How do you develop piaffe under saddle in dressage?

Developing piaffe under saddle requires the horse to have already established a high degree of collection in the trot — demonstrated through confirmed collected trot, passage preparation, and the beginning of piaffe from ground work — before the mounted demands of piaffe are systematically developed. The mounted development of piaffe typically begins from a highly collected trot or from the transition out of a walk, asking the horse for shorter and shorter trot strides while maintaining or increasing the activity and elevation of each step — the paradox of more elevated steps with less forward movement that defines the transition from collected trot toward piaffe. The aids for mounted piaffe require coordination of the seat, legs, and reins in a specific way: the seat creates the rhythm and asks for greater carrying in each stride; the legs alternate in rhythm with the diagonal footfall to encourage each hind leg's activity; and the reins receive the horse's energy while remaining light enough to allow the elevation and expression of the front end. Transitions between collected trot and piaffe — asking for piaffe steps within a trot, allowing the horse to trot forward after a few piaffe steps, and returning to piaffe — develop both the physical understanding of what is being asked and the physical capacity to perform it without tension or resistance. The half-halt is used intensively during piaffe development to continuously ask the hindquarters to carry more weight with each stride. The training of piaffe under saddle must always respect the horse's physical capacity and willingness — demanding too many piaffe steps before the horse is strong enough damages both the horse's physical condition and its willingness to perform the movement, making gradual development with many forward transitions the most consistently successful approach.