EXECUTION
Assume a standing position with the barbell resting on your upper trapezius. Use a wider than shoulder width grip.
Feet should be flat on the floor, slightly turned outward, and shoulder width apart. Your weight should be equally distributed on both feet.
Inhale slightly more than usual and hold your breath as you lower the body into the squat. As you lower the body keep your erectors (lower back muscles) contracted to maintain the normal slightly arched curvature in the lumbar area. Do not contract your abdominals.
As you begin the descent, move your hips first to the rear and then straight down. Your torso should incline no more than 45 degrees forward.
Lower the body into the squat until the thighs are level to the floor or until you can no longer maintain the normal lumbar spine curvature.
Keep holding your breath as you make the transition from the down phase to the up phase. Drive forcefully with the legs to make the change distinct but yet smooth.
Exhale as you pass the most difficult part of the up phase and as you return to the start position.
Be sure to maintain a slightly arched lumbar spine curvature during the descent and ascent.
Look directly forward during execution to maintain the lumbar curvature and your balance.
WORKOUT TIPS
For lower back safety and for effective execution of the squat be sure that you maintain the normal (slightly arched) curvature of the lumbar spine. If you round the spine you increase the chances of injury to the discs greatly. When you maintain normal curvature, your spine can withstand thousands of pounds of force in a very safe manner.
Inhaling slightly more than usual and holding your breath helps to stabilize the trunk and maintain spinal curvature. In addition, you create up to 20% greater force and create a firm connection between the legs and the barbell, i.e. as the legs straighten, the barbell is raised.
Be sure that your feet remain in full contact with the floor and the knees remain over the feet as you go into the descent. If the knees go forward of the foot, as for example when you place a plate under the heel, excessive stress is placed on the knees and can be injurious.
Be sure you maintain the head in proper alignment with the trunk. To do this, keep your vision focused forward. If you look down you get contraction of the abdominals which can round the spine and eliminate the curvature in the lumbar spine making it weak and more susceptible to injury. Looking up may hyperextend the spine excessively and you may lose orientation of your surroundings and lose stability.
For successful execution you should not pause in the bottom position. Make the transition from the down phase to the up phase quick and smooth with no abrupt or bouncy movements that can hurt the knees. Making a quick change in the bottom position also utilizes the energy built up in the down phase in the eccentric contraction and returns it in the concentric muscle shortening contraction as you rise up.
If you use very heavy weights be sure to exhale forcefully after you pass the most difficult point on the up phase.
Do not use excessively heavy weights. Doing so forces you to round your spine or to make other movements such as a twisting action when trying to push the bar up that can be injurious.
To strongly involve the gluteus maximus and hamstring muscles you must go to at least the thigh level position or slightly below. However, be sure you do not round the spine in so doing. Understand that when you have a rounded back the hamstring and gluteus maximus muscles will not be strongly activated until you go even deeper. Holding the spine in its normal curvature activates both of these muscles sooner.
Primary Muscles Involved
The quadriceps muscle group, located on the front of the thigh, it is made up of the vastus lateralis and medialis muscles whose mass is located close to the knee joint on both sides. They are commonly known as the teardrop muscles. Also active is the vastus intermedius whose mass is higher up in the middle of thigh and the rectus femoris which runs the length of the thigh. It crosses the hip joint and has an action at both the knee and hip. In the hip joint, the gluteus maximus and hamstring muscles are strongly involved if you go sufficiently deep (thigh-level or below). The gluteus maximus is the large muscle of the buttocks, the muscle that you sit on. The hamstrings are composed of three separate muscles, which includes the biceps femoris, semitendinosus and semimembranosus. These muscles cross the sides of the knee before inserting on the lower leg and provide lateral stability to the knee. The erector spinae of the lower back situated on both sides of the spine is involved isometrically to hold the normal curvature of the lumbar spine.
Muscle/Joint Actions
The quadriceps is involved in knee joint extension in which the thigh moves away from the shin. In the hip joint the gluteus maximus and hamstrings are involved in hip joint extension in which the thighs move from a parallel or below parallel position to the vertical to bring the pelvic girdle and trunk in line with the legs and upper body. The erector spinae muscles, especially in the lumbar area of the spine, remain under isometric contraction to maintain the normal curvature of the spine.
Sports Uses
The squat is one of the best exercises to develop and define the anterior thigh, buttocks and hamstring muscles. The muscles and actions involved are responsible for lowering and raising the body as when lifting weights off the floor. The muscles and actions are used in the deadlift and squat events in powerlifting and in the snatch and clean and jerk in weightlifting. Knee and hip joint extension and the muscles involved play a very important role in jumping activities for both height and distance, and in leaping and pushing with the lower body. The actions and muscles play a role in running and cutting actions. Thus, the squat plays an important role in sports such as the high jump, basketball, volleyball, long jump, diving, track, football, baseball and soccer.