The bicycle is the most efficient human-powered vehicle for travel over long distances. It turns up to 99% of the energy the rider applies to the pedals into kinetic energy that propels the bike forward over the ground. Riders can use the bicycle to get to work, exercise, train for races and compete in sporting events. The bicycle also has a number of other practical uses, such as transportation inside an automobile factory or delivery of goods. People who sustain traumatic injuries from cycling accidents may require treatment from physicians in emergency medicine, orthopedic surgery or neurology and those who develop overuse injuries from recreational cycling might need treatment from physical therapists.

The basic design of a bicycle has changed little since the first chain-driven bicycles were introduced in 1885. The wheels are mounted on a frame that is connected to a stem that is attached to the fork, which in turn is attached to the handlebars. The handlebars can be shaped to suit the rider’s needs. They can be upright, which curves gently back toward the rider for a comfortable, upright posture, or drop handlebars which curve forward and down for aerodynamic riding.

Stems and forks are made from a variety of materials, but steel is the most common because of its high strength-to-weight ratio. Modern bicycles are constructed with frames made from alloys of titanium, aluminum and carbon fiber for lightness and stiffness. These materials have replaced the old-fashioned cast iron and wood used in earlier years.

Many other components make up a complete bicycle, including a headset, derailleur systems, brakes and tires. Depending on the type of cycling, accessories might include a rack to carry cargo or a basket to hold groceries or flowers. Many children’s bikes have a child seat attached to the rear of the frame or to the handlebar. Some adults choose to add a trailer for carrying cargo or a child.

Riding a bicycle might look easy, but it requires complex movements by the feet and hands in order to balance and control the bike and to maintain momentum to move over rough terrain. It also involves learning to use the body’s natural balance and proprioception to overcome obstacles and keep the bicycle steady. The bicycle has become an important mode of transportation for millions of people and offers a healthy alternative to cars.

People who ride a bicycle to get around town or to commute to work often use the same routes, and this helps establish a safe, reliable network of public transit. Bicycles are also a popular means of exercise, and they can be a great way for families to get around without the expense of an SUV or a minivan. There are even dedicated bike paths and lanes that allow people to bypass traffic. Those who ride for sport, such as racing or mountain biking, can compete at local, regional and national levels. They can also participate in organized rides and races, which are governed by rules and regulations set by the International Cycling Union (UCI). Bicycles may be modified with different accessories to make them more suited to particular styles of cycling or for specific types of competition.