Saturday, January 15, 2011


Hitting the bag, the mitts or the makiwara, should be done at least few times a week for 10-20 minutes, it is a great and necessary way to develop your kime and impact power and to get feedback on your quality of movement.

There are few things to consider:

First, when you start hitting at the warm-up phase don’t concern with hitting hard, but rather with following the basic principles, move your foot first, let your body action drive your technique, snap with the whole body, pressure to floor at contact rather than muscling the technique, keep the elbow and shoulder soft, find your range and distance for each technique, don't over extend yourself, than gradually increase the speed without loss of coordination and sequence of muscles and joint activation.

Second, be careful of being tense too soon before impact, that will kill your speed, kind of like driving with the brakes on.

We need maximum speed and momentum and than pressure/contraction at impact. When I hit the bag or makiwara I let the contraction happen as I hit the bag, otherwise you might slow down before impact.

And if you tense while moving there is less potential contraction for kime, we need the contrast, the softer in between, the more contraction is available for impact.

Third, Sensei Nishiyama gave me very useful tip when hitting the makiwara, at impact I want to feel the reaction power coming back to my center (low stomach), rather than to the elbow or shoulders. That is a good feedback, that will tell me if I am aligned properly and/or if the contraction sequence is optimal, and if the technique was initiated properly from the body center. It also tells me that the whole body momentum is meeting the target.

Fourth, I like to think of “pouring” the energy from my body through the fist to the bag or mitt. This is helpful, because some people tense in a way that braces and “chokes” the energy, and energy is absorbed into our own body, this should be avoided.

Fifth, don’t push, it is not about muscular power, push is power delivered over long period and is ineffective.

Use total body snap, your body should be like a whip from the center out.

We need to teach the nervous system to recruit more motor units in shortest time.

Sixth, when you hit, nothing moves externally for a moment, yet inside momentum does not stop, kind of like a car crash, the sharper and more at once the car stops, the more momentum will the passengers inside will receive. Use the mitt or bag to understand how long does it take to transfer the full momentum to target, because kime should not be any longer or shorter than that, once energy is transferred the reaction should be Zanshin with the next breath.

Seventh, at contact have a strong stance, to deliver the energy from.

Remember, you cannot shoot a cannon from a canoe.

At the same token, you should also be able to deliver power of off one leg, even though it is not optimal, it is sometimes necessary so I spend some time hitting from one leg stance, especially during combination techniques.

Eighth, develop single techniques power first and than combination, you should be able to make 2,3 or 4 techniques with full speed and kime and completely relax in between. If one does not relax instantly from kime, the following action is likely to be stiff, pushing and lacking snap. Use your exhalation to relax and use the energy from one kime to next action.

Avoid the temptation to use top heavy power, don’t go after end results and muscle the techniques, make sure each action is from feet and ground reaction, if you cannot do it at first, slow down, coordination is more important than power at first. When moving from the feet it will be easier to relax the top muscles.

Powerful technique should appear relax, give up power at first to be powerful in the long run.


  1. Theanks again Avi for this fantastic explanation.
    Very clear and for sure people will work on it.

  2. A lot of people using "pushing" power, when working wiht bags or mitts. Especially beginers, they want to hit very hard, but at this moment they don't have good skills.
    Very nice guide how to use bags, mitts or makivara during karate classes.

    Thank you again, Avi:)))

  3. Dear Master
    Ad 6. The pasangers can only receive the momentum equal to p=m*v where v is a velocity of a car. The shorter the time of the collision, the bigger the force generated. That is the reason for practicing kime.
    Ad 7. One can shoot tha cannon from the canoe and even can destroy the target. The only trouble is that the canoe will move backward just after the shoot.
    Best regards. Nice job.

  4. Thank you Ian,
    Nice addition, but one can shoot a cannon from a canoe, but if I deliver force from a shaky, unstable base, I cannot maximize ground reaction force, and some energy will escape, I also cannot be accurate.

  5. Ok, but it is possible to shoot. If the speed of the bullet/fist is large enough, the momentum is also large enough and the energy delivered to the target can be sufficient. This is physicis. The bullet does not have ground reaction force too.
    Thank You for Your answer, Master Avi.

  6. Ian,
    That's true, the bullet does not have ground reaction, but in the case of a punch or kick, if I use a strong base to drive my technique, I'm can create more acceleration, thorough proper sequence and segmentation, each segment increases energy to accumulate bigger total energy, I will also have more Mass (weight) behind the technique, since all body muscles will engage rather than just the top body, and I can increase energy to the body center from ground reaction more effectively, no matter how strong the center, energy cannot increase without external force.
    Thanks for the input.

  7. Round Three ;-)
    One can engage the mass only by moving it. The lower part of the body does not move so it can not be a part of the total momentum (this part of the body is not accelerated). In my opinion, this part of the technique (kime, etc.) is important in order to keep balance after a collision with the oponent. It also can help to get ready to the next action...
    Many boxers use a very small preassure to the floor but they can knock people out.

    Very nice discussion.

  8. Hi Ian,
    The lower part of the body is moving in the case of shifting, but it is still and has to be driven from external force (stance) and than again at contact we have stance and make pressure to floor to deliver force, make balance and be ready for next.
    Sometimes techniques are stationary but still acceleration builds up segment by segment as chain reaction from the ground up, likewise in golf and other sports.
    Thank you

  9. Hi, Ian,
    please visit Sensei Awi in his dojo, he will explain you who is a Master here and who you are.

    Thank you Awi, last week I made mystake during training of Sen and my nose is not still O.K.

  10. Avi: I know the master (7th dan from H.Nishiyama) who tells that one can not moving and punching simultaneously. "In order to punch You must stop shifting": he tells. Then, only a part of the body (arm, leg) has the momentum and also energy. I'm sure, you know that sensei (one of the H.Nishiyama's best student)very well.

    Info: I belive You know what does the PhD mean. I'm sure that Avi sensei is very good karateka but this debate is about physics. And as you know, physics is a science about the fundamental laws. Not about the feelings.

  11. Ian,
    All parts of the body sequence with each other to increase energy and momentum to maximum and have to peak together and stop at the same instant, so maximum momentum is accumulated and peaked at impact, but at impact there is no movement externally, at this point the energy is being delivered. Think of a billiard ball hits another ball, it stop at once and the other ball is receiving all the energy.
    In physics this is called the rate of change of momentum.
    Thank you

  12. Thats right, but the ball is stopped because each of the balls have equal mass (at least). This is the law of conservation of the energy and the momentum. The ball that hits the another stops because the second ball generate the force that brakes first one. The first ball doesn't generate the force by stopping itself.

    Thank You Avi. I hope You agree that physics should be the part of the instructor's course.

  13. Ian,
    Force can be increased by increasing the mass or the acceleration, and also the billiard ball being dense transfers the force more fully, making for elastic collision, which is why we need sharp total contraction in karate at kime.
    I appreciate your knowledge of physics, and I try to understand the physics to make my understanding more complete, but I don't think it is necessary for every karate teacher to understands the physics, I think one develop intuitive feel of what necessary to produce and deliver force thorough good instruction and experience, on the other hand one can understand the physics and not being able to apply it.
    One has to get the "feel".
    I also think you misinterpreted what the 7th dan told you (who is it?)
    about shifting and punching and only the arm has the momentum, this is not true.
    Thank you

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  16. "Force can be increased by increasing the acceleration": Yes, but not the force You want to generate during punching. This is a misunderstanding. F=ma tells You that if You want to accelerate a mass=m with acceleration=a you must use the force=F. This is not the force that you hit Your oponent with. This is the force YOU HAVE to USE to accelerate YOUR body. It this case intuition fails.

    "...we need sharp total contraction...": That is the true.

    "I think one develop intuitive feel": practitioner-yes, but teacher-no.

    "you misinterpreted what the 7th dan told you": I don't think so. This man does not know phisycs at all. This is why i listen to him very carefully.

    "...this is not true.": if the mass has no speed, it has no momentum.

    "other hand one can understand the physics and not being able to apply it": one can also know nothing about kime, nothing about momentum and even nothing about preassure but one can be effective. Just like a boxers. But i prefer traditional karate training with strong physics support.
    And You can be sure: i don't want to contest Your karate knowledge and skills. I know a lot about You. My only goal is to correct traditional karate senseis's knowledge about physics.

    Thank You for You time. I think You also know me but You don't remember. :-)

  17. Thanks for the input, it is important to keep discovering and understand. I like criticism, that is how we keep thinking of how and why we do things.

  18. "...this is not true.": if the mass has no speed, it has no momentum.
    When I say everything stops at kime, it still reach the target at peak acceleration, so there is maximum momentum to deliver to target.

    Yes ground reaction accelerates your body, but than each segment of the body accelerate and create chain reaction from floor.
    I think you are wrong here.
    And I think you misunderstand some technical points.
    But I like to hear and discuss.
    Thank you

  19. "And I think you misunderstand"; it can be, of course. I use the same words to my biophysics students ;-)

    "each segment of the body accelerate"; Does it mean, that You treat the body (leg, hips, torso, arm) like a whip?

    "...stops at kime, it still reach..."; the acceleration of the body is rather constant or even decreasing, so there can't be peak acceleration. It should be "peak velocity". The force generated during hitting depends on how fast the momentum of the fist is decelerated by the hit body. Thats the proper interpretation of the F=ma or F=dp/dt formula.

    The last one (but substantial):"...everything stops at kime..." How do You think, Master Avi: Is kime the result of the collision, or the collision is the result of the kime?

    Than You for Your patience. I know that words are less worth than demonstration.

  20. As I hit the target the body will decelerate as impact force return to me, so in this sense kime is result of the collision.
    I think it is hard to discuss the technique details in terms of physics without demonstrating, misunderstandings are more likely.

  21. Ian: I've been reading this as an independent observer, and I think there are several elements of physics you are not factoring into your equations.
    1) When you say you can shoot a cannon from a canoe -- the canoe is pushed back at the same momentum as the cannonball (or projectile) is pushed out of the cannon. This is partly absorbed by the water, but still the cannonball will "bleed" a good bit of momentum as a result. It will thus fly out at a lower velocity, interfering both with its intended trajectory (or, as Avi says, accuracy) and its energy to deliver impact. If your firing solution takes all this into account, it is still possible to shoot out of the canoe -- but it's a lot harder to be effective that way vs. from a steady base.
    2) It is correct to consider the force delivered as m*a of the attacker, but remember that it can be very hard for you to tell what "a" is. At a microscopic level, dv / dt can be extremely high if dt is very short. Also, "v" is not just the v at the peak of the "outside" movement (as Avi calls it), or the shift, since the kime/contraction accelerates you forward, which brings us to;
    3) When the attacker has a solid base, kime produces driving force into the technique -- creating very minimal visible movement but crushing pressure into the target. Imagine standing with your back to the wall, with a rocket starting with its tip on your ribcage, and then turns on the engine. It does not need to have significant momentum at all to crush you, its engine generates thrust that pushes into you.
    In the same way, think of a bulldozer that has put down its rests (so has a steady base) and is now pushing its arm into you when your back is against the wall. The hydraulic pressure can be very substantial, even with very low momentum. When Avi puts down his foot (finishes shifting) and is generating kime into you through his fist, that is exactly what it feels like :)

    If you want to think of it with classic kinematic concepts, you need to consider the case of a car driving into another car while revving its engine (as opposed to idling) and letting go of a loaded spring attached to its bumper. It transfers more energy into its target than 1/2m * v^2... it's unleashing the spring's energy as well. This would produce higher deformation (and greater acceleration) of the target. The abrupt acceleration of your opponent over a very short dt is something that's hard for the body to absorb, and makes the difference between pushing him back and breaking his bones.

    My 2c,

  22. I think point (2) deserves another couple of sentences. A short dt is a product of everything "stopping at once", and the whole body becoming a rigid object that is supported against backward movement (by the feet's friction) and yet has muscle energy generating thrust forward. With a super short dt, the energy transfer becomes an impulse function ( F -> infinity ), which shatters the targets bones.

    OK, now I can rest :)


  23. Thank You Tamir very much. My comment is:
    1."...but it's a lot harder to be effective that way...";
    I agree.

    2." tell what "a" is...";
    I don't use such a interpretation of the F=ma, when 'a' is an acceleration. The 'a' coefficient should be a deceleration made by collision.

    3."When the attacker has a solid base...";
    I do not deny.

    4."...which shatters the targets bones.";

    I think, it's the end of our discussion. Thank You one more time. I have to go back to my country, so it could be difficult do rich any WiFi signal within a few days.

    Let's rest.
    Best Regards.

  24. Ian. You try to explain the kinematic chain, but what if the punch is done without any movement. It is possible and dV will be zero. Still some energy will be passed to recepient. Probably it is better to think about wave that comes from the attacekr and reaches the target.
    Hope you can cope with this problem.

  25. This is a very interesting discussion. When Sensei Nishiyama came for seminars he would teach people will less muscle power to use dropping power. Someone smaller would use Gedan Barai to block a punch without using any muscle or attempt at kime, but just simply by dropping their elbow and their body into the floor. This was incredibly effective. It was like using the force of gravity alone to block the punch, but it seemed it was much more effective than the force of gravity. Obviously there was some extra acceleration going on due to the sudden relaxation of muscles. It has always fascinated me, but it seems almost the opposite of the forces generating the power in the punch above. Is this a component of the force in a punch also?

  26. Hello.
    I would like to share my opinion about two points discussed here.
    1. Force F
    I think one should be careful about what F=ma really is, for quantizing the acceleration seems difficult to me. In my understanding I first generate force by pressure to floor, then I use ground reaction which, by sequential muscle contraction from the ground up, is transferred through my technique to the impact point. (talking about kime here, so one does not have to account for additional force production/acceleration through body dynamics). So I generate 2-3times my body weight (as mentioned in another article) that I transfer into the target, the amount of force thus being mainly determined by my ability to produce pressure to floor and to transfer the reaction to the impact point.
    Adding body dynamics will probably produce additional acceleration and force which adds to the one produced by kime.
    2. Moment of contact
    To my mind deceleration by collision is only part of the story. Consider the law of momentum conservation: at impact I stop my fist abruptly thus producing high deceleration a=dv/dt, by momentum conservation the same amount of force is transferred to the target. Deceleration only through collision would mean that I can give up my stance while maintaining the same power in the technique.

    Points that are a unclear to me:
    1. By using sharp or deep/longer contraction we can choose to deliver the force faster or over a longer period of time. Is it time of delivery/shocking power vs. amount of transferred energy, that makes us choose to use sharper contraction to head (more shock, not so much energy needed) and deeper contraction to stomach (more energy transfer)?
    2. How would one physically explain continuous pressure to ground? Does it have to do with the potential energy of total body contraction, that has not yet been considered here?

    In the end I don't think one can explain every tiny point with physics, maybe intuition at some point wins over the physical complexity.
    Best regards,

  27. i agree to roman's last remark , and i see another component as well .
    it is very human to "wish" !
    at the time of impact we also "wish"and we cant eliminate our desire to "feel better" and to full fill our ego in that specific time .
    i am not familiar with any physics equation to measure our own intentions.
    when we punch soft target , we cant use only "dry" physics rules to analyze it (different if we punch air and don't touch).
    human factors (physicians might call it negligible) have tremendous values here .
    our "will power" equivalent here to the "butterfly effect" , and this , as we all know , is impossible to measure , and certainly not negligible.

    love ,

  28. I think it is not unreasonable to try to model the physical components of a punch or kick, however I think it is quite a difficult problem to write equations describing what is happening. I think some kind of hybrid model between the force delivered at the end of a whip and the motion of a rigid body is necessary. I think the application of pressure to the floor described above may deliver an effect similar to
    that produced in a whip by grasping the handle. However our arms and legs are not exactly soft like a whip, so the model does not apply in that form. A hybrid model of this form would mean the force delivered in blocks such as Gedan Barai and punches would be produced in a similar manner. A model where our body becomes a rigid body between the floor and the target would not generate any force in a downward block because the target is almost between the body and the floor.
    However as many have commented above, the equations are not necessary to learn the karate.