Originally Posted by ErikaLynn
He could be using his neck to balance over the jump...instead of using his hind end to push up over the jump, he is throwing his neck down to gain balance and momentum over the fence.
Why don't you try gymnastics with him.
What ErikaLynn wrote was my first thought. I worked with a TB that was like this. Fairly fit and learning to balance and be supple on the flat but when you introduced jumps he didn't know what to do with this body. So he'd jump and on the landing throw his head straight down. Yes, when he was fresh there could be a buck in there (or if he was upset about something) but he wasn't trying to buck. And stretching down had nothing to do with it. It was from not knowing "how" to jump and then landing in a heap on the backside since he wasn't sure what to do with his body over the fence. Lots and lots and lots of gymnastics was what eventually taught him how to use his body and be more balanced through the jumps. Bounces, using poles ~9 ft before and after a single fence, etc etc. If we did singles I always did something after the jump like a transition, circle, leg yields... just something to get him to balance up afterwards. He was just more awkward with jumping. Eventually he got better and learned how to use his body.