So we’re working on improving my mare’s collected canter right now and her strength has improved dramatically in the last month despite me and my flaws.
The start of this video shows where we were a couple weeks ago - she was just starting to get the idea of lifting in the withers more. https://youtu.be/XdOfBXr8SoA
She naturally has an excellent canter, but not a collected one, so getting that sit and lift in front has taken strength. She also finds lateral work very easy (at the trot). We have been playing with lateral work in the canter, doing shoulder fore/shoulder in and haunches in to straight, at will. For her, she has also needed to have the freedom to mistakenly come above the bit at times as she has worked on figuring out how to sit and lift the front end. Yes, it’s her withers we want lifting, but she has needed to be able to make mistakes to figure out how to do it.
What is helping most is the walk-canter and canter-walk transitions, but really focusing on riding her hind end in them. A canter-walk with trot steps which really sits is preferable to one in which she lurches into a walk. We have been doing walk-jog transitions (not quite half steps as she physically isn’t quite there to be giving that much sit, but the feeling she is heading toward them) to get her more active and sitting behind before working on the canter transitions, and when she starts to feel like she wants to drop on her forehand again, we go back to them.
We have also did transitions in and out of the canter in shoulder in to help facilitate that collection and use of the hind end. It just makes sense to her, so we use that to help.
With collection really being the folding of the hind legs and lift in front to change to a more uphill balance, that work is getting her collecting. She also has the shorter and more active stride we want while maintaining high energy - more energy than she used to have in her working canter. I was shocked the first time I was talking to my trainer about collected canter and he had me in a working canter, then had me half halt upward and add a TON of energy. He said THAT is the canter from which the collected canter was going to come, and it felt as if she was working about 3x as hard as in her working canter. But that really is the energy level the collected canter has now.