One movement, most of your lower body
A squat looks simple: bend at the hips, knees and ankles, sit down, stand back up. In his 2010 review of squat biomechanics, Brad Schoenfeld lists the muscles that move you through it: the quadriceps, the hip extensors, the hip adductors and abductors, and the calves.
Other muscles work without moving much. Your abdominals, lower back and upper back hold the trunk steady for the whole rep. The review cites an estimate of over 200 muscles active during a squat.
- Quadriceps
- Glutes and hip extensors
- Adductors
- Abductors
- Calves
- Abdominals
- Lower back
- Upper back
Lower squats, harder-working glutes
Depth changes who carries the load. A study by Caterisano and colleagues, summarised in the same review, measured glute activity in barbell squats at three depths. Average activity was 16.9% in a partial squat, 28.0% at parallel and 35.5% in a full squat. Only the full squat stood out: the partial and parallel numbers were not significantly different from each other.
The hamstrings, at the back of the thigh, do less. The review puts their activity in a squat at roughly half of what a leg curl produces.
- 16.9% Partial
- 28.0% Parallel
- 35.5% Full
Ten weeks of full against half squats
A 2019 study by Kubo and colleagues ran a longer test. Seventeen men trained squats two days a week for ten weeks, one group going full depth and the other doing half squats. MRI scans measured their muscle volume before and after.
The knee extensors grew by about the same amount in both groups. The full-squat group gained clearly more in the glutes and the adductors, the muscles of the inner thigh. The hamstrings didn’t change in either group. Strength in the full squat went up 31.8% with full squats and 11.3% with half squats.
Both studies used a barbell. Your bodyweight is a lighter load, and these numbers don’t tell you how much you would gain with it.
17 men, 10 weeks, 2 days a week
Why the camera only counts deep squats
In Pushgard the phone’s front camera counts your squats, so the depth rule is built in. The counter measures how high your hips sit above your feet, in shoulder widths: about 2.5 standing, about 1.0 in a deep squat. A rep reaches the bottom once your hips drop about three quarters of a shoulder width, and it counts when you stand back up.
Leaning forward lowers your hips too, so the counter also watches how far your head stays above your hips. Standing, that gap is about 2.2 shoulder widths. In recorded squats it never fell below 0.77, and in forward leans it dropped to between 0.36 and 0.61. Below 0.7 the app says “Squat, don’t lean” and the rep doesn’t count.
Try it: drag the figure down and back up, then switch to leaning. A rep faster than 0.55 seconds or slower than 5 seconds doesn’t count either.
In shoulder widths, as the counter measures them.
Drag down and back up. The counter decides when you are standing again.
Strength you use outside a workout
Schoenfeld points out that most everyday tasks need many muscle groups working together, and that the squat pattern is close to some of them, like lifting packages or picking up a child. The review describes it as one of the best exercises for quality of life, for people outside sport as well as athletes.
For older adults the WHO 2020 guidelines go further. They ask people 65 and over to do varied activity that stresses balance and strength on 3 or more days a week, to keep functional capacity and to prevent falls.
- Lift Close to everyday tasks
Lifting packages and picking up children use the same pattern as a squat.
Schoenfeld, 2010 - 3+ Days a week at 65 and over
Balance and strength training to keep functional capacity and prevent falls.
WHO guidelines, 2020
How often to squat, by the WHO guideline
The same guidelines ask every adult to do muscle-strengthening work for all major muscle groups on 2 or more days a week, at moderate effort or harder. Squats cover your legs and hips. Your upper body needs its own work, push-ups for example.
The guideline team found no evidence that more strength work beyond that brings extra health benefit. If you want a plan, the 30-day squat challenge builds a month from your own max, and the squat form guide covers stance and depth. In the Pushgard camera counter, each squat it counts hits the monster in front of you.
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