Sleds and sleighs have been a part of the winter transportation used in cold climates for many hundreds of years. Two thin runners, first constructed of wood and later of steel, are an efficient device for travel over snow or ice. The downward force of the weight supported by the sled is applied over the entire length the runners, which reduces the friction.
At the Swiss resort town of St. Moritz in 1897, the bobsled was used for the first time. Visitors rode the invention for fun and recreation, descending along a natural ice track that was available on a hill at the resort. The early machines were simply a crude steering device attached to the runners of a sled; the name bobsled (spelled bobsleigh in Europe) derived its name from the rocking or bobbing motion that the occupants of the sled made in their attempts to make the sled go faster. It is a footnote of history that the name was the result of poorly applied science, as the laws of physics support the proposition that when sliding downhill, the less motion inside the sled, the less deviation from the optimal path of travel.
The International Bobsleigh and Toboggan Federation, known by its French language acronym of FIBT, was founded in 1923. The related but distinct sport of skeleton racing, which employs a small sled operated by a single racer propelled headfirst down the race course, is also governed by the FIBT. The bobsled event was a part of the inaugural Winter Olympics in 1924. An annual bobsled World Cup circuit gained popularity in the 1980s, where the competitors race in a series that declares an annual world champion, in both two-man and four-man categories. Once exclusively a male sport, women's bobsled became popular in the 1990s and is now included as a two-person category at the Olympics.
The modern bobsleds are a product of intense technological development, where science operates to the very limit of the prescribed rules of the sport. The two-man sleds are a maximum of 8.3 ft (2.7 m) long, and weigh 858 lb (390 kg); the four-man sleds are 11.8 ft (3.5 m) long, weighing a maximum of 1,386 lb (630 kg); the permitted weights are that of crew and sled combined. The steel runners must not be lubricated or heated in any fashion that would create less friction as the sled travels along the track.
The modern bobsled run is an artificial ice track, constructed with a series of banked turns and straight sections. The modern St. Moritz run is a typical bobsled track configuration, with a length of 1.05 mi (1,772 m), a vertical drop of 399 ft (129 m), and an average grade of 8.1%. A four-man bobsled will typically reach a top speed of approximately 85 mph (140 km/h) during a run.
The aerodynamics of the sled and the crew are crucial to bobsled performance. The sleds are a constantly evolving shape, a product of both racing and wind tunnel technology concerning the minimizing of drag on the sled. Drag is the force of the air resistance applied to both the bobsled and its crew as it moves through the air. The surface of the sled also generates skin friction, which can reduce the speed of the sled. The sleds for this reason are sleek and aerodynamically efficient; the crew members behind the driver take positions where their heads are below the line of the driver's head, who sits at a height where only the eyes are above the top of the sled. The crew all wear sleek helmets, with uniforms constructed from materials that also reduce drag.
Bobsled speed is a result of the power developed at the start and the piloting skills of the driver along the course. The start is initiated by the push from the gate, over a 165 ft (50 m) distance, within which the bobsled is pushed as hard as is possible, with the crew members "loading" into the sled in a synchronized sequence. As a general rule, every 0.1 seconds lost at the start, a cumulative 0.3 seconds will be lost in finishing time. The crew members wear specialized shoes with which to gain traction on the ice.
Once loaded, the race is the responsibility of the driver, who must pilot the sled through the various angles and curves of the course. A driver often does not reach a competitive peak until after 10 or more years of competition, as the subtlest of driving errors in the selection of the line of the bobsled through a curve can mean the hundredths of seconds between victory and a fifth place finish. Bobsled is scored cumulatively, meaning that the total time for four runs is the measure of the competition. Drivers will typically spend hundreds of hours per year studying the courses where they will race. Modern bobsled simulators have made this aspect much easier, as the simulators may be programmed with the specifications of any bobsled run in the world, and the driver can pilot the simulator over the virtual course. Much like a flight training simulator, the devices can replicate the effect of gravity (g force) on the driver, which on a world-class run will sometimes exceed 4.0 g forces.
All members of a crew must be extremely fit. However, the drivers' responsibilities create a specialized role for them, and they are not expected to be as powerful as the crew. Given the paramount importance of the starting push, the crew must be very fast and very powerful. In recent years, a number of former 100 m sprinters and American football players have been recruited into the bobsled for this reason. The bobsled start is a classic anaerobic exercise, lasting no more than approximately six seconds. Repetition of the sprinting starts, weight training directed at the development of muscle mass and strength (the heavier the crew, the lighter the sled and the easier the sled is to push faster), and plyometrics exercises to enhance explosion are all a part of bobsled physical training.