Chinkuchi

This expression (chikuchi) is used to describe the tension or stability of the joints in the body for a firm stance, a powerful punch, or a strong block. For example, when punching or blocking, the joints of the body are momentarily locked for an instant and concentration is focused on the point of contact; the stance is made firm by locking the joints of the lower body-the ankles, the knees and the hips-and by gripping the floor with the feet. Thus a rapid free-flowing movement is suddenly checked for an instant, on striking or blocking, as power is transferred or absorbed. Then the tension is released immediately in order to prepare for the next movement.

--- Higaonna Morio

This “chinkuchi” is sometimes written as “one cun power” and is a principle of movement related to the “cun power” of Chinese Quanfa. A simple explanation is, when punching for instance, to contract the muscles used when punching (especially the triceps and the trapezius), increasing the speed of the punch or block from within your own body.

--- Arakaki Kiyosi

When punching, the most important thing is that the “koshi” are in it, and that chinkuchi is being utilized. Chinkuchi, in a word, means to contract the trapezius, the triceps, the pectoralis major, etc. when thrusting the fist out. At that time, the armpit must also be closed when punching or blocking. This means that a punch with chinkuchi has an instantaneous increase in power. This is called “one cun power” and causes a great destructive power upon the opponent’s body.

--- Tokashki Iken

Shoot your loose, half-opened left hand straight along the power line at a chin-high spot [...]. But as the relaxed left hand speeds [...] suddenly close the hand with a convulsive, grabbing snap. Close it with such a terrific grab that when the second knuckle of the upright fist smashes [...], the fist and the arm and the shoulder will be ‘frozen’ steel-hard by the terrific grabbing tension. That convulsive, freezing grab is the explosion.

--- Georges Carpentier 

It seemed to me that the real secret lay in the delivery itself far more than the strength behind it, and I therefore aimed to make my punches the culmination of a perfectly coordinated action of the whole body, beginning with the legs. Incidentally, my punches including the one which I developed later and which was to win general admiration as ‘the lightning settler’, always started from the legs.

--- Jack Dempsey