Early extension is when your hips move forward towards the ball on your down swing. This will often make you come up away form the ball creating a hook or a block. All very technical…..Its going to help you keep a good swing plane throughout so you can generate greater force and consistency with your shots.
Try it before you practice and see how you feel. Ideally you should do this each day. You can sometimes feel instant improvements other times it can take 2 weeks or so.
Start by rolling a bath towel up very very tightly. Then lay on your back with the knees bent and place the towel in the middle of the upper back.
Support your head with both hands so that the chin can stay tucked throughout the movement.
Breathe in, then as you exhale slowly allow your upper body to wrap around the towel (you may feel a little discomfort where the towel is).
Hold this for 10 seconds then slowly raise yourself up, just enough that you can roll down about an inch on the towel (the towel moves up). Then repeat. Keep repeating this until the towel is in line with your armpits.