Just one side note -- it's true that cycling is low-impact on your bones, but that can actually be a problem. Studies have shown that both road and mountain racers have extremely low bone density, with guys in their thirties having the bones of a woman in her sixties. You apparently lose the calcium equivalent of a cup of milk for every hour you sweat heavily, so that doesn't help, either.

Anyway, especially as jplum4's going through menopause, I would strongly recommend cross-training. Yes, get that bike -- it's great fun and very empowering. But do other stuff, too -- keep lifting weights, especially free-weights if you can manage it rather than machines. Maybe do some hiking. Eat calcium supplements! I've also started with the calcium supplements, even though I'm only 26. There's a calcium supplement that tastes like a candy chew -- Viactiv, www.viactiv.com -- has a bit of a weird aftertaste, but good calcium content.

Cycling is great, awesome, a wonderful exercise -- I strongly encourage you to get a bike. But make sure you do more impactful stuff, too. (I wish I could get a bone density test, but at my age they're apparently not covered by insurance. Bah! I'd like to know *before* there's a problem.)