Cycling. Cycling, also known as bicycling or biking, is the activity of riding a bicycle or other type of cycle. It encompasses the use of human-powered vehicles such as balance bikes, unicycles, tricycles, and quadricycles. Cycling is practised around the world for purposes including transport, recreation, exercise, and competitive sport. Main article: History of cycling Cycling became popularlised in Europe and North America in the latter part and especially the last decade of the 19th century. Today, over 50 percent of the human population knows how to ride a bike. Main article: Bicycle infantry The bicycle 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 functions of horses in warfare. In the Second Boer War, both sides used bicycles for scouting. In World War I, France, Germany, Australia and New Zealand 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 Malaya 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. The last country known to maintain a regiment of bicycle troops was Switzerland, which disbanded its last unit in 2003. Main article: Bicycle Video of a recreational cycling ride in Alabama. In many countries, the most commonly used vehicle for road transport is a utility bicycle. These have frames with relaxed geometry, protecting the rider from shocks of the road and easing steering at low speeds. Utility bicycles tend to be equipped with accessories such as mudguards, pannier racks and lights, which extends their usefulness on a daily basis. Since the bicycle is so effective as a means of transportation, various companies have developed methods of carrying anything from the weekly shop to children on bicycles. Certain countries rely heavily on bicycles and their culture has developed around the bicycle as a primary form of transport. In Europe, Denmark and the Netherlands have the most bicycles per capita and most often use bicycles for everyday transport. 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, making use of stronger muscles and reducing air resistance at high speed. Road bikes are designed for speed and efficiency on paved roads. They are characterized by their lightweight frames, skinny tires, drop handlebars, and narrow saddles. Road bikes are ideal for racing, long-distance riding, and fitness training. Other common types of bikes include gravel bikes, designed for use on gravel roads or trails, but with the ability to ride well on pavement, mountain bikes which are designed for more rugged, undulating terrain, and e-bikes which provide some level of motorized assist for the rider. There are additional variations of bikes and types of biking as well. The price of a new bicycle can range from US$50 to more than US$20,000, depending on quality, type and weight. However, UCI regulations stipulate a legal race bike cannot weigh less than 6.8 kg. 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 are equipped with hub gears. If the rider plans a significant amount of hillclimbing, a triple-chainrings crankset gear system may be preferred. Otherwise, the relatively lighter, simpler, and less expensive double chainring is preferred, even on high-end race bikes. Much simpler fixed wheel bikes are also available. Many road bikes, along with mountain bikes, include clipless pedals to which special shoes attach, via a cleat, enabling the rider to pull on the pedals as well as push. Other possible accessories for the bicycle include front and rear lights, bells or horns, child carrying seats, cycling computers with GPS, locks, bar tape, fenders, baggage racks, baggage carriers and pannier bags, water bottles and bottle cages. For basic maintenance and repairs cyclists can carry a pump, a puncture repair kit, a spare inner tube, and tire levers and a set of allen keys. 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 and high-visibility clothing is advisable to reduce the risk from motor vehicle users.