Originally Posted by DropShotArtist
At what approximate point would you say the active use of the arm comes in from the beginning of the forward swing to contact point? Maybe halfway through the swing path such that the kinetic rotation of the body is best transferred?
at the very end when the chest is nearly facing the net. biomechanically the best time is when the trunk rotation has reached maximum speed and starts to decelerate.
look at this javelin thrower:
while his body rotates the arm barely moves and while the arm moves the chest barely moves (stopped). high level is to rotate early and separate the arm action from the rotation a lot.
the rotation adds some MPH but the actual shoulder velocites are quite low (under 10 mph). that means the main effect of rotation is not pulling the arm around (although that also plays a role) but to create potential energy and pre stretch the muscles above for their contraction.