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baseball_kinematics

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©JournalofSportsScienceandMedicine(),http:wwwjssmorgReceived:JulyAccepted:FebruaryPublished(online):MarchBaseballthrowingmechanicsastheyrelatetopathologyandperformance–AreviewRodWhiteleyUniversityofSydney,AustraliaAbstractItisacommonlyheldperceptionamongstbiomechanists,sportsmedicinepractitioners,baseballcoachesandplayers,thatanindividualbaseballplayer’sstyleofthrowingorpitchinginfluencestheirperformanceandsusceptibilitytoinjuryWiththeresultsofaseriesoffocusgroupswithbaseballmanagersandpitchingcoachesinmind,theavailablescientificliteraturewasreviewedregardingthecontributionofindividualaspectsofpitchingandthrowingmechanicstopotentialforinjuryandperformanceAfteradiscussionofthelimitationsofkinematicandkineticanalyses,theindividualaspectsofpitchingmechanicsarediscussedunderarbitraryheadings:FootpositionatstridefootcontactElbowflexionArmrotationArmhorizontalabductionArmabductionLeadkneepositionPelvicorientationDecelerationphaserelatedissuesCurveballsandTeachingthrowingmechanicsIngeneral,popularopinionofbaseballcoachingstaffwasfoundtobelargelyinconcordancewiththescientificinvestigationsofbiomechanistswithseveralnotableexceptionsSomedifficultiesareidentifiedwiththepracticalimplementationofanalyzingthrowingmechanicsinthefieldbypitchingcoaches,andwithsomeunquantifiedaspectsofscientificanalysesKeywords:Baseball,pitching,throwing,injury,analysis,biomechanicsIntroductionPlayedworldwideforoveracentury,baseballisagamethatinvolvesperiodsofapparentinactivitypunctuatedbythehighestrecordedangularvelocitiesofhumanmovementWhilstthegameisadelicatebalanceofattackanddefense,pitchingperformanceisintegraltosuccessonthebaseballfieldTheperceivedimportanceofoptimalpitchingmechanicsisreflectedinthepresenceofpitchingcoachesateverylevelofbaseball’sorganizationDespitetheemphasisplacedonpreventivecareandtheincreasingsophisticationofmedicalmanagementinjuryratesatthehighestlevelofbaseballwouldappeartoberising(Conte,etal,Hill,)Whilesomeauthoritieshavefoundnolinkbetween‘individualpitchingtraits’andpresenceofinjury(GranaandRashkin,)manymore(Albrightetal,Alexander,AltchekandHobbs,Andrewsetal,Atwater,Azar,BurkhartandMorgan,Dillmanetal,Duda,Escamillaetal,Feltner,Fleisigetal,Gainoretal,Lymanetal,Matsuoetal,Meister,Murata,Nadler,Pappasetal,bSakuraietal,TullosandKing,Wilketal,)believethemechanicsofthethrowingmotiontobeasignificantcontributortolikelihoodofinjuryDespitethisapparentlycommonlyheldperceptionofalinkbetweenthrowingmechanicsandpitchingperformanceandhealth,fewauthorsarespecificintheirrecommendationsforthethrowingathleteThispaperwillattempttodescribetheavailableliteratureregardingpitchingandthrowingmechanicsastheyrelatetopitchingperformanceandhealthInconcertwithaliteraturereviewarequestwasmadeofaninternetbiomechanicsdiscussiongroupforanyfurtherunpublishedorunindexedworkwithseveralpapersand‘worksinprogress’arisingAsbackground,manyinstructionalresourceswereviewed,andfocusgroupswereheldwithbaseballandpitchingcoachestoidentifygenerallyheldperceptionsof‘correct’and‘incorrect’throwingmechanics,alongwiththeirperceptionsastotheeffectsoftheseonperformanceandhealthTheliteraturesearchandfocusgroupresultsdisplayedalargerangeofsophisticationrangingfromsinglecaseobservationsofanindividualmakingasinglethrowtokineticcomparisonsofgroupsofsubjectsmakinggroupsofthrowsFigureTotalnumberofthrowsmadeasdescribedbyfieldingpositionfromdataofBarrettandBurton(ResearchQuarterlyforExerciseandSport(),,)BdenotesfirstbasemanB':Secondbaseman'B':Thirdbaseman'SS':Shortstop'OF':OieldersThevastmajorityofpeerreviewedpublishedresearchhasbeenconductedintothepitchingmotionasopposedtothrowingingeneralreflectinginparttheperceivedimportanceofpitchingtoultimatesuccessinbaseballperformanceInastudyofthrowsmadebyplayersduringcollegiategamesofbaseballwherethrowsweredetermined‘active’or‘inactive’astowhetherthethrowwasmadeinanattempttogetaplayerReviewarticleThrowingmechanics,pathology,andperformanceFigureDistancethrownandpositionofplayermakingthethrowforthedatadescribedbyBarrettandBurton(ResearchQuarterlyforExerciseSport(),,)Notethatthevastmajorityofthrowsweremadethroughthedistancetofeet,andthatthesethrowsweremadeprincipallybypitchersandcatchersNotealsothatalmostallofthelongestthrows(feetandabove)weremadebyoielders)outornotrespectively(BarrettandBurton,)Thisanalysisgaveaquantitativebreakdownofthedistancesrequiredofindividualfielders,andshowedthatpitcherswereindeedrequiredtomakethevastmajorityoftheiractivethrowsoverthepitchingdistance(ofthrowsmade),andthatthrowsmadebypitchersaccountedformorethanhalfofthethrowsmadeinthegameofbaseballThisanalysisalsogaveinformationregardingthenumberofthrowsmadeanddistancesfortheotherfieldingpositionsAsummaryofthisdataispresentedinFiguresandWhilstsomeauthorshavedividedthethrowingmotionintothree(Pappasetal,ab),four(XueandMasuda),andfive(AndrewsandWilk,BraatzandGogia,Walsh,)stages,morecommonlythethrowingmotionisdescribedascomprisingstages(Dillmanetal,FleisigandEscamilla,Werneretal,Werneretal,,Zhengetal,)Thesestagesaretermed:windup,stride,armcocking,armacceleration,armdeceleration,andfollowthroughArepresentationoftheseisshowninFigureLimitationsofinvestigationsAlongwiththeperceivedimportanceofpitchinginbaseballthereisaperceptionofhigherincidenceofthrowingarminjuryinpitchersincomparisontootherpositionplayers(McFarlandandWasik,)AccordinglythemajorityofinvestigationintothrowingmechanicshasbeenperformedonpitchersFewreportsareavailablecomparingpitchingtothrowingfromthefieldNorkus()investigatedthedimensionalkinematicsofthrowingsubmaximallyoverdistancesof,,andfeet,andthrowingmaximallyoverfeetThisinvestigationfoundverylittlekinematicsimilarityinthesubmaximaltrialsandthemaximumefforttrialswithonlymaximumelbowflexionangleremainingconstantacrosstrialsItremainstobeshowniftherearesignificantdifferencesbetweenthesethrowingformswhichwarrantfurtherclinicalinvestigationSeveraldifficulties,theoreticalandtechnological,havebeenencounteredwhenquantifyingthetimingandforcesinvolvedinpitchingInitially,dataforbiomechanicalmodelswerecapturedfromfilmatframeratesfromframespersecond(fps)(Atwater,)tofps(Atwater,)Theuseoffilmanalysisprovedtobetechnicallydemandingrequiringasignificantdelayforchemicaldevelopmentofthefilm,andthereforedelayedidentificationofanyproblemswiththecinematographyIncreasinglyhighspeedvideotapeanalysishasreplacedfilmanalysisduetoitslowercost,theavailabilityofimmediatefeedback,therelativeeaseinsynchronizationofindividualcameras,andtheincreasingsophisticationandeaseofcomputerdigitizationofthevideoanalysisThehighestrecordedangularvelocitiesofanyhumanmotionhavebeendisplayedduringabaseballpitchandthisdoespresentsomeproblemsforkinematicanalysisForexample,duringtheaccelerationphaseofthrowing,angularvelocitiesinexcessof,°sechavebeenrecorded(Werneretal,)StandardNTSCvideotapecapturesmotionatarateofframespersecond,atsuchhighangularvelocitiesverylittleinformationwouldbegleanedfromsuchananalysisEvenatextremelyhighvideotaperatesofcapturesuchasframespersecond,WhiteleyFigureDelineationsofthesixstagesofthepitchingmotionaredisplayedhere,viewedfromsixperspectivesThetoprowshowsaperspectiveviewfromthethirdbasecoachesbox,thesecondrowshowsaviewfromhomeplate,thethirdrowshowsaviewfromabove,thefourthrowshowsaviewfromthefirstbaseside,thefifthrowfromsecondbase,andthebottomrowshowsaviewfromthirdbaseThesixstagesofthepitchingmotionarewindup,stride,armcocking,acceleration,armdeceleration,andfollowthroughThedelineationsofthesestagesareshownhere,andare:Rest,maximumkneeheight,stridefootcontact,maximumarmexternalrotation,release,maximuminternalrotation,andfollowthroughthearmwouldbemovingthroughupto°betweenframesThisapparentlimitationwasaddressedbyFleisigetal()whocapturedbaseballpitchersperformingthepitchingmotionandAmericanfootballquarterbackspassingafootballatfpsNotingthattheonlypublisheddataavailableforcomparisonwascapturedatfps(RashandShapiro,)Fleisigetal()reanalysedtheirdataforseveraltrialsbyviewingonlyeverythirdframe(aneffectivecapturerateofapproximatelyfps)andcomparedthistotheiroriginaldatacapturedatfpsTheyfoundthattherewasnodifferenceinanyoftheparametersmeasuredexceptforshoulderinternalrotationangularvelocity–thefastestrecordedeventWhenanalyzingthetruncateddata(usinganeffectivecapturerateoffps)themeasuredangularvelocitiesofarminternalrotationwerereducedbyapproximatelyincomparisontotheoriginaldatacapturedatfpsforthesameindividualsThisdifferenceincalculatedvelocity(andthereforeforces)betweenthetwomethodsusingessentiallythesamedataleadstospeculationthatdifferentfiguresmaybearrivedatforcapturerateshigherthanfpsEachofthemodelingstudiespresentedconsiderstheshouldertobeasinglemultiaxialjointThiswouldappeartobeatleastinpartduetothedifficultyofobtainingaccuratereadingsforthethreedimensionalpositionofthescapulaandclavicleTodate,accuratemeasurementofscapularpositioninghasinvolvedplacementofsubcutaneousbonepinsintothescapulathenrecordingtheirpositionviaXRayanalysis(McClure,etal)SuchatechniquewhilstaffordingforaccuratemeasurementofbonypositioniscurrentlyimpossibleinthecontextofanalysisofmaximaleffortthrowingmechanicsAccordingly,itneedstoberememberedthatwhilstmanystudiesrefertomodelingandpredictingforcesatthe‘shoulder’,theyarereferringtotheglenohumeral,acromioclavicular,sternoclavicular,andscapulothoracicjointsasiftheycomprisedasinglejointTodate,thereislittleinthewayofpublisheddataregardingforcesatindividualjointsduringthethrowingmotionMuchoftheworkregardingkineticsduringthethrowingmotionisusedtopredictpotentiallyinjuriousbehaviorForexample,itisshownthatduringthethrow,theamountofshoulderanteriorforcepeaksatapproximatelyN(Fleisig,)Seleckyetal()usedaforceofNtoNintheirmeasurementofpassivetranslationoftheheadofthehumerusontheglenoidofcadavericsubjectsasforcesgreaterthanN“…oftenledtomarkedjointsubluxationanddislocation”Itiscouldbeerroneouslyinferredthattheanteriorlydirectedforceduringthrowingisbeingborneentirelybytheglenohumeraljoint,andclinicalandsurgicaldecisionsThrowingmechanics,pathology,andperformance(suchasthestrengthrequiredofsurgicalrepairtowithstandtherigorsofthrowing)maybeextrapolatedfromsuchmistakenassertionsDuringmotioncapture,skinmarkersareroutinelyplacedoverbonyprominences,andthenthepositionofthesemarkersistrackedandplottedinthreedimensionalspaceswithaninferencethatthepositionofthemarkersisreflectingthepositionoftheunderlyingbonyprominencesTheaccuracyofsuchaninferencehasbeencalledintoquestion(Kardunaetal,)ThedatacapturedintheseanalysesisoftenusedtocreateaninversekineticmodelfromwhichestimationsaretheninferredregardingforcesandtorquesatindividualjointsUnfortunately,therewouldappeartobeaninherentinaccuracyinthesemodelswhich,maybebydefinitionunquantifiableWiththeselimitationsinmind,thereadershouldexercisecautioninanyinterpretationoftheresultspresentedWhereavailable,estimationsoftheinherenterrorsarepresented,unfortunatelysuchdataarenotroutinelyavailableDuringcompetitivebaseballpitchersareallowedtothrowfromthe‘set’or‘windup’positionsastheychooseInthesetposition,thethrowingmotionbeginswiththethrowerstandingwiththeipsilateral(tothethrowingarm)footincontactwiththepitchingrubber,andstridingtowardhomeplatewiththecontralaterallegThewinduppositionallowsforashortstridebackwardsoracross(withthelegcontralateraltothethrowingarm)beforestridingtowardhomeplateLittleworkhasbeendoneininvestigatingdifferencesbetweenthesetwotechniques,anditisrarelystatedwhichtechniquewasadoptedduringanalysisofpitchingdespiteawidelyheldbeliefthatthrowingfromthewinduppositionconfersgreaterperformanceAnexceptiontothiswastheworkofGroveetal()whodocumentedanincreasedpropensitytothrowstrikesinagamesituationforpitcherschoosingthesetposition(Groveetal,)Thisgroupwentontoanalyzethekinematicsofthrowingfromthesetwopositionsfindingthesetpositionusuallyinvolvedareductionintheamountofthighrotation,andamoreverticallyorientedlowerlegpositionItwasalsonotedthatthedirectionofthestrideshowedlessdeviationwhenthrowingacurveballfromasetpositionTheseworkerssuggestedthatpitchersmaybenefitbythrowingfromthesetpositionmoreoftenthanisusuallythecasewhendictatedbygamesituations(thesetpositioniscommonlyusedonlytolimitanybasestealingopportunitiesbytheopposition)Thispaperassumesknowledgeofdifferentpitchtypes(eg“fastball”and“curveball”)andthesewillnotbedescribedfurtherKinematicfactorsofthrowingrelatedtoinjuryandperformanceThereviewoftheliteraturerelatingthrowingmechanicstohealthandperformanceuncoveredworkinmanydifferingdirectionsThisreviewispresentedarbitrarilyinthefollowingorder:MechanicalaspectsFootpositionatStrideFootContactElbowflexionduringthrowingArmrotationduringthrowingArmhorizontalabductionduringthrowingArmabductionduringthrowingLeadkneepositionduringthrowingPelvicorientationduringthrowingDecelerationphaserelatedissuesCurveballsTeachingthrowingmechanicsMechanicalaspectsFootpositionatstridefootcontactFleisig()performedakinematicanalysisofthepitchingtechniqueofbaseballersandafterconsultationwithpitchingcoachesconsideredeightproposedmechanismsof‘impropermechanics’Byaccumulatingthisdata,FleisigwasabletodescribeaverageornormativevaluesforeachindividualparameterThepitchesofindividualswerethencomparedtotheaccumulatedmeansforeachoftheseparameters,andthekineticscalculatedtoestimatevariationsassociatedwith‘impropermechanics’ordeviationsfromthesemeansOftheoriginallyconsideredeightproposedmechanicalfaults,fourwerefoundtobeassociatedwithincreasedkineticsatcertainphasesofthepitchingmotion,includingthepositioningofthestridefootFleisig()documentedaveragestridefootplacementtobeofbodyheight(measuringestimatedcentreofthestrideanklejointbacktotheleadingedgeofthepitchingrubber)ThisstridewasdirectedtowardtheplatewithincmineitherdirectionincomparisontoalinedrawnfromthecentreofthetrailingankletothecentreofthehomeplateThestridefootwasfoundtobe‘closed’orpointingtowardthethrowingarmsideatanangleof°±°withreferencetothisline(seeFigureforanexplanationoftheseterms)ThosepitcherswhowerefoundtodeviatefromthesenormstowardopenfootpositionandalignmentshowedincreasedkineticsattheshoulderForeveryextracentimeterthestridefootlandstowardthe‘open’side,anextraNofmaximumshoulderanteriorforcewasfoundduringthearmcockingphaseFurther,ifthestridelegwasplacedatanopenfootangle,thistooincreasedthemaximumshoulderanteriorforceduringthecockingphaseatarateofNperdegreeofopenfootplacementToplacethisdataintosomecontext,themaximumshoulderanteriorforcefoundduringthearmcockingphasewasfoundtobeonaverageN,soifapitcherweretoplacetheirleadlegcmtowardtheopensideand°furtheropen,thenthiswouldbeassociatedwithaN(orapproximately)increaseinshoulderanteriorforceduringthearmcockingphaseInterestingly,thosepitcherswholandedinamore‘closed’position(intermsoffootangle,andplacement)hadnoincreaseinstressfulparametersdemonstratedDuringtheassessmentoftheinjuredthrowingathlete,aroutinefindingisreportedshoulderpainduringthearmcockingphaseofthrowing(AndrewsandFleisig,CurtisandDeshmukhMeister)ThiscanbeassociatedwithapositiveRelocationSign(Jobe,etal,),andithasbeensuggestedthatthisisindicativeofsubtleanteriorshoulderinstability(Hamneretal,)MatsenamongstothersbelievethattheprimaryWhiteleyrestraintstoshouldersubluxationatextremerangeofmotiontobetheligamentousstructures(Matsenetal,)ItwouldfollowthenthatanyincreaseintheamountofshoulderanteriorforceduringthearmcockingphasecouldbedirectlyassociatedwithpathologyattheligamentousrestraintssuchasincreasinganteriorshoulderinstabilityFigureCalculationofstridelength,strideoffset,andleadfootangleatthemomentofstridefootcontactDistance'A'measuresthelengthfromcentreofthetrailingankletothecentreoftheleadankleDistance'B'measuresthedistancefromtheleadingedgeofthepitchingrubbertothecentreoftheleadankleDistance'C'measurestheoffsetofthecentreoftheleadanklefromalinedrawnfromthecentreofthetrailinganklethroughtothecentreofthetarget(homeplate)Positivevaluesbeingonthenonthrowingarm,or'open'sidewithourexampleshowingapositivevalueAngleTheta(Ө)measurestheanglem

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