There was a brief period of time, long ago, when a friend and I would hit the gym before dawn. I've never been a morning person, so the waking up was always the hardest part, but it sure did make the rest of the day feel pretty good.
Nowadays I have precious little reason or motivation to even attempt such a thing, so I tip my hat to those who do. (Except I get to stay up as late as I want drinking beer and farting around on the internet! Yeah yeah!)