If you're a middle-ager, it's increasingly likely that you or one of your friends will run a marathon. Folks in the 40-plus group are pretty much taking over the sport, accounting for a surprising 43% of all marathoners in the U.S. in 2004--up from 26% in 1980. The maturing baby-boom generation partly explains that growth. There are simply more folks over 40 out there. Yet there's more than demographics at work. Surging interest in marathons at middle age and beyond testifies to our longer, healthier lives and our growing determination to get the most out of that bonus time.
How much healthier...