The hack squat is a back-supported machine squat that lets you hammer the quads with a fixed, stable path — no balance or barbell setup required. Here's how to do it with good form, the muscles it works, the mistakes to avoid, and how to program it.
The hack squat is a machine compound exercise that primarily works the quads, with the glutes assisting and the hamstrings and calves helping stabilize. You stand on the platform with your back against a padded sled and squat down along a fixed track, then drive back up. Because the machine supports your back and guides the path, the quads take more of the load than in a free-weight squat, which makes it a strong quad-focused option.
The hack squat is a machine compound lift, so it trains the legs together with the back supported. The quads do most of the work, assisted by the glutes, while the hamstrings and calves help stabilize the knees and ankles through the range.
| Role | Muscles | What they do in the lift |
|---|---|---|
| Primary mover | Quadriceps | Extend the knees to drive the sled up out of the bottom |
| Assisting | Gluteus maximus | Help extend the hips, more so with a higher foot placement |
| Assisting | Hamstrings, adductors | Support the hip and knee through the squat |
| Stabilizers | Calves, core | Keep the ankles and torso steady against the pad |
Step-by-step form for the machine hack squat. Get familiar with the safety handles before loading it up.
If you want to train the same knee-dominant pattern with a different emphasis or equipment, these are the common swaps:
Want the free-weight and other machine leg options? Compare it with the leg press and the barbell squat.
The hack squat works as a main quad movement or an accessory after squats. General starting points:
| Goal | Sets × reps | Notes |
|---|---|---|
| Strength | 3–5 × 5–8 | Heavier load, longer rest (2–3 min), full depth with heels down |
| Quad size | 3–4 × 8–15 | Controlled tempo, full range, train close to failure on the last set |
| Frequency | 1–2× / week | Progress by adding a little weight or a rep when you hit the top of the range |
Want a full structured plan that includes the hack squat or leg press? See Push Pull Legs, and read up on RPE to gauge how hard each set should feel.
Log every hack squat set — weight, reps, and an RPE value — in LiftHero, and it charts your progressive overload and flags personal records so you can see your quad strength climbing over the weeks. You can add warm-up sets, supersets and rest-timer holds, then drop the exercise into a saved routine so it's ready the next time you train. LiftHero records what you log; it doesn't diagnose your form.
It primarily works the quadriceps, with the glutes assisting and the hamstrings and calves stabilizing. Because the back is supported, the quads take on more of the load than in a free-weight back squat.
They serve different roles. The barbell squat trains the whole body and demands balance, while the hack squat supports the back and lets you push the quads on a fixed path. Many lifters use the barbell squat as a main lift and the hack squat as a quad accessory.
A mid-platform, shoulder-width stance is a good default and biases the quads. Higher feet shift emphasis to the glutes and hamstrings; a lower, narrower stance emphasizes the quads. Pick what lets you reach depth with heels down.
For most healthy lifters it's not inherently bad when done with a controlled tempo and comfortable depth. If you feel knee pain, check foot placement, reduce load or range, and consult a professional if it persists.
For strength, about 5–8 reps; for quad size, about 8–15. Most lifters do 3–4 working sets, once or twice per week, as a main quad movement or an accessory after squats.
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This guide is educational and not medical advice. Consult a qualified coach or medical professional before starting or changing a training program.
By Meitar Lazimi, founder of LiftHero · Last updated July 9, 2026.