Well, slightly less extreme, unlikely to do harm to the horse and equally effective: on the ground, when the horse is rearing, rap them smartly with your dressage whip right on the cannons. My "deeply committed to rearing" horse who'd broken my foot with a rear/down, stopped after 2 incidents. You could see her thinking it over for a while, now she just knows better than to even think about it. It's crude, I agree (it was a Lyons method at the time I applied it), and I'm not sure that's how I would handle future horses with that problem, as I have subsequently learned the thinking that it's a "space" issue and that the horse is feeling squeezed, on the ground. The remedy being to develop sensitivity to that issue and work with the horse in creating a balance between his/her respecting my space and awareness of his/her concerns on my part. This insight has come as a result of working with Clicker Training, which has been transformational for my Lyons trained horse who was hot and aggressive to me. She's a "different person" now and boy, am I happy. Check it out if you're intriqued: http://theclickercenter.com/2004/