Are we talking about the issue of SORING or the dicipline of SADDLESEAT. They are two separate issues completely. Of all the breeds that actively participlate in the dicipline(Saddlebreds, Morgans, Arabs, KMHs, TWHs, Fresians, Andalusians, to name a few) ONE breed is known to sore, and that is the TWH. They are the ONLY breed who "Stack" thier horses, they are the only breed who "sore" thier horses, and they are the only breed(with maybe the exception of the KMH and other strictly gaited breeds) who do not trot.
The thing is, you cannot sore a Trotting horse.
Since I only know Saddlebreds, and only show Saddleseat(I'll add another dicipline soon), I will tell you how you can tell if a Saddlebred is sore(not sorED). And you CAN very easily, tell.
If a saddlebred is sore, he will travel "off". He will pick up his legs unevenly, meaning one knee will raise higher than the other.
If a saddlebred is sore, his head will bob noticeably when he steps on his sore foot.
If a saddlebred is sore he will not "use his legs", meaning he will not pick his feet up as high as he normally does.
A horse with great pain in his feet will have a tendency to lay down a lot and be reluctant or have trouble getting up. Do not mistake this for a sleeping horse. A lot of my horses, especially the younger ones, will sleep laying down noticeably more. Shows are stressful, and take a lot out of one.
As to them not picking thier feet up high naturally, meet my yearling Zoltan. He travels like this every day with no encouraging. Notice, no shoes, no chains, no stretchies....This colt has never seen a pair of chains yet, though he will when he is put in training to help develop his timing.
And here is Daniel, on his first outing after surviving Joint Ill in his stifle. If ANY horse would have a reason to be sore, this boy would have. He recovered fully, to our surprise and that of our vet. And he is turning out to be a FINE colt.
Being high stepping and high headed is what we BREED for. And if we are smart, we do a pretty good job at it.
And horse_luver, you are actually quite wrong about people adding a bunch of weight and then taking it off suddenly to make them pick thier feet higher, because it wouldn't work.
Horses pull against pressure, so "in theory" adding weight will make them lift their legs higher, and taking it off will do just the opposite, especially after the addition of weight.
The idea with saddlebreds is to achieve that high step without much weight. With careful breeding and good training, this can and is accomplished.
CH My-My, one of the greatest Saddlebreds in history, and trained by one of the greatest Saddlebred trainers in history, wore 12 oz shoes. One year at the Championships, she threw a shoe in the warm up ring, and instead of risking her performance to the show farrier, he had him pull the other shoe. She won that year barefoot. Her trainer was no stranger to strange shoeing either.