Ask anyone with big quads what they do for legs, and I can virtually guarantee that "hack squats" are one of the first exercises they mention.
As good as free weight squats are, no leg exercise is more effective than hack squats for developing a rock-solid outer quad sweep.
But what if your gym doesn't have a hack squat machine? Are you doomed to have puny thighs forever?
Enter the Smith machine hack squat...
By my reckoning, the Smith hack squat is the most reliable of all the Smith machine leg exercises for building huge quads fast.
And you'll soon learn why.
When you're doing a hack squat Smith machine style, it's essential to push your hips back and down so that you can achieve a full range of motion (ROM).
While you definitely want to allow plenty of knee flexion/bend to recruit your quads, breaking at the hips and knees together will ultimately make you stronger (two joints are stronger than one) and keep your knees out of harm's way.
In other words, don't let your knees come way over your toes unless you have iron patellas.
When you're learning how to hack squat on Smith machine systems, your foot position can mean the difference between building kick-ass quads and stunting your leg gains—or worse, causing yourself permanent knee damage.
You must strike the right balance between quadriceps activation and knee health.
Keeping your feet close to your centre of gravity will indeed maximise quad recruitment because it allows for the most ROM at the knee joint. However, this position also places the most stress on your patella. But, with a few modifications, you can somewhat mitigate this stress (especially if you also invest in a reliable pair of knee sleeves).
Firstly, take a step away from the Smith machine. As mentioned, this foot position makes you stronger because you're using more of your powerful gluteus maximus to lift the weight.
Secondly, make sure that your stance is at least hip-width, and if you have knee issues, shoulder width. This positioning opens up your hips which in turn enables you to flare your knees out .
Some old school bodybuilders think that this type of squatting decreases quad activation. However, modern-day exercise science proves their belief greatly wrong. A feet-together stance makes you significantly weaker and does nothing extra for your legs besides make your knees work harder.
I love doing hack squats on Smith machine stations as a finisher. It sets my quads on fire, and I have to hobble out of the gym (or these days, my home gym) like an old man. But the gains are worth it.
Essentially, you want to pick a weight that you can do for at least 20-30 reps. Perform about 3 sets, leaving 1-2 reps in the tank on the first and second sets. Then, on the last set, train to absolute failure (by which I mean finishing the final rep is impossible).
The beauty of hack squatting on the Smith machine is that you don't need a spotter. You can re-rack the bar at any point in the rep with an effortless turn of the wrist. And unlike a clumsy spotter, the safety catches will always have your back.
Naturally, this built-in safety gives you the confidence to train to failure, which in turn results in faster and more substantial quad development. The key is to only come 80% of the way back up on each rep. This way, you maximise the blood flow to your quadriceps.
And if you're really hardcore, you can try my high-rep technique while wearing occlusion cuffs.
While Smith hack squats are undeniably tough on the quads, they can also be harsh on the knees. And while wearing a pair of knee sleeves won't prevent injuries, it will speed up your recovery and help your injuries to heel sooner by reducing inflammation.
I've personally been wearing the Beast Gear Knee Sleeves during my leg sessions, and I have no complaints. I can go about 5kg heavier while wearing these bad boys and my knees definitely feel more "locked in place", if you will.
Before, my knees would shake and buckle while lifting heavy—and it was really frustrating. However, these 5mm neoprene sleeves provide just the right amount of support to where I can lift heavy without knee pain, yet not feel restricted in terms of hitting depth.
Since I have a home gym, I can squat barefoot without anyone yelling at me to put my trainers on. However, during the odd times that I train legs in a commercial gym, I don't lift without my squat shoes.
I've tried a few different pairs and finally settled on the Addidas Powerlifts.
They're not going to double your hack squat or anything like that. But if you're used to lifting in regular gym trainers, then you're going to feel considerably more stable while wearing them.
I tested my one-rep max in trainers and then a week later (to make the test fair) while wearing squat shoes. The result?
I was 10kg stronger in my Addidas powerlifts. Create a supplement that can increase strength that quickly and you'll become a billionaire overnight.
I wasn't going to recommend a bar par at first. However, my wife insisted that using one makes her stronger, so here you go.
And to be honest, I can see where she's coming from. If you don't have much meat on your traps, a thick bar pad can make a difference in your comfort. It ensures that your legs are always the limiting factor, not the pain in your neck.
However, unless you're lifting really heavy, then don't worry about using a bar pad.
To maximise quad activation, focus on keeping your torso upright while squatting as deeply as possible. You can easily achieve this positioning by breaking at the knees and hips together at the start of each rep .
And yes, while emphasising movement at the knees (rather than the hips) does lead to more quad activation, I'm not convinced that this technique leads to more quad growth.
You see, when you actively try to take your hips/glutes out of the movement, you naturally become weaker, meaning that you're actually overloading your quads with less weight. Fitness gurus disagree on a lot of things. But if there's one thing that they all agree on it's this: lifting heavier weights builds muscle faster.
You can maximise your glute gains during the hack squat by positioning your feet around 6-8" away from your centre of gravity. Doing this increases the hip ROM and provides an extraordinary stretch in the glutes (to the point where sitting down after a set becomes uncomfortable).
Bodybuilders love hack squats because it enables them to focus 100% of their attention on building the biggest legs possible—not on stabilising the bar.
And while the spinal erectors are active during any kind of deep squat, their role is much less pivotal to maintaining the proper form on machine-based exercises .
Hamstring activation increases in direct proportion to your feet's distance from the barbell. This is simply because, like the glutes, the hamstrings are subjected to a more intense stretch while in hip flexion.
The Smith machine reverse hack squat is a decent alternative if you want to work your hamstrings because the positioning enables you to stick your hips out.
That said, I wouldn't rely on Smith hack squats (or any squat variation, for that matter) to develop your hamstrings—you need to do some kind of leg curl and hip hinge to work the backs of your legs.
Hack squat machines are arguably the best tool in the gym for building massive quads. Get stuck at the bottom of the machine, however, and you—or more specifically, your knees and lower back—are in a whole load of trouble.
But this is never the case with Smith hack squats. Should you fail a rep, then you can simply turn your wrist about 15 degrees to get yourself out of harm's way by re-racking the barbell. Obviously, this encourages you to lift harder and heavier because you know that there's no consequence to training to failure—besides extra DOMS, of course.
Nothing works the quads like hack squats. And nothing enables you to test your limits as safely as a Smith machine. Add them together, and you have two of the four key components for building attention-demanding quads.
All you need to provide is intense effort and high-protein, high-calorie diet.
Regular squats are great for the glutes. However, in order to actually work your glutes during free-weight squats, you need to bend over at the waist, which places enormous pressure on your lower back.
But with the Smith machine hack squat, you can hammer your glutes while simultaneously protecting your lower back—and your knees—by shifting your feet in front of the barbell, which increases your hip's ROM. Try doing this with regular squats, and you'll immediately lose your balance—or worse, fall flat on your back.
Did you know that hack squats actually increase your leg power more than back squats?
According to one 2019 study, hack squats were just as good as back squats for improving agility, but they were more effective for improving jumping power. What does this mean for your physique? 
Well, by generating more squatting power, you'll naturally recruit more fast-twitch muscle fibres, which are the fibres that grow the biggest and the stronger. In other words, hack squats will make you quad sweep bigger and more formidable.
There are 3 amazing alternatives to doing hack squats Smith machine style (if you want bigger quads).
Regular Smith machine squats are incredibly similar—if not identical—to Smith hack squats.
Let me explain why. Traditional hack squats allow you to use any foot position on the machine's platform. Regular free weight squats, however, don't. You can only change your stance width, not how far out in front your feet are.
But when you throw a Smith machine into the mix, the playing field is automatically levelled because now you can change your foot position in relation to your centre of gravity on both exercises.
So yes, they're pretty much the same movement. And an effective one at that.
It wasn't until I saw Jay Cutler doing a Smith machine front squat that I realised what a great quad-builder this exercise is. In fact, from a bodybuilding perspective, it's just about the best quad exercise that you can do. Unlike the free weight version, you don't have to tax your core and upper back to stabilise the weight, which increases quad stimulation.
Since I'm so into bodybuilding, I actually saved up for a hack squat machine for my home gym. It was fairly pricey, but when you consider that it doubles up as a leg press, I think it's fair to say I got a pretty sweet deal.
Anway. I definitely prefer the hack squat machine to Smith hack squats because I can lift heavier and overload my quads with more resistance. I've put about 2" on my thighs in the past 9 months, so buying the Body Solid Leg Press/Hack Squat Machine was definitely worth the investment.
But I can't let the machine take all the credit. I've been training hard and eating like a horse! So I'm not too surprised that my legs are looking better these days.
Of course, the Smith machine hack squat is still an awesome movement (I use it as a finisher all the time). But given a choice, I'd always go with a dedicated machine .