Arena polo

Arena polo is a fast-paced version of polo played outdoors on an enclosed all-weather surface, or in an indoor arena. Hurlingham Polo Association (HPA, Great Britain) and US Polo Association (USPA, USA ) have established their own rules for arena polo, and these rules are often used in other countries as well.
Unlike outdoor polo, which is played on a 10-acre field, arena polo is played on 300 feet by 150 feet field, enclosed by walls of four or more feet in height. The normal game consists of four chukkas, or periods, of seven and one-half minutes each. A polo ball is similar to a mini soccer ball, larger than the hard plastic ball used outdoors. The arena game is played on a dirt surface with the ball bouncing on the uneven surface and off the arena wall.
Arena polo is typically far more financially accessible than outdoor polo. Club membership fees are usually lesser in comparison, in large part because an arena does not have the high annual maintenance cost of a grass field. Player investment is often smaller because, at a minimum, only two horses are needed to play a regulation arena polo match. Rather than a dedicated truck and large trailer, a bumper-pull trailer and a SUV is usually sufficient for transporting the horses of the arena polo player.
Arena polo can be played year-round, which is attractive to many players because it makes progress in the sport easier and quicker. The most popular season for arena polo is winter. 
The Horses.
While they don't go high speeds over long distances, horses need to utilize acceleration, strength, maneuverability and heart to play arena polo. It is especially important in arena polo for horses to be comfortable with other horses and riders, as they often run into one another in the smaller area. Just about any breed of horse can be used for polo, and mallet sizes allow players to use horses of differing height. Horses usually take a year or two to train to become polo horses, and can play into their twenties.
The Players.
Generally, there are three players per team in arena polo as opposed to four in the outdoor version. In 2016, Dallas Burston Polo Club in the UK became the first to build an arena suitable for four players on each team, nicknamed the ‘SuperArena’. Games can be very physical, and because of the smaller size of the playing field, opponents are almost always in close proximity. Players that enjoy arena polo are typically those who do not shy away from physical contact. Arena polo is often very fan friendly because the action is contained in a smaller area.
The Rules.
In the U.S., the USPA Rules and Rules Interpretations govern all sanctioned events. The rules of arena polo are very similar to those of outdoor field polo with the main differences accounting for the presence of the walls surrounding the playing field. Penalty shot lines also account for the smaller size of the field. 
Interscholastic and Intercollegiate Polo.
In the U.S., interscholastic and intercollegiate polo are played strictly in the arena.
As of 2017, there are 38 intercollegiate and 40 interscholastic teams. The interscholastic program has gained popularity in the past several years and teams have grown across the country. Interscholastic players are middle school and high school aged. Two divisions exist within Interscholastic (I/I): Girls and Open. At the Intercollegiate level, the two divisions and Men and Women. The USPA sponsors a program called Team USPA that trains and provides resources for talented I/I members who would like to compete as professional players. For both intercollegiate and interscholastic, after the regular season, regional tournaments are held to win a bid to the national tournament. These are held at facilities of the USPA's choosing. Polo is an NCAA Varsity sport at Cornell University, otherwise it is a club sport at the remaining schools. 