Running (and other exercise) helps you take care of your bones?

Another way exercise is good for you: it's good for long-term bone density, according to this New York Times piece sent to me by a running buddy of mine. I'd like to think that if the science here bears true that maybe folks who exercise will be less likely to break bones and have related issues when we are senior citizens. Besides, as a mom who will be in her early 60s when her youngest kid graduates from high school (she is due next month!), I need to stay strong to keep up!