(This exercise can also be done without barbell / weights)
Lifting a barbell off of a weight rack, position it on your shoulders. Place your feet slightly wider than shoulder width apart with your knees and toes pointed slightly outward. Drawing your abs in descend slowly by bending at the knees and hips as if you are sitting down (squatting). Lower yourself as far as you can control without letting your body shift towards your toes (this will cause you to loose balance). Pause in the downward position and slowly return upright to the starting position.