The shoulder-in is a dressage movement used to supple and balance the horse and encourage use of its hindquarters. It is performed on three tracks, where the horse is bent around the rider's inside leg such that the horse's inside hind leg and outside foreleg travel on the same line.
In the seventeenth century, Antoine de Pluvinel used the basic shoulder-in exercise especially around the pillar to increase the horse's suppleness and to get him used to the aids, especially the leg aids. He felt the exercise helped to make the horse obedient. Independently, the Duke of Newcastle found the exercise and also used it around the pillar.
In the eighteenth century, the French écuyer Francois Robichon de la Gueriniere adapted the movement for use on straight lines.
How to Ride the Shoulder-In
In the shoulder-in, the horse's hind legs track straight forward along the line of travel while the front legs move laterally, with the inside foreleg crossing in front of the outside foreleg and the inside hind hoof tracking into or beyond the hoofprint made by the outside foreleg. The shoulder-in can be ridden at any forward gait, but in dressage competition it is usually ridden only at the trot.
It is often recommended to introduce the movement coming out of a corner or a circle on which the horse is straight (i.e., correctly bent, from nose to tail, along the arc of the corner or circle), as it is usually easier to maintain bend than to establish it, at least in the young or green (untrained) horse.
- As in the circle or corner, the rider's shoulders are turned to mirror the angle of the horse's front shoulders, while the rider's hips and legs mirror the position of the horse's hind legs. As the circle becomes the shoulder-in, the rider's shoulders are turned to the inside, while his/her hips remain "straight" on the track.
- Coming onto the track from the circle or corner, the rider uses his/her inside leg at the girth (tack) to maintain the bend and encourage the horse to step under its body with its inside hind leg.
- The rider's outside leg prevents the horse's haunches from swinging out (i.e., into leg yield).
- The outside rein steadies the horse and helps maintain the correct bend, while the inside rein is used with a giving hand.
- The rider's back and position in the saddle discourage the horse from moving forward off the track, maintaining instead movement along the track. The sensation for the rider is as if she/he has shifted his/her weight toward the horse's outside shoulder.
The inside rein must not be used to create the bend for shoulder-in. The risks of doing so include creating too much bend in the horse's neck compared to its body, and/or pulling the horse off the track. Rather, the rider's inside leg is used to create the bend. The inside rein only maintains the bend if necessary, but if the horse is correctly on the aids, contact on the inside rein need only be very light at most.