Suppleness and straightness - Shoulder in
This is a good lateral exercise which helps supple the horse and should be worked on both reins equally.
This will then strengthen the horse evenly and increase his straightness throughout his work.
You should work with Shoulder Fore first
This is the same as Shoulder in but with a small angle.
You should be riding on three tracks for shoulder in - the inside hind leg and outside fore leg should work as a diagonal pair.
This is shown in the video.
Start this exercise coming off a circle so you already have the bend to start your shoulder in.
Your horse needs to bend slightly around your inside leg.
Maintain equal contact in your reins and half halt to put them in balance before you go into your shoulder in.
Keep the activity from the inside hind leg and look in the direction you are travelling in.
Start with a few steps and then go straight and progressively build the number of steps up.
Sometimes I will do a few steps then do a circle and then repeat.