Short answer: In most cases, the classic barbell squat is a very adequate quadriceps builder that can get you to your maximal quad potential. The strongest points of the squat are its closed-chain nature and the convenience that it offers in terms of programming. 

The squat allows you to overload the quads with very heavy weights without being limited by overwhelming balance requirements observed during other leg exercises (e.g., pistol squats, shrimp squats…etc.).

Nonetheless, the lifter’s anthropometry [skeletal leverages] determines the extent to which squats work the quads. In some situations, modifications will have to be made to target the quadriceps with more intensity.

What Makes the Squat an Effective Quadriceps Builder?

I can tell you that the squat has mythical properties that just happen to activate the right switches in your legs, but that would be inaccurate and a sales pitch for a squat routine.

The main benefits of the squat are as follows:

1. Natural Pattern. Humans are designed to squat as revealed by babies. After all, chairs and benches haven’t always been around. Squats overload that natural pattern and force the quads to exert force in a fairly joint-friendly “bio-mechanism”.

One can argue that putting heavy weights on top of the spine isn’t natural, and I would agree to a certain extent. Nonetheless, the fact that people have been squatting for decades and experiencing mostly benefits from the exercise is sufficient evidence that the back can be conditioned to handle the load.

Most of the injuries caused by squats are the result of bad form and pointless attempts to satisfy the powerlifting dreams of muscle scholars promising extraterrestrial growth if you reach an arbitrary squat number.

2. Convenient programming. Barbell movements do not bully you into changing the basic motion of an exercise to increase the difficulty. You just add weight, and that’s it. This characteristic makes programming easier since the number of variables is reduced. On the other hand, bodyweight training requires you to move on to more advanced variations which may or may not agree with your joints.

2. Infinite progression in the muscle-building rep ranges. When an exercise becomes too easy, and you start doing over 15-20 repetitions per set, you are building endurance. This is fine if your goal is to maintain muscle mass, but if you are after extra growth and strength, you will have to make the move more challenging by lowering the rep range to 5-10 per set. With barbell squats that is achieved easily by just adding more weight.

Which Squat Variation Works the Quadriceps the Most?

Let’s look at the main possibilities before deciding.

1. Front squats. In theory, front squats should hit your quads more intensely than regular squats because of the upright back angle and the increased depth. However, the exercise has a few peculiarities which reduce the potential stress on the quads:

a. Difficulties to comfortably accumulate volume. During front squats, the upper back works extra hard to support the weight and often gives up before the legs. The discomfort created by the barbell pressuring the clavicle area is also a distraction absent during back squats.

Thus, the front squat needlessly complicates the accumulation of volume.

You could certainly develop your quads with front squats, but it’s useful to be aware of those peculiarities.

b. More stress on the knees. Front squats come with additional knee travel in comparison to the back variations. This can cause knees issues in some people, especially when doing the exercise for lots of sets and reps. For that reason, crazy squat routines like Smolov are rarely if ever done with front squats as the main lift.

2. Low bar back squats

The low bar squat is a powerlifting invention designed to lift more weight by making the exercise hip [glute] dominant. This comes at a price – the quadriceps are robbed of two belongings – work and range of motion. The quads are still under pressure, but the stress is reduced in exchange for extra glute work.

The famous powerlifter Ed Coan squatted in the low bar position throughout his competitive career. To strengthen his legs, he added deep high bar squats to his routine as he saw value in them as quad builders.

3. Zercher squats

Zerchers are not a popular squat variation, but they are very potent “quad amplifiers” for two reasons:

a. Heavy weights. The Zercher allows you to handle a surprising amount of weight. After an introductory period, many begin to Zercher more than they can front squat, although that cannot be guaranteed for everyone.

b. Upright torso. The Zercher requires you to stay upright. The result is more leg/quad work.

The main downsides of the Zercher are the frequent forearm bruises and the restricted breathing [the rib cage cannot expand fully during this variation]

4. High bar back squat – the King

The high bar back squat offers the most balance. It places more stress on the quads than the low bar squat while allowing you to handle more weight than the rest of the movements on the list. Moreover, the position is easier to maintain and allows you to get copious amounts of volume.

So, which is the best variation?

If you can safely do the high bar back squats, it’s probably your best bet. Nonetheless, it’s also worth exploring the rest of the options if they fix a limitation preventing you from doing high bar squats.

Your personal preferences also come into play. You have to love what you do.

Is it True that Squats Elicit Growth Hormone Release?

Yes, according to a study from 2018 which examined the endocrine response of experienced powerlifters to heavy squats.

28 top tier lifters in their prime performed 3 sets of 3, 6 and 12 reps. The levels of their testosterone, growth hormone (GH), insulin-like growth factor (IGF-1) and cortisol (C)were measured after exercising and at rest.

The research concluded that “6 sets of squats seem to drive hormonal responses of GH, C and IGF-1, which may play a significant role in stimulating muscle growth and tissue regeneration.”

However, it would be naïve to think that a man can get steroids-like results from squatting. The muscle-building hormones released from lifting come in minuscule quantities and have a short half-life. Consequently, anyone selling you squats as a way to trigger amazing hypertrophy results is playing with your perception.

How Deep Should I Squat for Optimal Quad Development?

Squatting as deep as you can without compromising back alignment is ideal in most cases.

If you do quarter squats, you can overload the quads with very heavy weights, but the stress on the knees and the back is not worth it.

Deeper squats (below parallel) require the use of lighter loads, but the increased range of motion makes up for lost “stimulation”.

Does the Squat Work for Everyone? I have long femurs.

Nothing works for everyone, but the great number of squat variations and the possible modifications create an opportunity for almost anyone to squat.

However, not everyone’s anthropometry agrees with squatting. People with long femurs often turn the movement into a cheated good morning and deprive the legs [quads] of their rightful share in the exercise. Two changes can be made to diminish this effect:

a. Squat high bar. Low bar squats demand more forward lean for everyone due to the position of the bar. When you have long femurs, you bend over even more. The high bar will reduce the forward lean to some degree. Alternatively, you could also add front squats or leg presses to your routine to increase the quad volume.

b. Don’t lift too heavy. The shift to good morning happens when the weight is excessive or when you’re exhausted. By reducing the load and increasing the volume while trying to remain as upright as possible, you could prevent form breakdown.

If you’re doing the squat to build your quads, there’s no need to max out and go to failure. Just accumulate more volume [training tonnage].

How Heavy Should I Squat to Develop My Quads?

Contrary to popular belief, you don’t have to squat with insanely massive weights to reach your potential. If you listen to the strength fetishists, they will tell you that anything under 4 plates is a joke, but that’s not true. Getting your squat to 1.2-1.5BW for a solid set will be sufficient for most people. Of course, those values are subjective. If you are built for squatting [short femurs], you may do significantly better.

In general, playing the number game as a natural is a waste of time. As long as your routine includes a progression mechanism of some sort, and you can recover adequately, the major part of the work is done.

What If I Only Do Squats for My Legs?

Here’s what the effect will be:

1. Quads and Glutes – the squat can take your quads and glutes to their maximal potential.

2. Hamstrings – the squat is an inferior hamstring exercise. The leg biceps actively participate in the movement when you break parallel but are never the main focus. A pull like the deadlift will target them with a greater focus.

3. Calves – calf size is genetic for the most part. If you have high calves [long Achilles tendon], training them for growth is a lost battle.

In theory, the squat works your calves too as they stabilize the lower leg, but they are never the limiting factor in a squat. If you want to hit them, you will have to perform dedicated movements.

Conclusion: If you only do squats for your legs, your hamstring and calves may be lagging. Supplementary movements for those body parts could help. Nonetheless, you’re unlikely to develop dangerous imbalances, especially if you squat deep.

References:

Wilk, Michal & Petr, Miroslav & Krzysztofik, Michał & Zajac, Adam & Stastny, Petr. (2018). Endocrine response to high intensity barbell squats performed with constant movement tempo and variable training volume. Neuro endocrinology letters. 34.