Bruce severely injured his back in 1970—he was performing a weight lifting move called a 'good morning,' and he tweaked his sacral nerve. As a result, Bruce could not perform many of the aerial moves that he is famous for in Enter The Dragon, such as the forward flip in the O'Hara fight scene. Instead, stuntmaster Yuen Biao (who was also close friends with Jackie Chan and Sammo Hung) performed these acrobatic moves. Yuen Biao would later double for Bruce in the posthumous Game of Death as well.