Top 8 Squat Mistakes and Why Your Squat Form Matters More Than You Think

Want bigger legs? Squat. Want a stronger back, a harder core and glutes that actually fill out your jeans? Squat some more. There’s a reason the barbell squat has survived every fitness trend of the last 50 years: few lifts put your quads, glutes, adductors, spinal erectors and core to work all at once.

You’ve probably also heard that squats build muscle because they flood your body with testosterone and growth hormone. Nice story, but it doesn’t really hold up. When researchers at McMaster University tracked hormone spikes after training, they found those spikes had pretty much nothing to do with how much muscle people went on to build (West & Phillips, 2012). Squats work for a much simpler reason. They let you load big muscles heavy, through a long range of motion, week after week.

The downside is that a lift with this many moving parts is easy to mess up. And most squat mistakes don’t hurt right away – they just quietly eat into your progress until one day your knee or lower back complains. So let’s go through the eight I see most often, what the research actually says about them, and how to clean them up.

1. Not Squatting Deep Enough

Walk into any commercial gym and you’ll spot him: the guy with four plates on the bar, bending his knees about as far as you would to tie your shoes. Ask him why he doesn’t go lower and there’s a decent chance he’ll say deep squats are bad for your knees.

They aren’t. A big 2013 review in Sports Medicine looked at the load on the knee at different squat depths and found no good evidence that deep squats hurt healthy knees when your technique is decent. If anything, the authors were more worried about quarter squats, because people tend to pile on way more weight for them (Hartmann et al., 2013). A 2024 scoping review landed in roughly the same place (Frontiers in Sports and Active Living).

Going deeper also gets you more for your effort. In a 10-week Japanese study, 17 untrained people squatted either to full depth (about 140° of knee bend) or to 90°. Quad growth came out about even. The glutes and adductors, though, grew noticeably more in the full-depth group (Kubo et al., 2019). So if you’ve been wondering why your backside isn’t keeping up with your quads, depth is a good place to start.

To be fair to partial squats, they’re not worthless. Powerlifters and athletes use them for overload work. They just shouldn’t be the only squat you ever do.

The fix:

Get your hip crease to at least the level of your knees, and go lower if your back stays neutral. Can’t get there yet? Grab a dumbbell and do goblet squats for a few weeks. Holding the weight in front of you acts like a counterweight, and most people are surprised how easily they sink between their knees. Also, film a set from the side at some point. Almost everyone thinks they’re squatting deeper than they really are – I did too.

2. Letting Your Knees Cave In (Knee Valgus)

You’re grinding out of the bottom of a tough rep and your knees start drifting toward each other. That’s knee valgus, and pretty much every beginner does it at some point.

Now, I’m not going to tell you it’ll snap your ACL. A small inward wobble on a heavy rep is really common, even among strong, experienced lifters, and there’s no solid proof that it wrecks healthy knees during a barbell squat. Most of the scary ligament research comes from sports like basketball and soccer, where people land and cut at high speed. That’s a different situation.

But when your knees really fold in, rep after rep, your body is telling you something. Usually it means your glutes and hip rotators are weak, your ankle dorsiflexion is limited, or you just haven’t learned to control the movement yet. A 2020 review listed those same factors as the main drivers of knee cave (Wilczyński et al., 2020). On top of that, it’s a power leak. Any force that goes into your knees wobbling isn’t going into the bar.

The fix:

• Think “knees out” on the way up, and keep them roughly in line with your toes.
• Put a mini band just above your knees during warm-ups or goblet squats. Having to push against it wakes your hips up fast (IJSPT review).
• Give your glutes some direct attention: hip thrusts, banded side walks, even clamshells.
• If your knees can’t move forward over your toes, spend a few minutes on knee-to-wall ankle stretches.

3. Rounding Your Lower Back

Your spine can handle a lot of load when it stays in a neutral position. Round your lower back hard at the bottom of a heavy squat, though, and the stress moves off your big hip muscles and onto your discs and ligaments. They’re a lot less suited for the job.

The classic version of this is the butt wink. You hit the bottom, your pelvis tucks under, and your lower back curls for a split second. A little wink with no weight on your back? Totally normal, don’t lose sleep over it. A big one under a loaded bar for sets of five is a different story.

For years, everyone blamed tight hamstrings. I believed it too and spent way too long stretching them before squats. Turns out the hamstrings cross both the hip and the knee, so when you bend both joints at once they hardly change length. They’re rarely what stops you. The more likely culprits are your hip anatomy (how deep your hip sockets are and which way they face), stiff ankles and plain old motor control (Physio Network). Some people can sit ass-to-grass with a flat back. Others will always wink a bit past a certain depth, and that’s just how they’re built.

One more thing – don’t try to “fix” it by yanking your lower back into a huge arch. That’s just trading one problem for another.

The fix:

Start with your brace. Take a deep breath into your belly (not your chest), tighten your abs like someone’s about to punch you, and only then start the descent. Hold it until you’re past the sticking point on the way up.

Next, find your real depth. With an empty bar, squat down slowly and notice where your pelvis starts to tuck. Stop just above that for now. A slightly wider stance with your toes turned out a bit more often buys you a few extra inches. Paused squats and goblet squats will help you own that bottom position over time.

4. Lifting Your Heels Off the Floor

Watch your feet on your next set. If your heels peel up as you sink down, your body is borrowing range of motion it doesn’t have – almost always from stiff ankles.

The trouble is what happens next. Your weight rolls toward your toes, the bar drifts forward, and suddenly you’re fighting to stay balanced instead of pushing hard. It’s also much tougher to drive through your whole foot and get your glutes and quads working together when you’re basically on your tiptoes. With light weights you’ll get away with it. With heavy ones, not so much.

Quick side note, because this confuses a lot of people: raising your heels on purpose is fine. Weightlifting shoes and heel wedges exist for a reason. They let your knees travel further forward, which is great for hitting your quads. What we’re talking about here is your heels lifting on their own halfway through the rep.

The fix:

Keep your whole foot glued to the floor – big toe, little toe and heel. Before you squat, spend five minutes loosening up your ankles with knee-to-wall stretches or slow calf stretches on a step, then ramp up with a few lighter sets. If you’ve been doing that for a while and your heels still pop up, squat in lifting shoes or stick a couple of small plates under your heels in the meantime. Nobody’s handing out medals for squatting flat-footed.

5. Relying Only on the Smith Machine

The Smith machine has a bad reputation in some circles, and a lot of that is overblown. But it does have one obvious catch. The bar runs on a fixed track, so it balances the weight for you. With a real barbell, that job falls on your legs, hips and core.

There’s data on this. Researchers at the University of Saskatchewan had lifters squat their 8-rep max on both, and the free-weight version produced about 43% more muscle activity overall. The vastus medialis (the teardrop-shaped quad muscle) was 49% more active (Schwanbeck et al., 2009). That sounds huge, but keep two things in mind. There were only six people in the study. And more muscle activity during a set doesn’t automatically mean more growth over months.

In fact, when you look at long-term training studies, the gap mostly disappears. A 2023 meta-analysis pooled 13 studies with over 1,000 participants and found free weights and machines built about the same amount of muscle. Where they did differ was strength – people got strongest at whatever they practiced (Haugen et al., 2023).

So no, the Smith machine isn’t a waste of time. It’s just not a stand-in for the real thing if you want a squat that’s strong, stable and useful outside the gym.

The fix:

Build your program around the free-weight barbell squat. Bring in the Smith machine when it actually makes sense: extra quad volume at the end of a session, pushing close to failure when there’s no spotter around, or working around a tweaky joint. When you do use it, set your feet a little in front of the bar so your hips and knees can move naturally on that fixed path.

6. Doing the Same Squat Forever

Let me be clear first: sticking with your main squat is a good thing. You can’t get stronger at a lift you keep swapping out every week. But doing the exact same back squat, the exact same way, for three years straight? That’s how people end up bored, beat up and stuck at the same weight.

A few well-chosen squat variations let you hit your legs from a different angle and shore up weak spots, without giving up the basic pattern. These are the ones worth knowing:

The fix:

Pick one main squat and run it for a training block – somewhere around 4 to 8 weeks – while trying to add weight or reps. Pair it with one or two of the variations above, aimed at whatever’s holding you back. When the block ends, rotate those accessories if you like. Changing things every single workout just makes it impossible to tell whether you’re progressing.

7. Skipping the Safety Bars in the Power Rack

If you train hard, you’re going to miss a rep eventually. That’s not a question of if. And if you’re squatting alone in a rack with the safety bars (a.k.a. pins or spotter arms) sitting on the floor, a missed rep means either getting stuck under the bar or dumping it behind you and hoping for the best.

With the safeties set, missing is almost boring. You sit down, lower the bar onto them and crawl out. Knowing you’ve got that backup also makes it a lot easier to push your sets hard, which is kind of the whole point.

Small but important detour: rack safety bars and the safety squat bar (SSB) are two completely different things, and people mix them up all the time. The SSB is a specialty barbell with padded handles and a bend that shifts the load a bit forward. It’s easy on the shoulders and elbows and it’ll smoke your upper back, so it’s a fantastic variation. It won’t catch you if you fail a rep, though. That’s the rack’s job.

The fix:

Set the safeties about 1-2 inches (2-5 cm) below where the bar sits at the bottom of your squat. Too high and you’ll be clanking into them every rep. Too low and they won’t do much when you need them. Check the height with an empty bar before your working sets, and practice a controlled bail once or twice so you’re not figuring it out under a max.

8. Poor Bracing, Lazy Glutes and a Wandering Bar Path

You can do everything above right – good depth, knees out, heels down – and still have a squat that looks a bit shaky. Usually it comes down to what happens during the rep itself.

First up is bracing. When you brace well, your torso turns into a solid column and all the force from your legs goes straight into the bar. Skip it and your lower back ends up picking up the slack.

Then there’s timing. You’ve probably seen this one: the lifter comes out of the hole, their hips shoot up, and their chest stays pointed at the floor. Now the squat has become a good morning, and the lower back is doing most of the work. Ideally your hips and shoulders rise together at about the same speed.

Finally, watch the bar. It should move in a more or less straight line over your mid-foot, down and back up. Every inch it drifts forward makes the weight feel heavier than it is.

The fix:

• Before each rep, breathe deep into your belly, brace your midsection all the way around (front, sides and back), and hold it until you’re through the hardest part. Breathe out near the top.
• Keep your upper back tight. Squeeze the bar like you’re trying to bend it and pinch your shoulder blades together.
• Coming up, imagine you’re spreading the floor apart with your feet and pushing your upper back into the bar. Finish by squeezing your glutes at the top, but don’t lean back.
• Record a set from the side now and then. If the bar creeps out in front of your mid-foot, fix your setup before you add more weight.

Squat Mistakes FAQ

Are deep squats bad for your knees?

Not if your knees are healthy and your form is reasonable. The research doesn’t show deep squats raising injury risk, and very heavy quarter squats might actually be harder on the knee (Hartmann et al., 2013).

How deep should you squat to build muscle?

Go to at least parallel, and lower if your back stays neutral. Full squats grew the glutes and adductors more than half squats in one 10-week study, while the quads grew about the same either way (Kubo et al., 2019).

Are Smith machine squats bad?

Not really. They work fewer stabilizing muscles than barbell squats, but long-term muscle gains look pretty similar (Haugen et al., 2023). Just use them as an extra, not your main squat.

What causes butt wink?

Mostly your hip structure, stiff ankles and a weak brace. Tight hamstrings get blamed a lot, but they’re rarely the reason. Squat to the depth where your pelvis stays put, and build from there with paused and goblet squats.

Why do my knees cave in when I squat?

Usually weak glutes and hip rotators, tight ankles or just a lack of practice controlling the movement (Wilczyński et al., 2020). Think “knees out,” warm up with a mini band and add some direct glute work.

Fix Your Squat, Unlock Your Gains

Here’s the good news. Almost none of these problems have anything to do with genetics. They’re habits – cutting depth, letting the knees drift, forgetting to brace, never adjusting your stance to fit your own hips. And habits can be changed.

Don’t try to fix all eight at once. Pick the one or two that sound most like you, film a few sets, and only add weight when the form holds up. Give it a couple of months, and your squat (and your legs) will thank you for it.

Related:

• How to Squat Without Knee and Back Pain
• The 20-Rep Squat Routine: Brutal, Effective, and Time-Tested
• 7 Steps to an Impressive Squat

References

1. West, D. W. D., & Phillips, S. M. (2012). Associations of exercise-induced hormone profiles and gains in strength and hypertrophy in a large cohort after weight training. European Journal of Applied Physiology.
2. Hartmann, H., Wirth, K., & Klusemann, M. (2013). Analysis of the load on the knee joint and vertebral column with changes in squatting depth and weight load. Sports Medicine, 43, 993-1008.
3. Impact of the deep squat on articular knee joint structures, friend or enemy? A scoping review (2024). Frontiers in Sports and Active Living.
4. Kubo, K., Ikebukuro, T., & Yata, H. (2019). Effects of squat training with different depths on lower limb muscle volumes. European Journal of Applied Physiology. Summary: Stronger By Science.
5. Wilczyński, B., Zorena, K., & Ślęzak, D. (2020). Dynamic knee valgus in single-leg movement tasks. International Journal of Environmental Research and Public Health.
6. The use of elastic resistance bands to reduce dynamic knee valgus in squat-based movements: a narrative review. International Journal of Sports Physical Therapy.
7. Schwanbeck, S., Chilibeck, P. D., & Binsted, G. (2009). A comparison of free weight squat to Smith machine squat using electromyography. Journal of Strength and Conditioning Research, 23(9).
8. Haugen, M. E., et al. (2023). Effect of free-weight vs. machine-based strength training on maximal strength, hypertrophy and jump performance. BMC Sports Science, Medicine and Rehabilitation.
9. Physio Network. Butt wink is not about the hamstrings.