Re: Punch retraction
Posted: 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.
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.