FILL IN THE GAP TO STRAIGHTEN THE SPINE
To check if your spine has too much curvature when you set up to the ball, get into your address posture and hold a clubshaft down the center of your back. If there is a large gap between the shaft and your lower back (more than two fingers wide), you are in an S-posture. Or if you can't lay most of the shaft against your back, you're hunched over. Adjust your posture so the shaft lies flat.