How to watch the Olympic Track Cycling Keirin - a beginner's guide

The Derny

Keirin racing starts behind a pace bike known as a Derny. Combining a small engine with a traditional bicycle’s pedals-and-chain drivetrain, it’s capable of precisely controlled acceleration and deceleration, which makes it ideal for pacing riders up to speed. The Derny was traditionally used as a pacer in road cycling’s longer single-day events, such as the 560Km Bordeaux-Paris, but as those races fell out of favour the Derny became a fixture at track events where it’s now used to start the Keirin.

The Derny rider sits bolt upright to provide a windbreak for the following riders as the Derny gradually accelerates from a cruising speed of about 30kph up to a decidedly taxing speed of around 50kph before pulling aside two-and-a-half laps from the finish of the eight-lap race.

The Race

Not only do the riders have to keep pace with the accelerating Derny, they also have to manoeuvre for position behind it. Having been paced up to speed, Keirin riders will be able to launch incredibly fast attacks for the line once the Derny peels off. Some riders, such as the reigning Olympic champion, Team GB’s Sir Chris Hoy, favour an immediate attack from directly behind the Derny. Cagier riders prefer to carefully time their sprint so that they can accelerate just as the riders in front start to fade.

The Contenders

Sir Chris Hoy is the favourite by a wide margin: he has won four World Championship and one Olympic Gold medals in the Keirin, although he will face competition from France’s Mickael Bourgain and Germany’s Maximilian Levy. In the women’s event, old rivals Victoria Pendleton and Anna Meares are among the favourites for a medal, as are China’s Guo Shuang and Lithuania’s Simona Krupeckaite.

The heats of the women's Keirin start at 4pm today, with the finals at 6:38pm, on BBC2 and BBC Olympics 8