I'm sure this is a very very dumb question, so please forgive it.

I'm doing a few exercises with free weights. The instructions say to exhale while you're lifting and inhale while you're lowering, which seems counterintuitive, or at least unnatural, to me. (Not that it has to be natural, but...) My instinct is to breathe when I lift and let out when I let down. I'm sure there's a scientific reason for the reverse. Could someone explain it?

The fact that I'm totally uncoordinated doesn't help.....