Cyclo-cross has some obvious parallels with cross-country cycling and criterium racing. Many of the best cyclo-cross riders cross train in other cycling disciplines. However, cyclo-cross has reached a size and popularity that racers are specialists and many never race anything but cyclo-cross races. Cyclo-cross bicycles are similar to racing bicycles: lightweight, with narrow tires and drop handlebars. However, they also share characteristics with mountain bicycles in that they utilize knobby tread tires for traction, and cantilever style brakes for clearance needed due to muddy conditions. They have to be lightweight because competitors need to carry their bicycle to overcome barriers or slopes too steep to climb in the saddle. The sight of competitors struggling up a muddy slope with bicycles on their shoulders is the classic image of the sport, although unridable sections are generally a very small fraction of the race distance.
Compared with other forms of cycle racing, tactics are fairly straightforward, and the emphasis is on the rider's aerobic endurance and bike-handling skills. Drafting, where cyclists form a line with the lead cyclist pedaling harder while reducing the wind resistance for other riders, is of much less importance than in road racing where average speeds are much higher than in cyclo-cross.
A cyclo-cross rider is allowed to change bicycles and receive mechanical assistance during a race. While the rider is on the course gumming up one bicycle with mud, his or her pit crew can work quickly to clean, repair and oil the spares. Having a mechanic in the "pits" is more common for professional cyclo-cross racers. The average cyclo-cross racer might have a family member or friend holding their spare bike.
After Octave Lapize attributed his win in the 1910 Tour de France to his off season training in cyclo-cross the sport began to spread to countries bordering France. Belgium organized its first National Championship in 1910, Switzerland did so in 1912, then Luxembourg in 1923, Spain in 1929 and Italy in 1930.
Cyclo-cross proved itself as a sport extending beyond the boundaries of France when in 1924 the first international race, Le Critérium International de Cross-Country Cyclo-Pédestre, was held in Paris.
Like many international cycle sports, CX is administered by the Union Cycliste Internationale; although it wasn't until the 1940s, around 40 years after cyclo-cross' inception, that the UCI began its regulation and the first world championship was held in Paris in 1950.
Cyclo-cross began to become popular in the US in the 1970s and in 1975 the first US National Championship was held in Berkeley, CA. The Surf City race series held in Santa Cruz, CA holds a lot of history of cyclo-cross in the US. The sport has experienced a growth in popularity in the US since the mid 90s and now Portland, Oregon hosts some of the largest events in the country.
Due to different racing seasons, a cyclocross racer's "age" is always one year older than their road racing "age".
Each section of the course typically lasts no longer than a handful of seconds. For example long climbs are avoided in favour of short, sharp inclines. Sections are generally linked together, or long straights broken up, with tight corners. This not only allows a standard length course to fit in a relatively small area, but also forces competitors to constantly change speed and effort. Accelerating out of corners, then having to decelerate for the next before accelerating again is a common theme.
Obstacles that force a rider to dismount and run with their bike or to "bunny hop" include banks too steep to ride up, steps, sand pits and plank barriers. Besides the start/finish area, these obstacles may be placed anywhere on the course that the race director desires. Several race directors have tried to limit bunny hopping by placing barriers in pairs or in triple (although under UCI rule no more than two barriers can appear in succession), however this hasn't stopped some of the best bunny-hoppers from getting over them. The regulation height for a barrier is 40 cm although this is treated as a maximum at smaller events. Plank barriers seem to be more common in the US than in Europe and UCI regulations only permit one section of them on the course.
Since outside assistance is allowed, pits are included to provide a consistent area for this to occur. A pit to the right of the course is normal since most rides dismount to their left. In larger events a separate pit lane is featured so only those wishing a new bike or other assistance need enter the lane (this type was debuted at the Zeddam, Netherlands World Cup of January 1999). In some cases pits are provided in two different parts of the course.
An exception to this short course format include the Three Peaks, a 61 km single lap race held annually in Yorkshire.
A more recent development to overcome obstacles such as barriers and sometimes ditches is the bunnyhop which began its popularity in 1989 when Danny de Bie used it to his success in becoming World Champion. Bunny hopping is less popular today due to race directors setting up barriers two or three in a row to limit its use. Although, several skilled riders are still able to do so despite the back to back to back barriers. Today Sven Nys, an ex-BMX racer, proves the importance of technical skills as he continues to dominate the sport.