Originally Posted by toly
There is example of Chanelle Scheepers serve, where wrist flexion is the major contributor to the RHS and arm pronation supplies virtually nothing...
Puzzling that you quoted a post about badminton strokes to discuss a tennis serve.
Nonetheless, I clearly see quite a bit of evidence of pronation in this photo sequence of Chanelle's serve. Look at the orientation of the racket face and the hand in #1 compared to #6 or #11. That change in orientation is due primarily to forearm pronation with ISR.
Yes, there is flexion as an action
as well in the upward swing. However, we do not see a position
of flexion in your sequence at all. The wrist moves from a c0cked position (extension + wrist deviation) to a neutral position. Quite often, when a player is asked to snap the wrist w/o a proper demonstration (and correction), the player will often exhibit a much more radical flexion than this -- the wrist ends up in an extreme position
of flexion. This is my objection to the terminology.