"Some of the racers, young men in their 20s, had osteopenia in their spines, a medical condition only one step below full-blown osteoporosis... [M]ost recreational cyclists probably don’t need to worry too much about their bones.... [Elite racers] train for hours at a very high intensity. They sweat a lot. They never go for runs. They don’t usually do much weight-lifting... They’re strange."
Bikers, do some bone-stressing things before your bones decide they aren't needed!