Cycle sport is competitive physical activity using bicycles. There are several categories of bicycle racing including road bicycle racing, time trialling, cyclo-cross, mountain bike racing, track cycling, BMX, and cycle speedway. Non-racing cycling sports include artistic cycling, cycle polo, freestyle BMX and mountain bike trials. The Union Cycliste Internationale (UCI) is the world governing body for cycling and international competitive cycling events. The International Human Powered Vehicle Association is the governing body for human-powered vehicles that imposes far fewer restrictions on their design than does the UCI. The UltraMarathon Cycling Association is the governing body for many ultra-distance cycling races.