How do you develop impulsion without tension in dressage?

Developing impulsion without tension is one of the central challenges of dressage training because the energy and activity that impulsion requires can easily be produced through methods that also create tension — and tense impulsion, however active it appears, is not genuine impulsion but rather the anxious energy of a horse in flight mode rather than the elastic, controlled thrust of a horse genuinely engaging its hindquarters with confidence. The foundational principle is that impulsion must always be developed within a framework of relaxation and throughness: a horse that is tense through its back cannot transmit impulsion through a supple, swinging movement, and the energy of tension expresses itself as running, stiffness, and irregularity rather than as the elastic suspension of genuine impulsion. The safest approach to building impulsion is through transitions that ask for brief bursts of greater energy followed by immediate return to relaxation — transitions from trot to canter and back, from working trot to a brief medium trot and back — which develop the hindquarter engagement of impulsion while maintaining the frame of relaxation and rhythm within which genuine impulsion can express itself. Cavaletti and pole work at the trot can develop a more energetic, elevated step without creating the tension that strong driving aids sometimes produce. The classical instruction to work the horse long and low at various points in the training session serves the goal of maintaining relaxation within an active training context — a horse that can work actively and energetically in a long, relaxed frame is showing genuine impulsion rather than tension, and the relaxation visible in the long-and-low work provides reassurance that the energy is coming from genuine engagement rather than anxiety.