I wonder if someone could speak a bit more towards the physiological aspect of doing the IBR. I just got back from an 8 day, 6,000 mile tour of the west and was surprised to find that I had lost 6 pounds, despite being well hydrated. I can't imagine what an 11 day tour with many more miles per day does to a body. What can these folks expect? What parts of the body break down the most? How do they combat the ill effects of long days in the saddle?
I can't speak to the IBR, but I can tell you how to manage multi-day, multi-thousand mile rides ... although you just did one
I just completed a 48/10 in 9 days. That amounted to around 7500 miles in that time, then another 660 miles home.
I found out, and quickly, that the two of the critical factors are managing sleep and food. Eating fresh food, in small amounts but regularly along with maintaining good levels of hydration is half the battle. You should not be needing to pee any more or less than normal - and it should remain the normal color. Anything else and you are storing up trouble, including horrible constipation (yeah, I know this is not a nice subject), for later.
The same applies to sleep. If you start a major ride on little sleep (anticipation nerves), then ride a relatively easy first day, stop and sleep. You'll be good to go after that. A full sleep cycle is about 90 mins. You need multiples of these to stay alert. Two cycles is generally the minimum you can get away with for a few days, but at some point you will need six or 8 hours sleep. Short naps can help, but only once before you need sleep.
Many people vary on this. You need to learn what works for you but if you stay hydrated, rested and fed, you can remain on the bike almost indefinitely.
All of the above is really for the more extreme rides. An easier schedule of, say, 600 miles a day gives lots of time to eat and sleep normally.
The psychological part is tougher.
You have to find a way of staying on the bike when every fibre of your being just wants to stop. Calling home, calling friends, while riding can be a terrific aid. Just keeping your goal in mind helps two ... I imagine that in the IBR they thought of the expense, and that this is your moment, works wonders. When I wanted to quit halfway through my 48/10 due to the extreme pain in my ankles, my wife reminded me that if I quit now I would simply have to do again the 3000 miles already covered.
I play mental games all day while riding. Devise your own they do work very well. I also remind myself that this is supposed to be tough. If it were easy there would be no point, so I always expect it to be very hard, and I am usually ready for that.
"When the going gets tough, the tough get going"