[IIIBarsV]

I couldn't help but notice you said that you kick them in the chest when they rear or buck.

??????????????????

Normally when a horse rears, you should discipline the rear end for two reasons-
1) This prevents them from going up again and coming down- right on top of you.
2) This encourages forward motion. Rearing is a backward motion. You do not want to encourage the horse to rear again by pushing him backwards.

And.... when they buck... assuming you don't fall off... do you actually get off the horse and kick it in the chest? Whose goal is being accomplished by this? Yours, or the horse's? He did want you off his back. And maybe he'll prevent you from getting back on by rearing up when you kick him.

I am thinking that instead of looking at the horse, you should take a step back and ask yourself "What was I doing when he choose to do this?"

I have seen a horse throw itself to the ground and lay there when the rider had the spurs and the hands going a little too much a little too aggressively. Once in a while the horse who can't put up with western pleasure training will go passive by simply tossing themselves down. It's not often you'll see it, most of them will either just bronc you, rear, or skitz out in other various imaginative ways.

But that's what I'm thinking might be going on, just from reading your posts so far. Feel free to offer more information if I've misread/misunderstood/assumed something.