Once again: evaluation at a standstill DOES NOT reveal all cases of back soreness. I said that before. People here said that was <bad word, b word>. It's not. It's not at all. Many back problems do not result in 'tight muscles' at a standstill that a chiro or vet or masseuse can feel. Further, many back problems aren't back problems at all, they're hock problems, or stifle problems. Those are hard to diagnose at a standstill, especially if they're mild or intermittent. This is true of many problems, in fact. Breathing problems, for example, are very different with the horse in motion and tacked up. Soundness is very different at a standstill, vs a walk, vs a trot. Okay. Here's another view of how to make changes. First, with a trainer and vet's input if needed, pick ONE THING to change. The most likely thing to be the problem. Change that one thing, and wait several weeks to see if that is the solution to the problem. If you change a bunch of things, you don't know which change addressed the problem. But honestly? Usually when people make a bunch of changes, none of them works. Why? Usually because they aren't working off an actual diagnosis or an expert who sees the horse and examines him and watches you ride him. A laundry list from the internet isn't the same. Unfortunately, the reason a horse is sour is not always 'ulcers,' 'you're working him too hard/you're not sensitive to his needs/he needs more fun time/you are not bonded enough' or 'you need to watch XYZ video from Guru Trainer Joe.' WHAT to change? The one thing that looks most likely to solve the problem. How do I decide what that is? Let's say my horse were pinning his ears and acting sour, I would watch HOW he is sour, and when. I'd get into more detail. I'd observe. I'd watch how he acts when I come in the stall...is that when he seems 'sour?' How he acts when I get on, and I'd have someone else get on him so I could watch very carefully, those first 2-3 steps away from the mounting block(or after the person gets on, if she/he doesn't use a mounting block). Those first 2-3 steps are crucial. I'd observe exactly WHEN the sour behavior occurs, and when it does NOT occur. I'd break it down a lot further than 'sour.' I'd look at exactly what he was doing. Pinning his ears and biting as I got on? Walking away from the mounting block like he has a diaper-full? Fussing when FIRST asked to trot? Pinning his ears when asked to canter? I'd break it down into detail. That's how I'd decide what to change. But the key is, I'd change one thing at a time. Then I'd wait, and observe. Did it work? How well? Again, WHAT I chose to change, would be based on a lot of careful observation, possibly consulting with vet and trainer...and deciding that I had found something specific to respond to, and a specific way to respond to it. I'd also consider the possibility that he, like some horses, might get bossy or fussy at times. This can be a temperament thing. Or maybe there are physical reasons. I had a horse like that. There was a fix for him. He had a little arthritis in his hocks, a little arthritis in his ankles, "barely rises to the level of age appropriate changes," I was told. A little loss of peripheral vision. No one thing of it was serious, in and of itself. "None of this accounts sufficiently for his behavior," I was told. "What am I gonna DO with him?" I asked the vet. "Drop him down. Don't retire him, he needs to move." So he went to a lower level, pet home. He didn't do so well there, either. He was retired. He was still crabby and sour. My other friend's horse was like that, too. And there was no fix for him. He would snap at you when you were grooming him or tacking him up. He would kick out when you girthed him up. The first couple times you asked him to pick up a trot in the ride, he'd pin his ears back as if to say, 'You better back off, you know how I can get.' She had tried about fifty bazzillion different things - different girths, saddles, different bits, bridles, nosebands, different ways of getting on, the vet had gone over the horse a bazzillion times, there had been xrays, MRIs, ultrasounds, dentist specialists, chiropractors, big-time veterinary clinics, different trainers, all kinds of specialists(and a few self-proclaimed miracle workers, lol), all of it, for years. Finally, an elderly trainer listened to her years-long tale of woe, and told her, "He's just an <bad word>, you know? That's just how he is." I was grooming him once. He turned around to snap at me. He meant business. "Knock it off," I growled. He did it again. I smacked him very lightly on the shoulder with my hand and said, "Knock it OFF." He stopped. He stood there like a little lamby pie for 45 minutes. Butter wouldn't melt in his mouth, as they say. What a little stinker. He was a bully. A crabby bully. There was nothing wrong with him. That was just his temperament. I hear he was an absolute machine cross country. Mad as hades, too. Just 'get out of my way, I'm DOING THIS!' Never refused a fence. The bottom line is this. Enlist some experts in looking at the horse (in person, not on a website). Get ONE idea. Change ONE thing. Wait two weeks. See if it works. Then change something else. See if that works.