To possess strong, powerful, penetrating force you must seek to develop the attribute of outside flexible, inside inflexible which traditionally is referred to as hard-soft (剛柔).
This is consistent with how a bow stores and releases energy to power the flight of an arrow through the air, yet possessing penetrating power on impact with the target.
As a 21st generation Japanese longbow maker, Kanjuro Shibata, explained in a documentary “Why Japanese Longbows Are So Expensive” on the role of the inner core of the longbow known as nakauchi which is sandwiched between two layers of bamboo and why the nakauchi is harder than the outer bamboo strip :-
“If you make a bow out of only flexible materials it bends well when you draw the bow, but force to return to the original position is weak.
Japanese bows are made by combining inflexible and flexible materials and by combining bamboo and wood in this way, we can take advantage of their respective strengths.“
In the human body there are 5 bows, namely :-
a) Arm bow X 2
b) Leg bow X 2
c) Spinal bow X 1
In order to train the body to behave like a bow one must understand how to open up the body, stretch it out to make it strong yet inflexible like the nakauchi. Then the arms are trained to be supple so as to be able to go with and bend with the opponent’s force, receiving it into your body’s bow string, load it onto the body bow that is used, and then return the opponent’s strength to send him off, or impart a penetrating force to injure him.
When there is no opportunity to make contact to borrow the opponent’s strength then you load your own striking limb onto the relevant body bow and launch the striking limb like an arrow.