Competitive dressage takes place in a 20x60-meter arena, with 12 lettered markers placed at specific points along the rail.
Here, horse and rider perform a designated test, a series of movements for which the arena markers serve as reference points.
No one seems to know the reason for the peculiar sequence of the letters or when their use was introduced to the sport.
There are different levels of tests in "international" dressage competition.
In order of difficulty, they are, the Young Rider Tests, the Prix St. Georges, Intermediaire I, Intermediaire II and Grand Prix.
Within the Grand Prix level are the Grand Prix, the Grand Prix Special and the Grand Prix Freestyle--a musical ride choreographed by the rider. Although certain dressage movements must be performed and each performance has a time limit, the competitor can create a program, which suits his or her horse and is especially pleasing to the eye.
It is these International tests where we see the most spectacular movements: Piaffe, the highly collected, elevated trot in place; Passage, the suspended trot in slow-motion; Pirouette, a rhythmic turning in place at the walk and canter; Half Pass, a forward and sideways movement at the trot or canter where the horse crosses his legs; Flying Change, a skipping type movement at the canter where the horse changes lead every fourth, third, second and finally at every stride.
It is important to understand that none of these movements are tricks; all are natural and performed by the horse at play.
With careful training, the horse learns to duplicate these natural movements, willingly, on command, and with grace, while accommodating the weight of the rider. The trust and harmony, which makes this possible, are a tribute to the dressage rider's ability and the horse's generosity.
One to five judges, positioned at specific locations around the arena, evaluate the performance from their different perspectives. Scores are awarded on a scale of zero (not executed) to 10 (excellent) for each movement, with some particularly difficult movements earning scores that are multiplied by two.
Spectators tend to base their judgments on general impressions--on how pleasing the performance was as a whole.
The judges also take this into consideration when awarding the "collective marks" for paces, impulsion, submission and the rider's position. Dressage scores are tallied and divided by the total possible, and the final score given as a percentage.
These final percentages are somewhat misleading; the winning score may only be a 63%.
But keep in mind that the marks are given movement by movement, and are judged against a standard of absolute perfection.
The greatest dressage riders in the world today can only hope to achieve a final score in the 70% range.