Reining is a Western horseback riding competition. Early in American history, the American stockman didn't have many resources to manage his cattle. The cattle were moved, worked, branded, doctored, sorted, and herded without the benefit of fences, barns or other means of holding the animals. A good cattle hand needed a good horse, one that could change directions quickly, stop on a dime, and accelerate quickly after an errant cow. The cowboy had to be able to handle this animal with a light touch on the reins, so that the cowboy's attention could also be on handling the lariat (to rope the cattle).
The demonstration of these ideal characteristics evolved into the sport of reining, where the riders guide the horses through a precise pattern of circles, spins, and stops. All work is done at the canter (or "lope" or "run" in Western parlance). The patterns consist of small slow circles, large fast circles, spins, rapid changes of directions, flying lead changes, roll-backs and sliding stops.
The canter or lope is a three-beat gait in which either the left or right foreleg leads depending on direction. The horse and rider are required to perform a flying change where the rider cues the horse to change the leading foreleg in mid air; this is often cued upon changing a direction.
By way of analogy, imagine a human girl hopping on the playground, in which one foot always shuffles behind and the other leads. She can choose to switch the foot that leads at any time, and sometimes switches every hop, which is called skipping, or "one-tempi flying changes".
International competitions are regulated by the International Equestrian Federation. Reining is most popular in the United States, where two major organizations oversee the sport: the National Reining Horse Association and The American Quarter Horse Association, both governed by the United States Equestrian Federation.
Reining is one of the world's fastest growing horse sports. Its popularity has spread to Europe and beyond. For the first time in the history of reining, the 2004 top 10 horses were all owned by Europeans.
People who enjoy it say that reining combines the artistic appeal of dressage plus the crowd appeal of rodeo.