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.
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.
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.”
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.
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.
I am trying to point out
johnwang wrote:Yeung wrote:“punch retraction should be faster than the punch itself”,...
I had personal experience on this. Back in 1980. I went to China and met my teacher's young brother. He threw a punch at my chest. When he pulled his fist back, it caused a vacuum in front of my chest. My shirt was flying away from my body. In the past 40 years I tried to develop that ability but I was not satisfied with the result.
That was the only time in my life that I had experienced that. Since his punch didn't hit my body, I won't be able to tell the difference between a punch like that from a normal punch.
LaoDan wrote: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).
Michael Harto, 1 year ago (edited) wrote:actually there's almost no stomping if you do it correctly. it's more about the twist and snap rather than the stomp. imagine yourself as a whip, and your fist is the end of the whip. the the stomp is just the byproduct of the snap. realistically, if you snap too fast before you hit your opponent (the stomp is before or right at the moment of your fist impacting the target) most of the force created by the body twist is practically gone, absorbed by your stomp to the ground. so ideally you want to hit your target just right before your foot touches the ground, just like a jab punch. and this takes a loooooot of practice.
Sandro Vadacca, 1 year ago wrote:Correct, however in Bajiquan we practice with stomping first in the beginners' stage to get the mechanics right. In the advanced training, there is no stomping anymore.
Kinetic (GRF and impulse) variables
Based on previous studies which have highlighted the importance of the lead leg to lead hand punches and the rear leg to rear hand punches (Cheraghi et al., 2014; Turner et al, 2011; Yan-ju et al., 2013), it was expected that the lead leg would produce greater GRF during lead hand punches, and likewise rear leg for rear hand punches. However, the current findings revealed that uppercuts (lead and rear) generated the greatest peak resultant GRF values for the lead leg across punch types (see Table 1). Moreover, it was interesting to find that both uppercuts produced greater peak lead leg resultant GRF values than straight and hook punches.
Return to Xingyiquan - Baguazhang - Taijiquan
Users browsing this forum: No registered users and 23 guests