So in establishing a baseline and watching your horse move, how do we know WHAT to look for? What tells us IF the horse is moving in a balanced way? This is part of developing an 'eye' for it. Learning what to look for and what you're looking at.
At the walk, the hind feet should be overstepping where the front feet are on the ground. What do you mean, you might ask? As the horse walks forward, the hind foot comes forward and should land on or in front of the place on the ground where the front hoof on that side was already at. Over-step. Stepping Over where the front hoof was. The walk as it is developed more, will become more fluid and reaching. The stride will lengthen and the horse will naturally cover more ground. Kat has a beautiful extended walk. It didn't just happen overnight, but now that it is there, programed and ingrained in his mind, it's there for life.
So now what about the trot? If you take a picture of the horse in motion at the trot, when the horse is balanced, you *should* be able to draw parrallel lines thru the pairs of legs on the diagonals. From the knee to the pastern and hock to the pastern, the legs should be moving in a parallel and symmetrical motion. The horse may also reach forward and down, lifting the shoulders and stretching the back. When the horse does this it can be exciting as they move quite beautifully. This movement is what you're ultimately looking for.
Unfortunately it doesn't always happen right out of the gate. Even once you get this movement, it's an ongoing process of teaching the horse to maintain it. Part of it is developing the muscles for the horse to be able to maintain it. It's not like we can go out and run a marathon without preparing for it, right? So be reasonable about what you're asking and expecting from the horse.
One of the coolest things I've seen in training Kat and moving us up a level in competition, and this happened early on and still holds true today, is that once he learned to start using his body in the lines and then between the shafts, he continues to use his body differently even when he's turned out. Or maybe it happened the other way around and he moved balanced and fluid in turnout, I just figured out how to finally get it in harness.
Something else my pony did in the mornings when I fed, was that he would stretch all on his own. As I pulled in, I could see him stand up straight and arch his neck with his chin to his chest and he'd hold that for a few seconds before shifting back into the downward dog position for yoga. Again he would hold that stretch for a few seconds too. I always told him what a good boy he was and tried to be verbally excited about it with him. The barn he's at now, I can't see if he's still doing it or not. Bummer!