Movements
There are three ways a horse may turn: it can pivot around the forelegs, pivot around the hind legs (essentially a pirouette) or both (a lateral bend).
Lateral bend
A lateral bend turn is one in which the horse turns around a vertical axis located roughly where the rider's legs are positioned on a horse's back. These sorts of turns help with the collection and flexibility of a horse. The horse is essentially moving both forward and sideways with the hind legs. It should maintain an even bend throughout the body so that the hind legs follow exactly in the tracts of the front feet.
While completing circles, semi-circles and turns during a dressage test, a horse should be turning through the lateral bending of its body.
Turn on the forehand
A turn on the forehand, or a pivot around one front leg, is not a natural move for a horse and takes training. It involves a pivot with little to no movement forward. However, all four legs should be mobile, including the pivoting leg, which through never moving forward or sideways should lift slightly off the ground and touch down again. This can be done through 180 or 360 degrees. This move is used to make the horse more supple and obedient. In riding tests, it is often used to change the rider’s direction (180 degrees).
Andreas Helgstrand, on Blue Hors Matine, completes a pirouette at the canter.
Pirouette
A Pirouette is similar to the turn on the forehand, except centered around the inside hind leg. It can be done at either a 180 or 360 degree turn. A correct half pirouette should take three steps, while the whole should take 5 – 7 steps. The canter pirouette requires the greatest collection and is a strenuous movement for the horse, and thus is not often done.