I am interested in building my 3-year-old colts rear end muscles to achieve collection and solid backing skills. He is somewhat gangly, tall and does not have the desire to back. He braces on the bit. I have started him stopping by sitting deep, then saying whoa and then using my hands if necessary, but when I ask him to back he is reluctant. I ask, then tell, and then command. He is getting it, but I think if he had the rear end muscle, he would be more likely to back willingly. Does walking up hills or bitting up help? Thank you.
Building up rear end muscles has little or nothing to do with backing up. Your problem is in the front end. If he is heavy on his front end, he will lock up and not back up. Start by backing a few steps and then roll back and go the other direction. Do not contradict yourself by backing him up and then going forward again. Stop him along the fence and back a few steps and then roll him into the fence and trot or lope off. Every day, increase a few steps and in no time he will be backing better. Do not walk him forward over his steps and he will get better. If he is stubborn and locks up or rears, then you might be safer to ground drive him and teach him to back from a safe distance behind him. All my two year olds walk, trot, lope, stop, back, side pass, and are reasonably broke in the face before we ever get on them. I do all this by ground driving first.