Cycling is a recreation, a sport and a means of transport across land. It involves riding bicycles, unicycles, tricycles and other human powered vehicles. People seeking to improve their fitness and cardiovascular health commonly use bicycles. 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 involves 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.
First introduced in 19th-century Europe, bicycles evolved quickly into the design pictured. Numbering over a billion worldwide, bicycles provide the principal means of transportation in many regions, are a popular form of recreation, and have been adapted for use in many other fields of human activity, including children`s toys, adult fitness, military and local police applications, courier services, and cycle sports.
Cycling while seated is a relatively non-weight bearing exercise that, like swimming, does little to promote leg bone strength. 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. This latter style of cycling is considered less energy-efficient, and can cause damage to the knees.