🏋️ Training · 6 min read

The squat: what it does, how to recognise good execution, and which rules are outdated

What happens in the movement

The squat is a multi-joint movement: hip, knee and ankle bend and extend together. On the way down the muscles involved work to brake, on the way up to overcome.

Mainly involved are the front of the thigh, the gluteal muscles and the adductors on the inner thigh. The back of the thigh works too, but in a different function: it spans two joints and is lengthened at the hip while shortening at the knee — the two largely cancel out. The trunk musculature holds the upper body stable without much movement of its own.

This distribution shifts with execution. A more upright torso moves work towards the front of the thigh, a more inclined one towards hip and glutes. Both are valid squats, not one right and one wrong variant.

Why a squat looks different on everyone

The most visible reason is limb proportions. Someone with long thighs relative to their torso has to lean further forward to keep the centre of mass over the base — otherwise the movement tips backwards. With shorter thighs a more upright posture is possible.

Then there are differences in the hip joint itself. The orientation of the socket and the angle of the femoral neck vary considerably between people and are anatomically fixed. They influence how far apart the feet need to be and how far they should point outwards for the movement to run freely.

Ankle mobility plays in as well: if it allows little forward travel of the shin, a deep squat with an upright torso becomes difficult. A raised heel shifts that limit, which is why weightlifting shoes exist.

The practical conclusion: stance and foot position are not copied from a template but tried out. A position in which the movement runs through without evasion is the right one — regardless of how it compares with anyone else’s.

“Knees not past the toes” — where the rule comes from

This rule goes back to a study from the 1970s in which knee joint load was lower when forward travel of the knee was restricted. The decisive part of the finding is usually left out: load shifted into the hip and lower back instead. It did not disappear, it moved.

In practice, forward travel of the knee cannot be avoided entirely by many people without distorting the movement — particularly with longer thighs or a deeper squat. In a lunge or when climbing stairs the knee also travels past the foot, without anyone objecting.

More useful than the prohibition is watching whether the heel stays on the floor and whether the knee follows the direction of the foot. A knee collapsing inwards while the foot points outwards is a reasonable cue to reduce the weight — a knee moving forwards, on its own, is not.

How deep?

On depth there are two common camps — “always deep” and “only to parallel” — and both turn an individual question into a general one.

What can be said: a larger range of motion is associated in several studies with stronger adaptation of the thigh musculature, particularly in the lower part of the movement. At the same time, more depth almost always means less weight and higher demands on mobility and technique.

The usable limit is therefore not a number of degrees but the point at which the position is still controlled. If the pelvis tips backwards at the lowest point so that the lower back rounds, the movement has gone past controllable depth. That limit shifts with practice — and it is tighter on bad days than on good ones.

The back: straight does not mean vertical

“Straight back” is often misread as “upright torso”. Something else is meant: the spine keeps its natural shape while the whole upper body inclines as a unit. A marked forward lean can be entirely fine, as long as the position of the spine does not change in the process.

Stabilisation comes from the trunk. A deep breath before descending and deliberately tensing the abdominal and back musculature create pressure in the abdomen that braces the spine from within. This technique is widely used in training practice; its effect on stability is well described.

Slight rounding under heavy load occurs even in experienced people and is not synonymous with injury. If it happens regularly and early, it is nevertheless a signal: either too much weight, or too much depth for the current stage.

Variants and what they are for

The barbell on the upper back is the most common form; several others are just as usable. With the bar resting on the front of the shoulders, a more upright torso is enforced and work shifts towards the front of the thigh; the weight used is correspondingly lower.

A dumbbell or kettlebell held in front of the chest works similarly and is at the same time the most accessible variant for beginners, because the weight can simply be set down if needed. Guided variants on machines take away the stabilising work and suit additional volume when concentration fades.

Single-leg variants such as the split squat demand more stabilisation and need considerably less weight. They are not a replacement for the two-legged squat, but a complement that needs little equipment.

How progress shows

The most visible measure is the weight, but it is only one of several. The same load with greater depth, calmer execution, or without a bounce out of the bottom is a change — even if the log shows the same number.

For a comparison across weeks to hold, stance, foot position, depth and bar position should stay the same. Lowering the bar position or widening the stance in between means a different exercise has been logged.

And one point that belongs with the squat: pain in the knee, hip or back is not a training variable to adjust. It belongs in a medical assessment before further work on technique or weight.

Last reviewed: 14.08.2026

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