Originally Posted by Cheetah
internal shoulder rotation
If it was internal shoulder rotation or pronation this would not happen so suddenly. also internal rotation also closes the racket face when the racket and forearm are in line. however pros hit the ball with the wrist laid back which means the racket is staying at roughly the same angle but rotating around the arm.
Test for yourself. take your racket and internally rotate the arm with the wrist laid back and then with the wrist and racket being in line. only in one case the racket will close.
also why is feds racket face opening in the video at 3:00 when his arm is internally rotating?
Internal rotation of the arm is very important because in greatly contributes to RHS but it doesn't close the racket face.