Quote Originally Posted by Mike T View Post
It certainly feels like you are about to pass out, and I may have done so once. I had an unexplained fall on top of Fairfield - running up from Cofa Pike, I came across a couple heading towards me, held my breath, the next thing I was on the ground, scraping my shoulder on rocks. I don't remember tripping.

Breath holding is followed by slowing down, rapid breathing, and a sense of light headedness - lasts 5 - 8 seconds, but feels longer - as I say, no fun.
Don't do it then!