According to a 2009 Sports Illustrated article, 78% of NFL players are either bankrupt or are under financial stress within two years of retirement

Helmets were not mandatory for NFL players until 1939

After 18 college football players were killed during games in 1905, President Theodore Roosevelt personally intervened and demanded that the rules of the game be reformed to make the game safer. One of the changes was to make the forward pass a legal play

Prior to 1923, basketball teams could choose which player would shoot a free throw after a foul

NBA players run the equivalent of four miles during a game

For nine years following 1966, slam dunks were illegal