When most people think of inch power they generally think of Bruce Lee's demo. Although this seems to be the benchmark of short power I've never agreed with that. Though people don't take kindly to this I do not see this demo as indicative of inch power but more of an example of biomechanics. It is clear that Lee is thrusting his entire body behind the strike creating more of a push then the explosion that short power/fa jin/fa ging is supposed to create. In the Chinese martial arts fa jin is often described as scared or startle power; basically 'explosive power'. It means that when you are startled you react purely and effectively with your entire body expressing at the moment. I've seen examples of this on youtube that tend to be quite comical. People who look like zombies or shaking like a spastic and it's supposed to show great fa jin. If it works at all how is this supposed to be used in a fight? While you're standing there shaking your arms what is the opponent doing? Probably dancing on your body with fists. True fa jin expressed in a punch should explode the entire body's force into the target in real time at the expression of the strike like a cobra. When I was taught it the example given was from pool where a cue ball transfers all of its energy into another ball, expelling that ball while the cue ball remains in place. This is created by a snapping of the body from the core and expressing it forward into the hand. It's somewhat like a whip where the energy is transferred along the length of the whip and being fully expressed in the end in a quick explosion. The intention is to deliver the energy into the target and not through it. If you were to put a ball bearing into a sock and whip it into the body it would deliver great force into body and not through it. It's the whipping and return that propels the force forward. In striking with fa jin you are expressing the force forward in an explosive instant that is the sum whole of the body's power. It does not push through the body but delivers the power into it. I have demonstrated this by hitting someone holding a full sized phone book on their chest. I do it from about eight inches away instantaneously and with no wind up. The strike happens in such a way that the opponent cannot absorb it. It should stun them to their core.
Sifu once told me it is like having a wet arm and when you strike the body the arm returns but the water moves forward into the body. He often cautioned that this is hard to do on a heavy bag because we become obsessed with moving the bag to see demonstrable power. Rather, he said, the bag should fold around the strike point as the power is delivered into the internal organs. The som bo gin ( three step arrow) form is created to develop this power. You step forward shifting your weight into the strikes with the most subtle of movements. Each of the strikes delivers from the core (dan dian) in a complete and equal amount of power. This is why the form moves forward with the strikes, to put the body mass into it. Mass x speed equals force, even if the body is only moving a little bit. Without this body motion the power will be ineffective and without the recoil of each strike it will not go into the body. You cannot practice this for extended amounts of time because it is a quick twitch muscle movement. If you overdo it you tear down the muscle and stop doing quick twitch. The som bo gin form done correctly produces three distinct and powerful strikes in succession. Equally important is the return/pull back after the last strike.
At any moment in your technique you should be able to unleash this power. It is most effective in a forward strike but it is very effective in deflecting punches with a quick sideways flick. Done correctly fa jin will disrupt an opponent giving you the opportunity to deal heavier damage. Keep in mind that it is not easy to take someone down in a fight since their adrenaline is soaring and their capacity for pain is great. In a real fight it is imperative that you injure the opponent to disable them. Merely hurting them will not deter a determined opponent. Strikes into vital areas is most important and must be done with ferocity and speed. Fa jin is central to true Kwong Sai mantis practice.
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