Doing this during your squats and deadlifts? Check yourself before you wreck yourself.

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Weightlifting is getting crazy popular. And you don't even have to be a powerlifter to get up close and personal with weight training. Women taking boot camp classes, doing CrossFit, and working out in regular gyms are more likely than ever to encounter kettlebells, barbells, and more. Even celebrities like Kate Upton and Brie Larson are raising the profile of weightlifting workouts. (BTW, here's what really happens when women lift heavy weights.)

But when it comes to lifting heavy things, safety is super important. And there's one crucial mistake trainers see frequently with weightlifting newbies that makes them cringe. The upside? Fixing it is easier than you might think. Here's what you need to know.

What's the problem?

Have you ever watched someone squat or deadlift and seen them thrust their hips forward at the end of the movement? Sometimes, it's so far that they actually lean backward. Yeah, that's not a good idea.

"Thrusting too far forward at the end of a deadlift or squat is a really common compensation," says Nicole Ramos, D.P.T., a doctor of physical therapy and certified personal trainer. But why is it so bad? "What's actually happening is hyperextension of the lumbar spine." That's the part of your spine that makes up your lower back. Hyperextending it means you're pushing it out of its normal range of motion by forcing it to curve into a "c" shape that faces backward. You might typically think of hyperextension of the low back as when you stick out your butt (à la IG "booty popping" gym mirror pics). But it can also happen when you squeeze those cheeks so tight and press your hips so far forward that you're almost leaning back at the top of an exercise.

"Usually it comes from attempting to drive your hips forward to complete the lift," explains Ramos. Most people are taught to stand up completely and squeeze their glutes at the end of a squat or deadlift. But sometimes, this causes people to actually lean back. In other words, they can't squeeze their butt without hyperextending their back. "Hyperextending the lumbar spine causes a significant shearing force to the lumbar spine and sacroiliac joints (which connect your spine to your pelvis)," adds Ramos. In other words, it puts *a lot* of pressure on your lower back to bend in a way it's not supposed to-and it's an area that's pretty prone to injury to begin with. (Related: Is It Ever OK to Have Lower-Back Pain After a Workout?)

Experts agree that it's not great to do this in a deadlift, but it's *especially* dangerous to do it in a barbell squat. "An overly aggressive hip thrust at the top of the squat can(but does not always) cause the bar to ever so slightly fly up off the 'shelf' of your upper back," explains Greg Pignataro, C.S.C.S., at Grindset Fitness. "When gravity pulls it back down that half inch, it adds extra compressive force to your spine, which can cause injury." Ouch. While it's certainly not guaranteed that you'll hurt yourself if you lift this way, why risk it?!

How to Maintain Proper Posture While Lifting

So, how can you know if you're making this mistake in the first place, and what can you do about it? Here's what fitness pros recommend.

Ask for help. If you work out in a gym with trainers, ask one of them to check out your technique-or better yet, schedule a personal training session to ensure your form is really solid. "It's always great to have a second pair of eyes when you're doing heavy lifts," says Ramos. If recruiting a trainer isn't an option, you can still check yourself. "If you're working independently, videoing yourself is the best way to analyze your performance and correct suboptimal movement patterns."

Learn what locking out your glutes should feel like. "Oftentimes, movement compensations such as hyperextension of the lumbar spine are a motor control issue," says Ramos. In other words, your body just isn't used to moving that way yet. For a solid (and safe) glute lockout, Ramos' go-to exercise is a hip thrust on a bench. Use a lighter resistance (or no resistance at all) and focus on achieving a posterior pelvic tilt as you move the pelvis into hip extension (the top of the rep), she recommends.That means your hips are tucked under, almost like you're tucking your tailbone between your legs. "I also like cueing posterior pelvic tilts inside a plank," she says. "It's practically impossible to hyperextend your lumbar spine in a posterior pelvic tilt." And that's the key. If you're in posterior pelvic tilt, your lower back will be flat, not curved, so you won't be able to hyperextend your lower back. Once you can maintain a posterior pelvic tilt consistently in these exercises, go back to your squat or deadlift and see if you can integrate this new strategy by thinking about posterior pelvic tilt to achieve glute lockout and a neutral spine. (Related: Your Glutes Aren't Weak, They're Just Not Firing)

Practice squeezing your butt. Yes, really. If the posterior pelvic tilt strategy doesn't work for you, try this. "Rather than 'thrusting' your hips forward and 'tucking' the tailbone, you should practice engaging your glutes through an isometric contraction," says Timothy Lyman, a certified personal trainer and director of training programs at Fleet Feet Pittsburgh. "Think about 'squeezing' or 'clenching' your butt cheeks together, without allowing your hips to move forward. By isometrically contracting the glutes at the top of a squat or deadlift, you'll actively target your glutes and engage your core while keeping the hips level and your spine in a safe, neutral position."

Learn how to brace your core. If you keep your core steady and stiff during either lift, you won't be able to thrust your hips forward. Here's how to do it:

  • At the start of each rep, you take a deep, diaphragmatic breath, filling up your belly.
  • Then, while holding your breath, pull your navel toward your spine, tensing the abdominal muscles.
  • Don't exhale until you have completed the rep.
  • Before starting your next rep, take another diaphragmatic breath.

"This is the best way to prevent injury when lifting heavy weights because it keeps you from collapsing forward and placing undue stress on your lower back," says Pignataro. (Here are more tips on how to brace your core during your workouts.)

Keep it light. Until you've sorted your lifts out, there's one rule to live by: "By all means, reduce the weight you're using and work on form first!" says Gabrielle Fundaro, Ph.D., a nutrition and exercise consultant for Renaissance Periodization.