Chin-Na (catching or seizing and locking) is Chinese Ju-Jutsu and most likely the origin of Japanese Ju-Jutsu which was imported with many healing arts and cultural teachings. Some of these techniques came in from China to Japan directly as well as via China to the Ryukyu Islands and then to Japan.
Chin-Na covers various joint locks and take down techniques to control or lock an opponent's joints or muscles/tendons. These locking techniques can also apply to muscles and systems of the body to lock off and close these down.
Some Chinese martial arts instructors focus more on their Chin Na techniques than others. This is one of the many reasons why the Chin Na of one school may differ from that of another although all Chinese martial arts contain Chin Na techniques in some degree. There is no universally accepted systemized form of Chin Na. Instead, each school varies due to the instructor's training and/or personal preference of focus.While techniques of Chin Na are trained to some degree by most martial arts worldwide, many Chinese martial arts are famous for their specialization in such applications.
Chin Na can generally be categorised as:
1."Fen jin" or "zhua jin" (dividing the muscle/tendon, grabbing the muscle/tendon). Fen means "to divide", zhua is "to grab" and jin means "tendon, muscle, sinew". They refer to techniques which tear apart an opponent's muscles or tendons.
2."Cuo gu" (misplacing the bone). Cuo means "wrong, disorder" and gu means "bone". Cuo gu therefore refer to techniques which put bones in wrong positions and is usually applied specifically to joints.
3."Bi qi" (sealing the breath). Bi means "to close, seal or shut" and qi, or more specifically kong qi, meaning "air". "Bi qi" is the technique of preventing the opponent from inhaling. This differs from mere strangulation in that it may be applied not only to the windpipe directly but also to muscles surrounding the lungs, supposedly to shock the system into a contraction which impairs breathing.
4."Dian mai" or "dian xue" (sealing the vein/artery or acupressure cavity). Similar to the Cantonese dim mak, these are the technique of sealing or striking blood vessels and chi points.
5."Rou dao" or "rou shu dao" (soft techniques) which generally refers to the techniques deemed safe for sparring and/or training purposes.
Chin means to seize or trap, na means to lock or break, and while those actions are very often executed in that order (trap then lock), the actions can be performed distinctly in training and self-defense: A trap isn't always followed by a lock or break, and a lock or break is not necessarily set up by a trap.
There is large overlap between Chin Na theory and technique with the traditional Chinese medicine art of Tui-Na and it is hard at times to separate the techniques except for the amount of force and distance the technique uses which changes a healing technique into a damaging technique.