One of the books I read some time ago offered a solution. It was either...
1. Overdosed America, the Broken Promise of American Medicine by Dr. John Abramson.
viewtopic.php?p=14166#p14166 and
http://www.overdosedamerica.com/?m=0
or
2. Selling Sickness by Ray Moynihan and Alan Cassels
viewtopic.php?t=2131
Unfortunately, it's been so long since I've read these books that I don't remember the exact recommendation. It's also possible that it was a different book.
At this time, I would say the following. Bones are living organs of the body. They are not just simple scaffolding. As such, bones respond to stress or the lack thereof. This can be problematic for astronauts that spend time in microgravity on the space station. Their bones become weak and decalcified. Conversely, increased physical stress will lead to bones responding with increased strength and density. I would recommend exercise that increases physical stress. This would rule out aerobic exercise such as using an exercise bike (although aerobic exercise has its own benefits, bone stress isn't a leading characteristic).
