I think Teacherman and a few other readers have a problem understanding top-hand-torque because to them the term means the top-hand is pulling back and applying torque by its own accord. As I have been discussing for years on this board, this is not the case and I hope that my post below will assist them in understanding the role of the top hand.
Get in your stance, cock the bat over your head toward the pitcher, do not apply tht, slot the elbow and rotate. What happens to the bat head? <<<
You seem to imply that when a batter applies THT, the top-hand can just pull back independent of the shoulder, forearm and elbow movement. Well it can't. It should be obvious that for the top-hand to be pulled back and over the bottom-hand, the forearm and elbow must also be pulled rearward.
When most hitters (like Bonds and Sosa) apply pre-launch torque, they start with their hands away from the back-shoulder. Very importantly, good hitters then pull back the shoulder, forearm and elbow (like an archer pulling back on the bowstring) which pulls the hands toward the back-shoulder. The bat-head is accelerated back toward the catcher because the top-hand is being pulled back and over the slower moving bottom-hand.
I think the problem that some are having with THT is that they are assuming that the top hand is moving independently to create THT, but as I stated, it is not. THT is a fluid motion caused by the back shoulder, elbow, forearm pulling the top hand back in an arc toward the catcher. I termed this movement "THT" because in order to accelerate the bat-head back toward the catcher, the action of the top-hand should be pulling rearward on the bat instead of shoved forward during initiation.
Slotting the elbow does not by itself cause the top-hand to place torque at the handle. Just lowering elbow and tilting the shoulders is not enough. In addition to lowering the elbow, good hitters are also pulling rearward with the forearm and top-hand. This combination creates early bat speed and sweeps the bat-head rearward into the swing plane.
Suppose we performed Teacherman's example but substitute the top-hand and forearm with a torque wrench embedded in the handle. Do you think we would get a reading as we pulled the handle of the torque wrench down toward the slot? The answer is of course no. In order to accelerate the bat-head, the pulling back of top hand must be applying torque at the handle of the bat (bottom-hand serves as a pivot point) as the forearm rotates and the elbow lowers.
Obviously, rearward bat-head acceleration could occur as the elbow lowers - but does that alone generate it? No, as the clip below shows.
Similarly, at contact, the lead-shoulder is pulling back the lead-arm and hand (105 degree position) and because the bottom-hand is being pulled around the top-hand, I called this mechanic bottom-hand torque. This does not mean that the top and bottom hands are creating this push/pull action by themselves. Rather, it requires a force supplied through the arms to cause the hands to either push or pull.
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