The first mountain bike competitions were held in California (USA) in the early eighties. Since then the discipline has grown very fast, in all aspects. The first World Championships to be officially recognized by the UCI dates back to 1990. A World Cup was set up the following year. The mountain bike disciplines comprise the following formats: Cross-Country Olympic (XCO) Cross-country is part of the Olympic programme. Cross-country races are held over undulating circuits (with technical descents, forest roads, rocky paths and obstacles) of 4 to 6 km. The race varies from 1 h 20 minutes to 1 h 40 minutes depending on the category. Cross-country Marathon (XCM) The Cross-country marathon events are a long version of cross-country held over a course of 60 to 160 km. A special feature is that riders from all categories, from enthusiasts to professionals, race together. The marathon is held in a mountainous region. Downhill (DHI) Downhill is a race against the clock in which the rider negotiates a succession of fast and technical passages. The participant must demonstrate courage as well as sharp technical and piloting skills in order to affront tree roots, banked sections, bumps, jumps and other natural obstacles along the way. Speeds reach around 80km/h in the men’s races and 70km/h for women. Enduro (END) Enduro events includes several liaison stages and timed stages. The times achieved in all timed stages will be accumulated to a total time. An enduro course comprises varied off-road terrain. The track should include a mixture of narrow and wide, slow and fast paths and tracks over a mixture of off-road surfaces. Enduro racing requires athletes to use a combination of endurance, speed and technical skills. Cross-country Eliminator (XCE) The Cross-country eliminator event must be between 500m and 1000m. It’s is a fast-moving, dynamic, action-packed format in which four riders race in heats on technical tracks featuring obstacles such as jumps and bridges. Competitions begin with a qualifying heat  that takes the form of an individual timed lap of the circuit, as a result of which the fastest 32 men and 16 women qualify for the main competition. The fastest two riders in each heat thereafter qualify for the next round, with the format continuing until only four riders remain to contest the final. Four-Cross (4X) In four-cross (often abbreviated to “4X”), four participants set off together to ride down a track that alternates banked corners and jumps. The races are very rapid (between 30 seconds and one minute) and give rise to fierce and closely contested confrontations between the riders. The winner is the first to cross the finish line. The four-cross races take place over several qualifying rounds. Source: uci.org/mountain-bike/about-mountain-bike