This NY-Times article makes a pretty good case. It also tells us what Jack Lalane is up to at 93years old:
Mr. LaLanne, who once set a world record by doing 1,000 push-ups in 23 minutes, still does push-ups as part of his daily workout. Now he balances his feet and each hand on three chairs. "That way I can go way down, even lower than if I was on the floor,” he said. “That’s really tough.”
Mr. Lalane, I salute you.