To get a bigger squat and improve your mechanics, you need to have a complete understanding of the muscles used in the squat. Certain muscles in the squat will work more or less depending on the range of motion, whether you’re deep into the hole or driving through your sticking point, and which variation of the squat you’re performing.
So what muscles are used in the squat?
- In the bottom of the squat, your quads will be working the hardest since your knees will be at the greatest end range. Your core muscles, specifically your erectors, will also be activated in order to prevent falling forward or flexing at the spine.
- As you drive to standing, your hips will need to travel up and forward, which will require your glutes and adductor magnus (inner thigh) to extend the hips.
- Overall, the squat is one of the most compounded lower body exercises since it requires simultaneous action at all the primary joints, including hips, knees, and ankles.
In this article, I’ll discuss what each muscle is responsible for in the squat. I’ll break down how different muscles are used in variations of the squat, including the low bar squat, high bar squat, pause squats, pin squat, wide-stance squats, and front squats. I’ll also talk about how to identify weak muscle groups in the squat, and what you can do about it to become a more efficient squatter.
Squat Biomechanics: How Joint Angles Impact The Muscles Used
The squat requires joint action at the hips, knees, and ankles. As a result, several muscle groups in both the lower and upper body are required to overcome the forces on these joints to execute the movement properly.
The load in the squat should be directly over the mid-line of the foot as you descend into the bottom.
When your hips move back behind this line, and your knees move forward, you create additional stress on these joints. The greater the distance between the line of force and your joints, the harder your muscles need to work to overcome the external load.
Having your hips and knees travel in an opposing direction to the line of force in the squat is totally normal.
For example, if your knees do not travel forward during the squat, then they won’t experience any stress and your quad muscles won’t be significantly loaded.
This might seem advantageous…
However, it means that all of the stress gets transferred to your hip extensors, which requires your glutes and low-back to work much harder. Over time, this could result in injury if one joint or another experience greater stress than what they are accustomed.
If you’re interested in reading more about whether it’s safe to have your knees travel forward in the squat then take a look at my article where I discuss the biomechanics research.
The basic biomechanical principle you need to understand is that joint action will require certain muscles to contract in order to flex and extend that joint properly. Joints will experience more or less stress the further they are in relation to the load, which requires your muscles to work harder.
Squat Anatomy: Which Muscles Are Worked In The Squat
The muscles used in the squat are:
- Adductor Magnus (Inner Thigh)
- Abdominals and Obliques
- Upper Back and Lats
Certain muscle groups are more or less engaged depending on which variation of the squat you’re doing and the range of motion emphasized. We’ll explain more on this later, but first, let’s breakdown each muscle worked in the squat and their role.
The quads are the primary muscles used to extend the knee.
At the deepest range in the squat, the quads will be working the hardest in order to extend the knees out of the bottom.
Furthermore, as you remember from the biomechanics section, the knees will travel in front of the line of force as it descends into the squat. The further your knees travel forward, the stronger your quads need to be.
So the deeper you go and the greater forward knee bend you have, the more you can expect the quads to work.
The glutes are made up of three muscles: glute maximus, glute medius, and glute minimus. For the purposes of the squat, we’re going to discuss the glute maximus and medius.
The glute maximus is the ‘meaty’ part of the glute that you sit on. The glute maximus is used to extend the hips.
As you remember from the biomechanics section, the hips will travel behind the line of force as it descends into the squat. As you stand back up, the hips need to rise up and forward to come back in line with the line of force.
Therefore, the glute maximus serves an important function in the top range of the squat in order to bring the hips into full extension.
The glute medius is the side part of your glute
The glute medius is used to abduct the hip. In other words, taking the leg out laterally like a ‘side step’.
In the squat, keeping the hip abducted will ensure your knees track over your toes properly. Without having a strong glute medius your knees might cave in during the squat, which would increase the amount of shear force at the knee joint.
Adductor Magnus (Inner Thigh)
The adductor magnus muscle of the inner thigh also has a role in hip extension.
It performs a similar function to the glute maximus, which allows the hips to extend fully. However, it likely plays more of a role in the mid-range of the squat before the glutes take over for the final hip extension.
Furthermore, the adductor magnus will be working more to extend the hips if you have a wider stance squat, less so if you take a narrow (shoulder-width) stance.
If you want to learn whether wide stance squats are better for powerlifting you can read my article on squat stance.
The hamstring has two roles in the squat.
First, the hamstring acts as a synergist to support the glutes in hip extension. As the knees straighten, the hamstrings are engaged more in order to bring the hips to the bar. However, the hamstrings are only contracting a small amount here and the primary driver of hip extension is still the glutes.
Second, the hamstring acts as a stabilizing muscle to support the knee joint. When your knees are in the greatest flexion in the bottom of the squat, the tension of the hamstrings helps stabilize the knee joint by countering the forces of the quads to extend the leg.
Your erectors are the muscles that run along the outside of your spine. They attach at the top of the pelvis, ribs, and the spine itself.
The erectors have a role in keeping the spine stiff and extended throughout the squat. Essentially, they prevent the back from rounding or flexing forward.
This is an important function because if the back rounds while squatting, the stress at the level of the vertebrae will increase. The spine should stay rigid in order to transfer the force effectively from your knees and hips into the bar.
Let’s quickly discuss forward towrso lean in the squat and its impact on the erectors.
Everyone will have a natural forward torso lean in the squat based on their individual leverages. If you’re someone who has longer legs and a shorter torso, then you’ll experience more forward lean than someone who has shorter legs and a longer torso.
The more forward torso lean you have in the squat, the harder your spinal erectors need to work in order to keep your back rigid.
This is not a bad thing. This just means that your erectors will need to be much stronger if you have more forward torso lean.
Abdominals and Obliques
The abdominals and obliques are what’s called “antagonist stabilizers” in the squat.
An “antagonist stabilizer” will help maintain the postural alignment of specific joints.
In the squat, this means that the abdominals and obliques help stabilize the vertebral column and pelvis. They do this by preventing the erectors from pulling the spine into hyperextension.
As you’ll remember, the erectors’ job is to prevent the spine from flexion (rounding). The abdominals and obliques prevent the spine from extending (arching back) or twisting.
With weak abdominals and obliques, the erectors don’t maintain as much tension potential as it otherwise would.
Upper Back and Lats
The muscles of the upper back and lats are working to keep the bar position fixed in place.
If the upper back and lats aren’t tight enough, then the bar will likely shift up or down on the back throughout the movement. Even micro movements of the bar can cause instability through the core, which causes your spinal erectors and abdominals/obliques to work much harder to hold the same position.
The muscles of the upper back and lats also support the erectors in maintaining spinal stiffness, since the erectors attach at the upper back as well.
Many people might be surprised that the calves have a (small) role in the squat.
As you descend deep into the squat, your ankle flexes and your shins move forward. The soleus muscle, the outside of the calf, brings the shin to a vertical position as you stand back up in the squat.
Identifying Weak Muscles In The Squat
You should now have a strong understanding of each of the muscles involved in the squat, and how they function together to complete the movement.
Let’s now discuss how to identify any weak muscles in the squat so that you can target them more specifically through your exercise selection and programming.
Identifying weak muscles is important because they often contribute to technique deficiencies. What this means is that if a muscle is not doing its job properly, then the body will compensate in some way in order to prevent you from failing the movement. These compensations are generally not good because it means that other muscles are being overworked by additional stresses being placed at the level of the joint.
Technique deficiencies in the squat could be an entirely separate article, but I’ll broadly address weak muscles based on the ‘bottom’ and ‘top’ end range of motion in the squat.
Struggling At The Bottom Range
The deeper you squat, the more your knees bend forward, and the greater your quads need to work. This is the case when squatting ass-to-grass.
If you have difficulty in the bottom-end of the squat, you will struggle to stand from the deepest part of the squat up to about half range. This is likely due to your quads being too weak.
However, you’re not all of a sudden going to fail in the bottom range before at least grinding a few reps out. As you grind reps in the squat, you may notice some compensation patterns occurring that signal your quads are fatiguing.
You’ll want to pick up on these signals as much as possible.
What happens when your quads are fatiguing is that the body will want to shift the loading demands from your knee extensors to your hips extensors to finish the movement (putting you into a good morning squat position). Again, the body is not going to fail before trying everything possible to leverage the weight.
To shift the loading demands from the knees to the hips your body will hinge forward and your hips will pop up out of the bottom of the squat. This will look like you are in a ‘good morning position’ with your legs relatively straight and your back horizontal to the ground.
This is the body’s way to get your glutes and low/mid-back more involved in the range of motion in order to complete the movement.
If you find yourself in this position, you’ll want to recognize that you have a quad weakness and implement squatting variations that will increase the strength of your knee extensors. These are variations such as front squats or pause squats, which we’ll cover in more detail later.
Struggling At The Mid & Top Range
As you drive out of the bottom of the squat, and you enter the mid/top end of the squat, the greater your glutes, adductor magnus (inner thigh), and hamstrings need to work to extend the hips.
There is a sliding effect that happens where the closer you get to standing, the less your quads are activated, and the greater your glutes and other hip extensors need to work.
If you have difficulty in the mid/top end of the squat, you will find yourself able to stand up out of the hole, but fail somewhere above your thighs being parallel. This is likely due to your hip extensor muscles being too weak, which will fail to bring your hips up and forward underneath the barbell.
It’s much harder to compensate for a movement pattern in the top range of a squat. However, your hip extensors would shift the loading demand to your quads by trying to push the knees forward more. This is tricky to notice, but it would look like you’re squatting on the front part of your foot to try and bend your knees.
Even though this would be an effective compensation strategy to push through your sticking point, it would feel awkward because as you shift the load to the front part of your foot you might feel off balance.
So rather than grinding through a rep by trying to bend the knees forward more, it’s more likely that you’ll come up in the squat with decent speed and then all of a sudden stop dead in your tracks without having the ability to grind.
This would mean that your glutes and adductor magnus, and to a lesser extent your hamstrings, need to be addressed through several variations, such as high pin squats, wide stance squats, and Romanian deadlifts.
Muscles Used in Different Variations Of The Squat
Each variation of the squat will involve your knee and hip extensors more or less.
As part of your programming, you should select squatting variations that target specific muscle groups that allow you to focus on areas for development.
You can place more emphasis on your knee or hip extensors depending on where you are failing in the squat or notice the movement breaking down.
The variations that will be discussed are:
- Low bar squat
- High bar squat
- Pause squat
- Pin Squat
- Wide-stance squat
- Front squats
Muscles Used In The Low Bar Squat
The low bar squat is considered a hip-dominant movement and will use more muscles of the posterior chain, such as the spinal erectors and glutes.
You will place the barbell a few inches lower on the back. So rather than resting the bar on your upper traps, you’ll place the at the top of your rear delt.
With a low bar squat, you’ll have slightly more forward torso lean. In this position, you’ll be hinging from your hips more, and flexing into your knees less.
This is not to say that your quads aren’t working at the bottom of the squat. It’s just likely that they’re not working as hard as other squat variations that require more forward knee bend in the hole.
The low bar squat is considered the default powerlifting squat because you are able to lift more weight on a one rep max squat. This is because your quads will get maxed out eventually, and you’ll need to shift the loading demands to the posterior chain, which isn’t operating at ‘full capacity’ in other squat variations.
If you want to read more about low bar squatting and why it’s advantageous you can read my article where should you put the bar when squatting.
Muscles Used In The High Bar Squat
The high bar squat is considered a knee-dominant movement and will require your quads to work much harder.
In the high bar squat, you will place the barbell on your upper traps just below the big bony bone at the bottom of your neck (C7).
With a high bar squat, you’ll be slightly more upright. You’ll be hinging from your hips less, and bending your knees forward more.
When doing a high bar squat, you’ll want to think about actively pushing your knees forward as you get to the bottom range. This will require you to use your quads a lot more to drive up because of the greater angle at your knee joint.
The high bar squat is the choice of many Olympic weightlifters because the snatch and clean and jerk require an excessive amount of forward knee bent. Therefore, they need to squat using a variation that places large loading demands on the quads. In other words, the high bar squat will transfer more to their sport.
One quick note: the more you bend forward into your knees though, the greater your ankle mobility needs to be. So if you have any restrictions at the ankle it might be harder to drop your hips below parallel. If this is the case, then you likely won’t get the quad activation you’re seeking by doing the high bar squat.
If you struggle to squat below parallel, you can read my 9 tips to squat deeper.
Muscles Used In The Pause Squat
The pause squat is considered a bottom-end squat variation where you’ll pause for 1-3 seconds in the hole.
This will put more loading demand on your quads because you’re spending more time under tension with your knees bending forward in the bottom of the squat.
In order to get the most benefit from the pause squat, you’ll want to make sure you’re doing two things properly:
- Maintain as much muscular tension as possible and not ‘relax’ at the bottom of the squat. You’ll want to actively keep your quads tight and your torso position rigid.
- Drive up from the pause by extending from the knees, and not by shifting the loading demand to your hip extensors. If you are using your hip extensors, it will look like your hips are popping up out of the bottom where your torso becomes more horizontal to the floor.
If you can’t maintain muscular tension or drive up from the pause by extending from the knees first, then the load is likely too heavy, and you won’t be getting the benefit of activating your quads to the fullest extent.
You can perform the pause squat in either a high or low bar position. But, if you want even more quad activation then choose the high bar position.
Muscles Used In The Pin Squat
The pin squat can be considered both a bottom-end or top-end squat variation depending on how you set-up the movement.
In the pin squat, you’ll initiate the movement downard, and at some point the bar will hit the safety pins in the squat rack. The bar load will come to a dead stop, and then you’ll push up and back into the bar to drive it off the pins to standing.
If you want to target more of your quads, then you can set up the pins in a lower position so that the barbell hits the pins at or below parallel.
If you want to target more of your glutes and other hip extensor muscles, then you can set up the pins in a higher position so that the barbell hits the pins above parallel.
The pin squat is unique compared to the pause squat because the bar weight will completely deload on the pins. This means that your body will need to generate a higher rate of force development to initiate upward movement of the barbell — the speed at which your muscles need to contract and develop force. As a result, it’s a much more physically demanding variation.
For my athletes, I generally don’t use the pin squat to target the knee extensors. I only place the pins in a higher position, and use it more to target the glutes and other hip extensor muscles. I find most athletes respond better to pause squats to build quad strength, and doing low pin squats tend to beat athletes up a bit more.
Muscles Used In The Wide Stance Squat
The wide stance squat is considered a hip-dominant movement where you’ll use more musculature of the glutes.
A normal stance width for most people will be slightly outside of shoulder-width distance. A wide stance squat is considered somewhere between 1.5-2X shoulder-width distance.
To understand what muscles are involved in the wide stance squat I want to look at two studies.
A study by Escamillia et al. (2001) showed that a narrow, medium, and wide stance squat were all considered ‘knee-dominant’ movements. What this means is that regardless of the type of stance you have, you’ll still be required at some point to push your knees forward to get the required depth in the squat.
To back this up, a study by Paoli et al. (2009) showed that a narrow, medium, and wide stance squat all had the same level of quad activation. However, the biggest conclusion was that there was greater glute activation in the wide stance squat.
What this means is that no matter what stance you pick, you’re going to get the same level of quad activation; however, the wide stance squat will allow you to place even more loading demand on the glutes.
If you find that you squat in a fairly narrow stance, you can consider implementing wide stance squats as an exercise variation in your program in order to gain greater glute activation. This would be important if you had a mid/top end weakness in the squat.
Muscles Used In The Front Squat
The front squat is considered a knee-dominant movement and will require your quads to work much harder.
To set up the front squat, you’ll place the barbell on the front part of the shoulders.
This position will force you to maintain an upright torso, even more so than what I described previously for the high bar squat. As such, your quads will be working much harder because your knees will be driving forward more to get the required squat depth.
Unsurprisingly, this bottom position requires the most mobility in your knees, ankles, and wrists compared with other squat variations. For these reasons, it’s a more complex movement to learn. But it’s something worth getting better at if you want to work your quads in a squatting variation.
An added benefit to the front squat is also getting a lot more muscle recruitment in the upper back. This is because in order to prevent your elbows from dropping forward, and the barbell falling off your shoulders, you need to stabilize through the muscles in your upper back.
The front squat is the squatting variation of choice for all Olympic weightlifters because it’s a necessary movement pattern in the clean and jerk.
The squat will use the knee, hip, and back extensor muscles.
In the bottom of the squat, you’ll use more quad muscles to extend the knee out of the hole. As you transition into the mid and top end range of motion, you’ll use less quads, and more glutes, adductor magnus, and hamstring to extend the hips. The more forward torso lean you have, which will vary depending on your individual mechanics, the greater your erectors will work.
If you want more quad dominant squat variations, use the high bar squat, pause squat, front squat, or a low pin squat.
If you want more glute and other hip extensor variations, use the low bar squat, wide stance squat, or a high pin squat.
Escamilla, R., Fleisig, G.,, Lowry, T., Barrentine, S. (2002). A three-dimensional biomechanical analysis of the squat during varying stance widths. Med Sci Sports Exercise. 33(6): 984-998.
Paoli, A., Marcolin, G., Petrone, N. (2009). The effect of stance width on the electromyographical activity of eight superficial thigh muscles during back squat with different bar loads. Journal of Strength and Conditioning Research. 23(1): 246-250.