Cycling is a means of transport, a form of recreation, and a sport. It involves riding bicycles, unicycles, tricycles and other human powered vehicles. A bicycle, the most notable instrument of cycling, is a pedal-driven land vehicle with two wheels attached to a frame, one behind the other. As a sport, cycling is governed internationally by the Union Cycliste Internationale, headquartered in Switzerland.
Bicycles were introduced in the 19th century and now number about one billion worldwide. They are the principal means of transportation in many parts of the world.
Cycling is widely regarded as a very effective and efficient mode of transportation optimal for short to moderate distances. Bicycles provide numerous benefits by comparison with motor vehicles, including the sustained physical exercise necessarily involved in cycling, that cycling involves a reduced consumption of fossil fuels, less air or noise pollution, much reduced traffic congestion, easier parking, greater maneuverability, and access to both roads and paths.
Bicycle and motorcycle dynamics
is the science
of the motion
and their components, due to the forces
acting on them. Dynamics
is a branch of classical mechanics
, which in turn is a branch of physics
. Bike motions of interest include balancing
activation, and vibration
. The study of these motions began in the late 19th century and continues today.
Bicycles and motorcycles are both single-track vehicles and so their motions have many fundamental attributes in common and are fundamentally different from and more difficult to study than other wheeled vehicles such as dicycles, tricycles, and quadracycles. As with unicycles, bikes lack lateral stability when stationary, and under most circumstances can only remain upright when moving forward. Experimentation and mathematical analysis have shown that a bike stays upright when it is steered to keep its center of mass over its wheels. This steering is usually supplied by a rider, or in certain circumstances, by the bike itself. Several factors, including geometry, mass distribution, and gyroscopic effect all contribute in varying degrees to this self-stability, but long-standing hypotheses and claims that any single effect, such as gyroscopic or trail, is solely responsible for the stabilizing force have been discredited.
While remaining upright may be the primary goal of beginning riders, a bike must lean in order to maintain balance in a turn: the higher the speed or smaller the turn radius, the more lean is required. This balances the roll torque about the wheel contact patches generated by centrifugal force due to the turn with that of the gravitational force. This lean is usually produced by a momentary steering in the opposite direction, called countersteering. Countersteering skill is usually acquired by motor learning and executed via procedural memory rather than by conscious thought. Unlike other wheeled vehicles, the primary control input on bikes is steering torque, not position.
Although longitudinally stable when stationary, bikes often have a high enough center of mass and a short enough wheelbase to lift a wheel off the ground under sufficient acceleration or deceleration. When braking, depending on the location of the combined center of mass of the bike and rider with respect to the point where the front wheel contacts the ground, bikes can either skid the front wheel or flip the bike and rider over the front wheel. A similar situation is possible while accelerating, but with respect to the rear wheel.
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Gregory James "Greg" LeMond
(born June 26, 1961) is a former professional road racing
cyclist, entrepreneur, and anti-doping advocate.
LeMond was World Champion in 1983 and 1989, and is a three-time winner of the Tour de France. LeMond was born in Lakewood, California, and raised in ranch country on the eastern slopes of the Sierra Nevada mountain range, near Carson City, NV. He is married and has three children with his wife Kathy, with whom he supports a variety of charitable causes and organizations.
In 1986, LeMond became the first non-European professional cyclist to win the Tour (and to this day, the only American, following Lance Armstrong's and Floyd Landis' disqualifications). He was accidentally shot while hunting in 1987 and missed the next two Tours. LeMond returned to the Tour de France in 1989, completing an improbable comeback by winning in dramatic fashion on the race's final stage. He successfully defended his title the following year, claiming his third and final Tour victory in 1990, which made LeMond one of only seven riders who have won three or more Tours. LeMond retired from competition in December 1994. He was inducted into the United States Bicycling Hall of Fame in 1996.
During his career, LeMond championed several technological advancements in pro cycling, including the introduction of aerodynamic "triathlon" handlebars and carbon fiber bicycle frames, which he later marketed through his company LeMond Bicycles. His other business interests have included restaurants, real estate, and consumer fitness equipment.
LeMond is a vocal opponent of performance-enhancing drug use, and at times his commercial ventures have suffered for his anti-doping stance—as in 2001, when he first accused Lance Armstrong of doping and sparked a conflict that led eventually to the dissolution of his partnership with Armstrong's primary sponsor, Trek Bicycles, who licensed the LeMond brand. As recently as December 2012, LeMond even articulated a willingness to replace the UCI president on an interim basis if called to do so.
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