Punch retraction

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

Re: Punch retraction

Postby LaoDan on Thu Oct 29, 2020 2:15 pm

I really do not think that we are using GRF the same way. Since things happen so fast in a strike, let me use pole vaulting as an analogy. There are several places where one could talk about GRF:
A) When the athlete is sprinting forward on the track (the GRF is in the same direction as the jump will be)
B) When the pole is planted and the GRF bends the pole (the GRF is in the opposite direction of the jump and occurs before the jump)
C) When the athlete lands in the pit after the vault (the GRF is also in the direction opposite the direction of the jump, and it is used to brake the fall and the forward momentum of the athlete and occurs after the jump)

A is like pushing off from the back foot when punching. I do not think that either of us is now referring to that GRF.
B is like what I am trying to describe using the Newton’s cradle toy as an analogy using equal and opposite force from the forward foot.
C is like the forward foot braking the forward momentum of the body. This is what I think that you are referring to.

If most sports and the kinetic chain terminology used to describe them, go directly from A --> C without considering B, then it is not surprising that we are having difficulty communicating what B is. There does not appear to be an established terminology for it. It is the pole bending force, not the landing in the pit GRF. To me, B = 3A from my earlier list.
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Re: Punch retraction

Postby marvin8 on Thu Oct 29, 2020 4:41 pm

LaoDan wrote:I really do not think that we are using GRF the same way. Since things happen so fast in a strike, let me use pole vaulting as an analogy. There are several places where one could talk about GRF:
A) When the athlete is sprinting forward on the track (the GRF is in the same direction as the jump will be)
B) When the pole is planted and the GRF bends the pole (the GRF is in the opposite direction of the jump and occurs before the jump)
C) When the athlete lands in the pit after the vault (the GRF is also in the direction opposite the direction of the jump, and it is used to brake the fall and the forward momentum of the athlete and occurs after the jump)

A is like pushing off from the back foot when punching. I do not think that either of us is now referring to that GRF.
B is like what I am trying to describe using the Newton’s cradle toy as an analogy using equal and opposite force from the forward foot.
C is like the forward foot braking the forward momentum of the body. This is what I think that you are referring to.

If most sports and the kinetic chain terminology used to describe them, go directly from A --> C without considering B, then it is not surprising that we are having difficulty communicating what B is. There does not appear to be an established terminology for it. It is the pole bending force, not the landing in the pit GRF. To me, B = 3A from my earlier list.

Watching Chen's video (not referencing the pole vault), I see Chen's lead hand punch include:

A) Left leg forward bearing weight, push off right rear foot (GRF) taking full step forward.
B) Lead foot (right) starts to bear weight (e.g., toe-heel), body rotates, foot pivots and foot completely lands as punch finishes.
C) Punch is retracted as rebound force (GRF) travels in the opposite direction, towards body.

This is consistent with kinetic chain, Newton's law(s), studies, etc.
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Re: Punch retraction

Postby LaoDan on Fri Oct 30, 2020 7:22 am

Of course Chen’s Bajiquan strike “is consistent with kinetic chain, Newton's law(s), studies, etc.” I never said that they were not! You seem to consistently miss the added action that I am trying to point out.


In the paper that you referenced, this difference is clearly illustrated. The GRF for all three Muay Thai boxing champions shows a simple transfer of their body weight forward and back. The graph in Figure 1 shows the GRF for the forward leg (right foot). Pre strike the GRF is equal to the fighter’s body weight (at time 0%), and at the moment of the strike (time 100%) is also approximately the same as the fighter’s body weight. This is going from A to C without “bending the pole.” By contrast, Chen shows in the Bajiquan strike that his GRF at the time of the strike (at maximum hand velocity) is 3X his body mass. Chen “bends the pole.”

[GRF = Body mass] is different than [GRF = 3x body mass]. Unless you address this difference, you are comparing “apples to oranges.” Muay Tai is A --> C; Bajiquan includes B whereas Muay Tai does not.
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Re: Punch retraction

Postby marvin8 on Fri Oct 30, 2020 9:20 am

LaoDan wrote:Of course Chen’s Bajiquan strike “is consistent with kinetic chain, Newton's law(s), studies, etc.” I never said that they were not! You seem to consistently miss the added action that I am trying to point out.

I am not "missing the added action." I am trying to understand it.

LaoDan wrote:

In the paper that you referenced, this difference is clearly illustrated. The GRF for all three Muay Thai boxing champions shows a simple transfer of their body weight forward and back. The graph in Figure 1 shows the GRF for the forward leg (right foot). Pre strike the GRF is equal to the fighter’s body weight (at time 0%), and at the moment of the strike (time 100%) is also approximately the same as the fighter’s body weight. This is going from A to C without “bending the pole.”

No, it's not. The graph in Figure 1 shows the GRF for forward leg (left foot), not right. You skipped step (2) Lead Toe Off (Figures 1b-1c), where the weight is shifted from the front foot to the back foot. This is your B. It's not A to C without “bending the pole."

LaoDan wrote:By contrast, Chen shows in the Bajiquan strike that his GRF at the time of the strike (at maximum hand velocity) is 3X his body mass. Chen “bends the pole.”

[GRF = Body mass] is different than [GRF = 3x body mass]. Unless you address this difference, you are comparing “apples to oranges.” Muay Tai is A --> C; Bajiquan includes B whereas Muay Tai does not.

Again, you are comparing "apples to oranges" when you compare a Baji lead hand punch to a rear hand straight punch. Mechanics are different: lead hand vs rear hand, stepping (winding up) vs not stepping, GRFs will be different, hand and foot lands at the same time vs using lead leg as pivot point, then punch, etc.
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Re: Punch retraction

Postby LaoDan on Fri Oct 30, 2020 10:47 am

The forward leg is the forward leg, regardless of whether it is the left or the right. I did not skip the steps since the GRF for neither foot ever exceeds the GRF due to the body weight in the Muay Thai examples. In that study, stage 1 is preparatory and begins shifting the weight from the forward foot to the rear foot – this would be pre-A. Stage 2 begins shifting the weight from the rear foot to the forward foot – this would be A. Stage 3 ends with the weight on the front foot – this would be C. In no case does the GRF from either foot exceed the GRF due to the body mass of the boxer – this is lacking B.

B is the increase in GRF above the GRF caused by the mass of the body (and the result from this additional GRF). I would accept this increase from either or both feet, although the Bajiquan study only shows the front foot increase. That does not occur in the GRF measurements of the three Muay Thai boxing champions as neither GRF for either foot ever exceeds the GRF attributed to the fighter’s mass.
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Re: Punch retraction

Postby LaoDan on Fri Oct 30, 2020 11:01 am

marvin8 wrote:
LaoDan wrote:By contrast, Chen shows in the Bajiquan strike that his GRF at the time of the strike (at maximum hand velocity) is 3X his body mass. Chen “bends the pole.”

[GRF = Body mass] is different than [GRF = 3x body mass]. Unless you address this difference, you are comparing “apples to oranges.” Muay Tai is A --> C; Bajiquan includes B whereas Muay Tai does not.

Again, you are comparing "apples to oranges" when you compare a Baji lead hand punch to a rear hand straight punch. Mechanics are different: lead hand vs rear hand, stepping (winding up) vs not stepping, GRFs will be different, hand and foot lands at the same time vs using lead leg as pivot point, then punch, etc.

Yes, there are differences between the examples, but these are the studies that YOU supplied. If they are not appropriate for me to use, then why did you introduce them? To me the principle does not depend on which foot is forward, which hand strikes, etc. It is the increase in GRF above what would be attributed to body mass alone. This is absent in the Muay Thai examples but is present in the Bajiquan example. That is the difference that I am looking at. If the studies that you posted so far cannot be compared with the Bajiquan example, then find one that does.
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Re: Punch retraction

Postby suckinlhbf on Fri Oct 30, 2020 12:34 pm

I am trying to point out

It is the hard part. A doctor would not approach a person to tell him he is sick. The doctor would only treat the person when he feels sick and comes for solution.
Last edited by suckinlhbf on Fri Oct 30, 2020 12:37 pm, edited 1 time in total.
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Re: Punch retraction

Postby LaoDan on Fri Oct 30, 2020 2:12 pm

I do not know what other experiments on striking will show, but I can speculate on several things based on my understanding of the Bajiquan strike vs. most other striking arts (e.g., boxing, Muay Thai...). If asked to try and hit as hard as they can (their choice of method), whether stationary with or without shifting, or stepping and shifting, whether with the lead hand or the rear hand, whether with the right foot forward or the left foot, whether a straight strike or a hook, etc., there will probably be the following differences in the data:

1) I expect there to be a fairly broad range in the timing of the maximum GRF of the forward foot. In the Bajiquan example this is almost simultaneous with the maximal hand velocity, but in the three Muay Thai examples they occur well before the strike and show great variability (from ~ 75% time point for boxer #2, to ~90% time point for boxer #3, and ~ 95% time point for boxer #1) [Figure 1]. This style of boxing trains the front foot to be a pivot for the rotation of the torso, and would therefore be expected to occur significantly prior to the rotation of the body and the strike [as shown in Figure 2]. The Bajiquan example has much of the body rotation occurring prior to the maximum GRF of the front foot, and the front foot’s maximal GRF matches the timing of the maximal velocity of the striking hand [see the graph @ ~1:50 of the video].

2) I expect that the shift, or the step and shift, to be used primarily to accelerate the boxer’s mass forward (i.e., horizontally), and therefore would result in little increase in the GRF of the front foot beyond the GRF attributable to the body mass (e.g. during the “braking” of the forward momentum). There will probably be some increase when stepping and shifting since the body mass has been accelerated and the stepping foot has been raised (so the “falling” of the body when the front foot lands would add some force to the ground) but, if present, this increase would be minor compared with the 3X body mass GRF seen in the Bajiquan example.

I would be interested in seeing studies that show either of these expectations to be incorrect.
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Re: Punch retraction

Postby suckinlhbf on Fri Oct 30, 2020 2:47 pm

It will also be interesting to see are there any torque, forward force, and/or backward force when the foot (front foot and/or rear foot) lands. If any, would it help the forward momentum/power.
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Re: Punch retraction

Postby LaoDan on Fri Oct 30, 2020 3:23 pm

There are three differences that are obvious (at least to me) between the Bajiquan and Muay Thai data, but perhaps others have different explanations for them (e.g. different strikes being analyzed; different hand used; shifting vs. stepping...), and perhaps we will see different results from other studies. One is the magnitude of the GRF of the front foot (GRF = Body Mass in the MT examples, but GRF = 3x Body Mass in the BJQ example); one is the timing of the maximal GRF of the front foot (i.e. approximately simultaneous with the maximal hand linear velocity in the BJQ example, but significantly before the strike in the MT examples); one is that the body’s angular velocities peak before the maximal GRF of the front foot in the BJQ example (except for the hand linear velocity which is approximately simultaneous with the peak GRF of the front foot), but it occurs after the peak GRF of the front foot in the MT examples. To me these differences indicate that the BJQ example uses “?name?” that the MT examples do not.
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Re: Punch retraction

Postby LaoDan on Thu Dec 03, 2020 10:22 am

I have not really found much information that could help to explain the point that I was trying to make about the characteristics of the Bajiquan strike, but there are some ideas from Serge Gracovetsky that may apply. He tries to explain “axial rotation” (horizontal turning) of the hips in terms of the pull from the legs. The “spinal engine theory” describes kinetic energy producing axial torque from the leg muscles pulling on the pelvis and he looks at running (and walking) to describe a “heel strike pulse” that can be as high as “up to 19 times the body weight for runners in a 100 meter dash” when a runner’s heel impacts the ground. While this mechanism is described for running (and walking) rather than for striking, I think that it could be what is helping to power the Bajiquan strike. Perhaps the power generation in the Bajiquan strike is increased by the foot landing kinetic energy pulse used to power an axial torque in the hips, if it is properly timed with the strike (i.e., nearly simultaneously landing foot and strike).
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