Back in the dark ages, I wanted to compete in the toughest running challenges I could find. And there are some major ones out there.

100+ miles out of Death Vally
24 hours running around a track
a marathon a day

My knees don't share this ambition. But I do still try to keep active with walks and using my elliptical. It's not as much as I would like but it's not nothing.

These Olympic athletes are amazing to watch, and a good deal of them are so young and still competing under such pressure.