Josh

“The human body is a funny machine. When you want to move something - say, your arm - the brain actually sends two signals at the same time: "More power!" and "Less power!" The operating system that runs the body automatically holds some power back to avoid overexerting and tearing itself apart. Not all machines have that built - in safety feature. You can point a car at a wall, slam the accelerator to the floor, and the car will crush itself against the wall until the engine is destroyed or runs out of gas.
Martial arts use every scrap of strength the body has at its disposal. In martial arts training, you punch and shout at the same time. Your "Shout louder!" command helps to override the "Less power!" command. With practice, you can throttle the amount of power your body holds back. In essence, you're learning to channel
the body's power to destroy itself.”
― Hiroshi Sakurazaka, All You Need Is Kill