Back Squat

What the back squat actually trains

The back squat is knee and hip extension against a bar held on your upper back. The quadriceps extend the knee, the gluteus maximus and adductor magnus extend the hip, and the hamstrings contribute in a more complicated way, since they cross both joints and shorten at one end while lengthening at the other. The spinal erectors, abdominals and obliques hold the trunk rigid so the force generated by your legs reaches the bar rather than getting lost in a soft midsection.

Pocket Fit lists Quads as the main target with Glutes, Hamstrings and Abs secondary, which matches how the loading is distributed for most people at a shoulder-width stance and a moderate torso angle.

Schoenfeld's review of squat kinematics and kinetics is a good overview of how the details change the demand: stance width, torso angle, foot position and bar placement all shift the balance between hip and knee. None of them convert the squat into a different exercise. They tilt it.

Setting up and squatting

The bar sits on a shelf of muscle across the upper traps and rear delts, not on bone. Pull the shoulder blades together to build that shelf before you duck under.

Unrack with both feet under the bar and take one or two steps back. Set a stance you can repeat: roughly shoulder width, toes out 15 to 30 degrees.

Breathe into your belly, brace hard, and keep the ribcage down. Break at the hips and knees together and sit between your feet. Drive the knees out in line with the toes. Descend to at least parallel. Then push the floor away, keeping the bar over mid-foot and the hips and shoulders rising at the same rate.

The knees over toes myth

For decades people were told the knees must never travel past the toes. The study most often used to support that idea is the one that most clearly complicates it.

Fry, Smith and Schilling had seven weight-trained men squat in two conditions: unrestricted, and with a board preventing the knees from travelling forward. When forward knee travel was restricted, knee torque dropped from about 150 Nm to about 117 Nm. Hip torque, meanwhile, rose from about 28 Nm to about 303 Nm. The stress did not disappear. It moved, by roughly a factor of ten, to the hips and lower back. The authors' own conclusion was that restricting the knees likely transfers forces inappropriately to the hip and low back region.

So the honest version is this: preventing the knees from travelling forward does reduce knee torque, and it does so by dumping a much larger demand somewhere else. For most people with healthy knees, letting the knees travel naturally forward in line with the toes is the better trade. If you have a specific knee condition, that is a conversation with a physiotherapist who can examine you, and there are legitimate reasons to modify the pattern temporarily.

How deep should you squat?

The app's cue is thighs at least parallel to the floor, and the evidence supports going at least that far.

Bloomquist and colleagues randomised seventeen men to twelve weeks of deep squats to 120 degrees of knee flexion or shallow squats to 60 degrees, with repetitions matched. The deep squat group gained more front thigh muscle cross-sectional area, roughly 4 to 7 per cent more, along with greater isometric knee extension strength at both 75 and 105 degrees and a 15 per cent greater improvement in squat jump performance.

Kubo, Ikebukuro and Yata randomised seventeen men to ten weeks of full or half squat training and measured muscle volumes by MRI. Knee extensor volume rose similarly in both groups, around 4.9 per cent full versus 4.6 per cent half. But adductor and gluteus maximus volumes rose significantly more in the full squat group, 6.2 and 6.7 per cent against 2.7 and 2.2 per cent. Full squat one-repetition maximum also improved far more in the full squat group, 31.8 per cent versus 11.3 per cent.

Pallarés and colleagues' meta-analysis of range of motion across resistance training reached the same general conclusion: full ranges generally produce greater or equal adaptations compared with partial ranges.

Read together: squatting to at least parallel is well supported, deeper appears to add glute and adductor development rather than more quadriceps, and squatting shallow mainly buys you the ability to load more weight without the corresponding muscular return.

Is deep squatting bad for your knees?

Hartmann, Wirth and Klusemann reviewed over 160 papers on knee and spinal loading across squat depths and reached a conclusion that surprised a lot of people. They reported that the highest retropatellar compressive stresses occur around 90 degrees of knee flexion, and that with deeper flexion the wrapping effect and the increasing contact area between the back of the thigh and the calf distribute load more effectively, lowering retropatellar stress. They described concerns about deep squats causing degenerative knee changes as unfounded, and argued that half and quarter squats performed with the supra-maximal loads they permit are more likely to drive degenerative changes in the knees and spine over the long term.

Escamilla's earlier review of squat knee biomechanics covers the same territory in more detail, including the behaviour of the cruciate ligaments through the range.

Two caveats worth stating plainly. Hartmann and colleagues' conclusions are explicitly conditional on technique being learned properly under supervision with progressive loading. And a review is a synthesis of existing work, not a randomised trial. None of this says that any individual knee will tolerate any depth, and if you have knee pain, an existing diagnosis or a previous surgery, a qualified clinician is the right person to set your range. This guide is education, not medical advice.

How to programme the back squat

The squat is a primary compound in Pocket Fit:

• Gain muscle: 4 to 5 sets depending on experience, 6 to 10 reps, 120 seconds rest.
• Gain strength: 5 to 6 sets depending on experience, 3 to 6 reps, 180 seconds rest.
• Lose fat: 4 to 5 sets depending on experience, 6 to 10 reps, 90 seconds rest.

Progression runs reps first to a cap of 15, then load, and only after a confirmed plateau across two matching sessions. Barbell increments are 5 kg for male users and 2.5 kg for female users.

The plateau rule is doing something specific on this lift. The squat is the exercise where adding weight and quietly removing depth is easiest, and where a single good session can convince you that you are stronger than you are. Requiring two matching sessions before the load rises makes the app slower than your enthusiasm, which on a squat is a feature.

Where the back squat sits in your week

• Push/Pull/Legs: Legs day, opening lift. Runs on 3 or 6 day schedules.
• Upper Duo: Legs day, first exercise. Runs on 4 day schedules only.
• Bro Split: leg day, opening lift. Runs on 5 day schedules only.
• Upper/Lower plus Full Body: the primary knee-dominant lift in the lower session.
• Full Body: usually first, because nothing else costs as much. Runs on 1 to 6 day schedules.
• Glute-Focused: a knee-dominant lift alongside hip thrusts and Romanian deadlifts.

Variations and swaps

Front squats shift demand towards the quadriceps and punish a collapsing torso. Goblet squats are the best teaching tool for depth. Box squats standardise range. Hack squats and leg presses remove the balance and spinal loading. Bulgarian split squats are the unilateral option. Bodyweight and jump squats are what the Bodyweight PPL programme uses.

What the evidence does and does not say

The depth literature is unusually good for a training question, but it is still small. Bloomquist and Kubo each randomised seventeen men. Neither included women. Both ran for ten to twelve weeks, which is long enough to detect hypertrophy and short enough that long-term joint outcomes are pure inference. Hartmann and colleagues' review is careful but is a synthesis rather than an experiment, and its conclusions rest on biomechanical modelling and cadaver work as much as on training trials.

What none of this tells you is what your knees, hips and back will tolerate. It tells you that the general fear of depth is not supported, that going to at least parallel is well justified, and that the shallow heavy squat is not the safe option it was sold as. Use it as a default, not as a verdict on your individual case, and note that electromyography comparisons between squat variations, which are often quoted alongside this literature, cannot tell you anything about growth at all.

Back squat: common questions

How deep should I squat?

At least until your thighs are parallel to the floor. Bloomquist and colleagues found deep squats produced 4 to 7 per cent greater front thigh growth than shallow squats, and Kubo and colleagues found full squats produced significantly greater glute and adductor growth than half squats. Go deeper than parallel if you can do it without your pelvis tucking hard under.

Is it bad if my knees go past my toes?

No, for most people. Fry and colleagues showed that blocking forward knee travel reduced knee torque from about 150 to about 117 Nm but increased hip torque from about 28 to about 303 Nm. The load has to go somewhere. Let the knees travel forward in line with the toes.

Are deep squats bad for your knees?

The best available review says no. Hartmann and colleagues reported that retropatellar stress peaks around 90 degrees and falls with deeper flexion, and described fears about deep squats causing degenerative changes as unfounded, provided technique is learned properly and loading is progressive. If you have existing knee problems, get individual advice.

Why do my hips shoot up out of the bottom?

Almost always because the load is heavier than your quadriceps and trunk can handle together. Reduce the weight, focus on the chest and hips rising at the same rate, and consider front squats or pause squats for a block to build the bottom position.

Should I squat with a wide or narrow stance?

Whichever lets you reach depth comfortably with your knees tracking over your toes, and then keep it consistent. Stance changes shift the balance between hip and knee contribution but do not turn the squat into a different exercise.

Do I need to squat at all?

No single exercise is compulsory. Leg presses, hack squats and Bulgarian split squats all build legs. But the squat loads a lot of muscle in one movement with a very high ceiling, which is why the app puts it first in most lower body sessions.