The only thing that builds muscle is lots of feed, and the correct work. If he is not getting the correct type of work, than he can not develop the correct muscles.

Lunging is good to start with, but has to be done in a 15 m diameter round yard to be effective. I don't see how a lead pony can assist, as the whole situation of bad backs comes from a source of tension, and as a result- crookedness. A lead pony situation is only going to cause his neck to be at an odd angle to his shoulders and hips, and you would not be able to achieve any relaxation laterally, longitudinally or vertically in this situation. The energy to build muscle is not present either, because he would be on the forehand the whole time.

Hormone injections are a disaster, and should not be used under any circumstance. This is a quick fix only, and long term effects can cause major problems down the track.

The only way to develop the correct muscle is to use the classical system of dressage. If you already are trying this, then be sure to check that what you are doing is correct.

Charles de Knuffy has two books that will assist your understanding of the muscular/skeletal development through classical training methods, which state that first and foremost the training should be therapeutic and rehabilitative. The books are :Training Strategies for Dressage Riders and Manage Patterns.

Although these books cover high school training as well, the fundamentals are always the same and Charles speaks in a language that is easy and comfortable to read.

Create relaxation - rhythm, engagement and balance will follow. We have to however create circumstances for these events to occur. A 15m round yard is a good place start because the wall acts to bend the horse laterally , which in turn ensures that his spine is straight on the circle, and as the trainer in the middle you can create and support the engagement required for the rhythm to be maintained. Before long, you will have a horse that will relax through the back ( indicated by his neck and head stretching out and down ward ( never into the chest) and his hind feet tracking up into the forefeet foot prints.

Lunging with out a round yard can cause untold damage.

Our Tendon and Bone treatment can assist during this training to repair muscle tearing and damage created by tension.