The notion of cross-training in Jeet Kune Do is similar to the practice of Mixed Martial Arts (MMA) in modern times — Bruce Lee has been considered by UFC president Dana White as the “father of mixed martial arts”[2]. Many consider Jeet Kune Do to be the precursor of MMA because of its synteric nature. This is particularly the case with respect to the JKD “Combat Ranges“. A JKD student is expected to learn various combat systems within each combat range, and thus to be effective in all of them, just as in MMA.

Bruce Lee said:

I have not invented a “new style,” composite, modified or otherwise that is set within distinct form as apart from “this” method or “that” method. On the contrary, I hope to free my followers from clinging to styles, patterns, or molds. Remember that Jeet Kune Do is merely a name used, a mirror in which to see “ourselves”. . . Jeet Kune Do is not an organized institution that one can be a member of. Either you understand or you don’t, and that is that. There is no mystery about my style. My movements are simple, direct and non-classical. The extraordinary part of it lies in its simplicity. Every movement in Jeet Kune-Do is being so of itself. There is nothing artificial about it. I always believe that the easy way is the right way. Jeet Kune-Do is simply the direct expression of one’s feelings with the minimum of movements and energy. The closer to the true way of Kung Fu, the less wastage of expression there is. Finally, a Jeet Kune Do man who says Jeet Kune Do is exclusively Jeet Kune Do is simply not with it. He is still hung up on his self-closing resistance, in this case anchored down to reactionary pattern, and naturally is still bound by another modified pattern and can move within its limits. He has not digested the simple fact that truth exists outside all molds; pattern and awareness is never exclusive. Again let me remind you Jeet Kune Do is just a name used, a boat to get one across, and once across it is to be discarded and not to be carried on one’s back.

– Bruce Lee^[2]