Next to the various forms of competitive running, cycling is the most popular sport in the world where the human body provides propulsion power. The bicycle has captured the imagination of great thinkers and the mass of humanity alike for hundreds of years, commencing with the designs of the Renaissance scientist and thinker Leonardo da Vinci (1452–1519).

The first truly functional two-wheeled machines were developed in Europe in the early 1800s, usually built with a large front wheel to overcome the absence of a gearing system to assist with the efficient delivery of power to the wheels.

Bicycle technology grew quickly through the mid-1800s, and the first bicycle race was organized in France in 1868 in response to the rising popularity of cycling. The development of simple gearing systems, which made hill climbing and greater speeds more readily attainable, was followed by the advent of mass-produced bicycles. The twentieth century saw the introduction of rubber inflatable tires and the invention that made multi-geared bicycle systems a reality. Paul de Vivie (1853–1930), known by the evocative name Velocio, invented the first functional derailleur, which refers to the assembly of bicycle chain, sprockets, and supporting mechanism to move the chain between sprockets and therefore create multiple gearing.

Bicycle racing on the roads began in earnest in 1903 with the inaugural Tour de France, an annual event that is contested on a demanding race course that loops through the regions of France. The Tour is the most famous bicycle race in the world, and the desire of cyclists to succeed in the Tour de France and the other European races that followed it spurred further technological developments in cycling. Frames became lighter, as first aluminum (in 1977) and later, carbon fiber composite frames, made the bicycles faster. The gears, handle bars, and other components also became more aerodynamic and efficient.

The birth of the universally popular mountain bike is very difficult to pinpoint; there have long existed bicycle enthusiasts prepared to ride their machines over rough and difficult terrain. In California in the 1970s, there slowly grew a bicycling community that rode some of the uneven trails of the Sierra Mountains on modified, heavy-framed bicycles that could absorb a significant pounding. In the 1980s, the mountain bike became a recognized cycling form, as these machines also became lighter, stronger, and more maneuverable. With the insertion of both front and rear wheel shock absorbers, the mountain bike became a very durable and relatively speedy vehicle. Mountain bike racing itself grew into a world event, with a first inclusion in the Summer Olympics in 1996.

A third form of bicycle racing grew directly from the development of the road-racing bicycles in the early 1900s. The "velodrome" is a specially designed indoor oval circuit, typically 330 yd (300 m) in length, on which bicycle racers compete in a number of different formats. The velodrome became a prominent bicycle-racing venue in the early part of the twentieth century. These contests differed from the road races as they tended to be shorter, sprint races, often conducted as a time trial as opposed to the declaration of the race winner as the first racer past the finish line.

The three types of bicycle racing have been precisely codified into separate disciplines; the tactics and the training associated with each is sufficient to permit each a designation as a separate sport, as opposed to existing as a subset of the sport of cycling. All types of bicycle racing are conducted at various times in most regions of the world; the Olympic Games is the only venue where all three disciplines are contested at one time.

Road racing, of which the Tour de France is the most famous example, is today the preserve of year-round professional athletes. The most notable rivals of the Tour for international prestige are the Giro d'Italia and the Tour of Spain. Each of these races has individual and team components, in which the event is divided into segments referred to as stages; the overall individual champion is the rider who finishes the entire course in the shortest aggregate time.

The winner of the Tour de France is regarded as a true international sports hero, and the race encourages a dynastic quality in its champions; since 1969, Eddie Mercyx (Belgium, five victories), Miguel Indurain (Spain, five victories), Greg Lemond (United States, three victories), and Lance Armstrong (United States, seven victories) are examples of this multi-year superiority.

Road races that are conducted in one-day formats, as opposed to stages, are held either as a mass start, also referred to as an inline road race, or as a time trial. As the name suggests, the mass start involves the racers heading off from the starting line in a pack; the combination of riders attempting to secure a better position, acceleration, and inevitable collisions often results in falls near the start. A time trial is conducted with each rider starting in 1.5-minute intervals. The winner is not the first to cross the finish line, but the rider with the best overall time. Both types of road racing are contested at the Olympics; a Tour de France-style multi-day stage race is not.

The Olympic road-racing distances consist of mass start and time trial types of races. In the case of the mass start, the race is a number of circuits of a city road course; male competitors race between 135 mi and 150 mi (210 km and 240 km); women race between 50 mi and 75 mi (80 km and 126 km). The time trials type of race has more of what cyclists refer to as a sprint element; men race on a course between 28 mi and 34 mi (45 km and 55 km) long; the women race on a course that is between 15 mi and 21 mi (25 km and 35 km) long.

Mountain biking is also a men's and a women's competition at the Olympics. The race course comprises a number of circuits, often with dramatic changes in elevation; falls and crashes are not uncommon.

Track racing is the most varied of the Olympic cycling disciplines; it is common for an Olympic cyclist to race in a number of the distances provided for in velodrome racing. Velodromes are typically composed of a highly polished wooden track, two 180°-banked turns, and two connecting straights. Velodromes may vary in length; the Olympic velodrome at Athens used for the 2004 Games was 800 ft (250 m) long and 22 ft (7 m) wide.

The best-known forms of track racing include the individual and team pursuit racing, the time trial, and the match sprint. In individual and team pursuit racing, the racers start at opposite sides of the track. This form of racing does not permit a standard cycling tactic, known as drafting. Drafting is the technique used in sports (auto racing is a prominent example) in which an opponent in the lead generates a wake in the air that results in a partial vacuum being created in the air behind the opponent. Cyclists will position themselves as close as they can to the rear wheel of the leading athlete to take advantage of the reduced air resistance of the vacuum as well as the minor drag of the air being pulled by the opponent. At an opportune moment, the trailing cyclist will accelerate to "slingshot" themselves past the leader. In a time trial event, the racer competes against the clock. In the match sprint, two racers simultaneously start on the track, with the first 875 yd (800 m) a slow jockeying for position, and the

Mountain cycling race courses comprise a number of circuits, often with dramatic changes in elevation. Falls and crashes are not uncommon.
final 218 yd (200 m) a sprint for the finish. Tactics and position on the banked track are of critical importance in this form of racing.

The training programs employed by all cyclists have a number of common features, given that the dynamics of powering a bicycle are essentially the same for a road, mountain, or track bicycle. An important aspect of any cyclist's month-to-month training is a program of stretching and calisthenics, often accompanied by yoga or a Pilates program, to both increase flexibility and to assist with recovery from the rigors of long races. However, sprint racers will often add plyometrics exercises to assist in developing more explosiveness in the quadriceps and calf muscles. Mountain bikers must utilize their upper arm strength to negotiate the obstacles presented by the terrain; these athletes derive a significant benefit from structured weight-training programs. Road racers have found that a weight-training/resistance program directed at the abdomen, lumbar spine, and related muscle structures provides them with strength in the saddle in long daily cycles. All cyclists will develop a training system that will incorporate a form of interval training into the workout structure, in which the intensity of work, both sprinting-based and hill climbing, is performed in repeated segments of varying distance, time, and intensity.

As with many sports, the increase in professional competition and the corresponding financial rewards led to the use of a variety of performance-enhancing substances by cyclists. Prior to the development of reliable drug testing procedures in the late 1980s, a number of Tour de France riders were injured or

Lance Armstrong is one of only a few multi-year winners of the Tour de France.
killed due to heart failure caused by the combination of ingested chemical stimulants and the exertions of the race. Stimulant usage in cycling by way of amphetamines, used to assist riders in battling fatigue and keeping them alert, gave way to more subtle applications, including the naturally occurring ephedra, or ephedrine.

The demands of long-distance cycling had posed an often ultimate test for even the most skilled and fit of road racers. Blood doping, in the form of transfusions of the cyclist's own blood, had been experimented with by various cyclists in the late 1970s, prior to the practice being outlawed. The removal of blood from the body of the athlete, freezer storage of the extracted blood, and the reinfusion of the blood into the body in the week before a competition was a process known to increase red blood cells available to the body for better oxygen transportation during the activity. The physical transfusion carried with it a number of risks, including that of excessive blood clotting that might lead to stroke.

In the 1980s, the hormone produced by the body to stimulate red blood cell production naturally, erythropoietin (EPO), was first synthesized. Additional EPO was naturally generated by an athlete who had red blood cells depleted through injury, or when the athlete was training at an altitude where the body required more red blood cells to combat the lack of oxygen. When EPO could be injected into the body, with the resultant creation of additional red blood cells, a startlingly effective performance enhancement was created. EPO is a certain method for improving oxygen capacity, especially when combined with vigorous training. It was banned as a supplement, along with other plasma-expanding drugs, by various international sport bodies, including the International Olympic Committee, in 1996. Controversies have swirled over the reputations of a number of international cyclists regarding their actual or presumed EPO use. One example was the Phonak cycling team, competitors in many of the leading European races, had four of its members test positive for EPO or related compounds between the 2003 and the 2005 seasons.

SEE ALSO Cycling strength training and exercises; Endurance; Exercise and fluid replacement; Road rash.