Originally Posted by always_crosscourt
So what are the advantages of patting the dog on backswing?
Does it give more spin?
And if so, how?
I guess my answer would have to be I don't know what the precise advantages are, though I have some theories. At a very basic level, it sets the racket face more closed such that you can swing hard and not open it too much. It also seems to set a specific sort of racket lag which causes supination then followed by pronation. Whether this creates a stretch shortening cycle, or just forces the player to contract hard to pronate isn't clear to me. But the motion does seem to create more topspin.
Essentially, the closed face "pat-the-dog" elbow extension is being used a lot by today's top players. It doesn't seem to simply be an affectation, so people are trying to emulate it, thinking it has something to do with the quality of shots the pros are generally creating. SpeedMaster's blog highly touts it as crucial in creating topspin with a flatter racket path.
I guess I'd advise you to try it yourself and see if it helps your hitting.