>> When I hang out with horse oriented people at the track I sometimes hear very mysterious talk. Could you explain the terms "on the bridle" and "off the bridle" ?
"On the bridle" means in general that the horse accepts the bit and the connection to the reins and hands. In the case of a racehorse you can tell that there is a strong connection from the hands/reins to the bit and the horse because the horse wants to go on and run but is listening to the rider and the rider can feel the energy under him or her. When a racehorse is "off the bridle" he is not carrying himself with any energy, it feels to the rider like the horse wants to quit rather than race on, and there's no feeling of connection from the rider's hands to the horse's mouth so the rider may say "he spit the bit".
It's possible for a horse to rush from the gate and get his head up and ignore the rider. In this case he is not "on the bridle", he is "running off". Anyone who has ever been "run off with" know how terrible it feels because the horse is totally ignoring the rider, so this condition can't be called "on the bridle". In fact after the horse tires himself out, he will often "stop"- and this is a little different than "off the bridle".
As an aside, "off the bridle" to me is a european term. "He spit the bit" is an american old timer's term, maybe something Woody Stephens would have said.