Originally Posted by thingstodo

If you have that breath just before you contract you can use it in a psychological way as part of the contraction. You then breath in in the reverse mode. Like others have said, a contraction is the push on a pushing movement and the pull on a pulling movement. So on a bench press movement, take a deep breath (with your diaphragm) right before you press and then let it out as you go through the contraction. Air is a fuel used at one point in time.

And I think the point is to grow muscle, not the body cavity area.