The squat is the lift where small technique errors cost the most. A bar path that drifts two inches forward, a knee that collapses inward under fatigue, a pelvis that tucks at the bottom — none of it feels dramatic in the moment, and all of it shows up later as a stalled lift or a sore lower back.
The hard part is that you cannot see any of it while you are under the bar. This page lists the seven form mistakes that appear most often in gym squats, what causes each one, and the specific correction to apply on your next set.
Barbell Back Squat at a glance
Primary muscles
Quadriceps, gluteus maximus, adductors
Secondary muscles
Spinal erectors, hamstrings, core
Equipment
Barbell, squat rack
Level
Intermediate
Most common failure point
The bottom third of the ascent
Best camera angle for a form check
45° front, full body in frame
Correct barbell back squat technique, step by step
Set the bar and unrack
Place the bar on the rear delts, not on the neck. Set the hooks just below shoulder height so you unrack by standing up, not by pressing up on your toes. Take two steps back, no more.
Set your stance
Feet roughly shoulder-width, toes turned out 15 to 30 degrees. Screw both feet into the floor as if spreading it apart — that external rotation pre-loads the glutes and stops the knees from collapsing.
Brace before you descend
Breathe into the belly, not the chest, then tighten the abdominal wall in all directions as if bracing for a punch. Hold that pressure for the whole rep. Do not exhale at the bottom.
Descend by sitting between your feet
Break at the hips and knees at the same time. Keep the bar stacked over the middle of the foot for the entire descent. Control the eccentric over about two seconds.
Reach depth without losing position
Descend until the hip crease drops below the top of the knee, or until the point just before your pelvis starts tucking under. Depth is capped by the position you can hold, not by the position you can reach.
Drive up hips and chest together
Push the floor away and lead with the whole torso. If the hips rise faster than the chest, you have turned the squat into a good morning. Finish standing tall with the glutes squeezed, without hyperextending the lower back.
The 7 most common squat form mistakes
01Knees caving inward (valgus collapse)
What it looks like
One or both knees track toward the midline as you come out of the hole, usually on the last reps of a heavy set.
Why it happens
Weak or under-recruited glute medius, a stance that is too narrow, or simply a load that has outrun your control.
The fix
Cue "spread the floor" and actively press the knees out toward the little toes throughout the ascent. Add banded squats or lateral band walks as a warm-up primer, and drop the load 10 to 15 percent until the collapse disappears at every rep.
02Heels lifting off the floor
What it looks like
Weight rolls onto the forefoot in the bottom third and the heels visibly unload.
Why it happens
Limited ankle dorsiflexion, or a descent that pushes the knees forward before the hips move back.
The fix
Keep the whole tripod of the foot loaded — big toe, little toe, heel. Test your ankle range with a knee-to-wall test; if you are under 10 cm, add calf and soleus mobility work and use a shoe with a raised heel in the meantime.
03Butt wink (posterior pelvic tilt at the bottom)
What it looks like
The pelvis rolls under and the lower back rounds during the last few centimetres of the descent.
Why it happens
Going deeper than your hip structure and hamstring length currently allow, often chasing a depth standard rather than your own range.
The fix
Stop the descent one to two centimetres above the point where the tuck begins, and own that depth for several weeks. Widen the stance slightly and increase toe-out — most lifters gain real depth from hip position, not from stretching.
04The good-morning squat
What it looks like
The hips shoot up first out of the bottom, the torso folds forward, and the bar finishes the rep over the toes.
Why it happens
Quadriceps that are weak relative to the posterior chain, or a brace that fails as soon as you reverse.
The fix
Cue "chest and hips rise together" and think of pushing your back into the bar rather than lifting the bar. Add tempo squats with a three-second descent and paused front squats, which punish any forward drift immediately.
05Bar drifting off the mid-foot
What it looks like
Filmed from the side, the bar traces a curve forward instead of a near-vertical line.
Why it happens
Bar placed too high on the traps, an over-upright cue applied to a low-bar setup, or an unstable brace.
The fix
Match the torso angle to the bar position: high-bar tolerates a more upright torso, low-bar requires more forward lean. Film one set from the side and check that the bar stays within a hand's width of vertical.
06Losing the brace mid-rep
What it looks like
You hear the exhale at the bottom, and the rep that follows feels soft through the midsection.
Why it happens
Breathing at the wrong point in the rep, or bracing by sucking the stomach in instead of pressurizing it.
The fix
Take the breath standing, hold it through the descent and the hardest part of the ascent, exhale only once you are locked out. On sets above five reps, reset the breath at the top of each rep.
07Asymmetric loading
What it looks like
The bar tilts, one hip shifts sideways at the bottom, or one knee travels further forward than the other.
Why it happens
An off-centre bar, a leg-length or mobility difference, or an old injury you have stopped noticing.
The fix
Check your grip is symmetrical and centre the bar every set. Film from the front and watch the bar line against a vertical reference. Add unilateral work — split squats or lunges — to close the strength gap.
How to check your own form
Film from 45 degrees, not from straight on
A front view shows knee tracking but hides the bar path. A side view shows the bar path but hides valgus. A 45-degree angle at hip height captures both.
Get your whole body in frame
Feet included. Most self-recorded squat videos crop the feet, which makes it impossible to see the heel lifting or the weight shifting forward.
Judge the last two reps, not the first
Technique holds up on rep one for almost everyone. Form breaks under fatigue, so that is where the useful information is.
Compare against yourself over time
One video tells you very little. The same lift filmed weekly at the same angle tells you whether a correction actually took.
Angle
45° from the front
Height
Hip height
Distance
2 to 2.5 m away
Framing
Head to feet, plus the rack uprights
Stop guessing what your last set looked like
Film the set, and Stance returns the specific fault and the correction instead of a raw video to interpret yourself. The clip is analyzed and then deleted, never stored.
Coming soon
Frequently asked questions
How do I know if my squat form is correct?
Film a set from a 45-degree front angle with your whole body in frame, then check four things: the bar stays over the mid-foot, the knees track over the toes without collapsing inward, the lower back keeps its natural curve to the bottom, and hips and chest rise at the same rate. If all four hold on your last two reps, the form is sound. Stance runs that check automatically on a filmed set and returns the specific fault rather than a score.
Why do my knees cave in when I squat?
Almost always a combination of under-recruited hip abductors and a load beyond your current control. Cue pressing the knees out toward the little toes, add lateral band work in your warm-up, and reduce the load until the collapse is gone on every rep, not just the first few.
How deep should I squat?
Deep enough that the hip crease drops below the top of the knee, but never deeper than the point at which your pelvis starts to tuck under. Depth you cannot hold position in is not depth you gain anything from. Most lifters find real depth by widening the stance and turning the toes out, not by stretching.
Is butt wink dangerous?
A small amount of pelvic tilt at the bottom is common and not inherently harmful. It becomes a problem when it happens under heavy load, rep after rep, because it shifts shear stress onto the lumbar spine. Cut the depth back to the point just before the tuck and you keep the training effect without the exposure.
Can an app really analyze my squat form?
Yes, for the faults that are visible in the movement. Computer vision reliably detects knee valgus, heel lift, forward bar drift, depth and left-right asymmetry from a single clip. What it cannot see is intent or pain, so it complements a coach rather than replacing one.
