My Kung Fu teacher translated "kung fu" as "expedient means", a translation that has always been confusing to me since I really have no idea what the word "expedient" means (English is not my native tongue).
At any rate, for years he taught kung fu without doing any physical exercises at all, emphasizing mental practice, developing problem solving abilities.
He said the physical martial art aspect developed as a solution to a problem as well: The monks at Shao Lin spent hours sitting in meditation every day so they developed effective physical exercises to counterpoint any negative effect prolonged sitting might have had on the body.
Or, put differently, they worked on total evolution of man. Not being dualists, physical and mental advancement was of equal importance to them.
Occasionally he would hint that one of the reason for the martial art training at Shao Lin was the tradition in Zen Buddhism which makes it an acceptable reaction for a student to strike the teacher when the teacher answers a student's question in a way which confuses the student even more, and frustrates him. Of course, the teacher is not required to take the strike, so he learns how to avoid it.
I have never seen anyone strike my teacher, though I certainly went through periods, especially early in my training, when I felt like it! Though, come to think of it, I probably challenged him verbally more often than the rest of the students, especially again in the early stages of my training.
Recently, I have been giving kung fu some thought. It seems to me it is essentially a nice practice of the right effort factor of the Eightfold Path. The martial art of kung fu is very soft, almost "lazy" (certainly compared to tang soo do which I studied before). That is, you exert the exact amount of effort necessary to defend yourself, not a bit more.
Same holds true for the mental effort in kung fu (e.g., applied to computer programming, or any other problem solving situation).