# Why does instant recoil after a punch deliver a stronger blow?

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I practice kenpo karate, and in our technqiues for punching, we are told to deliver a punch but then as soon as it hits the target, recoil it back to yourself as fast as possible.

I've tested this out numerous times on a punching bag (hi-tech right?), and every time I throw a punch and then recoil it, I move the punching bag further than just throwing a

one direction punch.

-Just curious

~EE

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I practice kenpo karate, and in our technqiues for punching, we are told to deliver a punch but then as soon as it hits the target, recoil it back to yourself as fast as possible.

I've tested this out numerous times on a punching bag (hi-tech right?), and every time I throw a punch and then recoil it, I move the punching bag further than just throwing a

one direction punch.

-Just curious

~EE

That could the fault of the device that is measuring the punch. (That was not supposed to be a joke but is now!)

Edited by Robittybob1

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That could the fault of the device that is measuring the punch. (That was not supposed to be a joke but is now!)

That hurt more than getting punched in the face.

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That hurt more than getting punched in the face.

Now you are being a softy.

We were taught the same, to jab real fast, I thought it was to have your hands back in the defensive position as quick as possible.

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Now you are being a softy.

We were taught the same, to jab real fast, I thought it was to have your hands back in the defensive position as quick as possible.

Well ya thats the point, but it seems to be a stronger punch as well. I was wondering if it was something similar to how a bullet is spun down a barrel, making it more accurate

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It may have something to do with the speed of the punch. Without actually seeing you punch I would say that you are hitting faster when you recoil than when you throw your 'one direction punch'. Punching power is more appropriately mesured by how much you compress the bag (inelastic collision) than it is how far you move it (elastic collision). The more the bag moves the less impact the bag feels as energy that is meant for the bag is lost in the bags motion.

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Well ya thats the point, but it seems to be a stronger punch as well. I was wondering if it was something similar to how a bullet is spun down a barrel, making it more accurate

Rifling leverages conservation of angular momentum, which does not appear to be an issue with a jab.

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If this were a scattering interaction, the difference would be between a completely inelastic collision and an elastic one (or close to that). In an elastic collision, the final speed of the target is twice that as in a completely inelastic collision (the recoil means a greater transfer of momentum) (v2f = 2m1/(m1+m2) vs m1/(m1+m2) )

The problem is that this probably can't be modeled that way, since you are actively pulling the fist back, rather than it happening as a result of the dynamics of the collision. But if it's true that the collision is closer to elastic in one case, then you will transfer more energy.

edit: as I think about this more, I think recoil is the wrong metric. Inelastic collisions transfer less kinetic energy to the target, but that lost KE appears as heat, sound and deformation, much of which would count as damage of a blow. There's more to it than recoil.

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The way this was explained to me (read: I'm not certain this is is accurate) is that punching and leaving your fist there allows more of the energy to come back and be reabsorbed by your arm. Punching and withdrawing your fist rapidly ensures the energy stays with the target in full.

Whether or not that's true, the act of snapping your punch or tensing your muscles in such a way to allow you to pull back your fist from the target probably allows just that little bit of extra "oomph" to be added to the strike... Just those few extra muscles to add to the overall impact.

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The way this was explained to me (read: I'm not certain this is is accurate) is that punching and leaving your fist there allows more of the energy to come back and be reabsorbed by your arm. Punching and withdrawing your fist rapidly ensures the energy stays with the target in full.

Whether or not that's true, the act of snapping your punch or tensing your muscles in such a way to allow you to pull back your fist from the target probably allows just that little bit of extra "oomph" to be added to the strike... Just those few extra muscles to add to the overall impact.

There seems to be a high point as you pull back that your fist/arm/body is at its most rigid, somehow allowing energy to conduct better.

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I practice kenpo karate, and in our technqiues for punching, we are told to deliver a punch but then as soon as it hits the target, recoil it back to yourself as fast as possible.

I've tested this out numerous times on a punching bag (hi-tech right?), and every time I throw a punch and then recoil it, I move the punching bag further than just throwing a one direction punch.

-Just curious

~EE

I suggest taking some actual measurements rather than trusting your impressions. Put a scale with vertical markings on one side of the bag and a video camera opposite and on the other side of the bag and then deliver your blows from 90º relative to the camera's line-of-sight. Make multiple recordings and carefully review the results and report back.

There is no physical reason to expect a quickly withdrawn blow delivers more energy, though there is a physical reason that a quicker blow does.

The amount of energy delivered to the target by the hammer-blow is equivalent to one half the mass of the head times the square of the head's speed at the time of impact . While the energy delivered to the target increases linearly with mass, it increases quadratically with the speed (see the effect of the handle, below). ...

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Why not make a real experiment from this?

Get Force Gauge Analog/Digital Device.
http://www.industrial-needs.com/technical-data/force-gauge-gram-division.htm

Connect wire to it, then to bottom of bag.

Somebody with digital camera will have to record device while hitting it.

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Why not make a real experiment from this?

Get Force Gauge Analog/Digital Device.

Connect wire to it, then to bottom of bag.

Somebody with digital camera will have to record device while hitting it.

Are you suggesting my suggestion was not a real experiment!

That's a good addition however. I would also suggest having the camera positioned so that the entire puncher is in the frame so that it's possible to gauge the speed of the punch and any differences in stance or arm position.

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Are you suggesting my suggestion was not a real experiment!

Not at all my friend..

But you were suggesting using camera to record movement of bag (like in pendulum), isn't?

The more powerful hit, bigger deviation from natural vertical direction of bag.

It would be hard to get good precision. And better to have 1000 FPS camera with it.

BTW, I found that GoPro Hero 4 for just $500 can record at 240 FPS: Not bad, and has also quite nice configurable interval recording mode/time lapse 1s-60s. 120 FPS @ Full HD 30 FPS @ 4K UHD That's a good addition however. I would also suggest having the camera positioned so that the entire puncher is in the frame so that it's possible to gauge the speed of the punch and any differences in stance or arm position. Then we need two cameras. From my own experience of recording of experiments (and I am using Full HD) we need close look up to to see digits, not to mention analog arrow.. Edited by Sensei #### Share this post ##### Link to post ##### Share on other sites Not at all my friend.. But you were suggesting using camera to record movement of bag (like in pendulum), isn't? The more powerful hit, bigger deviation from natural vertical direction of bag. It would be hard to get good precision. And better to have 1000 FPS camera with it. Just joshin' ya Sensei. But yes, the more energy directed into the bag the further it swings out. BTW, I found that GoPro Hero 4 for just$500 can record at 240 FPS:

Not bad, and has also quite nice configurable interval recording mode/time lapse 1s-60s.

120 FPS @ Full HD

30 FPS @ 4K UHD

You find the nicest equipment! A bit off-topic, but if I didn't say elsewhere, I ended up getting a Coolpix 830L. It doesn't have the interval record but it has great macro, panaorama vertical & horizontal, and HD video. Thnx for putting me onto it.

Then we need two cameras. From my own experience of recording devices on digital camera (and I am using Full HD) we need close look up to to see digits, not to mention analog arrow..

Probably add at least a 3rd camera directly behind the bag looking toward the puncher to detect any angle in the swing other than directly away from the puncher.

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You find the nicest equipment! A bit off-topic, but if I didn't say elsewhere, I ended up getting a Coolpix 830L. It doesn't have the interval record but it has great macro, panaorama vertical & horizontal, and HD video. Thnx for putting me onto it.

Do you have wifi in your model?

If yes, then you could try what I can do in S6600, and control it by smartphone:

Then write code in C/C++/Java(?) in smartphone app to take photo on demand in schedule that you want!

Edited by Sensei

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Do you have wifi in your model?

If yes, then you could try what I can do in S6600, and control it by smartphone:

Then write code in C/C++/Java(?) in smartphone app to take photo on demand in schedule that you want!

No WIFI. It's L830; not 830L as I said. Here's the specs: >COOLPIXL830

Back on topic, besides an angled swing showing up as energy not straight onto the target, heavy bags are usually suspended by chains and any upward force in a strike will make the bag jump up and so swing out less.

All-in-all, I think the "instant recoil after a punch delivers a stronger blow" idea is a myth. Happy punching!

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...

All-in-all, I think the "instant recoil after a punch delivers a stronger blow" idea is a myth. Happy punching!

My cynical intuition agrees with you. There seems to be over-reliance on received wisdom and dogma in much of the eastern martial arts.

One of my major objections would be the taught technique of most striking sports where regain of posture and defence is not paramount. In any form of martial art the greatest part is not the power of the strike but the ability to be in control and command of both yourself and your opponent - you do not do this by over-extending, nor by being overbalanced by losing control of a strike. The ability to strike with maximum force is sacrificed for composure and to maintain stance that allows defence/counter/renewal of offence; the snapped back punch is just one method of ensuring that your attack is not a be-all-end-all gamble. However in many non-martial sports the object is to impart maximum controlled force in a one off situation; teeing off on the long par four, the straight six in cricket, taking three points from a penalty inside your own half in Rugby - and all of these rely on the long, controlled and fluid follow through. In these sports we are taught that to dampen the shot, we relax the wrist, collapse the elbow, pull the follow through; but that for a power shot the follow-through is crucial.

And a lovely excuse to post a video of the amazing Chris Gayle in striking form

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My cynical intuition agrees with you. There seems to be over-reliance on received wisdom and dogma in much of the eastern martial arts.

One of my major objections would be the taught technique of most striking sports where regain of posture and defence is not paramount. In any form of martial art the greatest part is not the power of the strike but the ability to be in control and command of both yourself and your opponent - you do not do this by over-extending, nor by being overbalanced by losing control of a strike. The ability to strike with maximum force is sacrificed for composure and to maintain stance that allows defence/counter/renewal of offence; the snapped back punch is just one method of ensuring that your attack is not a be-all-end-all gamble. However in many non-martial sports the object is to impart maximum controlled force in a one off situation; teeing off on the long par four, the straight six in cricket, taking three points from a penalty inside your own half in Rugby - and all of these rely on the long, controlled and fluid follow through. In these sports we are taught that to dampen the shot, we relax the wrist, collapse the elbow, pull the follow through; but that for a power shot the follow-through is crucial.

The difference with a Karate strike is that the target is not propelled with just a momentary contact unless the strike is recoiled. then, you have a similar scenario.

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I don't know if they still sell them but you can actually buy pads and punchinng bags that have force sensors built into them if you can afford them.

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The difference with a Karate strike is that the target is not propelled with just a momentary contact unless the strike is recoiled. then, you have a similar scenario.

I think - as this is in physics rather than the lounge - to be more precise in what we say and what we are seeking. Contacts are never instantaneous (and I note that you didn't say they were) - they last whilst compression waves travel back and forth and look amazing in slo-mo. It might be worth checking if the slow-mo guys have videos that could help in judging the action.

What does a strong punch do? What makes a karate blow powerful? Let us try to separate physics and mechanics from mysticism and the sporting/point-scoring ideas of much of modern martial arts

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When you guys have all finished discussing force gauges cameras and punch bags, perhaps you could address the difficult part.

How do you propose to eliminate the psychological factor of hitting the bag harder because you think you can hit it harder?

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When you guys have all finished discussing force gauges cameras and punch bags, perhaps you could address the difficult part.

How do you propose to eliminate the psychological factor of hitting the bag harder because you think you can hit it harder?

I bow to your superior intellect in explicating the matter for us.

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I bow to your superior intellect in explicating the matter for us.

Which is the implication in #2. It is the brain controlling the arm movement, so when you decide to jab quickly you are less concerned about reaching. So the arm moves differently in both cases.

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The way this was explained to me (read: I'm not certain this is is accurate) is that punching and leaving your fist there allows more of the energy to come back and be reabsorbed by your arm. Punching and withdrawing your fist rapidly ensures the energy stays with the target in full.

This is what I was looking for, relative to an explanation. Now to find out if this actually holds any truth.

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The way this was explained to me (read: I'm not certain this is accurate) is that punching and leaving your fist there allows more of the energy to come back and be reabsorbed by your arm. Punching and withdrawing your fist rapidly ensures the energy stays with the target in full.

This is what I was looking for, relative to an explanation. Now to find out if this actually holds any truth.

Since the energy delivered to the target is a function of the mass and speed of/in the punch, then that explanation strikes me as clearly inaccurate. Energy 'reabsorbed by your arm' makes no physical sense here. The puncher does not gain any mass which leaves speed as a factor and how does one absorb speed? Edited by Acme

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