when i was on the US development team(for alpine skiing not cycling) the coaches/trainers advised us to stay away from sex when we were at races and training situations. i believe the only reason for this was lack of sleep, or just to stay rested up. when i moved up to the senior rankings and numerous teams i never heard anything more about it, they just left what we were doing on our personal time up to us. i dont think having tons of sex or a massive lack of sex really makes a difference as long as your rested up when you need to compete/train... on second thought a massive lack of sex may screw with your performance, ha