The barbell back squat is the big mama of the squat, the one that all of the variations originate from. In performing barbell back squats, you center both the barbell and the trunk's center of gravity between the hip and knee. This exercise requires that many joints function and therefore activates many muscles, some even in your upper body and trunk. However, squats primarily stress the quads and glutes.
Place a barbell on the squat rack so that it is somewhat even with the collarbone.
Grip the bar with a wider than shoulder-width grip and pull the body under the bar so that the bar rests on the upper back.
Position the feet comfortably, approximately shoulder-width apart.
Inhale and bend the knees and hips to lower the body under control into a squat position.
Keep head up, heels on the ground, and back slightly arched.
After squatting as deeply as you can, quickly reverse direction and exhale through the sticking point (the most difficult part of the movement). Do not bounce out of the bottom position.