Posted by: tom.guerry (tom.guerry@kp.org) on Wed May 2 08:29:01 2001

>>> You asked: "I have often pondered why it would be more efficient to push off with the back leg and slide the hips forward and then convert some of that momentum into hip rotation. Why is that more efficient than just using the push off to turn the hips from the get-go."
> > my response - an analogy - why does a high jumper (or basketball player) run forward to jump higher? Why not just bend the knees and jump straight up? How can running forward add to vertical leap? In fact it is harder to bend the knees as much from a run, so it should result in less vertical leap. But it does not. The running start is energy in the system. It can be redirected/converted. If it is directed upwards, there is more energy for a running leap than for a standing leap, therefore you can jump higher with a running start.
> > The hip slide (stride or no stride) is the runnning start. The front leg redirecting the energy is the same as the jumper's jump - both convert linear momentum into something else. The jumper redirects it in another linear direction, the hitter redirects it into rotational/angular momentum.
> > The hip slide/weight shift happens before the torquing pushes that turn the hips. The sequence of hip slide then hip torque is more powerful than just hip torque with the legs.
> > A player with very strong legs and explosive quickness in those legs can probably generate more than enough energy to transfer to the bat to hit the ball very far, but not as easily.
> > An additional consideration- the body has its own properties. Elasticity of muscles, tendons, ligaments, etc. plays a role in hitting. The plyometric response ('stretch, then contract' gives a greater contraction than just 'contract') is a significant contributor here. Simply pushing with the front leg is not as strong as loading the front leg, then pushing the load back. It is the equivalent of jumping from a static knee bend vs. the usual quick bend the knees and jump that we all do.
> > If you take the exceptionally strong legged man and have them hit starting from a statically bent front knee and then from a flex-then-straighten front knee, the latter will produce more power, due to the plyometric response.
> > In fact, the latter movement is best accomplished by sliding the hips forward to put weight on the front leg, then pushing back with the front leg quads. This internal weight shift loads the front leg with a window of about .5 seconds response time (use it within .5 or start losing it). This is the imprecise timing needed to time a pitch from the lower body perspective.
> > This line of thought questions what is meant by ‘balance’ or ‘full balance’. If balance means coming to a complete stop and the body’s system giving up its energy, then all that motion is in vain/wasted. I doubt that a Griffey or Bonds is that inefficient. I suspect that in that ‘balance’ is a dynamic state where large muscles are being deeply loaded in order to unload more forcefully. The ‘delay’ is both the timing window and internal body workings to best redirect the built-up energy into rotation.
> > I have questions about what many consider balance and would be interested in responses concerning whether it is considered dynamic or static and the consequences of each.
> >
> > Two main issues here:
> > Conversion of linear(weight shift) momentum to angular momentum helps power the hip turn that feeds the transfer mechanics that rotate the shoulders to develop batspeed. This was the big issue of debate in April. Any more thoughts?
> >
> > Coming to balance after weight shift - is this a static stop or a dynamic moment that the hitter passes through as he goes from weight shift to conversion to rotational/angular momentum.
> > Any thoughts on this? <<<
> >
> > Hi Major Dan
> >
> > What some consider weight shift has really undergone some major changes over the years. Professor Adair and other noted authorities believed that the forward movement of the body developed energy that could be converted into bat speed. In Adair’s model, he claimed a 185 lb hitter moving forward 18 inches at 7 or 8 mph during the swing would generated sufficient kinetic energy that when the forward motion of the hands slowed to a near stop, the bat would be accelerated from around 40 mph to around 75 mph.
> >
> > Without going into detail, we how know that the conclusions drawn from that model were incorrect. But at least Professor Adair showed he understood the basic laws of the “conservation of energy.” He understood that for an action to generate energy that could cause an appreciable acceleration of the bat, an equal or greater amount (loss to friction and etc) of energy must be added to the system. -- Energy in = Energy out – Small energy in = Small energy out. This is why Adair could not accept the stationary axis model. For his model to work there must be a substantial movement of the axis during the swing.
> >
> > There seems to be such a need in some people to keep the weight shift theory alive that they seemed to have lost all sense of proportion. I think we could all agree that a player running at full stride could use that momentum to leap higher. But also consider the amount of added energy expended to gain those added inches. I fail to see how we can compare that action to a 4 or 5 inch slide of the hips in the baseball swing. From a short or no-stride stance, it requires very very little energy to let the hips slide forward a few inches before rotation. Why would we then think that when the slide stops there is this tremendous stored up energy released for the rotation. --- I’m sorry Major Dan but I just don’t buy it.
> >
> > Jack Mankin
> >
> >
>
> Jack -
> I hope this remains on a friendly basis. You don't have to buy anything I say, but do consider the argument before deciding.
>
> Consider 'transfer mechanics'. What is the point of transfer mechanics? I think that the torso takes energy built up in the lower body and turns it into shoulder rotation. This concept implies an indirect link between lower and upper body movements, not a one piece unit body turn, at least to me. I don't think an optimal swing has the hips and shoulders turning in unison.
>
> THe following is from a post on Fast Pitch Forum ( I believe the text is actually from Paul Nyman or some post at Setpro, but Shawn Bell posted it at FPF yesterday)
> ----------------------------------------------
> "Energy and power of a homerun
> The shortest homerun ball requires a launch velocity of 45 m/s and a bat velocity of 24 m/s when striking a 45 m/s fastball with a 30 oz bat. The kinetic energy of the 5.1 oz ball is Kball = 1/2*mv2 = 1/2*0.14*452 = 147 J. The kinetic energy of the bat before the collision is: Kbat = 1/2*0.85*242 = 245 J. Studies of batters have shown that they bring the bat around to hitting position in about 0.13 seconds. The average power to produce the kinetic energy of the bat is thus Pavg = 245/0.13 = 1884 watts. The peak power will be almost 3800 watts. From our study of power density of muscles, the agonist muscles involved must have a mass of 9.5 kg. Since each agonist must have an antagonist, the sum of the two must be about 18 Kg or 36 pounds of muscle. The muscle mass in the shoulders and arms are insufficient to generate the needed power. The power must be generated with the big muscles of the body. These are the muscles in the torso and hips.
> A big question is how does the power generated by the hips get delivered to the bat? The hips move rather slowly in the batting process. To understand how this occurs, we should reflect upon how a whip works. The driver of a horse-drawn rig will use modest forces and velocities but the tip of the whip will attain super-sonic velocities. Other examples of this are the crack the whip with a chain of people or the snapping towel in the locker room. The general idea is that the kinetic energy of the larger mass [moving at small velocities] is transferred to the smaller mass, but the velocity must be much larger to conserve energy.
>
> In the hit, the massive hips and torso are moved with a small velocity but the kinetic energy is large. This energy is delivered to the bat with a resultant high velocity. The process starts with the bat being relatively stationary and the hips and torso move forward leaving the bat behind. As the arms are stretched out, the bat is brought around at the end. It's important that the wrist remains loose so that the energy is efficiently transferred.
>
> The whip-like process is important for the pitcher as well. A study of the pitching motion shows the same process of leaving the ball and hand behind while the body is in forward motion, then whipping the arm for the pitch.
>
> Practice and timing are ways to achieve this whip-like action in hitting and throwing. When you try this, remember that you will always let the ball or the bat lag behind the rest of the motion and it only comes up to speed at the last moment.
> ---------------------------------------------
> Shawn Bell
> -------------------------------------------------------------"
>
> This post suggests the analogy of a whip. Move the handle a short distance at moderate speed and the tip can reach supersonic speed!
> The point here is that the body can be used as a whip. The hip movement (short distance and moderate speed with great mass) can be translated into batspeed if the transfer of energy goes from larger/slower moving body parts to smaller/faster moving parts with the kinetic chain properly sequenced to pass the energy along (good transfer mechanics).
> This is how a hip slide can add batspeed.
> There is no doubt that simply rotating with good transfer mechanics and proper upperbody mechanics creates batspeed. I think that what I am suggesting makes it easier to put that process in motion AND adds additional energy to the system, creating more batspeed. And it is the last 10%-15% that is the hardest to create/find and what separatest the elite from the very good hitters.

Jack,MD,RQL,et al-

Interesting stuff here.My interpretation is that Jack looked really closely and well for visual evidence based on sound physical principles of what distinguished the most productive hitters.He found no visual evidence of a certain kind of stride/weight shift being superior.It is possible these things are important from an internal/feel point of view,yet too subtle to be seen visually.It is possible that evidence is there,but not being looked for due to lack of understanding of more complex motor/elasticity,etc.principles.I think it is most likely that there are many ways to generate enough energy in the torso at the right time using kinetic chain/whip/elasticity,etc. and no one gets to the majors without figuring out how to do this.In both hitting and pitching,the ability to separate the upper and lower half and then shorten the muscles without breaking the chain is essential.For hitting,Jack has stated that a stationary spinal axis is necessary from launch to contact,but otherwise there is no discernable visual evidence of another such key.If you can teach good rotation without "excessive" lunging,many different "weight-shift" styles may be compatible with this.

If there is something else important in the body/generation of torso power,what is it? What should we look for? In general,I like to encourage students to stay back as much as possible to increase reaction time while the energy is going up the spine,but this may(????)work better for low pitches.If the strike zone is higher,you may need to come forward alittle more to get the axis more upright for better high ball contact,but I would still discourage coming way forward unless this is working well for the individual.

I also think there is a theoretical advantage in maximizing upper/lower separation.Not only could this give you a quicker bat,but you are probably able to make more "automatic" timing adjustments as the swing proceeds(as opposed to the more conscious/set-up adjustment you make by deciding when to stride for an individual pitcher).Epstein's way of putting kids through the stretch position may encourage learning more separation.

The major learning in Jack's work is how "transfer mechanics" work.The hands have to pull the bat in a circular path with good connection in the plane of torso rotation(harness ballon string principle).When the torso is fully energized,efficient momentum transfer is then triggered by the bathead being torqued out of the path of the hands.One area of controversy is whether or not acceleration(increased angular velocity of bat)can continue if the hands get away from the axis of rotation near contact or whether higher batspeed requires a circular path of longer radius be maintained(not increased) until contact.