Dressage is a competitive equestrian sport, defined by the International Equestrian Federation as "the highest expression of horse training." Competitions are held at all levels from amateur to the World Equestrian Games. Its fundamental purpose is to develop, through standardized progressive training methods, a horse's natural athletic ability and willingness to perform, thereby maximizing its potential as a riding horse. At the peak of a dressage horse's gymnastic development, the horse will respond smoothly to a skilled rider's minimal aids. The rider will be relaxed and appear effort-free while the horse willingly performs the requested movement. Dressage is occasionally referred to as "Horse Ballet". Although the discipline has ancient roots, in Europe, dressage was first recognized as an important equestrian pursuit during the Renaissance. The great European riding masters of that period developed a sequential training system that has changed little since then. Classical dressage is still considered the basis of modern dressage.