What is hyperflexion and what does the FEI say about it in dressage?

Hyperflexion in dressage describes the positioning of the horse's neck in an extreme overbent position in which the nose is drawn toward the chest and the poll drops well below the level of the withers — a position that places the horse significantly and sometimes extremely behind the vertical in a way that differs markedly from the classical training position in which the horse's face is approximately perpendicular to the ground. The term is used interchangeably with rollkur in many discussions, though some practitioners distinguish between hyperflexion as a description of the physical position and rollkur as the specific technique of actively pulling the horse into this position through rein pressure. The FEI addressed the controversy surrounding hyperflexion and rollkur after sustained pressure from horse welfare advocates, veterinarians, and classical practitioners who documented the technique's prevalence at international competitions. The FEI's official position, formalized after a round table discussion in 2010, distinguishes between rollkur — described as flexion of the horse's neck achieved through aggressive, unrelenting pressure that it prohibits — and low, deep, and round — a position achieved through light pressure and with the horse's cooperation that it permits as a training variation when used briefly. The enforcement of this distinction at competitions has been inconsistent and controversial, with critics arguing that the line between prohibited rollkur and permitted low deep and round is impossible to reliably identify in practice and that the FEI's response did not adequately address the welfare concerns that the original controversy raised. The FEI's steward system at major competitions is tasked with monitoring warm-up arenas for prohibited training practices, but the practical enforcement challenges of identifying training method violations in a busy warm-up environment have limited its effectiveness.