Impulsion is the movement of a horse when it is going forward with controlled power. Related to the concept of collection, impulsion helps a horse effectively use the power in its hindquarters. To achieve impulsion, a horse is not using speed, but muscular control; the horse exhibits a relaxed spinal column, which allows its hindquarters to come well under its body and "engage" so that they can be used in the most effective manner to move the horse forward at any speed.