What is schwung in dressage and how does it relate to impulsion?

Schwung is a German term used in dressage that describes the quality of energetic, elastic swing that flows through the horse's entire body when impulsion, suppleness, and throughness are working together — a quality that is sometimes described as the visible expression of impulsion in the horse's movement, or as the total of impulsion and suppleness combined into a single observable quality. While impulsion describes the energy generated by the hindquarters and the horse's desire to move forward with elastic thrust, Schwung describes what that energy looks like when it flows correctly through the horse's whole body: the back swinging freely with each stride, the tail swinging loosely in rhythm, the whole horse appearing to bounce and float rather than simply to move its legs. A horse with genuine Schwung appears to move as if the ground were bouncing it upward with each stride rather than as if it were simply lifting its legs — the upward component of the movement, visible as elevation and spring in the strides, reflects the elastic quality that Schwung encompasses. The concept helps explain why it is possible for a horse to have impulsion without Schwung: a horse with active, engaged hindquarters but a tight, blocked back will generate the energy of impulsion but will not transmit it through the body in the swinging, elastic way that Schwung describes. In this case, the impulsion is present at the source but blocked before it can express itself in the movement quality that Schwung represents. Developing Schwung therefore requires both the hindquarter engagement of impulsion and the back suppleness and throughness that allow the energy to flow freely — which is why Schwung is often used as a summary quality that encompasses much of what the Training Scale's middle elements are working toward.