Posted by: Jack Mankin (MrBatspeed@aol.com) on Fri Dec 16 13:09:48 2005

>>> Hip rotation is started and built by a complex coordinated action of both legs and lower core muscles. When numerous pros are viewed from the pitcher (Rightview Pro target view system clips), the first noticeable rotational movement occurs in the front leg. As the front toe is contacting the ground at the end of the stride (near the end of hip slide), the front knee shows a slight outward thrust followed immediately by the first clear rotational movement of the front hip. As the heel plants, the flexed front leg is beginning its straightening process which drives the front hip rearward. This is an acceleration process. I do not believe the front leg totally blocks hip slide, but rather redirects and adds to motion that already exists (from hip slide). The total energy supplied by the hips therefore comes from two sources. The bulk of it from rotation with supplemental energy added from the motion of the hip slide.

Meanwhile, as the front toe is touching, the back knee begins a slight inward twisting motion as the back leg is propelled forward off the toes of the back foot. As this energy transmits through the leg to the back hip driving it forward, the back foot is then relaxed (unweighted) and allowed to react to the forces of rotation. In many players this reaction manifests itself as dragging of the foot on the toes. In others, the foot may not actually drag. None the less, the heel becomes elevated due to unweighting even if the foot does not actually drag. The back heel should not stay low and spin around on the ball of the foot.

Many things can be seen in the clip http://www.rightviewpro.com/mantelvsichiro.php . The first frame is the stance. The second frame shows the negative move. The third frame shows toe touch. The fourth frame shows heel plant. The stride occurs from frame 2 to 3. Hip slide is occurring in frames 2-4. Note the change in position of the front and back knees from frame 3 to 4. This indicates the onset of hip rotation begins between frames 3 and 4. If we could put these clips in motion we would see that hip slide does not fully halt until after hip rotation has already begun. We would also see that all forward head movement has ceased by the time the heel is fully planted, usually slightly before hip slide has fully ended.

Frame 5 shows what is termed “connection”. This is the point by which rotational forces must have become fully connected to the bat. Without proper connection, rotational energy will be not be fully transmitted to the bat at contact (i.e. angular momentum, top and bottom hand torque). It is at this point that the back foot is becoming relaxed and is being allowed to react to the rotational forces of the body. Mantle allows his back foot to drag through the next 3 frames while Ichiro drags through the next 2. The length of the drag on any particular swing is probably related to the batter’s reaction to pitch location and whether or not the ball is pulled.

Frame 6 is termed bat lag. From this point the bat will accelerate very rapidly to contact provided proper connection has been achieved. It is during this time that small adjustments can be made with the hands to change where on the ball the bat head actually makes contact; outside half to pull, middle half for straight-away, inside half for opposite field. In this context, what is being called bat lag is not an indication of a linear swing unless connection has not been achieved.

Frame 7 shows contact. Note the difference in degree of flex in the elbows in frames 6 and 7. The fact that the elbows are more flexed in 6 than they are in 7 is an indication that the arms are extending from bat lag through contact. Both Mantle and Ichiro show extension here.

Frame 8 is referred to as extension. It is actually the limit of extension. We can see that Ichiro shows more extension at this point than Mantle. It could be concluded here that Mantle possibly has a more rotational hand path than Ichiro, at least on these particular swings. Extreme extension here can indicate a linear swing and is a signal to look carefully at what is happening at contact. However, some degree of extension is observable in most Rightview clips, including rotational hitters that are often used as examples on this discussion board. The arms can extend after contact and a rotational hand path be maintained at contact. Also, rolling of the wrists should not begin until this stage of the swing is reached.

Frames 9-12 are four stages of the finish, or follow through. Both players have very strong upper body rotation and allow it to continue through their finish. <<<

Hi Jim & All

I presented the reasons why I believe linear momentum does not significantly contribute to rotational momentum while Mark, Tom, Jim and other’s did an excellent job giving their reasons why they feel transferring linear momentum into rotation is a key factor. I thank you all for giving our readers information to form their own conclusions.

This discussion just re-enforces the conclusions I made from data collected while charting the lower-body mechanics of over 2000 professional swings. There is such a great a variety of lower-body mechanics that can produce powerful rotation about a stationary axis that I could find no absolute rules for saying one style has an advantage over another. As the clips of Mantle and Ichiro show, batters with very similar lower-body mechanics can produce very different bat speed and power numbers.

One other point I have found important to keep in mind is that the arms-forearms-wrists-hands and bat linkage is not connected at the hips. That linkage is connected at the shoulders. It is the rotation of the shoulders that transfers the body’s rotational momentum into bat speed – not hip rotation. The importance of hip rotation is its contribution to shoulder rotation. --- Note: the hips may, or may not, slide forward during the swing, but for the head to remain still, the shoulders must rotate about a fixed point.

In Jim’s post above, is the key to helping a batter progress. Jim states, “Without proper connection, rotational energy will be not be fully transmitted to the bat at contact (i.e. angular momentum, top and bottom hand torque).” – While analyzing the swings of batters with less than average bat speeds, I find many of them generated adequate rotation. The problems were flaws in their transfer mechanics that left the bat-head dragging 30 to 70 degrees behind shoulder rotation.

No matter how well a batter perfects his lower-body mechanics, he will never reach his potential with flawed transfer mechanics. – Of what use is a 1000 HP engine … if the transmission slips?

Jack Mankin