Eccentric in the realm of exercise refers to the downward motion of a particular movement. During the squat, the eccentric phase is the first part of the exercise, as you bend your hips and legs to lower your body. Learning which are the eccentric muscles during the squat will help you determine where to focus your mind as you engage in the squat.
Quadriceps Means Four Muscles
The first of the four primary movers during the squat are the quadriceps. This is a group of four muscles: vastus medialis, vastus lateralis, vastus intermedius and rectus femoris. All of these muscles reside in your front thigh region, and they are lengthened when you bend your knees during the squat. The more you bend your knees, the more you will lengthen your quadriceps. Always bend your knees at least to 90 degrees when you squat to reap the most benefits from the movement.
Gluteus Maximus, or the Butt Muscle
The second primary muscle of the squat is the gluteus maximus, which is the largest muscle of your butt. When you squat, this muscle is stretched during the eccentric phase because you are moving your hip joint forward. The further you squat down, the more you will stretch your gluteus maximus. Also, the more you lean your torso forward during the eccentric phase of the squat, the more you will lengthen this muscle.
Adductor Magnus is "In"
Another primary squatting muscle that is stretched due to movement of your hips is the adductor magnus of your inner thighs. When you squat down, your thighs move further apart and that causes this muscle to lengthen. If you have a close foot stance while squatting, then the stretch on the adductor magnus will be minimal. The wider your foot stance, the greater this stretch will be. Don't utilize a wide stance unless you have flexible hips and legs.
Sole Muscle Left
The smallest of the four eccentric muscles during the squat is the soleus. This muscle is located at the back of your lower legs and is a part of the calves. During the downward portion of the squat, your ankle become more and more flexed due to the forward movement of the joint. This motion stretches the soleus. To amplify the stretch on this muscle, squat as deep as possible while keeping your feet flat on the ground.