What does it mean to be black at the moment in martial arts?

This sentence has multiple meanings, and I try to explain them one by one:

1, first of all, it shows that strength is an instant thing. This need not be explained in detail. The overall coordination of the body is strength;

2. Being black at the moment is actually an explanation for blinking;

3. The state of the body at that moment is highly concentrated mentally, which leads to the visual nerve illusion caused by overall coordination and energy tradition.

To sum up, to put it bluntly, it is the optical illusion formed when the body reaches a high degree of coordination, which causes energy to be emitted with almost no self-resistance.