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.

I personally don't like being called Sifu or Sensei.  I know that many martial artists can't wait for the day to get those monikers but I really disdain them for myself even though this irks my Sifu.  When I think of the level of training that my Sifu went through from fighting to calligraphy and healing arts I find it hard to accept the title that he has earned.  I know Sifu simply means teacher and does not necessarily have a qualitative attachment to it but I still prefer to avoid that title.  However I seem to me alone in that category.
Americans are crazy about being called master, grand master, PHD of martial arts and any 'accreditation' they can get be it from certificates or trophies.  Guys adorn their web sites with scores of accomplishments from mastering 10 arts to being actual samurai's to having the ever so laughable 'licensed hands'.  They do anything to look great.  As one great actual 10 Dan Dutch Judo master once said, "Americans are all masters and no one who wants to practice".  I see people who are in their thirties claiming to have mastered 10 styles along with a myriad of other things.  It takes a lifetime to master one style how can you master ten?  As far as black belts go you can get them anywhere.  Decades ago when I studied Shotokan karate under Teryuki Okasaki one of the first things he said was, "In Japan you get a black belt in a couple of years and then you start your training but in America people get a black belt and then they stop their training".  It's all about the title here.  Several years ago I was invited to join a consortium of local martial artists and I declined.  A good friend of mine, who was highly accredited and  had fought internationally,  was also invited and he did go.  It was put together by a fellow that had studied karate for a few years and quit immediately after getting his black belt.  He was a very good business man and had established successful schools. At this meeting this fellow put forth the idea that they could test each other and advance each other to higher ranks. By being in a group this would give him some legitimacy since he had broken from his lineage.  My friend left the meeting disgusted and never returned.  For the record my friend had to return to Taiwan each year to get tested under their hierarchy to advance so the idea of a shortcut appalled him . The karate fellow still has successful schools and is now a 'tenth dan' red belt.  Who knows  certified him.
Where else is their this obsession with belts, degrees and certificates?  Are there the black belt, master equivalents in any other athletic endeavor?  "Hey, don't play pick up ball with him, he's a black belt in basketball , he'll kick your butt".  Or, "That quarterback is a 7th dan, you're screwed".  How about , "That guys not just a heavyweight boxer, he's 10th dan so he's great".  It just doesn't happen anywhere but in the martial arts and it's over the top insane with this stuff.  How many different masters can you get your picture taken with, how many certificates can you get, etc.  Then there's the guy who has a conversation with a cop or service man and is asked how to break a grip or some other mundane thing and the next thing you know posted on his web site is "I trained the LA cops" or "I taught the US army self defense".  It is ubiquitous.
It's hard to escape these things and a newbie doesn't know any better, in fact, they are drawn to it. But what can they do?  There are no national standards, no Bull shido police to call someone on their nonsense and no way to know unless you happen to have an acquaintance that can guide you.  Beware of those people that gather shiny things, they can blind you to the truth.
 
 
 

I just returned from the Glory 48 Muay Thai Competition in NYC.  Along with being a successful show I got and unexpected visit with my friend Bas Rutten who was there to support Tiffany Van Soest, an undefeated Dutch fighter.  Over the last few years we've had many conversations about the illusions martial artists have about what their ability is and what the ability of their opponents is.  There is a lot of trash talking from stand up fighters regarding MMA fighters and vice versa.  We often tend to live in our own bubbles when it comes to our styles.  I'll see someone observing an MMA fight and say, "well, if I were in that situation I'd just poke him in the eyes".  Bas talks about giving a demonstration where a young woman kept making these comments and he finally said to her " what would you do if I had you in this position?" , she replies, "I'd poke you in the eyes".  Bas said, "Ok, I'll get you in this position and you poke me.  As you do I'll break your neck, ok?  Ready in one...". The young lady protests and the conversation is over.  The reality vs the theory and they are quite different.  I know she wanted to believe she could handle it but it's better she finds out at this demo than on the street. I've said over and over again fights are never simple or clean but so many martial artists have these terrible misconceptions.  Here's some things I've experienced.
A long fist fighter is observing a Wing Tsun demonstration and comments, "That's why we have one punch kill techniques and they doing these multiple nothing strikes".  Really?  I've been to hundreds of professional fights and never seen anyone do this 'one punch' technique.  Of course I've seen one punch knock outs but they don't happen often.  I've never seen anyone consistently land a one punch knockout in a fight. One the other hand I've seen people overwhelmed by multiple quick strikes and then get knocked out in the volley.  I also experienced a WT fighter land about 10 punches on a guys face who then turned around and hammered him into the ground.  The 'one punch kill' shot is for the movies and the inexperienced.  There is nothing more eye opening then hitting someone with all of your power and having little reaction from them.
A Tae Kwon Do black belt is observing two stand up fighters going at it and says, "All you have to do is kick them once to the head and it's over".  My response was "well if he's crowding you what do you do?".  He said, " You can always make room, get your distance".  I asked, "How about in a bar?"  He insisted he could do it though he'd never been in a bar fight.  He said he could always create the distance in the ring so he could do it in a bar.  Not too smart thinking here.  I also commented that in the many fights I'd seen most knock outs are by the hand , not the feet.  On the other hand I've seen people say, " Tae Kwon Do is easy to beat , you just rush them".  You know, no one has ever had that idea before and I'm sure the TKD artist will be shocked and surprised as you do that while his axe kick lands on your head.
MMA artist says "all fights go to the ground where I will choke him out".  Maybe but then on the street there's no rules and while on the ground the guys buddies kick the living hell out of you.  I've seen this.  Then I've seen the guy who says, "I've never been choked out, it can't be done to me".  Then I introduce him to some BJJ buddies and suddenly his story collapses.
Martial artists constantly dis boxers and it amazes me.  One of my favorite moments on the job was an over the top MMA fighter taunting his opponent, a well skilled boxer, before the fight.  He did nothing but trash mouth this guy and was dancing around the ring during the intros swatting at him and belittling him.  The bell sounds and this guy keeps dancing and taunting while the boxer is moving very pointedly and deliberately. Then the guy dances by him a third time and BANG !  a well timed right hook lays him out.  He woke up after the count was over and did not believe that he got knocked out.  It was hysterical.
The point of this is that all of these arts were developed for a reason and are effective in their own way.  Learn from all of them and apply them to your art. There is something that each has to offer and if you aren't open to it, well it's your loss.  Do not criticize an art because you heard about it from someone else; go test them yourself and see what you can do against them.  You might be very surprised at what you learn.