A running friend of long standing--we met in the last half mile of a 50-miler in 1982--said a few years ago that her knees aren't up to much more than two or th

A running friend of long standing--we met in the last half mile of a 50-miler in 1982--said a few years ago that her knees aren't up to much more than two or three miles with the dogs lately. Now, she was a much more serious ultra-runner than I ever was: I took away from the 50 the knowledge that I really didn't enjoy that distance; she did at least one 100 (in less than 24 hours) and a multi-day run longer than that. But as HN likes to day, the plural of anecdote is not data. Nor the dual: but for what it's worth, I haven't run a marathon since 1986, not have I stopped running.