Posted by: Jack Mankin (MrBatspeed@aol.com) on Fri May 28 11:46:11 2010

>>> Jack

There are some people posting on the Internet who have differing opinions about the role of the shoulders.

One group is saying the shoulders "are bypassed." I don't know what it means, but I think they say shoulder rotation is bad and slows the swing.

Another group is now preaching "shoulder deceleration." They say hitters should intentionally stop the shoulder rotation at some point, which causes the arms and hands and barrel to "slingshot" forward.

Maybe these people are saying the same thing.

Point: Is there any truth to any of this? Do MLB hitters "bypass" or "decelerate" the shoulders?

Also, wasn't it the shoulder rotation of the Cuban national team many years ago that caught your eye, back when the US was sending college teams being taught linear and and knob-to-the-ball mechanics? <<<

Hi Melvin

Over the past couple years, there has been a good number of the "group" you referred to make those arguments on this site. In each case I received no reply when I asked them to explain any bio-mechanical principle that would allow the rotational energy generated by the legs, hips and torso to reach the bat if the shoulders remained static. -- They could not reply because it is bio-mechanically impossible.

I think it quite interesting to note the complete reversal the leader of the "group" has made regarding the role of the shoulders in the swing. For years after I defined the role of the arms in applying THT, he made numerous posts here stating there was "no arm torque" involved in the bat's rearward acceleration. He claimed the rearward acceleration occurred naturally as the shoulders rotated.

At the time of these discussions, I did not have the availability of video. I tried to point out to the "leader" that during the PLT (Pre-Launch-Torque) phase of the swing, there was rearward acceleration prior to shoulder rotation. In light of what he now teaches, his rejection of PLT is quite troubling to me. -- Now that we can show video. Below is a clip that addresses the PLT phase I defined years ago.

PLT phase to THT

Here are the three 'shoulder' concepts they use (1) The shoulder do not rotate, they are "bypassed". (2) Their rotation is to "slow". (3) Shoulder rotation must "decelerate" to accelerate the bat. -- I wonder how much "deceleration" can occur from something rotating to slow or not at all?

Melvin, if shoulder rotation is to slow, then rotating the hips is even worse. As the video below shows, while the hips rotate about 90 degrees, the lead-shoulder rotates through 149 degrees. Therefore, shoulder rotation is more than half again faster than hip rotation.

Lead-shoulder rotation

For the lower body to continue supplying power to accelerate the bat, the shoulders must continue to rotate to contact. Therefore, one of the first things I look for in analyzing a students swing is 'where was the bat when shoulder rotation was depleted.' With efficient mechanics, the bat should be brought to contact when the shoulders cease to rotate. The farther the bat is from contact (bat drag), the more inefficient the transfer mechanics.

I have studied over a hundred MLB swings from an overhead view. All their shoulders rotated and none of the top performers shoulders ceased to rotate before contact. Below is another overhead view of Pete Rose and an across the plate view of four good hitters. Note if (1), do their shoulders rotate and (2), do they rotate to contact.

CHP Mechanics

4 Good hitters - lead-arm

Jack Mankin