Bobsledding, also called bobsleighing, the sport of sliding down an ice-covered natural or artificial incline on a four-runner sled, called a bobsled, bobsleigh, or bob, that carries either two or four persons.

Britannica Quiz Winter Sports Quiz Which game is similar to lawn bowls but is played on ice?

Bobsledding developed in the 1880s both in the lumbering towns of upstate New York and at the ski resorts of the Swiss Alps. The first organized competition (among teams consisting of three men and two women) was held in 1898 on the Cresta Run at Saint Moritz, Switzerland. The sport earned its name after competitors adopted the technique of bobbing back and forth to increase the speed of the sled. In 1923 bobsledding became an internationally recognized sport with the organization of the Fédération Internationale de Bobsleigh et de Tobogganing and with its inclusion in the first Olympic Winter Games at Chamonix, France, the following year. Since 1931 both two-person and four-person world-championship competitions have been held yearly, except during World War II. Though women have participated in bobsledding since the sport’s creation, international competition for women did not begin until the 1990s. The women’s two-person bobsled event made its Olympic debut in 2002. The gold medal for the inaugural women’s event went to Jill Bakken and Vonetta Flowers of the United States. Flowers was the first black athlete to win an Olympic gold medal at the Winter Games.

The bob run used in international competition is between 1,200 and 1,600 metres (1,312 and 1,750 yards) long, with an average slope of between 8 and 15 percent. There are generally from 15 to 20 turns per course, ranging in size up to huge hairpins of more than 180°. Most bob runs have permanent foundations of concrete or stone, which are covered with several inches of ice. The straightaways have sidewalls of reinforced ice about 46 cm (18 inches) high. The large turns are banked very steeply, built up as high as 6 metres (20 feet), and may have an overhanging lip of ice to prevent the fast-traveling bobsleds from flying out of the turn.

Early bobsleds were built mostly of wood. Steel runners were adopted within a few years and, by the mid-20th century, steel and aluminum were used throughout. The four runners are generally mounted in pairs on two axles. Steering is accomplished by turning the front axle either with ropes or by a wheel linked to the axle by cables. The brake is a toothed bar that is pressed against the ice between the rear runners.

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Racing bobsleds have a streamlined cowling in front of the driver to reduce wind resistance. Two types are used: two-person boblets, as they often are called in Europe, and four-person bobsleighs. Rules limit combined team and sled weights to 390 kg (860 pounds) and 630 kg (1,389 pounds), respectively. The maximum team-and-sled weight for the two-women competition is 350 kg (770 pounds). Other sled dimensions are also specified.

Germany's Berit Wiacker and Sandra Kiriasis starting a two-woman bobsled run, 2009. Arno Balzarini—Keystone/AP

The start of the race is crucial to a team’s success. Riders, wearing cleated shoes, run alongside the sled, pushing it to achieve maximum velocity. As it builds speed, the riders jump in, the driver in front and the brakeman, pushing the back of the sled, entering last. The heavier four-person sleds attain speeds approaching 160 km (100 miles) per hour; the smaller, lighter two-person sleds are only slightly slower. A race consists of four descents by each team, the total time for the four heats determining the winner. Electric timing equipment measures elapsed time to 0.01 second.

A French national two-man bobsled team participating in a run. © Steeve ROCHE/Fotolia

Due in large part to their innovative sled design and construction, bobsledders from the United States were both successful and influential during the first half of the 20th century. Since then teams from Germany and Switzerland have dominated international competition.