Hack squat alternatives, and what to do when it's taken

The hack squat is a squat on a sled. The back pad holds your torso, your feet sit forward on a platform, and your quads do most of the work with little balance needed. A good swap keeps as much of that as it can. And if your gym has one but someone’s on it, the first job is the wait, not the swap.

If the hack squat is taken

Ask between sets: “How many have you got left?” Set yourself a limit of about 5 minutes, or the time for one other exercise. Standing by the machine for longer costs you more than any swap does.

Pick the swap by goal

If the hack squat is taken, go down this list and keep your planned sets:

1. Another quad machine, such as a pendulum squat or a second hack squat.
2. A Smith machine squat with your feet forward.
3. The leg press, with your feet low and hip-width.
4. A heels-elevated goblet squat or a split squat.

For the Smith machine version, this is a hack-style setup, with your feet farther forward than a normal Smith squat: 20 to 30 cm (8 to 12 in) in front of the bar, lean back into it slightly and squat as deep as you can with your heels down. Set the safety stops just below your lowest point.

For sore knees, stop just above the depth that bothers them. In a study of the squat and leg press, knee forces rose the more the knee bent. A wall sit only counts if you can hold it above that depth. Shallower squats train the glutes and adductors less, so add a bridge or a hip hinge if those matter. If the pain is sharp or lasting, stop the exercise and see a qualified professional.

Why your hack squat numbers don’t carry over

The back pad does the job your trunk would do in a free squat. In one study of 10 men, hack squat maximums and working weights were clearly higher than back squat ones at the same relative effort, while trunk muscles worked harder in the back squat. On top of that, every hack squat has a different sled weight, angle and foot platform.

So don’t try to match the number. For the first set of a swap:

• on a Smith machine or leg press, start near half your hack squat load; with a dumbbell, pick one you could squat for 15 easy reps,
• leave 2 to 3 reps in reserve,
• go heavier on the next set if you had more left, lighter if you missed reps,
• log the swap as its own exercise so your hack squat history stays clean.

Sets and reps on the swap

Rest about 2 minutes between sets of the two-leg swaps. For split squats, rest about 60 seconds between legs and 90 seconds between rounds, since each set is really two.

The dumbbell limit

A goblet squat runs out of dumbbell before it runs out of legs. Once you’re holding the heaviest one, your grip and upper back tire before your quads do. When that happens:

• switch to a Bulgarian split squat, which loads one leg with the same dumbbells,
• or keep the goblet squat and slow the lowering to 3 seconds with a 1-second pause at the bottom,
• or add 2 sets of leg extensions after the squat.

The leg extension is a fair add-on in any case. In a 10-week study, squats grew the quads overall but not the rectus femoris, the quad muscle that also crosses the hip.

If every leg station is taken

Hack squat, leg press and Smith machine all busy? If you only need to replace the hack squat, take a dumbbell swap from the table and do your planned sets. If it was the start of a full leg day, do this with one pair of dumbbells, 3 rounds:

1. Heels-elevated goblet squat, 10 to 15 reps
2. Bulgarian split squat, 8 to 10 reps each leg
3. Spanish squat hold with a band, or a wall sit, 30 to 45 seconds

Rest about 60 to 90 seconds between exercises and leave about 2 reps in reserve.

What the research says

• In 10 men, hack squat maximums and working loads were significantly higher than back squat loads, while trunk muscle activity was higher in the back squat at the same relative effort (Clark and colleagues, 2019).
• In a 10-week trial, squat-only training transferred more to maximum squat strength than leg press-only training. The jump and balance differences weren’t statistically significant (Rossi and colleagues, 2018). Transfer is specific: if a bigger free squat is your goal, train the squat itself.
• In 10 experienced lifters, the squat produced more quad and hamstring activity and generally higher knee forces than the leg press, and knee forces rose as the knee bent further (Escamilla and colleagues, 2001). That’s activity and force, not growth.
• Ten weeks of full or half squats grew the knee extensors by about 5% in 17 men, but the rectus femoris didn’t grow (Kubo and colleagues, 2019).

None of these studies tested the hack squat against the swaps above for growth. They show why the numbers differ, why a free squat trains a different skill, and why knee range matters for comfort.