Bench press and squat: the biomechanics behind your aches
Introduction
They're the two most performed exercises in the gym and also the two that generate the most complaints: a shoulder that hurts when pressing, a knee that protests on the way down, a back that flares up the next day.
In most cases it isn't that the exercise is dangerous. It's that it's being performed in a configuration that doesn't match the anatomy of the person doing it. Bodies aren't identical, and the "correct" technique from a manual isn't the same for everyone.
What follows are the biomechanical principles that explain why it hurts and what to adjust, with the usual caveat: persistent pain deserves an in-person professional, not an article.
Don't look for perfect technique. Look for the technique your levers allow.
Bench press
Shoulder space
The typical complaint is at the front of the shoulder and shows up at the bottom of the descent. The most common explanation involves the space available for the rotator cuff tendons and the position of the shoulder blade.
Scapular retraction and depression. Before unracking, pull your shoulder blades together and down "toward your pockets". That stabilizes the shoulder and gives the humerus a solid platform to work on. Hold it through the whole set.
Elbow angle. Flaring the elbows to 90 degrees relative to the torso is the position that most often causes trouble. Around 45 to 70 degrees is what's usually used in practice, though the comfortable range varies between people.
Aligned wrists. The bar rests on the base of the palm, not on the fingers, with a straight wrist.
The lumbar arch
There's a natural arch that appears when you retract your shoulder blades and plant your feet. That one is physiological and desirable: it shortens the range and improves shoulder position. What isn't desirable is a forced arch with your glutes coming off the bench, which is a powerlifting competition technique with its own rules and preparation.
Your feet should be planted firmly. Leg drive isn't about pushing upward but about generating tension that stabilizes the whole body against the bench.
Bar path
It isn't vertical. It comes down toward the lower chest and travels slightly back on the way up, finishing over the shoulder joint. From the side it traces a gentle curve. Forcing a straight vertical line usually puts the shoulder in a worse position.
Alternatives if it hurts
Before abandoning horizontal pressing, try: dumbbells — they let the wrist rotate freely and each arm find its own path — a slightly narrower grip, incline press, or dips if those don't bother you. And add pulling work: most shoulders that hurt when pressing belong to people who press far more than they pull.
Squat
The hip decides
Here's the point that saves the most arguments: the depth and stance width that suit you depend on the shape of your hip. Acetabular orientation, femoral neck length and the ratio of femur to tibia vary a lot between people.
Practical translation:
- Long femurs relative to the torso force more forward lean to stay balanced. That isn't a technique error: it's geometry.
- Some hips allow a deep squat with nearly parallel feet; others need more width and external rotation to get equally low without impingement.
- The way to find yours is to experiment: vary width between shoulder-width and somewhat wider, and toe angle between 15 and 30 degrees, and keep the position where you descend most comfortably with a neutral spine.
Butt wink
That's the posterior pelvic tilt at the bottom of the descent: the lower back going from neutral to rounded. It's been heavily demonized. With caveats:
- At light loads and controlled range, a little tilt isn't necessarily harmful.
- At heavy loads it's worth avoiding, because it adds flexion stress to the spine at a bad moment.
- It usually stems from limited ankle dorsiflexion, a stance that doesn't suit your hip, or simply descending beyond what the joint allows.
What to do: find your useful depth — as far as you can keep the pelvis neutral — improve ankle dorsiflexion if it's limited, try slightly elevating your heels (lifting shoes or a small plate), and adjust foot position.
High bar or low bar
High bar (on the traps) favors a more upright torso, more knee range and more quadriceps. Low bar (on the rear delts) means more forward lean, more hip and more posterior chain. Neither is superior: they're slightly different stimuli suiting different preferences and body types.
Useful variations
- Front squat: forces an upright torso, demands less of the lower back and is often better tolerated with back problems.
- Bulgarian split squat: unilateral, less axial load, very demanding.
- Box squat: teaches you to sit back and gives consistent depth.
- Leg press: not a squat, and a perfectly valid alternative if your spine doesn't tolerate axial load.
Common mistakes in both
Copying the technique of someone with a different body. The number one source of avoidable pain.
Chasing depth or full range at any cost. Useful range is the range you can control in a good position.
Progressing too fast. Muscle adapts before tendons and joints do.
Warming up too little. Two progressive sets before your working sets change the sensations quite a bit, especially at the shoulder.
Neglecting accessory work. Upper back and rotator cuff support the press; glutes, hamstrings and core support the squat.
When to stop and get it checked
Sharp localized pain, pain that worsens session after session, tingling or numbness radiating into an arm or leg, or loss of strength. None of that gets fixed by adjusting your grip.
Final thought
The two big gym lifts become far friendlier once you stop trying to fit a textbook technique and start adjusting the variables to your anatomy: elbow angle and bar path on the press, stance and depth on the squat. Spend a whole session testing configurations with light weight and note which feels best. It's the session that looks the least productive and turns out to be the best investment of your training year.