These guys are athletes!
I think a person can participate in an athletic activity, even seriously, but not be considered an athlete, unless they are participating in that activity competitively. If the goal of riding is fitness and strength, no matter how hard we are working at it, it is just exercise. It is like the body builders at my gym. They work hard, are reasonably fit, but do nothing with the results of their labor other than look in the mirror. They don't go to body building competitions or weight lifting competition; it is something they do for their own personal gratification. I don't consider them athletes.
Can a person in their 80s who is fitter/faster/stronger than most of their peers and still works at it be considered as much of an athlete as someone in their 20s.
I don't consider myself an athlete any more. I just consider myself fortunate that I am fitter/faster/stronger than most of my peers.