## Punch retraction

Discussion on the three big Chinese internals, Yiquan, Bajiquan, Piguazhang and other similar styles.

### Re: Punch retraction

Yeung wrote:The research variable of this post is stored elastic energy.

“Stored elastic energy” sounds like terminology that could be appropriate for the energy in the front leg when delivering force into the floor, although it appears to be released immediately rather than being “stored”. Since energy is conserved, that force from the front foot producing the “ground reaction force” needs to be either stored as potential energy, dissipated into the ground (or converted into heat), or bounced back through the structure that produced it (“rebound”). Isn’t this correct?

The Bajiquan video analysis mentions the “impulse” that adds power transfer/impact power when the fist/arm relaxes immediately after the strike impact, as shown in their graphing of the force (“time of maximum extension suggests short contact time”). Is this what you were trying to address in the initial post?
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### Re: Punch retraction

Newton’s third law of motion: When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.

Maybe this is what you mean by rebound, if you hit a very heavy bag you also get a rebound or a shock wave back to your body or in the case of stomping on the ground, etc. In the case of a punch you will also get a shock wave because you stopping the stretched out hand by contracting the arm and shoulder muscles. As discussed, this is a breaking action which produced a shock wave while the active part of the body come to a halt.

Stored elastic energy is a biomechanics’ term which is a result from stretched muscle, when muscle being stretched it will return back to its normal length. This can be said as a passive force which can be use to facilitate another muscle action such as punch retraction. The example of a palm strike with palm up stretching the wrist and forearm, elbow pointing downward, dropping the shoulder and not contracting the chest, then stretch out the as far as possible with the elbow pointing downward. Maintain the stretch for a while and release the tension in your arm and you will sense the recoil effect of your muscles. Try a reverse palm strike and you should experience the kinetic chain effect from the left forwarded leg through the back to the right striking palm for example.

You can observe and experience this phenomenon but the electromyography machine cannot tell the difference between a rebound, a recoil force, an eccentric force, and a concentric force. But it does register the intensity of force over time.
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### Re: Punch retraction

This brings me back to the analogy of the Newton’s cradle toy. I purposely did not use a ball as an analogy since the ball hitting the floor physically bounces, but the human body, as in the Bajiquan example, does not raise up (the torso does NOT bounce, and the foot is NOT pushing off from the ground like the rear foot often does). If the energy into the floor from the front foot creates an equal force back from the ground into the foot, then that energy from the foot can be directed up the leg, through the torso, and out the fist; at least as long as this force is not dissipated or lost in some manner (e.g., being stored as potential energy in the muscles, being lost to heat or friction, being directed to the head or some other body part other than the striking surface/fist, etc.). It is this equal and opposite force that I am concerned with. What would that be called in biomechanics?

For a pole-vaulter, the ground reaction force is fairly easy to understand since the energy from hitting the ground is stored as potential energy in the bending of the pole, which is then relatively slowly released as the pole unbends and transferred to the athlete to aid them in their vault. Less easily understood is when the energy is transferred quickly through what appears to be a minimally moving human body (other than quick torque and small extensions of the arm). This is that ground reaction force being transmitted through the body in a similar manner to the Newton’s cradle toy instead of like the pole.
Last edited by LaoDan on Tue Oct 27, 2020 11:56 am, edited 1 time in total.
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### Re: Punch retraction

tonus; the normal state of balanced tension in the tissues of the body, especially the muscles. Gale Encyclopedia of Medicine.

to·nic·i·ty (tō-nis'i-tē),
1. A state of normal tension of the tissues by virtue of which the parts are kept in shape, alert, and ready to function in response to a suitable stimulus. In the case of muscle, it refers to a state of continuous activity or tension beyond that related to the physical properties; that is, it is active resistance to stretch; in skeletal muscle it is dependent upon the efferent innervation.
Last edited by windwalker on Tue Oct 27, 2020 11:42 am, edited 1 time in total.
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### Re: Punch retraction

Tonus can be thought of like the air in a ball; properly inflated (tonus) and it can bounce, but under-inflated it may not bounce or at least not bounce as well (lack of tonus). But that describes the condition needed in the muscles in the human body to utilize the ground reaction force, and is not describing the ground reaction force itself. I was using “structure” for this required structural alignment that can be used to direct the ground reaction force through the body to the striking surface (like the intermediate balls in the Newton’s cradle toy), but that alone is not a good term since the structure needs to be held elastically by muscles with the proper tonus, so my terminology was not entirely descriptive of what I was attempting to address.
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### Re: Punch retraction

LaoDan wrote:If the energy into the floor from the front foot creates an equal force back from the ground into the foot, then that energy from the foot can be directed up the leg, through the torso, and out the fist; at least as long as this force is not dissipated or lost in some manner (e.g., being stored as potential energy in the muscles, being lost to heat or friction, being directed to the head or some other body part other than the striking surface/fist, etc.). It is this equal and opposite force that I am concerned with. What would that be called in biomechanics?

For a pole-vaulter, the ground reaction force is fairly easy to understand since the energy from hitting the ground is stored as potential energy in the bending of the pole, which is then relatively slowly released as the pole unbends and transferred to the athlete to aid them in their vault. Less easily understood is when the energy is transferred quickly through what appears to be a minimally moving human body (other than quick torque and small extensions of the arm). This is that ground reaction force being transmitted through the body in a similar manner to the Newton’s cradle toy instead of like the pole.

Force is lost vertically. Chen simultaneously stamps his foot, opens the front kua and completes fist contact (coordinates hand with foot) creating vertical force. This is different from the pole vault acting as a pivot (transferring weight forward), where the uncoiling (rotation) of stored elastic energy happens after the pole is planted.

Shifting weight to the lead leg, in the rear straight, acts as a pivot (less braking time) with front kua closing (transferring weight/fist horizontally), trunk and shoulder rotation and uncoiling occurring after the front foot lands, analogous to the pole vault. The rear straight stretch-shortening cycle is longer creating more stored elastic energy than the lead hand punch.

Excerpts from Kinematic and kinetic analysis of throwing a straight punch: the role of trunk rotation in delivering a powerful straight punch:"

RAT TONG-IAM1, PORNTHEP RACHANAVY2, CHAIPAT LAWSIRIRAT on December 08, 2017 wrote:Lead Toe In (when boxers began to bear weight on the lead leg) was extremely important in delivering powerful straight punches. As seen in Figure 2, the kinetic chain of straight punches occurred after 70% of total punching time meaning that the whole kinetic chain was created and ended at this final stage. ...

This paper dissected punching pattern into 3 stages, i.e., starting position, lead toe off, and lead toe in. The dissection utilised the pattern of GRFs and showed that the final stage (lead toe in) was extremely important in delivering powerful punches because the kinetic chain of punching started and finished in this stage. The first two stages acted as developing momentum or storing energy to deliver punches.

PS: Please see PM I sent.

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### Re: Punch retraction

LaoDan wrote:This brings me back to the analogy of the Newton’s cradle toy. I purposely did not use a ball as an analogy since the ball hitting the floor physically bounces, but the human body, as in the Bajiquan example, does not raise up (the torso does NOT bounce, and the foot is NOT pushing off from the ground like the rear foot often does). If the energy into the floor from the front foot creates an equal force back from the ground into the foot, then that energy from the foot can be directed up the leg, through the torso, and out the fist; at least as long as this force is not dissipated or lost in some manner (e.g., being stored as potential energy in the muscles, being lost to heat or friction, being directed to the head or some other body part other than the striking surface/fist, etc.). It is this equal and opposite force that I am concerned with. What would that be called in biomechanics?

Here Chen finishes the lead punch without using a "rebound." Afterwards, he takes a quarter step back, loads the rear foot (storing elastic energy), takes a quarter step forward, finally finishing by issuing the lead elbow. Chen loaded his weight (recoiled) again to issue the elbow.

In the clip below instead of slipping, Naseem can throw a straight left (from southpaw) to load the front foot (storing elastic energy). Now, Naseem only has to close the rear kua shifting weight to the back foot to throw a lead hook. He does not have to step, which makes it faster than Chen's elbow. You might consider Naseem to be using a "rebound." Again, the lead hook is more powerful, because of the longer shifting of weight and rotation (torque).

marvin8 wrote:However starting at 3:38, Naseem shows how he generates power which is documented in another video too. Naseem loads his front foot by slipping and shifting his weight to the front foot, taking his head off line. Then, he transfers his weight to the back foot, coordinating his hook with the rear heel landing.

Tyson uses jab to load back foot, then transfers weight to front foot and issues straight right. You might consider that a "rebound?"

marvin8 wrote:In the boxing clips below, Tyson and Hearns both throw jabs that bring their weight to the back foot carrying their head to the left of their opponent. Then, they push off the back foot (lifting heel up), rotate their waist and shoulders first, transfer their weight to the front foot where their head is to the right of their opponent, then finally issue/punch.

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### Re: Punch retraction

Are there any successful ba Ji fighters
Don't put power into the form let it naturally arise from the form
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### Re: Punch retraction

Sorry double posted
Last edited by wayne hansen on Wed Oct 28, 2020 4:14 am, edited 1 time in total.
Don't put power into the form let it naturally arise from the form
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### Re: Punch retraction

While I have not studied boxing, I thought that the Jack Dempsey drop (or falling) step probably was adding the energy of the ground reaction force from the front foot landing into his boxing technique – but I could be wrong. Of course, all of the torque, shifting of mass forward, extension of the arm, etc. also all contribute to the power of the punch. I am just looking for that extra thing (the “rebound”?) that allows power even with shorter distances (less windup...). Most sports seem to use their front foot primarily as a pivot for generating torque, rather than adding the ground reaction force to their power through direct transmission through the body as illustrated by the Newton’s cradle toy (i.e., not needing torque to transmit the force). Perhaps it is too difficult to see since all of the other aspects of power generation are still present (torque, moving the mass forward, pushing off from the rear foot, extension, kinetic chain...), or perhaps I am just imagining this type of power transfer (like that shown with the Newton’s cradle toy) when I practice this way.

Here are a few things to consider, however, from the short article about the research involving Chen Xiang. During his first visit they measured the amount of force that Chen could produce:

This level of force “astonished Rose and her students.” Presumably this means that more force was produced that for typical a person of his weight (although fighters of any other styles were not given comparative values for the power of their strikes). This probably means that Chen was either better at using the conventional power development methods (e.g., kinetic chain) than other strikers, or it means that he was generating some of his force in a different manner than other strikers.

Most seem to try to explain Chen’s force production using conventional terminology. For example, the robotics professor uses the data to “confirm his theory that these types of spiral movements may be a particularly efficient way to generate force in a small sphere of space.” Small spiral movements MAY be more efficient at developing power, but he ignores the possibility of the power coming from a different than conventional mechanism (i.e., the ground reaction force from the front foot being transmitted in a manner other than through spiraling torque).

There are several possibilities that I can think of:
1. Chen is so skilled that he can generate greater than expected power DESPITE generating it in a small sphere of space.
2. Chen generates greater than expected power BECAUSE he is generating it in a small sphere of space (using spiral movements).
3. Chen generates greater than expected power in a small sphere of space by adding a DIFFERENT mechanism (in addition to the spiral movements).
3A. This mechanism could have something to do with the ground reaction force with the front foot.
3B. It is due to qi/chi [note that the article does also mention this as a possibility, although they also recognize that qi/chi lacks an accurate definition].
4. Something else that I did not think of?

I think it is #3A. What do you think?

Although the researchers describe their results using conventional terminology, their decision to collect data from the front foot and its force to the ground (a force plate on the floor) provides supporting evidence for #3A. However, fighters of any other styles were not given comparative values for the front foot reacting with the floor, so it is difficult to know how Chen compares with others, so I do not know how unusual this may be.
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### Re: Punch retraction

LaoDan wrote:While I have not studied boxing, I thought that the Jack Dempsey drop (or falling) step probably was adding the energy of the ground reaction force from the front foot landing into his boxing technique – but I could be wrong.

No, it's not added because front foot GRF is a byproduct created after the front foot and hand simultaneously land. Therefore, it has no effect on punch force.

After Chen's front foot and punch lands, his "rebound" force from the front leg travels in the opposite direction to his punch. "Rebound" force from the braking front foot (in front of his body) travels at a vertical angle into the body. While, his punch travels in the opposite direction—horizontally away from the body. Therefore, rebound force would "discount punch force." However since the punch has already landed, the "rebound" has no effect on punching power.

Excerpts from "Kinematic and kinetic analysis of throwing a straight punch: the role of trunk rotation in delivering a powerful straight punch:"

RAT TONG-IAM1, PORNTHEP RACHANAVY2, CHAIPAT LAWSIRIRAT on December 08, 2017 wrote:The first two stage acted as developing momentum or storing energy to deliver punches. At impact, the direction of GRF of lead leg was opposite to the direction of punch force. As a result, the lead leg acted as a break and discounted punch force. This finding was counterintuitive where the maximum punch force should be created such that the directions of GRF of the lead leg and straight punches were in the same direction.

LaoDan wrote:There are several possibilities that I can think of: ...

3A. This mechanism could have something to do with the ground reaction force with the front foot.

I think it is #3A. What do you think?

No, it doesn't as explained above and evidenced in studies.

LaoDan wrote:Although the researchers describe their results using conventional terminology, their decision to collect data from the front foot and its force to the ground (a force plate on the floor) provides supporting evidence for #3A.

No, it doesn't. Front foot GRF is a byproduct of everything that happened before the fist and front foot landed. After the front foot and punch lands, any subsequent force produced is irrelevant.

LaoDan wrote:However, fighters of any other styles were not given comparative values for the front foot reacting with the floor, so it is difficult to know how Chen compares with others, so I do not know how unusual this may be.

GRF created after Chen's front foot lands had no effect on his lead hand punch force, making comparisons meaningless. Measuring force at fist point of contact is more important.

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### Re: Punch retraction

marvin8 wrote:
LaoDan wrote:While I have not studied boxing, I thought that the Jack Dempsey drop (or falling) step probably was adding the energy of the ground reaction force from the front foot landing into his boxing technique – but I could be wrong.

No, it's not added because front foot GRF is a byproduct created after the front foot and hand simultaneously land. Therefore, it has no effect on punch force.

Perhaps that is true in boxing, but it does not appear to be true for the Bajiquan strike.In the plot of the “Sequence of Angular and Linear Velocities During Master’s Strike” at ~1:50 of the video, the front foot peak (the grey arrow with box labeled “Peak floor reaction force occurs”) is shown almost simultaneously with the “hand force velocity” peak (red line and diamond)! It is certainly NOT after!
Last edited by LaoDan on Thu Oct 29, 2020 7:22 am, edited 1 time in total.
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### Re: Punch retraction

If the term “rebound” is causing confusion, then I will start calling it the “Newton’s cradle toy’s force” (although that seems to be rather awkward): the force that almost simultaneously transfers force from the ground (the ground reaction force – or in the case of the toy, from the ball striking one end) to the hand force velocity peak (the ball being launched at the other end of the toy). For a strike to be similar to the Bajiquan strike, this timing has to be synchronized in this manner.
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### Re: Punch retraction

marvin8 wrote:
RAT TONG-IAM1, PORNTHEP RACHANAVY2, CHAIPAT LAWSIRIRAT on December 08, 2017 wrote:The first two stage acted as developing momentum or storing energy to deliver punches. At impact, the direction of GRF of lead leg was opposite to the direction of punch force. As a result, the lead leg acted as a break and discounted punch force. This finding was counterintuitive where the maximum punch force should be created such that the directions of GRF of the lead leg and straight punches were in the same direction.

The “counterintuitive” result in the paper’s analysis is expected for the Newton’s cradle toy’s force (NCTF) where the direction of the ground reaction force (GRF) SHOULD be back into the body since the NCTF needs to be transmitted through the body (like the force transmitted through the ~ stationary balls in the Newton’s cradle toy) to reach the striking hand. Kinetic chain motion would seem to indicate that the force should be continued in the direction of the strike (adding momentum and mass in the direction of the strike), but the NCTF should go back through the body (the force innitially being transmitted away from the direction of the strike direction until it reaches the torso and the arm, when it is added to the direction of the strike [the NCTF does not travel in a straight line through the human body]). The GRF is not a “brake” in the NCTF model; instead it is a producer of force.
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### Re: Punch retraction

LaoDan wrote:
marvin8 wrote:
LaoDan wrote:While I have not studied boxing, I thought that the Jack Dempsey drop (or falling) step probably was adding the energy of the ground reaction force from the front foot landing into his boxing technique – but I could be wrong.

No, it's not added because front foot GRF is a byproduct created after the front foot and hand simultaneously land. Therefore, it has no effect on punch force.

Perhaps that is true in boxing, but it does not appear to be true for the Bajiquan strike.In the plot of the “Sequence of Angular and Linear Velocities During Master’s Strike” at ~1:50 of the video, the front foot peak (the grey arrow with box labeled “Peak floor reaction force occurs”) is shown almost simultaneously with the “hand force velocity” peak (red line and diamond)! It is certainly NOT after!

In our previous dialogue, I believe you were speaking of your rebound force when you used "GRF," which I highlighted in red. So, you can substitute "GRF" with rebound force in my statement.

The graph shows hand velocity was highest at the time the front foot impacted the floor (GRF). After that, hand velocity decreases—where your rebound occurs. "Rebound" IS certainly after! So as I said, "Therefore, it (rebound force) has no effect on punch force."

LaoDan wrote:
marvin8 wrote:
RAT TONG-IAM1, PORNTHEP RACHANAVY2, CHAIPAT LAWSIRIRAT on December 08, 2017 wrote:The first two stage acted as developing momentum or storing energy to deliver punches. At impact, the direction of GRF of lead leg was opposite to the direction of punch force. As a result, the lead leg acted as a break and discounted punch force. This finding was counterintuitive where the maximum punch force should be created such that the directions of GRF of the lead leg and straight punches were in the same direction.

The “counterintuitive” result in the paper’s analysis is expected for the Newton’s cradle toy’s force (NCTF) where the direction of the ground reaction force (GRF) SHOULD be back into the body since the NCTF needs to be transmitted through the body (like the force transmitted through the ~ stationary balls in the Newton’s cradle toy) to reach the striking hand. Kinetic chain motion would seem to indicate that the force should be continued in the direction of the strike (adding momentum and mass in the direction of the strike), but the NCTF should go back through the body (the force innitially being transmitted away from the direction of the strike direction until it reaches the torso and the arm, when it is added to the direction of the strike [the NCTF does not travel in a straight line through the human body]). The GRF is not a “brake” in the NCTF model; instead it is a producer of force.

The mechanics and timing of impact of the straight right are different from Chen's lead hand punch.

I believe the latter stage of Chen's lead hand punch:

1. Lead foot and hand impact the floor
2. Completes strike
3. Strike is retracted as rebound force enters body (after strike has been completed)

As the straight punch and Stanford study shows, the lead leg acts as a brake. After the punch and foot lands, hand velocity decreases and rebound into the body occurs.

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