A correct shoulder-in benefits your horse in several ways:
But when problems occur the benefits are lost and, in some instances, it can be detrimental to your training. In two of my previous blogs I have addressed some of the problems that can occur with riding shoulder-in: Loss of Impulsion and Travelling and Correcting Bend.
When shoulder-in has gone wrong it is usually better to ride out of the movement, set things up again and then come back to the exercise, paying attention to the necessary corrections as you start the movement.
Rider blocking the horse or behind the movement
If the rider sits to the inside during the movement, they will be moving against the direction of travel. Closing your body towards the outside elbow helps to maintain correct balance during the movement and release the horse’s inside hind leg, allowing it to cross under the body more easily. Be careful that you don’t sit too far to the outside or you will create a similar problem!
Asking for too much angle
Only ask for the angle that your horse can manage at that time. The exercise will supple your horse and the angle will increase as they become more supple. Also, be aware of your horse’s conformation; a short coupled, stocky horse will have different angles to those of a narrower horse.
Circles and shoulder-in are exercises to supple your horse, and so you must ensure you ride each side the same. On the easier side, ride with less angle, and, as your horse’s stiffer side supples more, the angles will even up and can be gradually increased.
Asking too many steps
Asking for too many steps before your horse is able to maintain them independently will be physically challenging for him, and he will lose the rhythm and angle. Build the number of steps progressively.
Asking for too much stretch
It can be tempting to push your horse for bigger steps in shoulder-in, which results in them running on, losing balance and negates the purpose of the exercise. Initially keep the steps small with the hind feet moving close together so your horse builds strength and suppleness.
Diane Followell Classical Dressage Trainer