Bruce,
I think that was an overstatement regarding Bob R. I think he hiked well into his upper 70s, not quite 80s.

Then there is Hulda Crooks who climbed Mount Whitney 23 times between the ages of 65 and 91.

I'm 65 now, and my right knee has shut down my jogging, and descending peaks has become a challenge. I was jogging 10 miles per week just a year ago.

Good luck and keep going!