“Doing” meets “not doing”
or “Ippon” meets “Koka”
Martial sport is about winning. Self defence is about not losing. Hence, there are different (but overlapping) strategies and tactics.
“Upper and lower mutually follow” refers to one’s own body. But the concept can be extended to include strategy and tactics. Being still when the opponent is moving, and moving when the opponent is still, allows you to “control the board” as one might say in chess analogy.
“Upper and lower Mutually Follow” is a concept that is usually applied to oneself during form practice. When it translates into combat, I sometimes call it “Doing and not doing are mutually adjacent.”
The opponent’s actions determine your response. So, adjusting your upper and lower to receive the opponent’s action, can set them up to fall. Understanding upper and lower allows you to understand doing and not doing. Understanding “doing and not doing” allows you to cause the opponent to defeat themselves.
Consider an aeroplane, and the difference between powered flight and gliding, or the difference between a powerboat and a sailboat.
In Judo, a full point (ippon) can be scored when you deliberately throw the opponent to the ground on their back. An untrained victim of such a throw will land forcefully on their back, and likely be injured and/or winded. A trained judoka, on the other hand, will likely execute an effortless breakfall or a graceful roll and be instantly back on their feet.
A koka is an obsolete part of the judo scoring system, and refers to causing the opponent to fall on their shoulder, hip, or thigh.
In my limited experience with judo, a koka is scored effortlessly, mostly by sabotaging the opponent’s own effort, whereas an ippon is scored through deliberate and well timed execution of a technique.
A good martial artist will be able to mix both strategies into a single tactic. You can execute a throw, while causing the opponent to be complicit in the technique.