Mr. V sort of made this point, but my study has shown that hits which TWIST the head, rather than knock it in a straight line, are more effective at KO ing an opponent. This is because the brain is suspended in fluid. When you twist the head quickly, the skull moves faster than the brain, causing a lot of shock when the brain catches up. (suspend something in a jar of water, then twist the jar.) Also, it twists the spinal column, which adds to the "shock" to the nervous system. Straight shots can achieve KO, but require far more force to do so.