensors (the backside of the hip), and your psoas muscle (extending from your ribcage down your thigh) all conspire to keep you walking/running/jumping/squatting/lunging in a beautifully wondrous and flexible way."

To build and maintain your butt strength and hip mobility, keep and eye on your squat depth and your ability to turn out for things like sumo squats, says Lewis. Feel sub-par? Get those hip joints moving, or it might backfire for your booty. (Example A: Weak hip abductors can cause glute pain in runners.)

From barre to biking to huffing up the stairs to your fifth-floor walk-up, your glutes get recruited in more movements than you may realize. Not only is a strong butt key to making it (safely) through whatever workout you're tackling, but it's also key to successfully completing day-to-day activities.

"Having strong glutes will make sure that all the muscles are firing in the way that they should be," says Lewis. "There are three main parts of the glutes with a laundry list of exercises to target each of them. Barre classes target your 'shelf' (aka the minimus), pliés are superior for your hidden but necessary 'middle butt' (your medias), and squats, lunges, and bridges will work the largest area of the group, your maximus." (Here's how to maximize those squats for butt-toning benefits.)

"Focusing on the glutes reinforces the hip region, but also the quads and your ACL and VMO muscle, which surrounds and support the knees," says Lewis. "A strong butt means strong knees." Without strong glute muscles, you won't be able to safely perform those movements with your knees in the correct position, putting you at risk for injury. (And ICYMI, women are way more likely to tear their ACLs than guys are, so this is super important.)

Because women are generally stronger in their glutes (and legs and inner thighs) than men, we should think of it as our number-one weapon—our source of strength.

"We always talk about our hips and our thighs and trying to make them thinner, more shapely, whatever" says Lewis. "But that's our power. Think about everything we do with that lower half of our body." We probably aren't going to defeat a zombie with our biceps. Everything from having babies to trekking up mountains to round-house-kicking the crap out of villains in action movies? We're going to do it with our lower body. And not a wimpy lower body, either.

"Shapely butts are beautiful," says Lewis. "But, really, it's all about working towards being strong—because that makes us feel strong."

So go ahead—train your booty for aesthetics and to rock those cheeky bikini bottoms like no one's business. But at the end of the day, know that a strong, sculpted butt is doing so much more than filling out your skinny jeans. (And being strong in itself is dead sexy—these women prove it.)