If you feel any "crunchies" in your shoulders while doing this, then try to outwardly rotate your arms more by placing the thumbs on the wall. It's like you have a bowl of soup in your hand and you are trying to spill it behind you. The technical term is supination of the hand and external rotation of the humerus (upper arm bone).
If this is easy than you may be sticking out your ribs. My next post will go into the details of why rib thrusting is a bad idea. In the meantime, practice makes perfect.
Here's a link to a previous shoulder health essay. Lot's of pictures!
