I lucked across a book called, The Anatomy of Riding by Sara Wyche. If you can buy it or check it from the library, please do so. I've only made it a bit of the way through it but it is chock-a-block full of info about how riding affects your horse.
One big deal is that I've never been a proponent of doubling a horse. Somehow I always thought it was the wrong thing to do. If your horse is so out of control, it's either you can't ride and shouldn't be aboard or your horse needs a LOT more work to stay under your command. It seems to me that a lot of the "Natural Horsemanship" people (did you catch my snark for those two words??) seem to think that doubling substitutes for training. You can't stop? Double your horse seems to the be order of the day.
To my mind, except in extreme cases, should a horse be doubled. If a horse is running away with you, I sure don't want to take his head away from him and let his rear end fling out, not to mention the strain on the front legs! If your horse is runaway prone, YOU need to do something to get that notion out of his mind and stay in the round pen then progressing to a small arena. Not doubling the horse.
Anyway, just wanted to point this out. Be leery of anyone who touts doubling as a 'fixer'. Not a good choice at all.
Now, go love on your brat! :-)