Originally Posted by sennoc
Also, this image is wrong:
Upper arm and shoulders should be colinear. The straight line along upper arm and shoulders is an axis of rotation of forearm. This axis should be tilted at ca 45 degrees at serves. Due to educational reasons, you should make corrections in the picture above and add an image with tilted axis.
read my post carefully - those images are not meant to depict what happens on the serve, but rather to illustrate abstract components of the rotations. They're for biomechanical illustration of the consequences of rotating certain joints while in different anatomical positions.