Cycling
Cycling  is the use of bicycles, unicycles, tricycles, quadricycles and other similar wheeled human powered vehicles (HPVs) as a means of transport, a form of recreation or a sport.  It is done on roads and paths, across open country, through tunnels, over bridges, on snow, or even over ice (icebiking).

# Introduction
As a sport, cycling is governed internationally by the Union Cycliste Internationale in Switzerland (for upright bicycles) and by the International Human Powered Vehicle Association (for other HPVs, or human-powered vehicles). Cycling for transport and touring is promoted on a European level by the European Cyclists' Federation, with associated members from Great Britain, Japan and elsewhere. Regular conferences on cycling for transport are held under the auspices of Velo City; global conferences are coordinated by Velo Mondial .

## Equipment
In many countries, the most commonly used vehicle for road transport is a utility bicycle.  These have frames with so-called relaxed geometry, protecting the rider from shocks from the road, and easing low speeds steering. Road bikes tend to have a more upright shape and a shorter wheelbase, which make the bike more mobile but harder to ride slowly. The design, coupled with low or dropped handlebars, requires the rider to bend forward more, which reduces air resistance at high speed.
The price of a new bicycle can range from US$50 to more than US$20,000, depending on quality, type and weight (the most exotic road bicycles can weigh as little as 3.2kg (7 lb)) ). Being measured for a bike and taking it for a test ride are recommended before buying.
The drivetrain components of the bike should also be considered.  A middle grade derailleur is sufficient for a beginner, although many utility bikes come equipped with hub gears.  If the rider plans a significant amount of hillclimbing, a triple-crank (three chainrings) front gear system may be preferred.  Otherwise, the relatively lighter and less expensive two chainrings may be better.
Many road bikes include clipless pedals to which special shoes attach via a cleat, permitting the rider to pull on the pedals as well as push. Other possible accessories for the bicycle include locks, mudguards (UK)/fenders (US), luggage carriers and pannier bags, water bottles and bottle cages.
For basic maintenance and repairs, cyclists can choose to carry a pump, a spare inner tube, a CO2 cartridge, a puncture repair kit and tyre levers. Cycling can be more efficient and comfortable with special shoes, gloves, and shorts. In wet weather, riding can be more tolerable with waterproof clothes, such as cape, jacket, trousers and overshoes.
Items legally required in some jurisdictions, or voluntarily adopted for safety reasons, include bicycle helmets, generator or battery operated lighting, and audible signaling devices such as a bell or horn.  Extras include studded tires and a bicycle computer.

## Skills
Learning to ride efficiently and safely in traffic is important. In the United Kingdom, many primary school children take the Cycling Proficiency Test, to help them travel more safely. However, the Cycling Proficiency Test has now been superseded, for children, by 'Bikeability'  and the National Standards for Cycle Training. In countries such as the Netherlands, where cycling is popular, cyclists sometimes ride in bike lanes at the side of or separate from, the main highway. Many primary schools participate in the national road test in which children individually complete a circuit on roads near the school while being observed by testers.

# Types of cycling

## City
Cyclists and motorists make different demands on road design which may lead to conflicts.  Some jurisdictions give priority to motorised traffic, for example setting up one-way street systems, free-right turns, high capacity roundabouts, and slip roads.  Others may apply traffic restraint measures to limit the impact of motorised transport.  In the former cases, cycling has tended to decline while in the latter it has tended to be maintained.  Occasionally, extreme measures against cycling may occur.  In Shanghai, where bicycles were once the dominant mode of transport, bicycle travel on a few city roads was banned temporarily in December 2003.
In areas in which cycling is popular and encouraged, cycle-parking facilities using bicycle stands, lockable mini-garages, and patrolled cycle parks are used to reduce theft.  Local governments promote cycling by permitting the carriage of bicycles on public transport or by providing external attachment devices on public transport vehicles.  Conversely, an absence of secure cycle-parking is a recurring complaint by cyclists from cities with low modal share of cycling.
Extensive bicycle path systems may be found in some cities.  Such dedicated paths often have to be shared with in-line skaters, scooters, skateboarders, and pedestrians. Segregating bicycle and automobile traffic in cities has met with mixed success, both in terms of safety and bicycle promotion.  At some point the two streams of traffic inevitably intersect, often in a haphazard and congested fashion.  Studies have demonstrated that, due to the high incidence of accidents at these sites, some such segregated schemes can actually increase the number of car-bike collisions.
Bicycles are considered a sustainable mode of transport, especially suited for urban use and relatively shorter distances when used for transport (compared to recreation).  Case studies and good practices (from European cities and some world-wide examples) that promote and stimulate this kind of functional cycling in cities can be found at Eltis, Europe's portal for local transport.
In the Netherlands bicycle paths are widespread and are (in the cities) not allowed for scooters. Cyclists in the Netherlands are well protected as the law assumes the stronger participant (i.e. the car) guilty party in all accidents involving weaker traffic unless evidence of the opposite is provided. Furthermore, drivers know to expect bikes, which are plentiful and treat traffic rules more as guidelines. Due to these issues the number of car-bike collisions with serious consequences is not alarmingly high in the Netherlands

## Commercial
The postal services of many countries have long relied on bicycles.  The British Royal Mail first started using bicycles in 1880; now bicycle delivery fleets include 37,000 in the UK, 25,700 in Germany, 10,500 in Hungary and 7000 in Sweden.  The London Ambulance Service has recently introduced bicycling paramedics, who can often get to the scene of an incident in Central London more quickly than a motorised ambulance.
Late in the 20th century, urban police bicycles became more common, as the mobility of car-borne officers was increasingly limited by traffic congestion and pedestrianisation.
Bicycles enjoy substantial use as general delivery vehicles in many countries.  In the UK and North America, generations of teenagers have got their first jobs delivering newspapers by bicycle.  London has many delivery companies that use bicycles with trailers.  Most cities in the West, and many outside it, support a sizeable and visible industry of cycle couriers who deliver documents and small packages.  In India, many of Mumbai's Dabbawalas use bicycles to deliver home cooked lunches to the citys workers.  In Bogota, Colombia the citys largest bakery recently replaced most of its delivery trucks with bicycles.  Even the car industry uses bicycles.  At the huge Mercedes-Benz factory in Sindelfingen, Germany workers use bicycles, colour-coded by department, to move around the factory.

## Recreational
Bicycles are used for recreation at all ages. Bicycle touring, also known as cyclotourism, involves touring and exploration or sightseeing by bicycle for leisure. A brevet or randonnee is an organized long-distance ride.
One popular Dutch pleasure is the enjoyment of relaxed cycling in the countryside of the Netherlands. The land is very flat and full of public bicycle trails where cyclists aren't bothered by cars and other traffic, which makes it ideal for cycling recreation. Many Dutch people subscribe every year to an event called fietsvierdaagse  four days of organised cycling through the local environment. Paris-Brest-Paris (PBP), which began in 1891, is the oldest bicycling event still run on a regular basis on the open road, covers over 1200 km and imposes a 90-hour time limit.  Similar if smaller institutions exist in many countries.
Many cycling clubs hold organized rides in which bicyclists of all levels participate.  The typical organized ride starts with a large group of riders, called the mass, bunch or even peloton.  This will thin out over the course of the ride.  Many riders choose to ride together in groups of the same skill level to take advantage of drafting.
Most organized rides, for example Cyclosportives, Challenge Rides or reliability trials, and hill climbs (Hillclimbing (cycling)) include registration requirements and will provide information either through the mail or online concerning start times and other requirements.  Rides usually consist of 25, 50 and 100 mile routes, each with a certain number of rest stops that usually include refreshments, first aid and maintenance tools.
Mountain biking grew in the late 20th century, including recreation and racing.

## Racing
Shortly after the introduction of bicycles, competitions developed independently in many parts of the world. Early races involving boneshaker style bicycles were predictably fraught with injuries. Large races became popular during the 1890s "Golden Age of Cycling", with events across Europe, and in the U.S. and Japan as well.  At one point, almost every major city in the US had a velodrome or two for track racing events. However since the middle of the 20th Century cycling has become a minority sport in the US whilst in Continental Europe it continues to be a major sport, particularly in France, Belgium and Italy. The most famous of all bicycle races is the Tour de France. This began in 1903, and continues to capture the attention of the sporting world.
In 1899, Mile-a-Minute Murphy became the first man to ride a bicycle a mile in under a minute.
As the bicycle evolved its various forms, different racing formats developed.  Road races may involve both team and individual competition, and are contested in various ways. They range from the one-day road race, criterium, and time trial to multi-stage events like the Tour de France and its sister events which make up cycling's Grand Tours. Recumbent bicycles were banned from bike races in 1934 after Marcel Berthet set a new hour record in his Velodyne streamliner (49.992 km on 18 November 1933). Track bicycles are used for track cycling in Velodromes , while cyclo-cross races are held on rugged outdoor terrain.  In the past decade, mountain bike racing has also reached international popularity and is even an Olympic sport.
Professional racing organizations place limitations on the bicycles that can be used in the races that they sanction. For example, the Union Cycliste Internationale, the governing body of international cycle sport (which sanctions races such as the Tour de France), decided in the late 1990s to create additional rules which prohibit racing bicycles weighing less than 6.8 kilograms (14.96 pounds). The UCI rules also effectively ban some bicycle frame innovations (such as the recumbent bicycle) by requiring a double triangle structure.

## War
The bicycle is not suited for combat, but it has been used as a method of reconnaissance as well as transporting soldiers and supplies to combat zones. In this it has taken over many of the function of horses in warfare.  Bicycles were used in the Second Boer War, where both sides used them for scouting. In World War I, France and Germany used bicycles to move troops. In its 1937 invasion of China, Japan employed some 50,000 bicycle troops, and similar forces were instrumental in Japan's march or "roll" through Malaysia in World War II.  Germany used bicycles again in World War II, while the British employed airborne "Cycle-commandos" with folding bikes.
In the Vietnam War, communist forces used bicycles extensively as cargo carriers along the Ho Chi Minh Trail. There are reports of mountain bicycles being used in scouting by U.S. Special Forces in the U.S. invasion of Afghanistan and in subsequent battles against the Taliban. British troops, designated Light Bicycle Infantry LBI, used bicycles to patrol in Basra, Iraq in January 2005.
The last country known to maintain a regiment of bicycle troops was Switzerland, who disbanded their final unit in 2003.

# Activism
Two broad and correlated themes run in bicycle activism: one is about advocating the bicycle as an alternative mode of transport, and the other is about the creation of conditions to permit and/or encourage bicycle use, both for utility and recreative cycling. Although the first, which emphasizes the potential for energy and resource conservation and health benefits gained from cycling versus automobile use, is relatively undisputed, the second is target of much debate.
It is generally agreed that improved local and inter-city rail services and other methods of mass transportation (including greater provision for cycle carriage on such services) create conditions to encourage bicycle use. However, there are different opinions on the role of the use of segregated cycle facilities and other items of the cycling infrastructure in building bicycle-friendly cities and roads.
Some bicycle activists (including some traffic management advisers) seek the construction of segregated cycle facilities for journeys of all lengths. Other activists, especially those from the more established tradition, view the safety, practicality, and intent of many segregated cycle facilities with suspicion. They favour a more holistic approach based on the 4 'E's; education (of everyone involved), encouragement (to apply the education), enforcement (to protect the rights of others), and engineering (to facilitate travel while respecting every person's equal right to do so). In some cases this opposition has a more ideological basis: some members of the Vehicular Cycling movement oppose segregated public facilities, such as on-street bike lanes, on principle. Some groups offer training courses to help cyclists integrate themselves with other traffic. This is part of the ongoing cycle path debate.
Critical Mass is an event typically held on the last Friday of every month in cities around the world where bicyclists take to the streets en masse. While the ride was originally founded with the idea of drawing attention to how unfriendly the city was to bicyclists, the leaderless structure of Critical Mass makes it impossible to assign it any one specific goal. In fact, the purpose of Critical Mass is not formalized beyond the direct action of meeting at a set location and time and traveling as a group through city streets.
Midnight Ridazz is a massive established bicycle ride in Los Angeles based on recreational activism. The ride incorporates themes and ride routes designed to maximize fun and comraderie without any overt political agenda that might fracture the group of diverse riders. The one goal of Midnight Ridazz is to have fun riding a bike and thus inspire others to ride and have fun as well.
There is a long-running cycle helmet debate among activists. The most heated controversy surrounds the topic of compulsory helmet use.

# Associations
Cyclists form associations, both for specific interests (trails development, road maintenance, urban design, racing clubs, touring clubs, etc.) and for more global goals (energy conservation, pollution reduction, promotion of fitness). Some  bicycle clubs and national associations became prominent advocates for improvements to roads and highways. In the United States, the League of American Wheelmen lobbied for the improvement of roads in the last part of the 19th century, founding and leading the national Good Roads Movement. Their model for political organization, as well as the paved roads for which they argued, facilitated the growth of the automobile.

# Health
Bicycles are commonly used by people seeking to improve their fitness and cardiovascular health. In this regard, bicycling is especially helpful for those with arthritis of the lower limbs and who are unable to pursue sports such as running that involve more impact to joints such as the knees.  Furthermore, since cycling can be used as a form of transportation, there can be less demand for self-discipline to maintain the exercise because of the practical purpose of the activity.
Cycling while seated is a relatively non-weight bearing exercise that, like swimming, does little to promote bone density. Cycling up and out of the saddle, on the other hand, does a better job by transferring more of the rider's body weight to the legs. However, excessive cycling while standing can cause knee damage.  It used to be thought that cycling while standing was less energy efficient, but recent research has proven this not to be true. There is no wasted energy from cycling while standing.
Cycling on a stationary cycle is frequently advocated as a suitable exercise for rehabilitation particularly for lower limb injury due to the low impact that it has on the joints. In particular cycling is commonly used within knee rehabilitation programs. 

## Benefits
The physical exercise gained from cycling is generally linked with increased health and well-being. According to the World Health Organisation, physical inactivity is second only to tobacco smoking as a health risk in developed countries, and this is associated with many tens of billions of dollars of healthcare costs. The WHO's report suggests that increasing physical activity is a public health 'best buy', and that cycling is a 'highly suitable activity' for this purpose. The charity Sustrans reports that investment in cycling provision can give a 20:1 return from health and other benefits. It has been estimated that, on average, approximately 20 life-years are gained from the health benefits of road bicycling for every life-year lost through injury.

## Injuries
Cycling is not generally considered as a high-risk activity. In the UK, casualty rates per kilometre are comparable with walking, but are higher than for car occupants. Most cycle deaths result from a collision with a car or heavy goods vehicle.  A Danish study in 2000 concluded that cycling to work was linked to a 40% reduction in mortality rate; this included all causes of death, including road deaths.
Injuries can be divided into two types:
- Physical trauma (extrinsic)
- Overuse  (intrinsic).
Acute physical trauma includes injuries to the head and extremities resulting from falls and collisions. Since a large percentage of the collisions between motor and pedal vehicles occur at night, bicycle lighting is required for safety when bicycling at night.
The most common cycling overuse injury occurs in the knees, affecting cyclists at all levels.  These are caused by many factors:
- Incorrect bicycle fit or adjustment, particularly the saddle.
- Incorrect adjustment of clipless pedals.
- Too many hills, or too many miles, too early in the training season.
- Poor training preparation for long touring rides.
- Selecting too high a gear.  A lower gear for uphill climb protects the knees, even though your muscles are well able to handle a higher gear.
Overuse injuries, including chronic nerve damage at weight bearing locations, can occur as a result of repeatedly riding a bicycle for extended periods of time. Damage to the ulnar nerve in the palm, carpal tunnel in the wrist, the genitourinary tract or bicycle seat neuropathy may result from overuse.
Note that overuse is a relative term, and capacity varies greatly between individuals.  Someone starting out in cycling must be careful to increase length and frequency of cycling sessions slowly, starting for example at an hour or two per day, or a hundred miles or kilometers per week.  Muscular pain is a normal by-product of the training process, but joint pain and numbness are early signs of overuse injury.
Cycling has been linked to sexual impotence due to pressure on the perineum from the seat, but fitting a proper sized seat prevents this effect. In extreme cases, Pudendal Nerve Entrapment can be a source of intractable perineal pain. Some cyclists with induced pudendal nerve pressure neuropathy gained relief from improvements in saddle position and riding techniques.
The National Institute for Occupational Safety and Health (NIOSH) has investigated the potential health effects of prolonged bicycling in police bicycle patrol units, including the possibility that some bicycle saddles exert excessive pressure on the urogenital area of cyclists, restricting blood flow to the genitals.  NIOSH is currently investigating whether saddles developed without  protruding noses (which remove the pressure from the urogenital area) will alleviate any potential health problems.
Riding a Recumbent bicycle or quadricycle where ergonomic principles are more closely respected will largely address these health issues, particularly those related to chronic nerve damage at weight bearing locations, simply because the body is supported in the normal sitting position.
Also your back can suffer from strain; this can be induced  by pushing big gears, incorrect positioning on the bike, poor core strength and a poor riding style.

# Notes
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