Wrist Action or Torque
Most coaches think the wrist play an important role in producing power and quickness for the baseball swing. But the muscle groups that flex and un-flex (abduct and addult) the wrist are a comparably small muscle group and could have only a limited impact on the generation of bat speed. Therefore, I would like to offer a different observation I drew from my research of what appears to be the "snapping of the wrist."
For a ball to be hit over 400 feet, the bat head must be accelerated to a speed in excess of 70 MPH in less than 5/30 of a second. About half that speed is developed in the last 1/30 of a second. The large amount of inertia that must be overcome to accelerate the bat head 35 MPH or more in 1/30 of a second requires far more energy than the muscles in the hands, wrists and arms can produce. That kind of energy (about 3 torque HP) must come from the large muscle groups in the legs, back and shoulders.
The question then becomes; how is the energy transferred from the large muscle groups of the body up and on out to the bat head? I'm not going to cover the entire sequence at this time (omitting the initiation mechanics of the swing), but confine my remarks to the mechanics that appear to be wrist action or snapping of the wrist just prior to contact.
To explain the mechanics of how the large muscles are involved in this transfer, I am going to describe the swing mechanics of a Ken Griffey Jr., or hitters of his caliber, just prior to making contact. --- The large muscles in his legs and back have rotated his hips and shoulders to a point where the belly button and chest are now facing the pitcher. His lead shoulder is now starting to rotate back in the direction of the catcher. This means that the lead arm, and thus the bottom hand, are now being pulling back toward the catcher as the bat approaches contact. --- At the same time the rear shoulder (and top hand) are rotating around toward the pitcher.
This "pulling back" of the bottom hand as the top hand is being "driven forward", generates a tremendous amount of TORQUE on the bat. Torque is the result of forces being applied to the bat from opposing directions that causes an object (the bat) to rotate about a point between the two hands.
So, in the swing of a great hitter, what appears to be wrist action is actually the "push - pull" action of the hands generating a large amount of torque. This torque was developed from the large muscle groups and causes the bat head to be greatly accelerated. --- If the batter does not initiate the swing with torque and rotational forces, he will not be able to obtain the position of power required to apply maximum torque to the bat before contact. This is especially true for pitches on the outside part of the plate.
NOTE: Mechanics that would have both hands being thrust forward (both applying forces in relatively the same direction) produces much less torque. --- This type of mechanics just can not generate enough bat speed and power to produce a great hitter.