When I got on, she was no longer sore and was moving normally. But something else was going on that's been sneaking up on us for several days. She was very bracey, doing a lot of pushing on the bit, leaning very hard and not wanting to soften. I think this happens a lot as a horse learns new things that require changing old habits, particularly if the changes are in body posture and carriage which require remodeling of muscles as well as learning. We started with some backing, and it took a while to get things unlocked. She was also bracey at the walk, although after we got 5 good steps I moved right up to trot, since I suspected that it was the higher gaits that were the origin of the problem. In Dawn's case, I think the reversion to the old way of going after having pretty consistent softening at the trot was due to my daughter's rides on her.
Now my younger daughter is an exceptionally fine and skilled rider. But she rides Dawn on the trail, and they go long distances with lots of trotting, cantering and galloping. Dawn's natural tendency is to brace and lean on the bit, particularly at speed, and there are very few opportunities to circle or do other things to interrupt the bracing. So what Dawn was saying to me is "I know how to do this bracing thing and I'm used to it and my body is used to carrying a rider while I do it - I think I'll go back and do that again." There's nothing defiant about this sort of behavior - it's perfectly natural for a horse to do this. She's just at the point of being convinced that carrying herself softly is more comfortable - she does it just fine in the field with no rider - but was trying out going back to the more familiar braced behavior.
This alternation between an old and new way of going is very common as horses learn new things - they have to decide that the new way of going is more comfortable and the rider has to consistently and softly ask for the new way of going and reward the new behavior consistently. I wasn't concerned about this at all and thought it could be pretty easily fixed. The reason I went immediately to trot without repeating a lot of softening work at the walk is that I didn't think work at the walk was going to solve anything. So we trotted and trotted and trotted some more - it took a while to begin to get the softness back.
Instead of asking for consistent softness, we went back to the 3, then 5, then 7, then 11 soft steps at the trot exercise, starting to the right. And instead of letting her find her own release as I would do if we were looking for consistency, I did a big "throw-away" release as she achieved each set of steps - but making sure I wasn't releasing on a brace or letting her pull the reins out of my hands. I wanted her to very clearly get the message of what I wanted. It took a long time to get the first 3 steps to the right - big release - trot around on a loose rein - 3 steps and repeat. Once we had 3 steps repeatedly for several laps, I moved to 5 steps, and so on. She worked hard, but we got there after a good long time. In each case, I made sure we could get a number of repetitions of the soft steps before moving on. Once we hit 11 soft steps to the right, we walked around for a while on a loose rein, doing a little bit of neck-reining practice.
Then we moved on to trotting to the left. Once again, we did a bit of backing, then I got 5 soft steps at the walk and we moved immediately up to trotting. Things went a lot quicker in that direction - she was clear on what I wanted and was trying to do it. Pretty soon we had 11 soft steps, and we took another walking break.
Now for the test - my objective was to immediately get at least 11 soft steps at the trot to the right, reverse direction while still trotting and immediately get at least 11 soft steps to the left, and preferably with consistent softness through the change of direction. Immediately we had it to the right - she would have gone a lot farther than 11 steps as the consistency was clearly back - reversed while maintaining softness and did 11 steps to the left. Big release, halt and I immediately jumped off, praised her lavishly, ran the stirrups up and loosened the girth, and took her in to untack and get turned out. She seemed very happy too with her progress.
It'll be interesting to see how she starts out on our next ride!