Originally Posted by toly
IMO you are right.
When pros hit flat serve they often use intense wrist extension and then wrist flexion. The wrist extension brings the racquet in semi open position, so they cannot ‘swing up on edge’...
Disagree with this. When this wrist is c0cked, it is not "intense wrist extension" (whatever that means). The c0cking of the wrist is partly wrist extension and partly radial deviation
. On the upward swing to contact, the wrist moves from the c0cked position to a fairly neutral position at contact. I would not characterize this wrist action as a "wrist snap".
The problem with that phrase is that it is very misleading. Many/most players mistakenly assume that the wrist will be in flexion (position) either before or after contact when told to "snap the wrist". The wrist should not be in a position of flexion before contact or after contact. It is not even necessary to assume a position of flexion after contact either. However, some elite players may have a slight flexion well after contact.
The racket does move up on edge. However, for a flat serve,most of this "on edge" motion is prior to the big L (prior to image #1 in your sequence). For a spin serve, the racket moves "on edge" longer.