Turned 50 in '06. Had back issues in '05, PT told me bicycling wasn't a good idea. Didn't do much riding at the time so it didn't bother me. Walked about 3mi/day.

Started gaining weight. In '08, circumstances forced me to ride in the heat to fetch parts for my car. End of day calculating calories I thought, "What?"

Burned more calories riding than possible walking. Back felt fine. Started riding again. It was great!

Slowing down the last couple of years.