Vertical and horizontal momentum components in Xingy
In reply to:
Re vertical component, I agree there is some. The main issue for me is still the horizontal one. After your foot lands, much of your forward horizontal momentum is lost, hence xingyi punches land with the front foot, not after, to use this momentum (as well as any downward moment).
If the focus is on maintaining forward momentum, then there are ways to translate the force without losing it when the leading foot comes down.-Dan
Judging by the Xingyi form sequences, the stance they used gets them in range and will reflect the force from the initial upper body strike, but it’s not 100%. There’s some dissipation due to the back leg not actually being on the ground but picked up and moved forward. The dissipation comes from the target being hit, the force traveling back into the attacking body, and then pushing their back foot down unto the earth. The time it takes to push that foot down until it connects, is a time where force is not being reflected. With exact timing, that’s not usually an issue, except that exact timing isn’t as certain as some preparation work.
From around .55 onwards.
By putting the back foot on the ground in that position, one can lower the stance at the end by using the knees and the hips to transfer more momentum forward. That isn’t done in the upward stance you demonstrated or in Xingyi because the stances are different. Instead of moving the back leg up with a quick step drag, the body continues moving forward, but into a lower stance. Done this way, you can preserve a modicum of forward momentum without having to rely on the immediate burst transition. It does mean you are not going to access the upper body’s target, but the lower body. If the strike starts from an upper body stance to the foe’s upper body, then you can only access the lower body’s target afterwards or if you are still in contact, drive the force forward and downwards at 45 degree angle. This is the vice a versa of the momentum transfer of the hand strike in Xingyi’s stance. That had mostly forward, and a little bit of vertical adding to the forward. Now with a lower stance momentum transfer, you have mostly vertical, with a little horizontal.
The video sequence shows a similar movement, that is the alternative to the xingyi opening or its start anyways. It doesn’t show the transitioning to a lower stance, because the bag goes flying. But for the purposes of visualizing what I am describing, the beginning movement to the hit of the bag, has put the body in the right position to translate more momentum forward if the stance then becomes lowered.
The lower stance transition strike from an upward stance is much more offensive minded. Instead of relying on a burst of momentum in the beginning, and then pulling the back leg up to remain in range, this is more of a displacement move to go through an opponent’s space and replace it with yours. Rather than staying in the same melee range, this is replacing bodies with bodies. It has the most effect there, because if a person is too far away, the lower stance can’t input enough applied force before the body is able to move away.
Also, instead of relying on applying all the kinetic force in the .25 seconds it takes for the strike to hit, the type of hit I showed in the video relies more upon a longer duration contact and steady application of force. Instead of 500 newtons over .25 seconds, we have 400 newtons every second, applied for 1.5 seconds. For the sake of argument, if the xingi hand strike lasts for .25 seconds to .5 seconds, it has 125 -250 impulse. Assuming I’ve used the equation correctly, my video link’s strike relies upon the same or lower momentum transfer, over a long period of time. Thus it would be 400 to 600 impulse.
In math, it’s an anti-derivative. In laymen’s speak, more impulse and applied force is generated the longer a constant force remains applied in duration to the target. If one loses the initial total impact from the foot being on the ground before the hand touches the target, momentum can still be conserved and loaded up to be used in a forward strike. The person just has to be closer and move farther, in a lower stance, and remain in contact with the target longer.
This was mainly to address the question of “If the primary concern is conserving forward momentum in a strike, what options are available to the attacker”.
Vertical and horizontal force vectors reminds me of those physics pendulum questions about how fast the pendulum is moving if gravity is pulling on it at 90 degrees or 45 degrees.