^ There is no concise definition for wrist snap. When most students are asked to snap the wrist, the most common response is to attempt to move the wrist from an extreme laid-back position (extension) to an extreme flexion position (bent forward) very quickly. In reality, the wrist is usually c0cked back at the start of the forward swing or the upward swing (in the case of the serve) and moves to a position that is either neutral or a position that is less c0cked than it was before. The c0cking of the wrist can be a combination of wrist extension and wrist deviation (ulnar or radial).
The wrist should not move to a position of flexion prior to contact (or at contact). The wrist is fairly neutral after contact as well. In some cases, for some players, the wrist might go slightly past a neutral position after contact. However, it should not assume an extreme flexion (as one might be tempted to do if told to snap the wrist).
Pronation is not an articulation of the wrist -- it is a forearm rotation -- an action to turn the hand. On the serve and overhead smash, what many refer to as wrist snap is really a combination of forearm pronation with some unc0cking of the wrist.
You are wrong about the forehand. It can be hit very effectively without a wrist action. The classic FH (typically with an Eastern FH grip) is usually hit without unc0cking the wrist at all -- it remains laid-back. I have also seen some decent FHs hit w/o c0cking the wrist at all -- it remains fairly neutral for the whole stroke. However, this variation is/was less common.
These classic FHs typically employed a moderate amount of pronation on the forward swing. The modern (WW) forehand uses some wrist action on the forward swing with, perhaps, more pronation than the classic FH.
Last edited by SystemicAnomaly; 12-03-2012 at 04:01 AM.