What is suppleness in dressage and how do you develop it?

Suppleness in dressage encompasses two related but distinct qualities: longitudinal suppleness, which is the horse's ability to swing through its back and allow energy to flow freely from the hindquarters through the topline to the contact, and lateral suppleness, which is the horse's ability to bend evenly through its body in a curved line without resistance or stiffness. Both forms of suppleness are prerequisites for the development of contact, impulsion, and eventually collection, because a horse that is stiff through its back cannot transmit the hindquarter energy that impulsion requires and cannot carry a rider's weight efficiently through a supple, swinging back. Longitudinal suppleness is developed primarily through forward, rhythmic work at all three gaits — particularly through the active, swinging trot that allows the horse's back to move freely — and through transitions that encourage the horse to reach forward and down with its topline rather than bracing against the rider's hand. A horse with good longitudinal suppleness shows a characteristic swing through the back visible to observers on the ground: the back appears to undulate slightly with each stride rather than appearing rigid and dead. Lateral suppleness is developed through circles, serpentines, and eventually lateral exercises that ask the horse to bend uniformly through its length from poll to tail rather than only at the neck. A horse that bends only at the neck while its body remains straight is showing insufficient lateral suppleness that will limit its ability to perform correct lateral work at higher levels. Suppleness is maintained and improved throughout the horse's training career — even Grand Prix horses begin each warm-up with work designed to restore and confirm the suppleness that is always the physical precondition for quality work.