An offshoot of motorized dirt biking, this pedal-powered version of the sport made its Olympic debut in Beijing. On smallish but sturdy bikes, helmeted, comprehensively armored riders will make their frenetic way around a track roughly a quarter-mile long laced with berms, banks and corrugated "whoop" sections designed to ensure they spend as much time hurtling through the air as they do on terra firma. Crashes are common.
After a seeding phase in which riders take an individual lap, races switch to a mass-start format. After three runs, the best two riders from each quarterfinal progress to the semis, which also follow a three-run format. Top four riders from each semifinal advance to the final, where the medals are decided over one run.
British BMX rider Liam Phillips will line up at the start of the men's BMX event despite snapping his left collarbone cleanly at the Worlds in Birmingham in May. "I had surgery and it was plated," he told BBC News, "which means I can get back to training almost immediately."
On the Olympic program since 1996 in Atlanta, mountain biking features a mass start, followed by riders making multiple laps on a rugged, technical course (think narrow, rutted, roots, rocks) featuring at least one nasty climb. The circuit at Hadleigh Farm, in Essex, east of London, is 5.1 kilometers, and features 210 feet of climbing per lap. Officials will decide the number of laps just before the race, which will last around two hours.
No American has medaled in this made-in-the-USA sport since Susan DeMattei took bronze at the '96 Games in Atlanta.