Tchoukball is an indoor team sport developed in the 1970s by Swiss biologist Hermann Brandt. Brandt was concerned about the number of injuries in sport at the time and as part of an educational study he wanted to create a sport that reduced injuries, was not aggressive between players and enabled people of all shapes, sizes, genders, cultures, and backgrounds to play together. The sport is usually played on an indoor court measuring 27 metres by 16 metres. At each end there is a rebounder (a device similar to a trampoline off which the ball bounces) which measures one square metre and a semicircular D-shaped forbidden zone measuring three metres in radius. Each team can score on both ends of the court, and comprises 12 players, of whom 7 may be on the court at any one time. In order to score a point, the ball must be thrown by an attacking player, hit the rebounder and bounce outside the 'D' without being caught by the defending team. Physical contact is prohibited, and defenders may not attempt to intercept the attacking team's passes. Players may take three steps with the ball, hold the ball for a maximum of three seconds, and teams may not pass the ball more than three times before shooting at the rebounder. Tchoukball is most popular in Singapore, Switzerland and Taiwan, but has become an international sport, with national federations in over 60 countries. It is governed by the International Tchoukball Federation (FITB), which was founded in 1971.