Showing posts with label physics. Show all posts
Showing posts with label physics. Show all posts

10 February 2013

The Value of Patterns (Part 2): Kinaesthetics (Part 2: Accelerated Body Mass—Not Speed)

In the first instalment on what I consider to be the kinaesthetic value of the ITF patterns I mentioned firstly it's heavy emphasis on relaxation and moving from a state of relaxation. Furthermore, I mentioned how the relatively slow tempo of the patterns helps with improving body awareness—understanding how one's balance changes both statically and dynamically, how your centre-of-gravity changes, how your centre of mass changes, how your weight shifts from one foot to another, and so on. Related to this is an acquaintance with Taekwon-Do's formal stances, Taekwon-Do's basic movements, and the added benefit of improved coordination.

In this second instalment on the kinaesthetic value of the ITF patterns, I will focus on the acceleration of body mass.

Quick Movements versus Forceful Movements


People are often surprised at how slow, unhurried the ITF patterns seem to be. This is true as far as the tempo of the patterns is concerned. With few exceptions there is no urgency to rush from one technique to another technique. The techniques are seldom bundled in clusters of frantic defences and attacks. The patterns are not the primary place for acquiring fighting skills; they are rather “drills” for teaching certain concepts of movement; i.e. kinaesthetics. One such a kinaesthetic concept that patterns are primarily concerned with is to differentiate between mere quick movements versus forceful movements. Therefore, the focus of the ITF patterns is not on moving the limbs very quickly, like for instance in American Kenpo or Whin Chun where the opponent is overwhelmed with a barrage of very rapid strikes.

The video below shows American Kenpo Grandmaster Ted Parker demonstrating their Short Form 3. Once the form gets going, notice the hurried urgency with which it is performed.



Such a urgency is most likely to reflect the hurriedness of a real combat situation. The purpose of the ITF patterns is not shadow-boxing, requiring a flurry of attacks and defences.

Instead, the purpose of the patterns is to teach the practitioner to “accelerate as much body mass as possible in the direction of the technique, with emphasis on strong exhalation, and without compromising your balance and posture.” The Fundamental Movements, as practised in the patterns, are primarily concerned with Newton's Second Law of Motion; i.e. Force = Mass x Acceleration. For nearly every movement in the patterns there must be a lot of mass accelerated. Practising flailing the limbs quickly is not the purpose of the patterns. Rather, the whole body mass should be activated for each technique.

Sequential Acceleration 


In the patterns, the aim is not really to learn how to move quickly; instead, the aim is to learn how to truly accelerate as much of the body's mass behind the technique as possible, but also in a whip-like manner known as sequential motion or kinetic chaining. This entails that different parts of the body initiates the movement at different times.

In the video below Grandmaster Choi Jung-Hwa looks at an exampled of a 90° turn into a forearm block as found in the pattern Chon-Ji, and speaks about the importance of employing  the waist to activate more of the body's mass, rather than just the arm for blocking. If one turns the waist too early it doesn't contribute to the momentum of the block. Different parts of the body is activated at different times in order to create the most momentum.



To quote Bruce Lee¹ on the subject of sequential motion:

The timing is such that each segment adds its speed to that of the others. The shortened lever principle is used to accentuate many of the particular speeds of this uncoil or whip. The rotation of each segment around its particular joint-fulcrum is made at high speed for that particular part; but each segment rate is accelerated tremendously because it rotates around a fulcrum already highly accelerated.

In the ITF patterns the techniques are often started with deliberate relaxation—corresponding with the first part of the sine wave motion. From here, however, the technique is accelerated in such a way that as much of the body mass as possible is engaged, adding to the force of the technique. For instance, when punching it is not merely the weight of the arm that is accelerated for the punch, but the mass of the whole body is engaged behind the punch, while sequential motion is applied to accelerate the punch in a whip-like fashion.

Bruce Lee, again, explains how this would work with analogies from sport:

In throwing a ball, all the accumulated speeds of the body are present at the elbow when the forearm snaps over its fast-moving elbow-fulcrum. . . An important aspect of this multiple action of acceleration is the introduction of each segment movement as late as possible in order to take full advantage of the peak acceleration of its fulcrum. The arm is kept so far behind that the chest muscles pulling against it are tensed and stretched. The final wrist snap is postponed until the last instant before release or, in striking, before contact. In football, the punter puts the last snap into his knee and foot as, or a shade after, he makes contact with the ball. It is this last moment acceleration that is meant by ‘block through the man’ in football or ‘punch through the man’ in boxing. The principle is to preserve the maximum acceleration up to the last instant of contact. Regardless of distance, the final phase of a movement should be the fastest. Maintaining this increasing acceleration as long as there is contact is sound. . .

Controlled Falling


One of the simplest ways to get the whole body's mass accelerated is by employing the constant pull of gravity. Much of the patterns, therefore, is concerned with teaching the practitioner “controlled falling”. In many of the techniques, the practitioner is actually “falling” into them, dropping his or her body weight from a higher position to a lower position and thereby converting potential energy into kinetic energy. Also, when stepping or sliding the body momentum is in a manner of speaking thrown into the technique, so that one is falling towards the target. In ITF Taekwon-Do we use this “falling” as a way to activate our body's mass, and then further accelerate the technique, using the aforementioned sequential motion method, which usually piggybacks on the “fall”; or put differently, while “falling” one accelerates different parts of the body sequentially in a whip-like fashion, thereby adding gravity's force with your own force.

It is important here to understand why I'm referring to it as “controlled falling” and not merely “falling”. One of the cardinal concepts in ITF Taekwon-Do is “to bring the action of [ones hands and feet] into one singe coordinated action . . .” at the same focused moment. Many martial arts believe it proper to first root, then punch when stepping. For instance, one would find in most systems of Karate that they will step, first plant the foot, and then punch. This is to ensure good structure and stability before punching. While this is a valid strategy, it does lose out on some of the power that can be gained from the forward momentum of the step. The problem with first placing your foot and then punching, is that once your foot lands—roots—the momentum dissipates into the ground.

Therefore, ITF Taekwon-Do, and some other martial arts like Xingyi, coordinate their movement so that their stepping foot lands at the same moment as the striking hand. In this way, the technique properly employs the whole momentum of the moving body and transfers this force through the technique (hand) into the target. Of course this is a basic concept in ITF Taekwon-Do and is practised constantly as part of our fundamental movements, but it is particularly in the patterns where we are constantly confronted with this principle in various types of techniques and contexts.

Using Gravity for Initiating Motion


Something I particularly find interesting about this principle when combined with ITF's focus on relaxation is how one learns to initiate movement of the body by using gravity's force, rather than one's own muscular force.

Doing so allows you to stay in a state of relaxation much longer than if you were to initiate your movement through muscular force. (The emphasis on relaxation was addressed in the previous post.)

For instance, a typical forward stepping punch in Karate requires that the Karateka thrusts forward with his rear foot. On the other hand, in ITF Taekwon-Do the way to initiate motion in the patterns is not by immediately thrusting with the rear leg, but rather by first relaxing the forward leg which causes the body to “fall” forward, so that the body's mass is brought forward onto the front leg in a natural, literally effortless way. This “falling” momentum is then capitalised on by the sequential acceleration of the different parts of the body later in the step. It is true that from start to finish the Karateka's forward stepping punch would be faster; however, the ITF practitioner's emphasis on accelerating more body mass is greater. Of course, it is important to remember that the aim of the patterns is not to teach fast, hurried defending and attacking, as might be the case in Karate. For more realistic defending and counter-attacking training other parts of the ITF pedagogy is used. The ITF patterns is building kinaesthetic awareness, and in this instance the goal is to acquire the ability to accelerate body mass sequentially and use gravity where appropriate to help with this, while emphasising relaxation.

Unhurried Tempo, but Hurried Acceleration 


It would be wrong to think, however, that the practitioner is not learning to move quickly. Actually, because there is a focus on acceleration, not merely on hurriedness, the practitioner learns how to accelerate quite dramatically.

Take a look at this video that shows a pattern in slow motion—the slow motion starts at 3:22. Notice, although each movement starts very slow, how fast they accelerate towards the end of each movement.




Even in a video that is artificially slowed down, one can see that the techniques are not slow throughout—in fact, at the moments just before impact, the techniques are extremely fast (even while shown in slow motion!).

So what is it that encourages this sudden acceleration? There is a principle in ITF Taekwon-Do that states that movements of the hands, feet and breath should finish at the same time—“To bring the action of [everything] into one singe coordinated action . . .”

In other words, for example in the case of a stepping back-fist strike, by the time the stepping foot is planted, the attack (the back-fist strike) should have landed also. In ITF Taekwon-Do one would generally not first step, root your foot, and then strike, as the moment your stepping food lands (and roots your body weight) the body's momentum is dispersed into the ground. So the back-fist strike should occur at the moment or slightly just before the stepping foot roots, causing the accelerated mass of your whole body to “fall” into the strike.

However, in the whole sequence of body parts being accelerated sequentially the striking arm actually starts quite late in moving towards it's target. The motion starts in the legs, then the hips, then the shoulders, then the elbow and lastly the forearm and wrist is flicked. This means that the arm should move very quickly to catch up with the motion of the rest of the body. While the patterns have no urgency in tempo, they definitely have an urgency in finishing the technique before the stepping foot has rooted (or before the “controlled fall” is finished). The focus is therefore not merely on moving quickly from technique to technique; rather, the focus is on accelerating every individual technique sequentially and as quickly as possible so that “the final phase of [the] movement [is] the fastest,” with a significant amount of body mass engaged behind it.

Conclusion


In conclusion, a primary value of the patterns is to supply an environment in which to drill the acceleration of body mass in techniques, while using sequential motion to create a whip-like effect, and using gravity's force as an aid where appropriate. Moving with a sense of relaxation is a key ingredient in this regard. Although there is generally no sense of urgency in between techniques (with some exceptions), there is a definite sense of urgency in accelerating each individual technique quite rapidly.

In the next instalment(s) on what I consider the kinaesthetic value of the ITF patterns I will look at rhythm and timing, and breathing.



1. Bruce Lee, “The Tao of Jeet Kune Do”

19 September 2011

Another Perspective on the Reaction Arm

I wrote about the reaction arm in fundamental techniques, particularly traditional punching, a few weeks ago. In that particular post I basically said that there are two main views regarding the function of the reaction arm. The one view sees it as critical for maintaining proper structural balance. The second view holds that these reaction arms act as pulling techniques. Therefore, an interpretation for a traditional punch would basically be that you pull your opponent towards you with the one hand (reaction hand) while pommeling him with the other. There is a third view which I did not mention in that post, partially because it is such a very traditional view that is dismissed by many people, and because it doesn't apply to most techniques—only a small group of techniques may actually benefit from this interpretation of the reaction arm.

This third view considers the spine of the body as one's central axis and your arms as extensions on opposite sides of each other that rotates around this axis. There are two objects that can help you envisage this view.

A Korean pellet drum,
which is called a do 도 in Korean.
The first object is a pellet drum, known in Korean as a do 도 / 鼗 or nodo 노도 / 路鼗. A pellet drum has two membranes on opposite ends of the barrel. On the sides of the barrel are two strings with pellets attached at their ends. A pole is attached through the drum (through the barrel, not the membranes).


A Japanese pellet drum toy,
known as a denden daiko でんでん太鼓.
One plays a pellet drum by swiftly rotating the pole in one direction and then in the other direction, which causes the pellets to swing because of the centrifugal force that occurs when the pole is rotated. The pellets hit the membranes and create sound.

Aeolipile, aka Hero's Steam Engine
The second object is an aeolipile, sometimes refered to as Hero's steam engine, after Hero of Alexandria that described its mechanics in the first century A.D. An aeilipile is basically a boiler that is so set-up that it can rotate around an axis. On opposite sides of the boiler are two curved nozzles pointing in opposite directions to each other and perpendicular to the axis of the boiler. When steam escapes from these nozzles, thrust is caused, based on the the rocket principle in accordance with Newton's Third Law of Motion. This causes the boiler to spin around its axis.

Both objects are somewhat flawed to describe what happens in the human body in the third view of the reaction arm. Nonetheless, they help to illustrate the underlying idea. Note that in both cases there is a pair of opposing elements: the two strings-and-pellets on the drum and the opposing curved nozzles on the aeolipile. In both cases the pair of opposing elements rotate around a central axis. The traditional martial art idea is that the one opposing element contributes to the force of the other opposing element. In other words, by forcefully swinging my arm in one direction, this adds to the force of the other arm moving in the opposite direction.

Me trying out Pak Hok Pai in Hong Kong
In some of the Chinese martial arts one sees this idea flamboyantly applied. Sometimes the arms are literally flung in opposite directions just like the strings-and-pellets on the pellet drum. A good example where this idea is applied is Pak Hok Pai, the (Tibetan) White Crane Kung Fu system.



There is definitely power in these techniques caused by the centrifugal force, but I would be hard pressed to say that the arms moving in opposite directions cause the noticeable force in each other. It is probably more correct to say that the arms swing because of the centrifugal force. It is not the arms in themselves that cause the force. It is easy to demonstrate that the arms do not directly influence each other's reaction to the centrifugal force. Stay on one spot and then start to spin around, keeping both arms relaxed so that they naturally swing away from your body because of the centrifugal force acting on them. Now bring one arm towards your body, keeping it tight against you. The fact that this arm is kept from acting on the centrifugal force, contrary to the other arm, does not influence the other arm from still swinging normally as before while you keep on spinning on the spot. The essence of the force, therefore, lies not in your arms working in opposite directions, but lies in the actual rotation of your body that is spinning around an axis. (What is properly influenced when you use only one arm during this spinning exercise is your balance. You have better equilibrium with both arms out.)

The important thing is therefore not the opposite directions that your arms are moving in; the important thing is the rotation of the body around its axis which causes centrifugal force. While I don't believe that the arms moving in opposite directions contribute to each other's force, that doesn't mean that they could not contribute in another way. If pulling back my arm helps me in rotating my body around it's axis faster, then it can actually influence the centrifugal force, which in turn will influence the other arm.

Sanko's Imaginary Jet-Propelled Rotating Glove-Weapon

To explain this, imagine a ridiculous weapon I invented for this post that works similar to an aeolipile. The weapon is made up of a structure with two beams attached at opposite ends of an axis. At the far end of one of the beams is the attacking tool—a boxer's glove—attached perpendicularly to the beam. Perpendicularly attached at the far end of the other beam is a rocket engine. The jet propulsion of the rocket, in accordance with Newton's Third Law of Motion, causes the structure to rotate around the axis, resulting in the glove hitting a person standing close by. We see here that the beam moving in one direction causes the motion of the beam moving in the opposite direction—the glove's force is equal and opposite to the force of the rocket.

Speaking of this principle of Reaction Force, i.e. Newton's Third Law of Motion, the ITF Encyclopaedia states that “A punch with the right fist is aided by pulling back the left fist to the hip” (Volume 2, p. 15). The encyclopaedia doesn't expand on this topic, so it is unclear how pulling back the left fist contributes to the punch with the right hand. The only way I see this to be feasible is if the reaction arm (the one that is pulled back) contributes to the acceleration of the body's rotation around its axis. This in turn will help to push the punching arm which is structurally on the opposite side of the body, just like the glove is opposite to the rocket as depicted in my imaginary weapon.

Many traditional martial arts are of the view that the reaction arm contributes to the force of the acting arm; that pulling back the non-punching arm aids the punching arm. It must be remembered, however, that the reaction arm is not directly affecting the acting arm; instead, it is possible for the reaction arm to contribute to the rotation force of the body. If the reaction arm is not positively affecting the rotation of the body around its axis, then it is not contributing to the force of the strike. On the other hand, if the reaction arm contributes to the rotation of my body around its axis, then it may very well contribute to the force of the punching arm.

It is important to remember, as I mentioned at the beginning of this post, that only some techniques—those that potentially benefit from centrifugal force—will benefit from the reaction arm in this way. For many techniques the reaction arm does not contribute to centrifugal force; instead it contributes to better structural balance and its associated benefits.

Read the previous post on "The Reaction Arm."

31 August 2011

The Reaction Arm

The reaction arm in traditional martial arts punching and other fundamental movements is quite controversial. The reaction arm is, for instance when doing a front punch, the arm that is pulled back to the hip, while the other fist is flung to the target. Although controversial, for the traditional martial artist there are many proposed reasons for employing the reaction arm. In this post I will mention the two most prominent reasons that I am aware of, as this topic is viewed within ITF Taekwon-Do.

A front fore fist punch with the
reverse arm pulled back towards
the hip. (Image Source)
First, the “reaction arm” functions exactly as its name implies, as a reaction to the punching arm's action. This has a counter-balancing effect. If you were to punch with all your strength and with your whole body weight behind the punch, the resultant force will actually jerk you off balance. Always keeping good structural balance and good posture is paramount in traditional martial arts as the moment you are off-balance or your body structure is unsound, you are strategically disadvantaged, something that your enemy can exploit.

A lot of Taekwon-Do training occurs without hitting an actual target and many of the punches and kicks are done in the air, without any contact. During such training the reaction arm is crucial for keeping good balance and structural alignment. Not doing so may lead to bad habits and overextension of joints, which could lead to long term ailments. However, when you actually do hit something, the reaction arm is not necessarily required because the object you are hitting is providing the reaction force as we know, based on Newton's Third Law of Motion. In other words, when you train against a punching bag or when you actually hit a person, you may at times, and sometimes should, opt to do it without the reaction arm. In ITF Taekwon-Do we actually see this. Certain training is done with the reaction arm (e.g. fundamental technique training), while other exercises are done without the reaction arm (e.g. tournament sparring drills). The discrepancy doesn't mean that the one is “traditional” and the other “practical,” it merely means that one form of training assumes more force that could affect your structure and another form of training that assumes that you will be hitting actual objects.

A knife-hand inward strike with
the reverse arm covering the torso.

(Image Source)
Furthermore, some reaction arm techniques, while aiming to ensure proper balance, also act as guards, covering vital spots on your anatomy. Take for instance the knife hand inward strike where the reaction arm covers the front of your body which has many targets that are potentially easy for your opponent to reach at this close distance. There are quite a number of techniques where the reaction arm seem to have this auxiliary defensive function.

Me demonstrating an arm
bar: pulling with one hand,
while pressing with the other.
The second interpretation for the use of the reaction arm is that it functions as a pull. This is another example where ITF Taekwon-Do seem to base its technical philosophy on Newtonion physics. In this case it suggests that a technique will be more forceful if one combines the oncoming (pulled) momentum of your opponent plus the forward momentum of your own strike. Basically, one can actually pull your opponent into your punch and this will theoretically increase the effectiveness of the strike. It also prevents your opponent from dodging the attack. This is not something one see in most combat sports, not because it is not feasible, but probably because of the nature of the sport and sport equipment—sport rules that discourage grabbing or gloves preventing you from grabbing. When one look at gloveless combat sports like certain forms of Karate, one does occasionally see such pulling-while-punching techniques as in the video below. I personally also like to teach applications where the reaction arm is used to great effect as a grab and pull while attacking with the other arm. This combination of pulling and pushing is a common theme in martial arts.




These are the two main ideas regarding the reaction arm in ITF Taekwon-Do. The first is that it acts as a reaction force that helps with proper balance and postural structure, which is especially necessary when practicing without the presence of a physical target. If you do hit an actual target you may often omit the reaction arm because the object will provide the reaction force according to Newton's Third Law of Motion. The second interpretation of the reaction arm is that it functions as a pull, which combines with the forward momentum of your attack, resulting in a more forceful collision. The reaction arm may also be part of other pull-push combination techniques.

What are your thoughts on the reaction arm?

Read my follow-up post on the reaction arm, which presents a third view based on centrifugal force: "Another Perspective on the Reaction Arm."