In Mountain Bike events, riders may carry out their own repairs, and are only allowed to receive outside assistance in dedicated assistance zones should they have any mechanical problems.
Mount Tamalpais in California is widely considered to be the birthplace of Mountain Biking.
Mountain Biking originally consisted of stripping down cruiser bicycles and racing them down fire roads and trails.
Having won gold in 2004 and 2008, Julien Absalon is going for a hat-trick at London 2012.