How do you get confused between chores and sports? The differences are obvious!
I think you are confused about what constitutes a "sport". If I go for a 30 mile ride in 5 or 6 hours I've given my horse a real good workout and if it's warm enough might even work up a sweat, but that doesn't make it a sport.
You came out saying
We finally have proof!
... that riding is a sport.
Doug Payne has posted a helmet cam video in which he's wearing a heart monitor, and it shows his heart working at about 88% capacity throughout. I don't know a lot about sports but I bet that's more than most people would expect."
Well, I hate to say it, but the only thing you have proof of there is that Dog Payne (whoever he is) had an elevated heart rate while riding cross country. Now....tell me how much of that was from "work" and how much from adrenaline? Riding a horse is not, in and of itself, a sport.
The rate of a heart beat means absolutely nothing with regards to something be a sport.
NASCAR is a sport (whether I think so or not), but that doesn't make driving my car a sport.
Shooting can be a sport, but qualifying with the M16A1 rifle is not (even though your shooting for score in both cases)
So actually, in point of fact, I'm not sure what you have proof of beyond that the gentleman's heart was beating at a certain rate, but you've presented no proof that riding a horse is a sport. People have always said that the horse does all the work (and from a point of view it does). That doesn't preclude certain competitive horseback riding activities from being a sport. A 10 mile Competitive Trail Ride on an easy trail will likely meet the definition of a sport while going on a 25 mile trail ride with friends over a very difficult trail is not going to be a sport (regardless of how much more you exert yourself or how fast your heart is beating )