Written by Ben Bunting: BA(Hons), PGCert. Sport & Exercise Nutrition. L2 Strength & Conditioning Coach.
When it comes to training legs, few exercises compete with squats.
Regardless of which squat variation you choose, they are all designed to work many of the legs and lower body muscles.
This guide will provide a detailed analysis of a squat's anatomy, walking you through all the major and minor muscles used throughout the movement.
As with all exercises, you will find certain muscles working harder during different stages of the movement. We will also go through some of the benefits of adding squats to your sessions.
What Is A Squat?
A squat is a specific movement pattern that refers to different variants of the same exercise. The video below provides a visual demonstration of a back squat, which is the most common squatting form.
The basic movement principles behind a squat are that you hinge at the hips, slowly bending your knees and descending to the bottom.
You then push through the floor to drive yourself back to the top, extending at the knees and the hips.
Regardless of what squat variant you do, this movement pattern remains the same. The main things that change are the positioning of your feet and the weight.
An Overview Of The Muscles Worked In A Squat
The squat is an incredible exercise as it calls upon so many different muscles:
- Spinal erectors
- Upper back
As you can see, it's an exercise that mainly targets the legs, yet it has an effect on almost all of the major muscle groups. Now, some of these muscles have bigger roles than others. In human anatomy, muscles have five main roles:
What are agonistic muscles?
Agonists are muscles that contract to have a direct influence on the movement of a body part.
In essence, they are responsible for causing the body part to move. A classic example of this is the bicep; it plays an agonist role when flexing the elbow. You can have two types of agonistic muscles:
- Prime mover: the main muscle responsible for initiating a movement
- Assistant mover: a muscle that aids the movement but is not the main one responsible for it
What are antagonistic muscles?
Simply put, these muscles are the opposite of antagonists; they oppose the movement of a contracted muscle.
When the agonist contracts, the antagonist will relax to allow the movement to happen. If we didn't have antagonistic muscles, we wouldn't be able to move at all - our body would be stuck in a constant state of tension as opposite muscles contract against one another.
When a muscle is an antagonist in a movement, the opposite muscle tends to be the agonist. In the previous example of elbow flexion, the triceps on the back of the arm are the antagonists to the biceps.
What are the fixator muscles?
A fixator is a muscle that contracts to prevent unwanted movement. They are essential in all body movements, specifically the squat. You will see that many muscles act in the fixator role to support and stabilize the body during the movement.
Again, you have two types of fixators:
- Stabilizers: these muscles contract to stop unwanted movement caused by the active contraction of another muscle.
- Supporters: these muscles contract to stop a movement that would occur due to external forces. For example, the force of gravity pulling you down.
What are neutralizers?
Muscles that contract to prevent another muscle's unwanted action while also permitting the desired action of that muscle. The best example of this is in arm adduction; the lats extend the shoulder, and the pecs flex it. But, they work together to neutralize these actions, resulting in the adduction of the arm.
What are the synergistic muscles?
Lastly, we have synergists, which are muscles that contract to assist with a movement by making the agonist's actions stronger. This is similar to the role of the assistant move agonist muscle, but with a subtle difference. A synergist isn't responsible for the desired movement; it just helps the agonist perform its role a lot better.
After learning these different roles, we can look at the muscles worked in a squat to understand what roles they perform throughout the movement.
The quadriceps are a group of four muscles sitting on the front of your thigh. This muscle group consists of:
- Rectus femoris (found running down the very front of your thigh)
- Vastus lateral is (found on the outer portion of the front of your thigh)
- Vastus medialis (the 'teardrop' muscle on the lower inner part of your thigh, close to the knee)
- Vastus intermedius (a slightly deeper muscle running underneath the rectus femoris and vastus medialis)
Your quads are the prime movers in a squat. These muscles are used to extend the knee when you are at the bottom of a squat. During this portion of the movement, they are agonistic muscles.
Consequently, your quads are worked harder than most of the other muscles during a squat. They kick in during the concentric part of the movement, which demands the most force and work from the muscles. The deeper you go into a squat, the more your quads will work. This is because they end up in a stretched position with the knees bent and the hips lower than the knee joints. As they contract, your quads are taken through a full range of motion from this flexed position back to extension.
Your glute muscles play a pivotal role in squatting. The glute itself is made up of many different muscles, the main ones being:
- Gluteus maximus (the main glute muscle)
- Gluteus medius (found on the side of your glutes, just below the iliac crest)
- Gluteus minimus (a small muscle found under the gluteus medius)
The gluteus minimus is too small to have an impact on this movement, so we don't need to focus on that. The gluteus maximus is the main muscle to look at as it acts as an agonist muscle during a squat. The function of the gluteus maximus is to extend the hips. When you're at the bottom of a squat, you need the glutes to contract to extend your hips, which will extend the legs. As with the quads, the deeper you go into a squat, the more stretched the glutes become. Therefore, the more muscle recruitment you get when extending out of the crouched position.
As for the gluteus medius, it also has a slight fixator role as a stabilizer. This muscle helps to abduct the leg, pushing it out to the side. In a squat, abduction is necessary to prevent the knee from caving inwards. This can happen with overactive adductor and quadriceps muscles. A strong gluteus medius allows for abduction to protect your knees.
The quads and glutes are the main agonists when squatting, and they make up two of the three major leg muscles. Your hamstrings are the third, and they have some interesting roles during a squat. While they are shortened during the eccentric phase of a squat, you don't activate them enough to see any benefits. If you want to perform a compound movement that targets the hamstrings more, try the deadlift.
Primarily, the hamstrings will work as synergists to help the glutes when extending the hips. You will see some slight hamstring engagement as you stand up from the squat, usually right at the junction where this muscle meets the glutes. However, it's a small contraction that doesn't assist the movement but allows the glutes to recruit more force.
Secondly, the hamstrings act as fixators that stabilize the knee joint. The shortening of these muscles in the bottom phase of a squat act against the quads to prevent knee instability.
The adductors are a series of muscles that run along the inner section of your thigh. The adductor magnus is the largest of these muscles and is the only one of importance here. Effectively, it acts as an assistant mover during the concentric phase of a squat. The adductor magnus plays a role in hip extension and will contract during the middle portion of the concentric phase. This is usually when your knees are between flexion and extension, helping the quads before the glutes kick in to extend the hip.
Some squat variants use the adductors more than others. Generally speaking, the wider your stance, the more adductor engagement you will find.
Many muscles run either side of your spine to keep it upright. These are called the spinal erectors, and they take on the role of fixators in a squat. The nature of a squat means that your upper body will lean forward slightly. The only way to avoid this is by using a hack squat machine. As a result, your body is fighting against gravity at all times. The external force of gravity wants to pull your body forwards, causing you to fall over.
However, your spinal erectors are contracting to keep your spine rigid and prevent this from happening. They also take on more of a stabilizing role to stop any spinal flexion in the lower back. This is a common cause of injuries as people's spines round at the bottom of a squat, increasing pressure on the vertebrae and causing back pain.
All of your abdominal muscles - along with the internal and external obliques - will be worked during a squat. Many people claim that the squat is one of the best core exercises of all time. It's a fantastic way of training core stability as your abs and obliques are contracted the entire time.
Your abdominals look to prevent the hyperextension of your spine. In essence, they work with your spinal erectors to maintain neutral alignment. This is key if you want to keep a good posture when squatting. The obliques contract on either side of your abs to prevent any lateral spinal flexion. This can often happen due to muscular imbalances that cause a person to lean slightly to one side. The obliques stop this from happening, maintain good posture, and prevent injuries.
Calves are made up of the gastrocnemius and soleus muscles. They have a tiny role to play in squats, and they do get worked slightly. Your calves kick into action at the bottom portion of a squat when your ankle enters flexion. You need your calf muscle to contract to pull the ankle out of flexion, allowing the tibia to go back into a vertical position.
This will mainly recruit the soleus muscle, which lies below the gastrocnemius and is pretty much impossible to see. Squats aren't known for creating huge calves, but they are worked.
Finally, we have the upper back. While the squats are primarily a lower body movement, you get a surprising amount of upper back activation. It's worth mentioning that this is only relevant on back squats - front squats won't contract the upper back muscles as much.
To keep the bar on your back, you need to do two things:
- Externally rotate your shoulders
- Retract your scapula
Both movements require the upper back muscles - particularly the upper/lower traps and rhomboids. These muscles are contracted throughout the movement to keep the bar in place. Therefore, they play a supportive structure against this external object. If you relax these muscles, the bar will slide around and be uncomfortable.
What are the benefits of the squat?
Why should you add squats to your workout routine? For one, it is the best compound movement for your leg muscles.
As seen above, all the muscles in your lower body are worked in some way throughout a squat. What's more, you're working your body in a natural movement. Squatting has been around since the dawn of man and is seen as one of the most functional movements you can do.
It is essential to learn how to squat if you want to do regular daily activities. Squatting is also key for generating strength when lifting things from the floor.
As well as being an excellent leg exercise, squats have some additional benefits:
Burn more calories
The more muscles your body uses, the more calories you burn. Let's compare the squat to a leg extension machine. Here, you still target the quadriceps muscles by moving your leg from flexion to extension. However, you will burn hardly any calories on a leg extension machine as it isolates this one muscle group.
By comparison, all of the muscles listed above will be worked in a squat. This puts increased demand on your body's energy systems as they need to provide oxygen for all the working muscles. In essence, you burn more calories because your body has high energy demands throughout the movement.
Improve glute strength
Squats are seen by many as the best exercise for targeting your glutes. Various studies back this claim up by showing that the glutes are highly active during this movement. As a result, squatting will help you improve glute strength and contractions. In essence, it lets you develop the gluteus muscles, so they are bigger and more powerful.
This has a knock-on benefit when it comes to your posture. Strong, active glutes are required to prevent an anterior pelvic tilt, causing an aggressive arch in the lower back. When left untreated, this can lead to persistent back pain. Squatting turns on your glutes, so they keep your hips in natural alignment and prevent back pain.
Improve hip mobility
As you saw in the anatomy section of this guide, many muscles around the hip joint are worked in a squat. The glute medius fires up, as do other hip abductors on the outer thigh. Your hip adductors will also be worked, along with hip extensors. The act of squatting down requires hip flexion, so all different modes of movement are covered.
The squat will train all of the muscles responsible for hip extension, adduction, abduction, and flexion. In turn, this can aid in balancing hip internal/external rotation. Sitting in a squat is also seen as an excellent way to ease hip pain and relieve tension. Therefore, regular squatting is a fantastic way to improve hip mobility.
Build a stronger core
Your core muscles work overtime during a squat, which is essential for building a stronger core. In doing so, you will see endless benefits in both athletic performance and day-to-day life. Lots of research claims that enhancing core stability is common in preventing injuries. A stable core leads to a more balanced body where many joints are protected.
Furthermore, a strong core is needed in many other compound movements - such as the deadlift and overhead press. Squatting trains your core to be stable and helps you learn how to contract those muscles.
It's no secret that core strengthening exercises such as the squat (but includes movements such as pull ups, bench press, deadlifts) help your body produce more testosterone.
Why is this important? Testosterone is great for many physiological functions within the body, from improved muscle growth, increased blood cell production, mood regulation and libido. You can read more about the benefits of testosterone, here.
So with that in mind, hit the squats, it utlilizes a load of muscle and improves your hormone levels.
To summarize, squats work almost every muscle in your body. The prime movers are your quadriceps and glutes, which get worked the most throughout the movement.
Your adductors also assist in the concentric phase of a squat, so they get a good workout as well. Other muscles of your lower body also contribute in various ways to improve stability and prevent injuries.
Squatting is one of the most beneficial exercises anyone can do if they want to develop lower body strength and core stability.
Always accompany any exercise with fluids to maintain optimum hydration.