The first step in getting a horse to use their hind end is giving them the ability to do so by building the muscles in the hind end. Do LOTS of transitions (mainly upward transitions), do a lot of long trotting, walk or trot up hills. Once your horse is feeling comfortable doing these exercises add lateral exercises. For example: Leg yields, Haunches in, Shoulder in.....and so on.
In conjunction with muscling the hindquarters and getting them in the right shape to be used, you want to work on topline muscles. Trotting over ground poles that are spaced a little narrower than normal are good to get the horse to use its back and hindquarters more effectively. Your goal is to get the horse to stretch its back muscles and to reach under with the hind legs.
