What is the difference between a horse that is forward and one that has impulsion?

The distinction between a forward horse and one with genuine impulsion is fundamental to dressage training philosophy and one that many developing riders do not fully grasp until they have ridden horses at significantly different levels of training. A forward horse moves with energy and sufficient pace — it does not resist the leg, it maintains its gait without constant driving, and it covers the ground willingly. These are valuable qualities and necessary prerequisites for impulsion, but they are not impulsion itself. Impulsion adds to mere forwardness the specific quality of elastic, stored energy generated by engaged hindquarters and transmitted through a supple, swinging back — a quality of contained power that gives the horse's movement its spring and elevation rather than simply its pace. The most useful way to understand the difference is through the concept of throughness: a forward horse moves its legs with energy and covers the ground, but that energy may not flow through the back in a way that reaches the contact and produces genuine suppleness and connection. A horse with impulsion has energy that flows from behind through the entire horse's body — the hindquarters generate the thrust, the back swings and transmits it, the contact receives it elastically — producing a movement that feels from the saddle like riding a bouncing, coiled spring rather than a willing but ordinary forward movement. Impulsion is also more adjustable than simple forwardness: a horse with genuine impulsion can decrease its tempo while maintaining the same elastic energy in a shorter stride, something a merely forward horse cannot do without losing its energy when the pace is reduced. This adjustability is what makes impulsion the prerequisite for collection, because collection requires reducing tempo while increasing carrying power — precisely the adjustment that impulsion makes possible.