Top British dressage rider, Michael Eilberg, explains the three steps he works through when teaching any horse to rein back
Take your horse in hand on the left rein on the long side of the arena. Firstly achieve a square halt. Then give a little feel on the reins and see how your horse reacts first of all. You are looking for your horse to walk forwards in a four-beat rhythm and to rein back in a two-beat rhythm, their legs moving in diagonal pairs.
If your horse doesn’t quite know what you are asking for, then carry out the exercise from the ground as described above, but touch your horse on their shoulder with the handle of your schooling whip as you ask them to move back. Remember to praise your horse when you get a positive reaction.
Next, once mounted on your horse, with a person who knows what they are doing on the ground, ask your horse to walk forwards and then into a square, established halt.
Then, with the aid of your helper on the ground with the schooling whip, ask your horse to move backwards. You want just four or five steps before asking them to walk forward again.
Next, with the helper just walking towards the horse, not using the whip, ask for the rein-back with your aids.
The third stage of the rein-back is to ask for it using no additional help from the ground. Essentially you want some activity from your horse within the rein-back.