This seems to be as good a place to post this as any, the other day I was feeling a little sore so when I was standing on a hill I intentionally moved my body back more than usual to stretch out. It seemed like I got a lot more power. Of course, that comes at a price.
I've also heard that pros stand when they are afraid they are going to be attacked. That has never really been of much consequence to me, if I'm attacked on a climb I always just watched them go.