Cycling, with all it's troubles, is an incredibly demanding sport, which is part of the problem I guess. Competitors have an almost freakish intake of oxygen to their bloodstream. They're just not like other people, even top conditioned athletes in other sports. Even within the ranks, they hit the mountains and some just walk away from others. Doping, drugs and steroids notwithstanding, these people are self-selected for a kind of superhuman metabolism. With all the shenanigans, you don't know just what you're watching, but I can't deny it's interesting.