Palm Up or Palm Down

[warrior-scholar]

There are several instances in the angle defenses when a palm down angle 12 is executed instead of the standard palm up. It seems as though palm down angle 12 strikes follow a downward blocking motion with the weapon hand, while palm up angle 12 strikes often follow through from an angle 6 or angle 2 with the weapon hand. Then again, Angle 4.1 defense follows the angle 6 strike with a palm down thrust. Another comparison exists between Angle 1.4 defense and Angle 2.1 defense in which palm down and palm down are utilized respectively after a pin with the shield hand. Angle 10/11.1 defense follows up in the same manner as Angle 2.1 defense, but seems more related to the beginning of Angle 1.4 defense.

I am just wondering about reasoning behind the choice of the palm up versus palm down. Does it have more to do with the zone of attack, the inside versus outside of the arm or is there another determining factor?