In competitive dressage circles, impulsion is defined by the German Training Scale, which states that impulsion is only possible in gaits having a moment of suspension, such as the trot and canter, but not the walk. This is the current position of the USDF. Others differ, however. Oliveira described impulsion as necessary at all paces: "If your horse goes from walk to trot without changing the head and neck position, the walk had good impulsion." Outside the world of competitive dressage, impulsion is considered necessary at all gaits, encouraged in gaited horses, and in horses used for western riding. Impulsion at the walk is encouraged and judged in many lower level dressage and combined driving competitions that do not necessarily follow the current trends in international judging.
Impulsion is particularly important in dressage. It not only makes the horse's gait more elastic, light, and expressive, but providesg the animal with the power needed to perform the required movements. This is especially true for those requiring collection, such as passage, piaffe, pirouette, tempi changes. In jumping poor impulsion is often linked to horses failing to clear obstacles
Good riding is needed to create impulsion in any horse, although some horses may be built in such a way that they can more naturally create impulsion (such as those with an "uphill" build). The horse must be forward, yet relaxed, and coming correctly "on the bit" by coming up through the back. Additionally, a horse must be straight, with "throughness." The rider should use correct driving aids, and contain the energy created by the engaged hind legs. Ideally, this is accoumplished through persuasion of the horse, not bullying.
Impulsion occurs in all gaits: the walk, the trot, and the canter and even the ambling gaits of gaited horses. Because the walk has no moment of suspension, it is a difficult gait to perform with impulsion. Impulsion at various gaits may not always appear the same. In the walk, it is seen when the hindquarters are engaged and the gait is "purposeful yet relaxed." The USEF describes impulsion at the piaffe as follows: "The piaffe must always be animated by a lively impulsion and characterized by a perfect balance. While giving the impression of being in place there may be a visible inclination to advance, this being displayed by the horse’s eager acceptance to move forward as soon as he is asked."