To help build more muscle, back up a hill a lot of times. If your horse is not laterally soft, your horse wont be vertically soft to build the muscle. To get your horse laterally soft you pull and release at the same time, but don’t release all the way. Pull and release your horses neck around until your horse is not pulling on you or making you pull its head. You want to do this on both sides of the horse. Collecting your horse will definitely build muscle. When you collect your horse up, you will need to change leads every now and then. When you have your horses head like in picture 2, you will need to release the pressure to reward you horse, so your horse will get better and enjoy it.