Bringing the horse’s shoulder a bit to the inside in canter is called shoulder fore. It is a schooling movement that (to my knowledge) is not asked for in any test, yet is incredibly useful.
Why should this boring (until you try to do it correctly!) and little-used movement be so important?
1. If showing is you goal and you have ever got a comment about your medium canter down the long side “Haunches in,” or haunches drifting,” this movement is your friend.
2. If your horse understands shoulder fore in canter he or she also understands that you may use your inside leg to activate the inner hind in canter–without the horse offering a change of lead unasked–and that you may freely straighten the horse on your outer rein–also without them offering to change the lead unasked. These are two absolutely essential things to be able to do at will.
Note: In flying changes sometimes it can happen in the course of the work that the horse blackmails the rider into taking away necessary positioning influences: “If you use your leg or hand to straighten me I’ll get behind you and switch my lead!” “I will, I really will!”
Shoulder fore is a way to make this concept clear to the horse: “I am on the right lead canter, and the rider can actively use the right leg and left hand to influence my angle. They can also send me forward on the angle and bring me back onto my neatly positioned inside hind leg.”
What it looks like: it looks like a shoulder in with almost no bend, done in canter, typically down the long side.
The typical problem riders have with this movement is they approach it by attempting to use a lot of inner leg, seat and hand. Effectively driving the shoulders of the horse to the outside and the haunches in–the opposite effect to the desired one!
The easier way to approach it is to first teach the horse to counter flex just a bit in the corners so they are familiar with the influence of the outside rein. Then use the outer rein to line up the outer shoulder–an absolutely straight horse, directly in front of the rider’s pelvis and directly behind the rider’s pelvis. Even on both sides. (The angle is initiated with a slight, correct, angle of the rider’s body, weight centered.)
We are not approaching this like pushing the broken egg back into the shell! It should feel like lifting the horse forward into the movement. The better the rider is and securing their own core the easier the horse will be able to understand what is expected.
And in schooling, take it easy at first if the horse has difficulty. Just do a few steps and go on down the line again. Once they understand to keep this angle until straightened on the line, you can send them forward to a nice medium canter and bring them back with no trouble. It’s pretty easy, but the horse has to be straight or it will not work. No bend, just positioning of the shoulders to the interior side.