Posted by: tom.guerry (tom.guerry@kp.org) on Sun May 16 22:03:30 2004

Terms are impossible to define without a shared swing model.even with such a model, definitions can be hard to agree on.I have my own personal idiosyncratic (or as Nyman might say,totally unsubstantiated) swing model hypothesis which integrates many aspects of especially Mankin,Williams,Epstein,Nyman and Hodge.The phases are to some degree
universal.The whip,bow-arch and scap load terms are included.communication is further hindered by the cue/reality problem(nyman).

1- cock hip(Williams),bow/"beachball"(nyman),pinch at waist(Dixon),internal rotation of back arm(hodge) synchronized/"mapped"(nyman) to internal rotation of lead leg.The hips are cocked/"pinched" with bend at waist and elevation of the front of the pelvis supported by internal rotation of limbs as the stride knee turns in/stride foot starts to lift.bat cocks up from horizontal to vertical.Hands may "hitch"/drop

2-cock hands(Williams),load/pinch/horizontally adduct back scap toward
spine(nyman),load up to throw a punch with back arm(cue from Doug M's minor league coach for example).Entire body makes slight "inward turn".Weight stays on inside of back foot and center of gravity begins steady shift forward and down on line to pitcher(nyman principles of "flatbed" and "alignment).Hands load up and in.Bat cocks toward pitcher

3-coiling/xfactor/separation of upper and lower body begin.bat uncocks while torso still back (must be torque,can't be reactive force since torso not turning forward yet.back elbow slots via external rotation(hard to do this unless internally rotated earlier with hip cock).back scap continues to load/pinch.lead arm internally rotates/"works up a little"(epstein) to assist in accelerating uncocking of bat as well as firming up front shoulder connection.Hips rotate open.torso stays back as you "wind the rubber
band"(epstein) and "rotate into toe touch"(nyman).front leg and back arm externally rotate together in support of hips turning open and torso staying back.center of gravity continues forward and down.major plane setting adjustment also being made via degree of bend in waist as well as flex in back knee(which also controls progress of weight shift).Except for absence of upper body details (THT/back elbow slotting),Epstein's description is good: "wind the rubber band as you stride to toe touch with the weight slightly forward".

4-xfactor stretch,total body eccentric to concentric muscle action(nyman),last quick bit of coil,"drop and tilt"(epstein),body turns together with some lag(mankin),tht at launch(mankin),circular handpath starts(mankin).torso begins to turn forward,but hips turning forward faster due to assist from front foot blocking weight shift as front heel drops.The shoulder link "tilts"(epstein) rather than immediately turning with the hips.This stretches the front side(seen nicely in griffey motion analysis at peaveynet.com for example-you can see the distance stretch between the front hip marker and the front shoulder marker as the bat turns to the "lag" position.The "hinge angle" would be
expected to narrow at this point,but instead stays stable(see griffey motion analysis angles)then widens/stabilizes until uncoiling starts.Again,this means torque("THT" from front and back scap/arm forces transmitted to handle) must be applied up to this point as the hinge angle does NOT narrow as it would for pure double pendulum(whipping/ball on string) action(two body whip with hinge,first body being torso,second body being bat,wrists/hands being hinge,angle of lead arm and bat being hinge angle.This is the end of coiling.The center of mass of the bat needs to be at/within the arc of the handpath to avoid interfering with coiling up to this point.axis stabilized.weight shift stopped.

5-Next,uncoiling/momentum transfer happens as rapidly as human tissues will
allow,including assistance of muscle contraction and soft tissue elastic
properties(nyman).Momentum is directional.levers/loops for whipping must be aligned for "postural efficiency"(nyman) or kinetic link(epstein).center of mass of bat swings out of arc of handoath.hinge angle rapidly widens as batturn rapidly accelerates.Timing of uncoiling is related to degree of hooking of handpath.handpath shape is controlled by front scap/arm action.forces on hands at handle are more purely reactive/related to whiping as acceleration proceeds.fully stretched front side at end of coil is assisted in uncoiling by deceleration of lower body using front foot as base and arching of spine(bow-arch/get off back side/back hip starts up) which efficiently channels/transforms momentum into batspeed(stages/sequences momentum transfer so it efficiently gets out of the lower body and torso and into the bat as angular acceleration).acceleration is maximum at contact.


in addition to previous references linked by me here (setpro/best of max;
skilltechnologies/xfactor stretch;carini/double pendulum/hinge angle)the motion analyses at peaveynet.com are worth looking at.especially note the hinge angle and front side stretch as the torso begins to turn.

with regard to optimizing the swing for max batspeed vs bat quickness,i would say you need to optimize/minimize timing error which means shortening the swing and traversing the short path as fast as possible(nyman-schmidt).This requires eliminating "bat drag"(nyman). part,but not all of which involves application of torqueing force(THT- mankin) to the bat handle("uncocking" the bat before and after the torso turn begins) until
uncoiling is underway.