Bending through the poll
Just a little note:
Some time ago a student asked me what I meant by retaining flexion through the horse's poll even on a long or loose rein. I had asked her to do this while riding my stallion Prazer. Basically, she had flung the reins at him at the end of an exercise and he had - not surprisingly - dropped his back.
As I explained to her, if you still feel gently on the fingers on a long and even loose rein (as in the pic) still sit up and ask the horse to go forward from the leg at the girth, he can move more correctly and carry the rider in a much better frame. This photo wasn't staged, but it still shows what I mean. Horse still bending through the poll, nose partially down - not poking up- horse still engaged. We should never expect the horse to carry us in a dropped hollow frame if at all possible.