James, how does your horse get anywhere on the trail? When does it know to turn around and go home? Are you just a passenger letting the horse go wherever it wants to? How do you turn left? How do you back up?
She gets places by putting one foot in front of the other. Now I may tell her what pace to go, to move to one side or another, to take the left fork instead of the right, to follow a particular path through trees & bushes when we're off-trail - but I'm NOT telling her which foot goes first. Or sometimes I may indeed just be a passenger, talking with my friend or admiring the scenery while she does the walking. If I want to turn left, I tell
her to turn. I don't control each body part that has to move in order to make that turn. I wouldn't even know how to control the parts.
Are you riding a green horse or an experienced trail horse? Do you think you could just tell a green horse walk, trot, canter? Clearly, you are reaping the rewards of someone's hard work.
She's an experienced horse, but not, I think, an experienced trail horse. I don't know any of her history before I got her, other than that she spent several years living in a field and not being ridden, but I suspect that at one point she may have been trained for dressage or showing. Certainly a lot of things out on the trails seem new to her.
There's an example of intention vs control of body parts. The first time we came to a creek (just a little one, about a foot wide), she would not cross it. I could not (not surprising given my inexperience) get her to cross, nor could my vastly more experienced buddy/teacher. But after about half an hour of trying, I got off and led her back & forth across it a dozen times, then got back on and she went right over and has never had a problem with creek crossing since.
Now if I'd had that 100% control you talk about, she should have gone across that scary thing right away, no? Suppose the next scary thing that I pushed her into turned out to be a serious hazard?
I agree, it's training, but what exactly are you training for? There I did a little bit of training to teach her that little creeks aren't a threat, and it's ok to jump over or wade through them. I didn't do 100% control of body parts: "Ok, bunch up your hind quarters, and extend your front legs while pushing off from the rear, and now when the front hooves hit the ground pull the back legs in..."
And how would you teach creek-crossing in an arena, anyway? Or how to react to cows, deer, cattle guards...?