“Butt wink” may sound like a dance making the rounds on TikTok, but it’s actually code for a common form issue in the squat exercise. 

Whether it’s with dumbbells on your shoulders, a kettlebell held in goblet position, a barbell across your back, or no weight at all, the squat is a foundational movement pattern that people do in the gym and throughout daily life (you squat every time you lower yourself onto the toilet, for example). As such, proper squat form is essential for reducing injury risk in life and sport. This means you’ll want to recognize if and when you have a butt wink and resolve it ASAP. 

Below, the details on what exactly a butt wink is and why it happens, plus three tips for undoing it. 

What Is The Butt Wink, Exactly? 

At its most distilled, the butt wink is a specific form flaw during the bottom portion of the squat. “It happens when an individual’s lumbar (a.k.a. lower) spine rounds and their pelvis takes on a posterior pelvic tilt while they are sitting into the bottom of the squat,” explains exercise physiologist Pete McCall, M.S., C.S.C.S., C.P.T.,  host of the All About Fitness Podcast. During a posterior pelvic tilt, the front of an individual’s pelvis rises while the back of their pelvis drops, he explains. 

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Here’s what that looks like: When you watch someone with a butt wink squat from the side, you’ll see their lower back round and their tuchus tuck under their tailbone as they approach the bottom, he says. This creates motion much like a wink, which is how the flaw got its name. 

What Causes The Butt Wink

The culprit here? A lack of mobility somewhere in your lower body. In order to squat properly you need a certain degree of hip rotation so that your hips can physically open in the squat stance, as well as ankle dorsiflexion so that your full foot can stay on the ground while you sit into the squat, explains McCall.

If a person has sound mobility, their lumbar spine can remain in a neutral position from the starting position all the way down to the bottom of the squat, McCall says. However, if an individual has tight ankles or hips, the lumbar spine moves suboptimally. “The mobility required for a squat has to come from somewhere, so if the ankles, knees, and/or hips don’t have that mobility, the lumbar spine will compensate,” he explains.

That said, in some instances it’s a lack of body awareness or pelvic control that causes a butt wink, according to certified strength and conditioning coach Jake Harcoff, C.S.C.S., head coach and owner of AIM Athletic. “To complete a squat with adequate depth, you need to simultaneously be able to tilt your hips bones anteriorly (forward) while tilting your sacrum posteriorly (back),” he says. When you can get the pelvis to do both motions at once, you can descend to the bottom position of the squat with sound form. A hardcore butt wink, though, could reflect a lifter’s inability to control their pelvis, Harcoff notes. 

The Risks Of The Butt Wink 

Don’t worry, the butt wink isn’t inherently dangerous, says Harcoff. The spine is designed to contract and relax, extend and rotate, and bend forward and backward so that we can execute daily tasks and exercises like getting out of bed or bending over, he says. So, some lumbar spine rounding (a.k.a. spinal flexion) isn’t necessarily cause for alarm.

However, spinal flexion can become dangerous if it occurs while an individual has weight on their back, as they would during a barbell back squat, for example. Loading weight on your back puts load onto your spine itself, explains McCall. When your spine rounds while bearing an external load, the lumbar spine and surrounding spinal tissues endure an excessive amount of stress.

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In extreme instances, butt winks can lead to bone fractures in the vertebrae, lumbar spine disc bulges, and disc herniation, McCall says. Most commonly, though, butt winks lead to inflammation in the lower back, which further limits mobility, causes discomfort, and impairs movement freedom even further. What’s more, because butt winks are caused by other immobilities in the body, people who have a butt wink could be more susceptible to other joint injuries, too, adds McCall. 

Also worth noting: Having a butt wink while you squat changes the main muscles being called on, according to Harcoff. “It inevitably de-loads the quadriceps, and instead places a greater amount of load and tension through the erectors, glutes, and hamstrings,” he says. Ultimately, it makes the move a miss for the quad gains people do it for.

How To Fix A Butt Wink

Whether you want to reduce your risk of injury, put on muscle mass more effectively, or increase your squat PR, you’d be wise to remedy your butt wink if you have one. Here are three ways to do it.

1. Work on ankle mobility 

In order to send your knees forward—as you need to do in the squat—you need an adequate amount of dorsiflexion in your ankles. Without this, the lumbar spine can “take over” the role of the ankles, which can create a butt wink, says Harcoff. 

“One of the most effective exercises for improving ankle mobility is eccentric heel drops from a ledge or elevated surface,” he says. To do them, start by standing on the balls of your feet on an elevated surface (like a step or textbook). Then, slowly and with control, lower your heels as far as you can, until they are lower than whatever you’re standing on. Then return to the top and start again, aiming to drop your heels further and further. He suggests doing at least 20 reps per day to move the needle. 

While you work on gaining greater ankle mobility, you could also consider using squat shoes, he adds. Squat shoes place your heel in a heightened position, which artificially gifts your ankles some extra range of motion. 

2. Stretch your hip flexors

“When your hip flexors are tight, they can keep your pelvis from moving properly during squats,” says McCall. As such, improving your hips’ range of motion can help you course-correct a butt wink. For this, he recommends the kneeling hip flexor stretch. 

To try it, start in a half-kneeling position. Brace your midline, place both hands on your front knee, and lean forward until you feel a stretch in your other hip flexor. You can increase the stretch and make it more active by squeezing your glutes once you’re in position, McCall says. Hold here for 30 seconds before switching sides. “Repeat three to five times per side, aiming to sink your hips deeper into the stretch each time,” he says. Make it a part of your daily routine to see notable change.

3. Improve overall body awareness.

If you have adequate mobility for squatting but your form is still off, Harcoff recommends focusing on establishing control over your pelvis. How? With the help of an exercise known as the “foam roller squat,” which involves placing a foam roller horizontally between your upper back and a wall, then squatting down without letting the foam roller drop. 

This exercise forces you to keep your upper body upright because the foam roller will fall out from behind you if you don’t. “It also gives you a reference for where your hips are in space,” Harcoff says. “If your hips hit the wall on the descent, you know you are losing your hips too far backward, and are likely going to butt wink.” 

Just 10 slow and controlled reps of these each day will slowly help you understand your pelvis in space, which can help you adjust your form to avoid any winking, he says.