The so called “handshake” position of a vertical mouse has been discussed by many ergonomists.
Some claim that the handshake is a “neutral position” but research has shown that this is not the case at all.
In general a neutral posture refers to a relaxed position, so minimal tension of tendons, ligaments and muscles.
With respect to certain positions of the forearm though, there is a misunderstanding.
Handshake: Interosseous Membrane is Taut
It is generally assumed that the handshake position is neutral.
However, the forearm bone, called radius, is arched with respect to the other bone, the ulna. These two bones are connected by the interosseous membrane.
When one rotates the forearm into the handshake position, the distance between radius and ulna increases to a point where the membrane is taut.
Finger and thumb muscles which we use to lightly grip and hold an object are connected to this membrane.
One must therefore realize that gripping an object in the handshake position will actually introduce additional tension in the already taut membrane.
If we rotate the forearm to relax the membrane we will remove this harmful high tension.
Mouse Hand Must Be Supported at Angle of 25 Degrees
A hand supported at an angle of around 25 degrees with respect to a desktop realizes a truly neutral, tensionless membrane.
This prevents potential muscular and other damage during longstanding and repetitive movements.
Watch this short, one minute video:
An other interesting article addresses “Action is Reaction“; Have a look there to understand the full picture.