I don't like to hate on any exercise subcultures, but there's a certain set of bike guys--usually middle-aged, serious amateurs tricked out with expensive gear and even more expensive bikes--who just seem to radiate an annoying smugness about their ability to bang out a century or two every weekend. I've had examples of this breed--complete strangers--stop me as I'm sweating my way up a hill to critique my use of gears (I don't like to downshift. So sue me.)
But this week, I feel bad for those guys. Because as annoying as they might be, nobody deserves to have their bones turn into lace.
It turns out that competitive male road cyclists have lower than average bone densities in their spines. They also develop osteoporosis at higher rates than than other physically active males. Apparently this is because road cycling, being low-impact, does not put enough stress on the bones to make them grow stronger. Mountain biking, however, does seem to provide some protection from osteoporosis.
So if you're addicted to a low-impact sport like cycling or swimming, consider adding a bit of jogging to your routine. Or, you could always consider one of the best bone-builders around--weight training. I'm still available as a lifting partner ...