Originally Posted by Gidji
Some pilates instructors also run Horse-riders classes which do specific exercises that target the muscles you use.
That's the sort of thing I meant, specific exercises for horse-riding muscles, though I'm far enough out of town that going to actual classes would be a bit of a hassle.
The rest seem to be more general conditioning exercises, which I do already. I've done yoga since my teens, do my weights &c when I have time left from the hiking, biking, and other activities, and otherwise generally stay in pretty good condition.