A squat is one of the most effective strength-building, lower-body exercise when done properly. Squats primarily use 3 different muscle groups; your quads, hamstrings, and gluts. In addition to the large muscle groups in your rear and thigh, several other muscles are used to perform a squat. These muscles include: your adductor muscles (adductor magnus, longs, brevis, and gracilis), calve muscles (gastrocnemius and soleus), and your hip flexor muscles.
Quadriceps: The quads are located on the front of your thigh and composed of 4 different muscles (rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius). They extend the knees and flex the hips. When you lower yourself down during a squat, you perform hip flexion, and when you stand up, you perform knee extension, so the quads get worked through the movement.
Hamstrings: The hamstrings consist of 3 different muscles (bicep femoris, semitendinousus, and semimembranosus), which are located on the back of the thigh. The hamstrings function to flex the knee and extend the hip. During a squat, you perform knee flexion as you lower your butt toward the floor. As you rise, you are also working your hamstrings be cause you are extending your hips.
Glutes: The glues are commonly referred to as the buttocks. It contains 3 muscles as well, (the gluteus maximus, medius, and minimus). All these segments get worked during a squat. The main function of the glutes is to extend the hips. Secondary Muscles
Adductors: The adductors, which are found on the inside of the thigh are made up of 4 muscles (adductor magnus, longus, brevis, and gracilis). Collectively, these muscles are known as the adductors and their main function is to move the thigh inward.
Calves: The calves consist of 2 muscles (the gastrocnemius and soleus). The main function of these muscles is plantar flexion, which takes place when you point your toes downward. When you perform a squat, the calves are recruited isometrically to keep the lower legs stable.
Hip flexors: The hip flexors are small muscles that run over the hip bones toward the thighs. As the name implies, they function to flex the hip. In a similar fashion to the quads, they get worked when you move your thigh toward your body.