In the film's training montage, you see Kurt McKinney, who plays Jason Stillwell, doing one arm fingertip pushups. First off, Kurt didn't know how to do one arm pushups, so had to be shown the correct form. Then, he tried to do it for the camera and it just didn't have the impact. So, Yuen Kuai, the director, decided that it would be much more effective for the pushups to be faster and to be off two fingers. When asked: "He can't even do one arm push ups fast enough, how's he going to do this?" Yuen Kuai just smiled and held up a piece of wire cable. They affixed a wire to Kurt's back with a special harness and every time he goes up and down, there are really three Chinese stunt men off screen pulling on a wire that takes him up with ease, and keeps the pressure off his fingers! He looks great doing it, doesn't he? The wire doesn't show because they hid it by having the trees in the background and what wire did show they spray painted white so it would blend in with the sky!
Contributed by: Andrew Ellis
Another interesting point is that the Korean actor playing Sensei Lee (Kim Tai Chong) had been a double for the real Bruce Lee in his films. He couldn't speak any English so a Korean dialogue coach had to construct sentences in Korean that matched the timing of the English script. English was then dubbed over the Korean. So when we see Kurt McKinney and Kim Tai Chong talking to each other neither had a clue what the other was saying.
Contributed by: THIEN VO 864
Before and during filming Kurt Mckinney (Jason Stillwell) would only refer to Kim Tai Chong (Sensei Lee) as Sensei Lee on and off the set. He thought this would help his performance. Kim Tai Chong got very mad that Kurt wouldn't refer to him by his real name and because of this a fight between the two almost happened on more than one occasion while filming.