Many consider cyclocross to be a steeplechase with modified road bikes on a 2km course over hill and dale; others consider it muddy hell. Its roots can be traced to the early 1900s, when French army private Daniel Gousseau would ride his bicycle along horseback-riding friends through the woods.
The cyclocross scene is strong in Europe, with some of the most aggressive and successful racers hailing from Belgium, the Netherlands, France, Italy and the Czech Republic. But it's currently enjoying a massive boom in the US, along with a renaissance in the UK.
Traditionally, the cyclocross season runs from September to January, ending with the UCI World Championships.
Video: Andy Hargroves and Steve James explain cyclocross
Like triathlon, cyclocross mixes multiple athletic endeavours, namely riding and running, with a strong emphasis on skillful bike handling. The pace, barriers, climate and technical aspects of the course weed out the weak and make for good theatre. Spectators with horns and cowbells provide a festival environment, especially in Europe.
Most races are held on 1km to 3km courses, mixing tarmac, sand, dirt, mud, run-ups and sometimes steps. Races typically last a set timespan – between 30 minutes and an hour – plus a final lap. However, if you're lapped by the leaders then you have to pull out at the end of that lap to avoid confusion. The pace at the sharp end is unrelenting and brutally fast, and the stop-go nature of the courses and racing means you get an intense workout.
Man-made barriers, usually 18in high, pepper the course, sometimes staggered close enough to force racers to shoulder their bikes or carry them by the top tube. Speed demons with incredible BMX skills have been known to bunnyhop the barriers, much to the chagrin of their fellow racers but awe of the spectators.
There are a few ways to address the barriers, but for efficiency and speed the best way to dismount is to unclip your right foot as you're approaching the barrier or run-up, swing your leg around the saddle and in between your left foot and the bike. Unclip your left foot as your right strikes the ground, catapulting yourself forward just in time to hop over the barrier or clamber up the hill.
If there are several barriers in a row, it's sometimes best to shoulder the bike (see why it pays to have the lightest bike you can afford?). Or, if you're tall and have good upper body strength, carry the bike by the handlebar with your left hand as your right lifts the top tube. Run-ups are always best accomplished by shouldering the bike, and pumping your left arm for momentum.
The ideal cyclocross race bike is a road/mountain bike cross-polination: lightweight aluminum, carbon, steel or titanium frame; carbon fork; drop bars (for leverage on climbs, and for sprinting); integrated shifters/brake levers; 700c x 30-38c (1.2-1.5in) knobby tyres; mountain bike clipless pedals; and a double or single chainring (smaller than on a road bike) with guard. Mud clearance is a big issue; the fork and rear stays need room for mud to build up on the tyres without clogging.
Frames and forks are tougher than on standard road bikes, top tubes are shorter and bottom brackets are often slightly higher. Disc brakes are now allowed for cyclocross racing, potentially giving powerful all-weather braking. Many racers still use linear-pull (V) brakes or cantilevers, which give plenty of power when set up right. Top-bar brake levers are often added for better control.
Many cyclocross bikes play to their utility potential, with mudguard and rack mounts for commuting/weekend exploring work. There's also a growing number of crossover-style bikes, which trade race weight and jarring rigidity for a heavier and more forgiving chassis, often in smooth-riding steel.