Set-up: Set up inside of a power-rack and set the safety pins to just above hip-height. Put the bar on pins at a point that is easy to contact, somewhere between your shoulders and the middle of your back. Set your feet at twice hip width width and point your toes out slightly - in-line with your knees. Duck underneath and in front of the bar, raise your chest, brace your stomach and establish a netural spine posture. Grip the bar with your hands at roughly twice shoulder width. Select the grip that gives you the most control and stability.
Lift: From this position lift the bar out of the pins driving through the legs. While maintaining a neutral spine position and tight brace through the core, descend until your upper legs are parallel to the floor. Drive the weight up in a straight-line.
Emphasis: Brace through your core at all times. Keep a neutral spine throughout the duration of the movement - if a neutral spine cannot be maintained, either reduce the weight or shorten the range of motion. Do not let the knees cave inward on the movement.
Muscle Roles in back squat - wide stance - parallel depth