A 21 year study at my alma mater (Stanford University) found that elderly runners have fewer disabilities, a longer span of active life and are half as likely as nonrunners to die early deaths. The study began with all subjects older than 50. The farther the study went, the greater the gap in the abilities of the runners over the nonrunners. The initial disability of the runners averaged 16 years later than the nonrunners. My take is that exercise not only helps you live longer but perhaps more importantly, better.