How do dressage riders get high scores? How does someone cut a cow? How does an eventer run a course? Because they are controlling 100% of the horses movement.
I don't think so. Perhaps we have different ideas of what's meant by "control"? Take for instance the cutting horse: I don't think the cowboy (or girl) riding that horse is 100% in control of every part of the horse's body. Rather, the horse has learned to do the job of cutting, and does it with little direction from the rider, who is concentrating on his part of the job. If the rider was controlling 100% of the horse's body, then an experienced cowperson should be able to do cutting on any healthy horse, an experienced dressage rider would get the same scores riding any horse, etc.
Really, I wouldn't even know how to control my horse's body parts. I just tell her "walk", "trot", "canter", etc, and she handles the business of making her legs move appropriately. I don't control the parts
, I control (usually: sometimes there's a little discussion
) the intention.
The other point here is where people learn. Some don't have access to arenas, or even nice open fields. In my case, the first time I rode was on a trail (actually a nice, smooth dirt road).