How do you fix a horse that loses rhythm in the canter transition in dressage?

A horse that loses rhythm in the canter transition — breaking to a rushed trot before departing, producing an unbalanced, falling transition, or breaking in the first few strides of canter before establishing a rhythm — is showing that either the preparation for the transition is inadequate or the horse lacks the balance and collection to make a smooth transition at its current training stage. Identifying which cause is most relevant guides the correction: a horse that consistently loses rhythm at the moment of the transition but settles into a good canter afterward is showing a preparation problem; a horse that loses rhythm in the first several strides of canter after the transition is showing a balance and collection problem in the canter itself. For preparation-based rhythm loss, the correction focuses on the quality of the half-halt and the forward energy in the trot immediately preceding the transition: the horse must be genuinely balanced and forward in the trot when the canter transition is asked, not slowing and falling onto the forehand, because a horse already losing its trot rhythm is in no position to make a clean transition into canter. The timing of the leg aid for the canter transition — applied at the moment the inside hind leg is leaving the ground, where it can most directly influence the first canter stride — is another important preparation factor. For horses whose rhythm loss is in the first canter strides rather than in the transition itself, returning to basic canter work — developing the horse's balance in working canter through large circles and transitions within the canter — builds the collection and self-carriage that allow a cleaner transition and better-maintained rhythm. Riding many trot-canter-trot transitions rather than sustained canter develops the horse's balance in all three phases of the transition and gradually improves the overall quality.