Cyclists go for days on end with little or no sleep, pushing themselves into total physical and mental exhaustion. There was an incredibly sad scene where one rider was killed by a car. Another dropped out due to pnumonia, another had foam pieces taped around his neck to ease pain and one rider hallucinated to the extent of having to pull off the road to rest after being chased by dolphins. Typically 48% of cyclists finish the race, and those who do turn themselves inside out to do it.
Lance Armstrong commented that endurance athletes are trying to run away from themselves. I agree with this. All the riders interviewed did not come off as nut cases, but rather as athletes in top form. But there must be something that would make somebody want to spend that much time on a bike. I can tell you that, for me, 100 miles is plenty. Although I can appreciate what the mind & body must go through in this race. It is mind blowing and intense.
If you get a chance, do see this film. It is well made and has a lot of interviews with the riders and race coverage.