 In addition to the current five categories, two additional categories for tumbling (men's and women's) were included until the 1999 World Championships, though some groups still involve tumbling events.In the United States, the first national sports acrobatics organization was called the United States Sports Acrobatics Federation (USSAF).Founded in 1975, its name was changed to the United States Sports Acrobatics (USSA) in the 1990s.