Hack Squat: How to Do It, Muscles Worked and Benefits

The hack squat is a machine leg exercise where you sit back against an angled pad, put your feet on a platform and squat the weight up and down along a fixed track. Because the machine supports your back and torso, you can pile the effort straight into your legs without worrying about balance, which makes it one of the best exercises for building strong, muscular quads. It suits beginners who find free squats intimidating and experienced lifters chasing extra leg size after their main lifts. Here is how to do it properly, the muscles it trains and how to get the most from it.

How to do a hack squat

These steps cover the standard angled hack squat machine, the type in most gyms.

1. Set up. Load the weight, step onto the platform and sit back so your shoulders are under the pads and your back is flat against the backrest. Set your feet shoulder-width apart, roughly in the middle of the platform, with your toes turned out slightly.
2. Unrack. Push up to take the weight, then rotate or release the safety handles so the sled is free to move.
3. Brace. Take a breath, tighten your abs and keep your whole back pressed into the pad. Your head stays neutral against the rest.
4. Descend. Bend your knees and lower under control, letting your knees travel forwards and out over your toes. Go down until your thighs are at least parallel to the platform, or a little lower if your knees and hips allow.
5. Drive up. Push through your whole foot, mid-foot and heel, and straighten your legs back to the start. Stop just short of locking your knees hard at the top to keep tension on the muscle.

Muscles worked

The hack squat is a quad-dominant leg exercise, and the back support means nearly all the effort lands on your lower body.

• Quadriceps. The four muscles on the front of your thighs are the main movers, straightening your knees as you stand. The upright torso and knees-forward path put a big emphasis here, which is why the hack squat is a favourite for quad size.
• Glutes. Your glute max drives your hips out of the bottom of the rep, and squats are a reliable way to load it (systematic review of gluteus maximus activation). Raising your feet up the platform brings them in more.
• Hamstrings and adductors. Your hamstrings assist hip extension while your adductors, the inner-thigh muscles, fire hard out of the deep position.
• Calves. Your calves stabilise the ankle and help keep your foot driving into the platform through the rep.

To keep loading these muscles as you get stronger, pair the hack squat with free-weight work like the back squat and front squat so you train the same muscles through different ranges.

Benefits

• It builds quads fast. With your back braced against the pad, you can focus entirely on driving with your legs, so the quads get a big, direct stimulus. It is one of the most efficient ways to add thigh size.
• It is beginner friendly. The fixed path removes the balance and bar-position skills a free squat demands, so a nervous beginner can train legs hard and safely from day one.
• It is easy on the lower back. The backrest takes the spinal loading out of the movement, which makes it a smart choice on days your lower back is tired from deadlifts or heavy squats.
• It lets you train close to failure safely. Because the safeties catch the weight, you can push a set hard without a spotter, which is useful for building muscle.
• It complements your main lifts. Used after squats, the hack squat adds quad volume without re-loading your spine, so you get more leg work with less fatigue. The NHS recommends muscle-strengthening work for all the major muscle groups on at least two days a week.

Common mistakes

Cutting the depth short. Quarter reps short-change your quads and glutes. Squatting through a fuller range tends to build more strength and size than partial reps (review on squat depth and range of motion), and a deep squat is safe for healthy knees when done with control (scoping review on the deep squat and the knee joint). Aim for thighs at least parallel.

Knees caving inwards. Letting your knees collapse in wastes power and stresses the joint. Actively push them out so they track over your toes for the whole rep.

Heels lifting off the platform. If your heels rise, you tip the load onto your toes and your knees. Move your feet a touch higher, keep your whole foot planted and drive through the mid-foot.

Bouncing out of the bottom. Dropping fast and rebounding off your knees feels powerful but loads the joint sharply. Lower under control, pause briefly, then drive up.

Going too heavy too soon. The machine makes big numbers feel achievable, which tempts people to load up and lose depth and control. Pick a weight you can move cleanly through a full range for every rep.

Foot placement and variations

Small changes to your feet and setup change what the hack squat trains.

• Mid-platform, shoulder-width. The default. Balanced quad and glute work through a full range.
• High foot placement. Feet higher up the platform open the hips and shift more work to your glutes and hamstrings. It also reduces how far your knees travel forward, so it is kinder to cranky knees.
• Low foot placement. Feet low on the platform maximise quad work by pushing the knees further forward. Effective for quad size but harder on the knees, so build up gradually.
• Barbell hack squat. The original version, with no machine. You hold a barbell behind your legs and stand up, which trains the quads with a barbell and a bit of floor. A great option for a home gym.
• Heels-elevated goblet squat. No machine needed. Raise your heels and hold a dumbbell at your chest for a quad-biased squat that mimics the feel. See our goblet squat guide for the technique.

Sets and reps

A simple plan that works for most people:

• Muscle and size: 3 to 4 sets of 8 to 15 reps, resting 90 to 120 seconds. This is the sweet spot for growing your quads.
• Strength: 4 to 5 sets of 5 to 8 reps with a heavier load and longer rests of 2 to 3 minutes.
• Learning the move: 3 sets of 10 slow, controlled reps with a light weight, focusing on depth and knees tracking over toes.

Add a small amount of weight or an extra rep once you can hit the top of your rep range with clean form on every set. If you are training legs hard, the hack squat pairs well with the leg press for a full lower-body session.

Recommended reads

1. Leg Press: how to do it and muscles worked
2. Back Squat technique guide
3. Front Squat: how to do it
4. The best squat rack in the UK