reckonerHack squat
A squat on rails with your back on a pad. The machine balances the load and holds your trunk, so what is left is your legs. That is the point of it, and it is why the number runs higher than your back squat2.
Back flat on the pad, knees track the toes.
- Pattern
- Squat
- Trains
- Quads, glutes
- Kit
- Machine hack squat
- Loading
- A weight you choose
- Reckoner prescribes
- 4 sets of 5 to 8 reps at RPE 8
- Progression step
- 5 kg once the top of the range is clean
- Skill
- Some technique
- Recovery cost
- Moderate
- Not prescribed if you have declared
- Knee, hip
Muscles worked
How to do it
Set the shoulder pads before you load it
Your back sits flat on the pad from hips to shoulders, and the pads rest on your shoulders without pushing your head forward. Pads set too low fold you over at the bottom, so get this right with the sled empty. Check that the safety handles release and catch before the first rep.
Feet mid platform, about shoulder width
Whole foot on the plate, toes turned out a little. Pick a stance and keep it for the block, because a foot moved a few inches changes the lift, and this week's numbers only compare with last week's if the lift stayed the same.
Release the handles and sit down between your knees
Lower under control with your knees tracking over your toes, as deep as you can while your lower back stays on the pad. Depth is worth chasing here: in one ten week trial, full squats grew the glutes and inner thighs more than half squats did, and the quads the same either way3.
Press through the whole foot, then lock the handles
Drive up until your knees are nearly straight, without snapping them into lockout. Stopping short of a hard lockout keeps the load on the legs rather than parking it on straight joints. Turn the safety handles back on before you step out.
What goes wrong
Letting the hips curl off the pad at the bottom
It feels like extra depth, and the plates did travel further. What moved was your pelvis, not your knees, so the extra range is not leg range at all. Stop each rep where your back is still flat on the pad.
Cutting depth to move more plates
Plates go on easily and nobody watches your depth, so the load climbs while the reps shrink, and a bigger number feels like progress. Deeper squats built more glute and inner thigh than half squats did3. A half rep with more plates is a worse set that reads as a better one.
Heels lifting as you sit down
Your weight drifts onto the toes because that is where the sled's angle wants to put it, and the heels peel off without you noticing. Push the whole foot down, and if they still rise, move your feet a little higher on the platform.
How Reckoner progresses this lift
Six weeks of this lift, from 40 kg, run through the real engine. Nothing below was typed in: the prescription, the decision and the sentence beside it all come from the same code that writes your week.
| Week | Prescribed | What it did |
|---|---|---|
| 1 | 4 x 5 at 40 kg | More reps 5 → 6 repsYou finished every set with three reps left in the tank (RPE 7) and room left in the range, so the reps climb before the load does. |
| 2 | 4 x 6 at 40 kg | More reps 6 → 7 repsYou finished every set with three reps left in the tank (RPE 7) and room left in the range, so the reps climb before the load does. |
| 3 | 4 x 7 at 40 kg | More reps 7 → 8 repsYou finished every set with three reps left in the tank (RPE 7) and room left in the range, so the reps climb before the load does. |
| 4 | 4 x 8 at 40 kg | Load up 40 kg → 45 kgYou hit the top of the range with three reps left in the tank (RPE 7), so the weight on the machine goes up 5 kg to 45 kg. The weight went up, so the reps come down to five. You are now working 5 to 8. |
| 5 | 4 x 5 at 45 kg | Deload 40% of sets offFive weeks of building, then one week lighter. About 40% of the sets come off. The load holds and your reps stay where you earned them, so you keep the strength and lose the fatigue. |
| 6 | 2 x 5 at 45 kg | More reps 5 → 6 repsYou finished every set with three reps left in the tank (RPE 7) and room left in the range, so the reps climb before the load does. The lighter week is over, so this is back to four sets. |
Real engine output, not an illustration. Every row was produced by running the engine itself when this page was generated.
The full rule, and why the reps move before the load does, is in how Reckoner decides to add weight.
Questions people ask
Is the hack squat as good as a back squat?
For the legs, it does the job. In young women, ten weeks rotating the leg press, the hack squat and the Smith machine squat grew the thighs as much as the leg press every session did1. The back squat works your trunk harder2, and the hack squat lets you skip that. Reckoner keeps them as separate lifts with separate records.
Why is my hack squat so much heavier than my squat?
Because the machine is holding you. In trained men the hack squat one rep max came out higher than the back squat, with the trunk muscles doing less2. Reckoner records the plates you add, not the sled, so compare the number with itself and not with your squat.
Will Reckoner put this in my plan?
It can, when your gym has a hack squat machine. Knee and hip are both recorded against it, as they are against the leg press, so declaring either in setup takes it out of your plan.
Similar movements
Reckoner eases the load first when this lift stalls, and offers one of these only if it stalls again after that. A lift already as light as your kit goes has no load left to ease, so the offer comes straight away. Each of them has a page.
Sources
- Kassiano and colleagues, Research Quarterly for Exercise and Sport, 2025. Muscle Hypertrophy and Strength Adaptations to Systematically Varying Resistance Exercises seventy young women over ten weeks, one group doing the leg press every session and one rotating the leg press, the hack squat and the Smith machine squat, with thigh muscle thickness and leg press strength rising similarly in both
- Clark, Lambert and Hunter, Journal of Strength and Conditioning Research, 2019. Trunk Muscle Activation in the Back and Hack Squat at the Same Relative Loads ten men, with a significantly higher hack squat one rep max than back squat measured as system mass, and trunk muscle activation higher in the back squat at every relative load tested
- Kubo, Ikebukuro and Yata, European Journal of Applied Physiology, 2019. Effects of squat training with different depths on lower limb muscle volumes seventeen men over ten weeks of full or half squats, with knee extensor volume rising similarly in both and adductor and gluteus maximus volume rising significantly more in the full squat group. A barbell squat study, cited here for depth