What's the right to squat: Focus on driving up and down, or on sticking one's backside out?
From what guys at the gym say, and many pictures online, you need to be sticking yourself out. Yet from Starting Strength's instructions: focusing on tightening lower back, chest up, hip drive - it seems to be more of an up down motion, without as much protrusion. Which is correct? Does the backside need to protrude?