Before I sat behind a desk & the wheel of a car 18hrs a day, I was a time trialist & I used to race triathlons.
The most I did was 160 miles a day on a bike, 540 in a week twice (SF to LA) and a Half Ironman.
I never got to this level but it always fascinated me.
http://www.cervelo.com/movie.aspx?id=1
But, I've been working out solid for a month & I'm getting my fat ass on a bike every day of the tour just to see if I still got it in me. I'll report my miles & embarassing average speeds here on this thread till Paris... who is with me?