Oakleaf, you hit it on target. People i know who use that phrase are not worrying about recovery periods or trying out a new sport.
Sky King, I am not offended by you, I just think that it's something people say when they have aged poorly, because maybe, unlike most of us, they have not given a thought to the long term effects of their lifestyle on their health. And, I just hate the negativity it projects.
I think I have strong feelings about all of this because when I was a kid and into my teens, I was totally unathletic. I'm still uncoordinated in a lot of ways, but once I had a inkling that I had some endurance ability, my feelings about a lot of stuff has changed. Being fit secretly boosts my ego in a way that could have helped a lot when I was younger.