Swimming is an individual or team sport that requires the use of one's arms and legs to move the body through water. The sport takes place in pools or open water. Competitive swimming is one of the most popular Olympic sports, with varied distance events in butterfly, backstroke, breaststroke, freestyle, and individual medley. In addition to these individual events, four swimmers can take part in either a freestyle or medley relay. A medley relay consists of four swimmers who will each swim a different stroke. The order for a medley relay is: backstroke, breaststroke, butterfly, and freestyle. Swimming each stroke requires a set of specific techniques, and in competition, there are distinct regulations concerning the acceptable form for each individual stroke. There are also regulations on what types of swimsuits, caps, jewelry and injury tape that are allowed at competitions. Although it is possible for competitive swimmers to incur several injuries from the sport, such as tendinitis in the shoulders or knees, there are also multiple health benefits associated with the sport.