1. Increased power from the shoulder
2. Reduces the strain on your wrist. Ergo Spade is made with the physiology of the hand in mind.
The end of the shaft should rest against the palm of your hand. This means that you can apply more force without increasing any strain on the wrist. The force should be applied to the top of the shaft.
The position of the shovel in the hand means that you do not need to grip the shaft which fills your hand with its ergonomic shape. A truly ergonomic shovel.