The Single-Leg Squat Mistake That’s Breaking Your Body Down

Matt Korman STACK

The Single-Leg Squat (a.k.a. Pistol Squat) has gained popularity in recent years as the use of unilateral training has increased. There’s no doubt that a well-executed Single-Leg Squat is an impressive display of fitness, but as the movement has become more widespread, the typical quality of the move has decreased. People like to talk about the importance of going deep on Squats, and it certainly has merit. But when we prioritize depth above all else, it can create some serious issues—particularly with movements like the Single-Leg Squat.

In my article, “What is Range of Motion, and Why is it So Important?”, I discuss the importance of getting a full range of motion on your exercises. Using a greater range of motion will increase the total work while decreasing the load on the body, increase flexibility and mobility, and reduce overall risk of injury. That being said, as I discussed in that article, greater range of motion is not always better. An exercise should be performed to the greatest range the athlete can go (that are in the recommendations of the movement) while still maintaining form.

The Single-Leg Squat is a prime example of form breaking as you get deeper into that range. I see two big issues often arise from this—one being related to something called “butt wink,” and the other to spinal alignment. Let’s break both down and provide fixes for each.

Mistake 1: Butt Wink

Butt Wink describes an error in the pelvic position at the bottom of a deep squat. With a butt wink, the pelvis tips upwards at the bottom of the squat and then, as the individual stands up, it returns to neutral. The problem with this error is that the body is one chain, and this change in pelvic position puts significant strain on the low back.

Most athletes who have experience squatting understand the issue with butt wink, but very few seem to think it necessary to fix when performing a Single-Leg Squat.

A perfectly executed deep Single-Leg Squat is incredibly rare for a couple of reasons. First, with only one leg on the ground, it is easier to get into a deep squat position, so simply getting “deep” can’t be used as a signal of quality movement. The second reason relates primarily to how I have seen the Single-Leg Squat taught. The TRX Single-Leg Squat is readily used as a way to teach a Single-Leg Squat, but it creates more harm than good in regards to movement patterns. When done correctly, the individual should only use the TRX to assist the movement as needed, but instead, people often lean back and fully rely on the TRX. This forces them to sit back as they go down, which makes it nearly impossible for the pelvis to remain neutral (thus, butt wink).

Many people believe butt wink to be caused by tight hamstrings, but I have found that to be treating symptoms rather than the cause. The error is more directly an issue of improper coaching, specifically when athletes have been taught to sit back on their heels when they squat. Don’t get me wrong, I do not want my athletes squatting on their toes, but correcting that by putting the athlete entirely on their heels is not any better.

When the athlete sits back in this way, the torso usually comes forward and the hamstrings contract to keep the athlete from falling back. If the athlete tries to squat below parallel, that pull of hamstring usually causes the pelvis to tuck under into the butt wink position. The easy fix for this is to instead cue the athlete to try to sit straight down onto their heel (This does require a significant amount of mobility at the ankle). When this is done correctly, the torso is upright and the hamstrings are relaxed, allowing the pelvis to remain neutral. Start with trying to maintain that spinal alignment while squatting to an 18-inch box (you can start bigger if needed). If you are able to maintain, gradually increase the range until you have a full depth Single-Leg Squat. If you still fall into butt wink, you may have a limitation in ankle, hip or t-spine mobility forcing you to sit back on your squats. Work on those limitations while gradually increasing range of motion.

Mistake 2: Poor Spine Alignment

Beyond butt wink, I have seen many videos of fitness celebrities and athletes performing Single-Leg Squats where they’re completely rounded in the thoracic and lumbar regions of their spine. It does not matter the exercise—being able to maintain a neutral spine is strength training 101. You may argue that the Single-Leg Squat is a bodyweight exercise, therefore it does have a significant load on the spine. I would argue that the legs still need to produce a significant amount of force when performing a full range Single-Leg Squat and I would seriously caution having a rounded back while the legs are forcefully contracting. Also, many athletes are now loading their Single-Leg Squats, which makes spinal position even more important.

How can we fix this rounding? Most people round their backs in the Single-Leg Squat as a way to maintain balance. With no load and only one limb on the ground, rounding your torso and reaching forward counter balances the weight shifting back. This problem can be partially fixed by making the butt wink correction. But to fully alleviate that urge to round as a way to achieve better balance, use Mike Boyle’s technique of holding a five-pound dumbbell or plate in each hand as you perform the Single-Leg Squat. Jessica Biel can be seen doing this here:

By holding those weights out in front of you, you create a natural counter balance and eliminate a common cause of rounding. To give you a clear visual of a bad Single-Leg Squat vs. a well-executed one, look at this side-by-side comparison:

If you find that you have either of these errors in your Single-Leg Squat, it is time to stop so low toward the ground. Reduce your range of motion, work to make these two corrections, and go as deep as you are able to while maintaining a neutral spine and pelvis. For as much as people like to obsess over squatting deep, it’s better to do a shorter range of motion well then to do a full range of motion poorly!

Photo Credit: BraunS/iStock


Topics: SQUATMatthew Korman – the director of strength and conditioning at Charlotte Christian School in Charlotte, North Carolina. He develops and implements year-round strength and conditioning programs for all 19 sports programs at Charlotte Christian. Along with his CSCS, he is USAW certified and has trained