Flexion is the ever so slight rotation of the horse's head either left or right. Proper flexion would allow the rider to barely see the horse's inside eye (if moving in a circle). Hyperflexion forces the horse to overflex and is done by an exertion of strength on the part of the rider. It forces the horse to carry his head in what is considered to be an impure and compromised manner. In classical dressage the use of artificial methods to 'teach' your horse is a departure from the 'art' of dressage. Draw reins are traditionally thought to be such a departure. Since hyperflexion is done by exertion as opposed to finesse, it falls into the same category. The force with which the exertion is applied varies from rider to rider. The USEF (or USDF?) recently ruled that hyperflexion is now illegal-even in the warmup arena. Most trainers who utilize this technique do so because horses, when excited as they are in a show environment, tend to bring their heads up above the vertical detracting from their score. It is thier contention that if the horse is trained behind the vertical and overflexed that this 'problem' is cured.