A recent affliction of the eye has left me unable to ride my little bicycle out in the real world. Instead, the miles passing beneth my wheels have been virtual...in the basement, on the trainer. While, at this time of year, the trainer has some advantages, it sure does get boring. After an hour-and-a- half, my will to live starts to wane. The two-hour mark seems to be my psychic limit, and I have to take a break of an hour or so before getting back on. Usually, this time of year, I am getting in rides of three-and-a- half to five hours. Now, on a good day I get in three or four, and that's with an hour break in there. So the question is, from a training standpoint, how much difference is there between an uninterrupted four-hour ride, and four hours, with an hour break somewhere in there?