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 accomplished through persuasion of the horse, not bullying.