Exaggerated flexion of a horse’s poll and neck, although surely practiced in the past, became popularized (so to speak) in dressage in the 1980s when Nicole Uphoff of Germany used it as a training technique with her horse, Rembrandt. Riding the notoriously spooky gelding in what was then referred to as a “low, deep, and round” outline helped Uphoff to manage the horse, according to much of what was published at the time. Switching to a competition-acceptable outline or “frame,” Uphoff piloted Rembrandt to back-to-back team and individual dressage gold medals at the 1988 Seoul Olympic Games and the 1992 Barcelona Olympics.

Uphoff’s methods, not surprisingly, were emulated by other dressage riders, both professional and amateur. The German champion Isabell Werth, who won a string of team and individual Olympic gold and silver medals from 1992 through 2000, reportedly schooled some mounts low, deep, and round. The rider whose name has become most closely associated with the method is the Dutch star Anky van Grunsven, Werth’s chief rival in the 1900s and 2000s and who herself racked up a running string of team and individual dressage medals, ending with individual golds aboard Salinero in Athens 2004 and Hong Kong 2008.

As the years progressed, some dressage enthusiasts became increasingly alarmed by what they viewed as an improper training technique that violated the principles of classical horsemanship. Allegedly less egregious when used by knowledgeable riders, “rollkur,” as detractors dubbed it, could be downright harmful to horses when used by inexperienced riders, they asserted. In the mid-2000s the German veterinarian Dr. Gerd Heuschmann, working with German Olympic dressage champion Klaus Balkenhol, created headlines when they publicized the findings of Heuschmann’s anatomical and biomechanical studies of hyperflexion. Heuschmann said that hyperflexion not only fails to develop the proper musculature for upper-level dressage, but the exaggerated flexion can also restrict the horse’s airway. Heuschmann published a book, Tug of War: Classical Versus “Modern” Dressage, detailing his findings and arguing against the practice of hyperflexion.

Before long, rollkur had gone from innovative training method to dressage dirty word. The change in public sentiment happened to coincide with the rise of the Internet and the social-media age, and as a result the practice and the practitioners found images of themselves posted online as dressage spectators and media alike snapped photos and shot video of riders apparently using hyperflexion in schooling and in competition warm-up arenas. Meanwhile, Heuschmann, Balkenhol, and other like-minded people founded an organization, Xenophon, to bring attention to what they said was a harmful practice. And the dressage community began to press for change