I think English race horses have it better than American ones. They live at home, they train on the local gallops, in the countryside, they haul out for a day of racing and come home to their own stables at night. I don't know how much turn-out time they get (American race horses get next to none, I think).
I have read that racing greyhounds are kept crated almost all the time they're not on the track, but I don't know if that's true or not. The only greyhounds I've known were rescues -- and couch potatoes!
But the fact that these guys lose their riders and keep on running and jumping for miles tells me they don't exactly hate racing, and must be in good health or they couldn't keep up:
Herd instinct might keep a horse running with the others, but for a horse at liberty to jump means he must enjoy jumping.