I don't know if anybody reads it, but the Road Bike Rider website (http://www.roadbikerider.com/) has a long debate going on in their newsletters. If you search you can find the info. The doctors they have interviewed suggest that the problem comes from a lack of weight-bearing exercise in the legs. They also suggest that minimal weight-bearing workouts, such as one run a week, can countermand the effects. The problem only applies, according to their research, to people who get no exercise off the bike. If you think about it, osteoporosis isn't a problem for the average man, so as long as you don't live on a bike you should be OK.