I'm not just talking about soring. Yeah, that's obvious that some are sored. But the overall stress that lifting their limbs ridiculously high brings upon their bodies. If horses were meant to march high like that, they'd do it naturally. Now imagine lifting your limbs high like that whilst carrying a human upon your back that's being stressed from every flexation of your muscles whenever you lift your limbs high like that. That can cause major spinal issues for some horses, and others can end up crippled. In all it's a stressful sport for their bodies. Then of course, so are many others so. ;Shrug.;
Many diciplines put stress on a horse. That's what conditioning is for.
I am from the saddlebred world......they DO move like that naturally. I personally don't like the big shoe packages either ( My saddle seat horse trots level and square barefoot, hasnt had a shoe since I've had her) , but they don't cause crippled horses unless someone ignorant ran them into the ground without the proper conditioning. I know of many horses that worked until late 20s....its no diffrent than any other dicipline......they all have skeletons in the closet.
Asking a horse to drop its head, causes pressure along the back, but if conditioned and muscled properly its not a problem. Its about the muscling to do the job. Not much in the horse world doesnt stress a horses body in one way or another.