Posted by: JJA () on Mon Nov 1 13:48:41 2004

>>> Ray,
>
> I actually did go out and purchase the golf paper you recommended some time ago: "Examining the delayed release in the golf swing using computer simulation" by Springings, and Mackenzie, Sports Engineering (2002) 5, 23-32.
>
> According to this paper, page 27, the maximum muscular torque generated by the torso was 112 Newton-meters, for the shoulder joint 87 Nm, and the wrist joint peak torque was 22 Nm, which the authors state compares well with direct measurements on low handicap golfers. Thus, the torques generated by the wrist are rather small compared to the large muscles of the body, which I hope isn't a surprise to anyone.
>
> Of course this is the golf swing, but the baseball swing seemingly can't be appreciably far from this model. Furthermore, as you know, this article does quantify that late wrist release can increase clubhead speed (albeit less than 5%). In particular, it is advocating exactly the opposite of what is shown by Jack in his video: keeping the wrists angle at a 90 degree angle (or even more, as Tom Guerry likes to note) as late as possible, not "casting the fishing pole" at swing initiation as given in the video.
>
> Your excellent reference has cemented, for me, what I had concluded by other reasoning. That wrist torque (i.e., top hand torque and bottom hand torque) is only a small component of the swing and that Dr. Adair's explanation of the whip like action in his book is the correct way of looking at the swing process. Indeed, the last line of your paper reads "In the simulated golf swing, the main source of power delivered to the golfclub originated at the wrist joint as a result of the whip-like kinematics produced by the torso and arms."
>
> Thanks again for the great reference. I don't advocate most people buy it at $30, but for me it was a great reference.
>
> -JJA <<<
>
> Hi JJA & All
>
> JJA's October 31 post raises interesting points that warrants further discussion. His main point contends that since only a small percentage of club-head speed is attained from "wrist torque" in the golf swing, the percentage of bat speed attained from torque (THT + BHT) would also be appreciably small. -- I agree with JJA that the amount of bat speed gained from "wrist torque" in the baseball swing is quite small. In fact, it is even appreciably smaller in the baseball swing than with the golf swing. This is due to the difference in the grip taken in the two swings. The over lapping of the hands in the golf grip allows the wrist to work together in applying torque at the handle, whereas the baseball grip actually restricts "wrist torque."
>
> I have often pointed out that the comparably small muscle groups that control wrist movement could only have a small impact on the bat speed generated - even if the grip allowed unrestricted movement. However, torque applied in the baseball swing (THT & BHT) does not rely on "wrist torque." Torque applied at the handle in the baseball swing results from the push/pull action of the forearms applying force from opposing directions through the hands. The push/pull action of the forearm is driven by the large muscles in the upper back, torso and legs. This results in a large amount of torque being applied at the handle.
>
> Note: (1) The golf grip restricts any push/pull action of the hands and forearms. (2) I have often stated that "pre-launch torque" was a low-energy movement and the un-cocking of the wrist may play a role in accelerating the bat-head back to the launch position. Whereas, THT & BHT are high-energy movements that require the larger muscles in the legs and torso. (3) I will address Adair's flawed swing model as the discussion continues.
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> Jack Mankin
>
>

We are definitely in agreement that the wrists apply only a small (but not negligible) amount of torque to the bat. Apparently now our only disagreement is whether the differential forces on the bat from the hands can apply significant torque to the bat.

I maintain they do not and the argument is very simple indeed. Consider the bottom hand wrist joint. Consider the top hand applying a force to the bat by either pulling back or pushing forward (i.e., top hand or bottom hand torque, as you call it). This force creates a torque about the wrist joint, being the product of the force on the bat created by the top hand times the lever arm of that force, i.e., about 3 inches. Note that the bottom hand force in this example is irrelevant, since a bottom hand force cannot create a torque about it's own wrist joint since the lever arm is 0.

Thus, a torque is created about the bottom hand wrist joint! This torque means that the wrist must elongate or contract since the wrist is nearly a perfect pin joint, i.e. it is free to rotate. Of course, the wrist itself has the ability to resist this torque by it's own muscles, but we are now in agreement that the torque generated by the wrists are small.

Since the wrists do not appreciably elongate or contract during the swing, this means that the forces applied by the top hand in a direction perpindicular to the bat must be small. In other words, the fact that the wrists don't elongate or contract during the swing means that little torque is applied by the hands to the bat. This explanation, by the way, is consistent with all of the experiments that Jack has presented on this web site.

-JJA

P.S. In a future post, I may give the explanation as to why the wrists, although supplying only a small amount of torque to the club, actually supply a large component of muscular POWER to the golf swing. This may in fact be the point of confusion between Jack and me.