One Simple Tip To Avoid Shoulder Pain
Posted on July 2, 2012
... retract those blades, keep that joint in a secure position.
Example:
When benching, don't bench too much. And don't EVER bring your arm forward, if you feel your scapulae sliding sideways and forward, you're pushing too far forward.
It should look like this:

The picture on the right is correct, see those shoulders being pulled back.
Good luck making those pecs summer ready!
JVB