Why are many characters in old action movies and martial arts movies long and thin?

Because early TV was still the traditional 4:3 ratio (PAL system), and movies were "widescreen" (1.5: 1). When the movie is broadcast by TV signal, the image has to be displayed according to the aspect ratio of TV, which leads to the narrowing of the image, the thinning of the fat man and the lengthening of the round face. So, so this phenomenon is caused. If you put that video (if you can still find it) on the current 16:9 TV and play it in full screen mode, you will find that the characters are a little fatter than normal. Therefore, to put it bluntly, it is nothing more than the abnormal aspect ratio caused by the difference between the display scale of the display device and the shooting scale (but you can't cut the picture, which will make some content invisible).