Squats work nearly every muscle from your waist down, plus a few up top that fight to keep you upright under the bar. The primary movers are your quadriceps and glutes. The hamstrings, adductors, calves, spinal erectors, abs, and traps all pitch in as secondary muscles that stabilize the load and help drive you out of the hole.
This breakdown is built around the barbell back squat, which spreads the work across more muscle than any other squat variation. Switch the variation and you shift the emphasis. Front squats, goblet squats, and hack squats keep your torso more upright and lean harder on the quads, so dial in your front squat form if that’s your focus. Single-leg versions like split squats and lunges load one leg at a time, and you’ll find plenty of options in our Bulgarian split squat alternatives.
Below I break down all eight muscle groups the back squat trains, what each one does during the lift, and how to bring up the ones lagging behind.
Table of Contents
- 1 Back Squat Muscles Worked
- 2 Primary vs Secondary Muscles
- 3 Back Squats Muscles Worked FAQs
- 4 Other Exercise Posts
- 4.1 The 5 Best Benefits of Planks
- 4.2 How to Perform the Overhead Press with Proper Form
- 4.3 Side Plank Benefits, Form, and Muscles Worked
- 4.4 Bear Crawls: Benefits, Proper Form, and Muscles Worked
- 4.5 Lat Pulldown Benefits and Muscles Worked
- 4.6 Arnold Press Benefits and Muscles Worked
- 4.7 The Top 10 Pull-up Muscles Worked
- 4.8 The Landmine Press: Muscles Worked, Benefits and Form
- 4.9 The Top 10 Muscles Worked by Planks
- 4.10 Barbell Row Benefits, Muscles Worked, and Form
- 4.11 Inverted Row Benefits and Muscles Worked
- 4.12 How to Bench Press with Perfect Form
- 4.13 Hack Squat Muscles Worked and Benefits
- 4.14 How to Do a Lat Pulldown with Proper Form
- 4.15 The 7 Best Compound Chest Exercises
- 4.16 Front Squat Benefits and Muscles Worked
- 4.17 How to Front Squat with Proper Form
- 4.18 Bulgarian Split Squats Muscles Worked & Benefits
Back Squat Muscles Worked
- Gluteal muscles
- Quadriceps
- Hamstrings
- Adductors
- Calves
- Spinal Erectors
- Abdominals
- Trapezius
Here’s Dr. Gains with a quick overview of the muscles worked by the squat. For the most effective muscle growth it’s essential to perform the squat with correct form.
Primary vs Secondary Muscles
The eight groups sort into two buckets based on how much of the work they actually do during a back squat. The primary movers generate the force that stands the weight up. The secondary muscles stabilize you and assist the lift without driving it.
- Primary movers: Quadriceps, Glutes
- Secondary muscles: Hamstrings, Adductors, Calves, Spinal Erectors, Abdominals, Trapezius
Gluteal muscles
Your glutes are one of the two prime movers in a back squat. They handle hip extension, which is the main job the squat is asking for, and the lift trains both the gluteus maximus and the gluteus medius. On the way down they control the descent and decelerate you. Out of the bottom they fire to extend the hip and drive you back to standing.
If your glutes are the weak link, our list of the best cable glute exercises covers accessory and isolation work to bring them up for heavier squats.
Quadriceps
The quads are the largest muscles in your legs and the other prime mover in the squat. They drive knee extension and stabilize the knee joint through the whole rep, and the outer quad (vastus lateralis) does much of that stabilizing work. To load them directly, slot in some quad isolation exercises, and if the outer head is the part falling behind, here are the best outer quad exercises to bring it up.
Hamstrings
The hamstrings are a key player in the back squat. They control knee flexion as you lower into the squat and assist hip extension as you stand back up.
Weak hamstrings show up as an excessive forward lean or a technique breakdown, which raises your injury risk and stalls your progress. Hit them directly with some hamstring isolation work, and if they’re underdeveloped, here’s how to grow underdeveloped hamstrings for a stronger, more stable squat.
Adductors
The back squat trains the adductors, the adductor magnus in particular, which handles hip adduction and extension. At the bottom of the squat it contracts isometrically to keep your pelvis stable, then helps the glutes extend the hip as you rise back up. A wider stance with your feet farther apart loads the adductors more than a narrow stance does.
Calves
Your calves don’t move much in a squat, but they’re working the whole time to keep you balanced over your mid-foot. As you sink into the squat your ankles flex and the calves contract to hold you upright, and pressing back up they assist the drive. That keeps the gastrocnemius and soleus under tension rep after rep, which builds strength and size over time.
Spinal Erectors
The spinal erectors run up either side of your spine and work isometrically to keep your torso upright and your posture stable under the bar. They also contract to extend the spine as you stand up out of the bottom. Let them give out and your back rounds, which is where squats start to get risky.
Abdominals
Your core, including the rectus abdominis, obliques, and transverse abdominis, braces to keep your spine stable and your torso upright through the rep. Keep it tight and you stop yourself folding forward or leaning back under load. A weak core makes it hard to hold position and transfers less force from your legs to the bar, which caps how much weight you can move.
To shore it up, here are the best ways to grow underdeveloped core muscles.
Trapezius
The traps are a secondary muscle the back squat hits indirectly. They contract across your upper back to hold the bar in place and keep it from sliding. Weak traps make it tough to stay upright under a heavy bar, and that posture breakdown is how form falls apart and injuries creep in. Our guide to the best ways to grow underdeveloped traps can help you build a stronger shelf for the bar.
Back Squats Muscles Worked FAQs
The back squat works the most muscle of any variation, which is why it’s the default for building lower-body strength and size. Switching variations shifts the emphasis around and keeps your training from going stale.
The front squat and goblet squat load the quads and core harder while keeping your torso upright. The split squat trains one leg at a time, so it’s the one for evening out a side-to-side imbalance. The bodyweight squat is where beginners should start to groove the pattern, and it doubles as a warm-up once you’re more advanced.
Both build serious strength and size in your lower body, so it comes down to your leverages and what you’re training for.
The low-bar squat sits the bar lower on your back and forces more forward lean, which brings the hamstrings, glutes, and lower back into it more. The high-bar squat keeps you more upright with the bar higher on your traps, so it leans harder on the quads.
How much any one muscle fires still comes down to your own build, your technique, and how long you’ve been training.
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