Introduction

In Western culture we have come to believe that bigger equals better (e.g. house, car, food, etc.) and that there is a direct correlation between size and strength (i.e. physically muscular and capable of lifting an enormous amount of weight).  This can be demonstrated by our extreme interest in such activities as body building, football, “strong man” competitions, monster truck rallies, etc.  Whereas there is some truth to the thought process that the larger a person is the stronger they are, it is not entirely correct, is not recognized (as readily) in Eastern societies and more importantly has little relevance in martial arts.  Besides acknowledging that this perception exists, it is also important to understand how this diversion of thought developed between the East and West and recognize how each culture’s separate and distinct evolutionary history created these differences. 

From the time of neo-lithic man Westerners (Europeans) have been shaped by the relatively harsh environment of Europe.  This harsh environment in turn gave rise to the idea that only the strongest will survive and the strongest of the strong should lead.  As Westerners developed from organized clans of hunter-gathers into more unified societies and ultimately nations, this idea continued to prevail.  Examples of this can be seen through the rise of empires and barbarian warrior tribes such as the Vikings, Huns, Celts, Goths, etc. whose ranks were dominated by physically superior individuals who fought and conquered using shear strength and brute force. 

The polar opposite of this Western societal development can be seen in Eastern (Asian) cultures where different environmental conditions, human physical features, cultural ideals and philosophies allowed for a different sense of what makes a “good warrior” and the combat tactics used by these warriors to arise. 

There is evidence of indigenous fighting systems in areas such as Okinawa as far back as the early middle ages. At that time, it was probably a simple combat system likely similar to jujutsu, combining grappling, striking, etc. along with simple battlefield weapons many derived from farming implements and the like. It was most certainly not karate, as we know it today and not nearly as refined. There is no one single accepted theory as to how karate really was developed; either by peasants trying to defend themselves against armed Samurai warriors, as a result of a weapons ban, or simply Okinawan's interpretation of a Chinese fighting art.  Chinese influence goes back a long way, as various masters continued to incorporate new things into Okinawa-te, and finally karate distinguished itself from Chinese kempo.  Many katas were taken from various kempo forms, and small changes were made, e.g. open hand changed to closed fist.  Regardless of how and why martial arts developed in Eastern societies, because of the cultural and physical differences between these people and Europeans, size and strength do not seemed to have played a large role in the development of Eastern armed and un-armed combat.  By their very nature, Eastern combat techniques are more affected by the components of speed, agility, precision and economy of motion than the brute force used by the European warriors.  This way of thinking allowed for the development of martial arts where it was more important to deliver a well executed technique to a specific target than to pummel the opponent into submission.  In order for this approach to be effective, it is necessary for the technique to elicit the most damage in a single instance as possible.  For this to occur and a specific strike to be devastating enough to disable and opponent, it is necessary for it combine as much speed, efficiency and explosive energy as possible. 

The concept that best summarizes this approach of an efficient, devastating technique is described by the Okinawan or Hogan term Chinkuchi.  It is thought that like many Japanese and Okinawa bushido concepts, Chinkuchi originated in China and was then brought to Okinawa via knowledge transfers between practitioners.  However, the concept of Chinkuchi, although widely discussed, is not well understood and even less well chronicled in writing.  Directly translated, it means “chin” muscle (sinew), “ku” (bone) and “chi” (energy or control) and can be described as a physical conditioning process which focuses the elements of mind and body into a single moment in time with the desired effect of a quick, strong technique. 

Chinkuchi Basics

Simply defined, Chinkuchi is the concentration or focus of strength and power.  It can be further defined as the simultaneous contraction of the muscles in the body at the point of impact that brings karate techniques from a fluid, relaxed stated designed for speed, to a solid, tense state that is designed for strength.  The process of “whipping” out a technique, tensing upon impact and then immediately relaxing again allows a karateka to achieve maximum power while exerting minimal energy.  In doing this, the majority of the technique’s energy is directed into the target, while little is wasted on bio-mechanical processes.  If a person tenses while executing a technique, opposing muscles contract and energy that would be available for the strike is wasted. 

A second, equally important part of Chinkuchi is the instantaneous relaxation and slight return of the body part performing the technique after impact.  Proper execution of a technique utilizing this flow from “soft” to “hard” and then back to “soft” is characterized by an audible “snap”.  This sound is evidence of the transference of energy from the kick or punch, into and through the target.  It has been presented in other articles and discussions on this matter that this “snap” represents an improper execution of a technique, as it does not “drive” the force of the technique into the target.  However, it is important to note that there is a difference between the results of technique thrown for demonstration/training purposes and those thrown in actual combat situations.  When demonstrating a technique, a karateka with proper chinkuchi will generate an audible snap, not because this is the desired goal but rather the result of the transfer of energy in the absence of a striking surface.  In this instance, the transfer of energy takes the form of sound whereas in a combat situation, it would result in the force of the blow.  Many fighters (particularly untrained street fighters) will continue a punch after maximum speed is obtained and even after contact is made.  Such follow-through is usually not made in karate for the following reason:  If contact is made just as follow-through begins, then the resulting energy transfer is derived from “pushing”, and since pushing and displacement do not result in deformation damage (see preceding physics discussion for further information) they are normally not worth the loss of the attacker’s energy.  

In order to achieve the desired result of Chinkuchi, a karateka must not only tense the particular body part involved in the execution of a technique but rather a series of muscles throughout the body in a certain order called muscle chains.  This refers to the connection of muscle, sinews and bone which are linked and controlled by a practitioner in the way that rings of a chain are connected to one another.  What this means, is that in executing a technique utilizing proper Chinkuchi, a karateka would simultaneously tense all the muscles in their body in order (i.e. feet, ankle, calf, thigh, hip, waist, torso, shoulder, bicep/tricep, forearm, fist), drawing the energy from the ground, transferring it through the body and then delivering it through the fist, foot, etc.  Not only is this tensing of the entire body important in offensive techniques but also defensive techniques such as blocking.  Through the tightening of various body parts upon impact of an opponent’s blow, a karateka utilizing Chinkuchi can make themselves better able to withstand the force of the attack. 

One kata in particular teaches proper usage of Chinkuchi more so than any others and it is Sanchin.  Sanchin literally means “three conflicts” but this is a bit misleading as in performing this kata, one is working to combine three elements (mind, body and spirit) together to bring out Chinkuchi.  In kata Sanchin, emphasis is placed on proper posture/stance (to give a rooted base), proper movement (advancing forward and retreating backward while staying in the stance) and proper breathing (inhaling and exhaling to achieve the flow of energy).  But above all else, this particular kata teaches us to go from a fairly rigid state instantaneously into a fluid state and then back to a rigid state in order to move from one position to another and execute a technique.  Conversely, in Sanchin shime (testing) Chinkuchi is used to tense (harden) our bodies in order to endure and withstand blows to the various parts of the body.  Proper utilization of Chinkuchi in Sanchin shime allows a karateka to become virtually impervious to the force of a blow that would otherwise cause serious injury or damage if they were not in a state of tension.  Through practicing of this kata and testing, a karateka is taught to reflexively use Chinkuchi in both offensive and defensive moves. 

Physics of Chinkuchi

Now that we have an understanding of how Chinkuchi is achieved and properly applied to a specific technique lets look at it in terms of physical science.

It goes without saying that large objects moving a high speeds hit harder than smaller objects moving more slowly.  Therefore, it stands to reason that if one wants to strike a target as hard as possible, that they would want to move the weapon (e.g. hand, foot, etc.) as quickly as possible towards the target.  But what makes for a “hard strike”?  Two ways exist to answer this question, both equally accurate.  The first looks at the collision in terms of force and momentum; the second in terms of energy.

Force (F) is acceleration (a) multiplied by mass (m) is represented by the equation F=m*a.  Momentum (p) is mass times velocity (v) or p=m*v.  Since acceleration measures change in velocity over time (t) (put another way, acceleration is the derivative of velocity with respect to time), force is the derivative of momentum with respect to time.  Equivalently, force multiplied by time equals a change in momentum or impulse (Dp) or Dp=F*t.  This is significant because momentum is a conserved quantity.  It can be neither created nor destroyed, but is passed from one object (the hand) to another (the target surface).  The reason for this conservation is Newton’s Third Law of Motion, which states that if an object exerts a force on another object for given time, the second object exerts an equal force in the opposite direction (force being a vector quantity) on the first object for the same amount of time so the second object gains exactly the amount of momentum the first object loses.  Momentum is thus transferred.  With Dp a fixed quantity, F and t are necessarily inversely proportionate.  One can deliver a given amount of momentum by transferring a large force for a short time or by transferring small amounts of force continuously over a longer period.  Therefore, if the hand is moving as quickly as possible, it is will decelerate (or accelerate in the opposite direction initially traveled) more quickly in response to the force the target surface exerts on it upon collision.  If the amount of time involved in the transfer of momentum is small, the amount of force transferred to the target, all at once, will be large.  This sudden transfer of a large amount of force, therefore, causes the strike zone to accelerate relative to the surrounding surface.  If this acceleration is great enough, breakage will occur. 

This same phenomenon can be analyzed in terms of energy transfer and resulting deformation damage.  Given an object with mass m₁ at rest (target surface) and another object of mass m₂ (the karateka’s hand) moving at velocity v, upon impact and ignoring the negligible amount of energy lost as thermal energy (heat), the amount of energy in the system lost to deformation damage (DE) is given by the following:

                              DE = (1-e² )  x m₁ x m₂  x v²

                                           2         (m₁ + m₂)         

where e is the coefficient of restitution, which measures how elastic the collision is.  It is a function of the hardness or softness of the colliding objects, which along with velocity determines impulse (Dp).  If hard objects collide (for a perfectly inelastic collision e=0), they will accelerate one another quickly, transferring a large amount of force in a small amount of time while soft objects colliding (for a perfectly elastic collision, e=1), transfer smaller amounts of energy to one another for longer periods of time.  As DE is proportional to the square of velocity, the more velocity the hand has, the more energy will be transferred into the target.  In the simple terms, if the target is infused with more energy than its structure can handle, it will break.  More rigorously analyzed, energy transfer causes the target surface to dent.  This process of transferring energy is work (W).  Work is force times distance (d) or W=F*d.  If the area of the target surface that is struck dents a sufficient distance, it will break.  Since the distance it dents depends on the energy transferred to it and the amount of energy transferred depends on the velocity of the karateka’s hand, a high-speed strike is most likely to break the board. 

Also important in understanding the physical laws that effect Chinkuchi is the understanding of Kime or the point of focus.  On the website Street-wise.org, Kyoshi Terry Bryan, PhD. stated the following about Kime:  ‘The translation for kime is focus, but in reality it also includes the concepts of synergy or teamwork as well. The physical expression of kime is the ability to analyze and implement several separate motions that come together at the same time and place, creating maximum efficiency. Successful execution of this concept allows a small individual to deliver a technique with sufficient power to defeat a much larger opponent. Examples of different actions that are included in delivering maximum focus of energy in a strike include hip rotation, forward movement of mass, snapping and rotation of the striking limb, and the tightening of all muscles at the spilt second of impact. Breaking down the action into individual components is a mental exercise and each element is developed based on priority of importance. Once each element is developed, the key becomes one of timing, allowing all of the elements to come to bear at the same split second.’  So as one can see, the concept of Kime is integral to that of Chinkuchi.  When teaching breaking techniques, Sensei’s typically instruct the Kyu’s (or lower belts) to place their target point several inches beyond the actual target surface.  This is to insure that the hand does not decelerate prior to contact with the actual target, a mistake than beginners, fearful of injury and therefore mentally hesitant, often make.  High velocity of the hand is essential to proper execution of a technique.  It has been determined that maximum hand velocity (approximately 7 m/sec) is achieved when the arm reaches 70-80% of its full extension.  Based on this, it must be assumed that the hand decelerates significantly prior to reaching the full extension point.

The final physical component to consider in the physical application of Chinkuchi is the use of body mass when executive a technique.  Mass is the co-efficient in the formulae for force, momentum and energy transfers as all three are directly proportional to mass.  Since a person’s mass is constant during the execution of a strike, mass is often mistakenly dismissed as a constant in the equations for force, momentum and impulse.  However, what is often not considered is how much of that mass is involved in the strike.  Although actual body mass is beyond the karateka’s control; how much of that mass is contributed to the strike is very much within their control.  Therefore, getting back to the concept of the “chain” discussed above, it is crucial not to use the arm alone to extend the weapon and hope for sufficient force and energy to break the target.  The entire body should be used by snapping the hips and pushing with the legs in the direction of the target.  This explains why fighters are seldom knocked unconscious by jabs, where little more than the mass of the arm contributes to the punch, but can be knocked out by other techniques such as a round-house punch where the entire mass of the body is thrown behind the punch.

In conclusion, although the “art of Chinkuchi”, if you will, takes quite a bit of practice to master, there really is no mystery to this concept.  The absence of thought and ability to relax is the key to executing a high speed, fluid movement which can then be turned into a devastating technique by transferring the energy of the motion at the moment of impact, through the sudden contraction of the muscles and drawing upon the mass of the body.  As the famous line goes in the movie ‘The Matrix’ “Free your mind”.  Once you have done this and stopped thinking about the technique you are about to execute, the less you will try to control/muscle it and the more effective it will be.