BMX, an abbreviation for bicycle motocross, is a cycle sport performed on BMX bikes, either in competitive BMX racing or freestyle BMX, or else in general on- or off-road recreation. BMX began when young cyclists appropriated motocross tracks for fun, racing and stunts, eventually evolving specialized BMX bikes and competitions.
Eight riders compete on a track filled with jumps, tight bends, berms and obstacles. Athletes wear full-face helmets in this rough-and-tumble discipline. Bikes have one gear and one brake and must be strong enough to withstand the rigors of the course, yet light and fast.
"BMX racing action photo" by Fabrizio Tarizzo - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:BMX_racing_action_photo.jpg#/media/File:BMX_racing_action_photo.jpg