How to teach a horse shoulder-in on a circle?

Teaching shoulder-in on a circle — sometimes called shoulder-fore on a circle or curved shoulder-in — is a more advanced and more specifically demanding version of the shoulder-in exercise that takes the movement off the straight long side and places it on a curved track, requiring the horse to maintain the shoulder-in positioning while simultaneously navigating the constant bend of the circle. This combination produces a compound gymnastic demand significantly more engaging than either a fixed circle or a straight shoulder-in alone. The prerequisite is that both elements — correct circle work with uniform bend and genuine shoulder-in on the straight long side — must be independently confirmed before the combination is introduced. The combination exercise is a test of both elements done simultaneously, and both must be genuinely available independently before the combination makes sense as a training demand. Begin on a twenty-meter circle where the arc is gentle enough to allow the shoulder-in positioning without creating excessive physical demand from the curve alone. At the walk, establish the correct circle bend — inside leg pushing the ribcage out, inside rein asking for soft inside flexion, outside rein maintaining the arc, outside leg guarding the hindquarters. From within that correctly bent position, bring the forehand slightly further in off the circle track — not dramatically, but a slight additional positioning so the horse's front feet travel on a slightly smaller arc than his hind feet. That additional inside positioning of the forehand is the beginning of the shoulder-in circle. Transitions within the shoulder-in circle are the tool that develops the exercise from an isolated position into a genuine gymnastic experience. Ask for shoulder-in positioning for several strides, release back to the normal circle position for several strides, ask for shoulder-in positioning again. That alternation prevents the horse from settling into a mechanical pattern and requires him to actively respond to the change in aid each time the positioning is asked for or released. Spiral work that incorporates shoulder-in positioning is a natural development from the basic shoulder-in circle. As the circle decreases in the inward spiral, progressively increase the degree of shoulder-in positioning to maintain the balance between circle size and forehand displacement. As the circle increases in the outward spiral, decrease the shoulder-in positioning and allow the horse to push from the inside hind into a more forward extended stride — using the release of the shoulder-in positioning as the invitation for the horse to open his stride and push from behind.