The reason that I brought up the subject of fitness and a century is that I have friends that are fairly active and have talked about doing a century with me. I have no doubt that they could complete one. No, they aren't "Zac fit" but they know how to ride a bicycle and I know that they are more fit than I am. However, many of them have this attitude that they must train for a century ride. They think that if they are slow (8-10 hours,) they will be embarrassed. I don't think you have to be bike fit and properly trained to complete a century. If you're goal is a fast century, then yes... you're most likely going to have to train to complete it in less than 5-6 hours. I'm not exactly sure how you would "hurt yourself" by not being properly trained... if you know how to ride and keep your bike upright, I don't see you getting hurt. I couldn't complete the double century... but I didn't get hurt. However, I do know of a rider that had completed several centuries and doubles and was properly trained, but he fell and broke his arm within the first 300 yards of the ride - his fitness had nothing to do with that... just an accident.