*Author ([email protected]) for correspondence Avenue, Cambridge, MA02138,USA. Washington University, 2110GStreetNW, Washington, DC20052,USA. © 2014.PublishedbyTheCompanyofBiologistsLtd|JournalExperimentalBiology(2014)217,2139-2149doi:10.1242/jeb.103275 Received 31January 2014;Accepted17March2014 2 1 al., 1995;Hirashimaet2007;2008;Hong et al., motions areprimarilyresponsible(Dillmanetal.,1993;Fleisig et projectile velocities,andwhichjointsjoint-specificangular considerable inquiryintohowthiscomplexmotiongenerates high throwing handastheprojectileisreleased.Therehas been quickly upthetrunkandarm,endingwithrapidmovementof the stereotypic, whip-likemotioninvolvingthewholebody. purpose, high-speedoverhandthrowsareproducedusing a against predators,andaggressiveinteractions.Regardlessof their in thepastthrowingwasprobablycrucialforhunting,defense velocity. Today, mosthigh-speed throwingoccursduringsports,but ability tothrowobjectsoverhandwithbothaccuracyandhigh human shouldermaybesodifferent isselectionforhumans’ unique earlier hominins(Larson,1993;Larson,2007).Onereasonthe The humanforelimbisderivedrelativetootherhominoidsand Kinetic chain,Humanevolution KEY WORDS:Throwing,Biomechanics,Elasticenergystorage, first developedtheabilitytoproducehigh-speedthrows. insight intotheevolutionofupperbodyandwhenourancestors help explainsomecommonthrowinginjuriesandcanprovidefurther data alsosuggestthatheavyrelianceonelasticenergystoragemay hyperextension enhancesperformanceonlymodestly. Together, our larger proximalsegments,suchastheshoulderandtorso.Wrist the powergeneratedtoproducethesedistalmovementscomesfrom velocities attheelbowandwrist,restrictionsconfirmthatmuchof power therapidaccelerationofprojectile.Despiteangular pectoralis major)isusedtoloadelasticelementsintheshoulderand and muchofthiswork(combinedwithsmallercontributionsfromthe most oftheworkproducedduringthrowingisgeneratedathips, generation atkeyjointsduringthethrowingmotion.We foundthat braces thatinhibitspecificmotionstotestamodelofpower of kinematicdatafrom20baseballplayersfittedwithfourdifferent are notcompletelyunderstood.We usedinversedynamicsanalyses segments. However, thebiomechanicalbasesofthesemechanisms transfer ofkineticenergyfromproximalbodysegmentstodistal combination ofelasticenergystorageattheshoulder, aswellthe Achieving fastprojectilespeedsduringthrowingrequiresa High-speed andaccuratethrowingisadistinctivehumanbehavior. Neil T. Roach overhand throwinginhumans Upper bodycontributionstopowergenerationduringrapid, RESEARCH ARTICLE INTRODUCTION ABSTRACT Department of Human Evolutionary Biology, HumanEvolutionary University, of Harvard Department 11Divinity HominidPaleobiology,Center for the Advanced Study of The George The throwbeginswithmovementofthelegsandprogresses 1,2, * andDanielE.Lieberman 2 However, likeallkineticanalyses, thesestudiesestimated onlythe (Alexander, 1991;Atwater, 1979;Feltner, 1989;Putnam,1993). producing veryrapid,‘whip-like’ accelerations ofthearmandhand as thehips,torsoandshoulder) istransferredtothethrowingarm, the hypothesisthatpowergenerated atmoreproximaljoints(such forces generatedbyelbowextension. Thesedatastronglysupport flexion duringthrowingismostly drivenbyvelocity-dependent (Hirashima etal.,2008).Thesamestudyalsofoundthat wrist forces generatedbytorsorotationandshoulderinternal extension duringthrowingisdrivenprimarilybyvelocity-dependent analyses oftheseinteractiontorquesfurthershowthatelbow et al.,2003;Hong2001;Putnam,1993).Inducedacceleration interaction torques(Feltner, 1989;Hirashima etal.,2007;Hirashima at theelbowandwristjointsreleasearelargely duetothese equations ofmotionhasshownthathighangularvelocitiesobserved Mathematical decompositionofthrowingkinematics using dependent, centrifugalorCoriolisforces(Hirashimaetal.,2008). directly frommuscularactionsatotherjointsorvelocity- Ben KiblerandSciascia,2004).Theseinteractiontorquescan result 1979; Fleisigetal.,1996;Hirashima2008;Hore2005; can betransferredfromjointtoviaa‘kineticchain’ (Atwater, movements generatedinadjacent,connectedbodysegments,which to powerlarge angularvelocitiesduringthrowingcomefrom force production(Bell,1993;Gans,1992). lack ofanysimplerelationshipbetweenEMGintensityandmuscle the rolesofmusclesingeneratingtorquesupperbodyis (Roach etal.,2013).A furtherproblem withusingEMGtoevaluate generate approximately50%ofthepowerforthisrapidmotion experimental dataonshoulderpowershowthatthesemusclesonly internal rotation(DiGiovineetal.,1992;Gowan1987), shoulder internalrotatormusclesindicatehighactivityduring its own(Roberts,1971).Inaddition,althoughEMGrecordingsof indicating thatthetricepsdoesnotpowerrapidelbowextensionon brachii canstillachieverapidelbowextensionduringthrowing, generated. Forexample,anindividualwithaparalyzedtriceps patterns alonecannotfullyexplainhowthrowingpoweris motion (Hirashimaetal.,2002).However, muscleactivation activation ofmusclesmirroringtheprogressionthrowing patterns ofmuscleactivityduringthrowingshowsequential and angularvelocity. Asexpected,electromyography(EMG) most torquesandarethuskeycontributorstojointpowerproduction generating mechanicalworkandpower. Musclesarethesourceof velocities areproducedintheupperbody. Pappas etal.,1985).Thisstudyfocusesonhowtheselarge angular (Fleisig etal.,1995;Fleisig1996;Hirashima2007; 1) of releaseandsignificantlycontributetoprojectilespeed(Fig. rotation, elbowextensionandwristflexionalloccuratthemoment that large angularvelocitiesoftorsorotation,shoulderinternal 2001; Pappasetal.,1985;Putnam,1993).Previousworkhasshown Previous researchhassuggestedthatadditionalsourcesoftorque Angular movementsareproducedwhentorquesactacrossjoints, 2139
The Journal of Experimental Biology 2140 They areinstead designedtoinducemodestperturbations thathelp movements, asthiswouldmake throwingdifficult orimpossible. Note thatthesebracesarenot intendedtofullyremovethese or modifyjointpositiontoinduce variationinthrowingkinematics. We usedtherapeuticbracesthatlimitjointrangeofmotion (ROM) 2). shoulder internalrotation,elbow extensionandwristflexion;Fig. hypothesized toberesponsible forprojectilespeed(torsorotation, during throwingbyexperimentallymanipulatingfourkeymotions throwing motion. kinetic transferandelasticenergy storageinteractandpowerthe restrictions allowustonon-invasivelyexaminehowmuscular force, perturbations ofthethrowingmotionusingtherapeuticbraces.These study combinesinversedynamicsanalysiswithexperimental methodologies, suchassonomicrometry. Accordingly, thepresent 1982; Pourcelotetal.,2005)andtheinabilitytouseinvasive measurements (Finnietal.,2000;Komi1987;Lewis et al., complicated bythedifficulty ofcollectingdirectstrain the workingsofsuchamplificationmechanismsinhumans is Anderson andPandy, 1993;KomiandBosco,1978),understanding is wellknownandstudiedinthehumanlowerlimb(e.g. rotation ofthehumerusthatfollows.Althoughpoweramplification elastic energy beingstoredandreleased,poweringtherapidinternal inferred thatpassivestretchingresultsinsignificantamountsof maximum powervaluesforallmusclespotentiallyinvolved,they comparing actualpowerproductionduringthrowingtomodeled passively stretcheselasticelementscrossingtheshoulder. By rotated) justpriortotherapidshoulderinternalrotationmotion et al.,2013)foundthatthepostureof‘cocked’ arm(externally energy storageinthemuscleitself.Inaddition,Roachetal.(Roach throwing musclesjustpriortotheiractivation,resultinginelastic athletes enhancetorqueproductionby‘pre-stretching’ numerous throwing. Wilk etal.(Wilk etal.,1993)argued thatthrowing elastic energy alsoplaysaroleinpowerenhancementduring mechanisms. produced byparticularmusclesorelasticenergy storage internal/external rotation)withoutmeasuringhowmuchenergy was contributions ofjointrotationalmotions(i.e.shoulder RESEARCH ARTICLE Here, wetesthowtheupperbodycontributestopowergeneration Several studieshavesuggestedthatthestorageandreleaseof Shoulder externalrotation End ofstride Elbow flexion Arm-cocking phase Shoulder extension Maximum externalrotation Torso rotation Shoulder internalrotation Wrist extension Elbow extension Acceleration phase Shoulder flexion Release found solelyinextinctfossiltaxa. Sugiyama andKoman,1979)intermediatemorphologiesare different kinematics(Goodall,1964;Goodall,1986;Kohler, 1925; joint positionsandROM,asapesthrowpoorlywithvery recreate evolutionarilyrelevantchimpanzee-likeandhominin-like have comparable,highskilllevels.Thebracesusedalsoservedto associated withperformanceinastudygroupwhereallindividuals restrictions allowedustotesttheeffects ofmorphologicalvariations upon theothercriticalmotionsinupperbody. Further, these illuminate theeffects eachmotionhasonoverallperformanceand shoulder andflexing theelbowastorsorotation reachesitspeak Roach etal.(Roachal.,2013) proposedthatbyabductingthe vertebrae andnotatthehips. because wearelimitingrotational motiononlybetweenthe and work.Thesereductions,however, are expectedtobemodest significantly reducetorsorotationangularvelocity, torque,power most torso/pelvicrotationwilloccuratthehip.Thisshould therefore predictthatbylimitingintervertebralrotationwithabrace, power asthebodyisvaultedoverlegsduringthrow. We extensor musclesinthethighsmayalsoincreasepelvicrotation respectively. Additionalcontributionsfromthelarge hipflexor and throwing motionatthecontralateralandipsilateral hips, piriformis andsartorius)canbeactiveatthesametimeduring the maximus, quadratusfemoris,bothgemelli,obturators, and tensorfasciaelatae)thelateralhiprotators(gluteus together. Boththemedialhiprotators(gluteusmediusandminimus, the large hiprotatorspowertherapidrotationoftorsoandpelvis through bilateralcontractionoftheintrinsicspinalrotatormuscles, 2004). We proposethatbystabilizingthetorsorelativetopelvis performance (Matsuoetal.,2001;StoddenWight etal., component ofthethrowingmotionthatcorrelateswith Previous studieshaveshownthathiprotationisanimportant energy attheshoulder Hypothesis 2:torsorotationprimarily powersthestorageofelastic torso rotationpowerduringthrowing Hypothesis 1:thehiprotatormusclesgeneratemajorityof Hypotheses timing of‘acceleration’ motions. timing of‘cocking’ motions,whilethedarkgraybarsindicate with thereleaseofprojectile.Lightgraybarsindicaterelative rotates, theelbowextendsandwristisflexed.Accelerationends acceleration phaseoccursinwhichthehumerusrapidlyinternally external rotation.Followingmaximumrotation,theverybrief phase, thehumerusexternallyrotatesuntilitreachesmaximum the endofalargestrideintargetdirection.Duringcocking Arm cockingbeginswiththecontralateralfoottouchinggroundat Fig.
.Thearm-cockingandaccelerationphasesofthethrow. 1. The JournalofExperimentalBiology(2014)doi:10.1242/jeb.103275
The Journal of Experimental Biology RESEARCH ARTICLE more passivedistal joints(elbowandwrist). shoulder) willcausesignificant decreasesinangularvelocity predict thatbracesrestrictingmore activeproximaljoints(torsoand al., 2003;Hirashimaet2008; Putnam,1993).We therefore proximal joints(Feltner, 1989;Hirashimaetal.,2007; derived fromthekinetictransfer ofpowergeneratedatmore to achieverapidangularmovements intheelbowandwristare Previous researchhassuggestedthattheworkandpowernecessary acceleration. rotation angularvelocity, torque,powerandworkduring done attheshoulderduringcocking,andthusreduce that thiswillsignificantlyreducetheamountofnegative work cranially rotatingthep.major’s majorlineofaction.We expect abduct theshouldershouldcauseasuboptimalrealignment by cross theshoulder. We thereforepredictthatusingabrace to the forelimb’s masstolag,thusstretchingelasticelementsthat around thesameshoulderaxisastorsorotationtorque,causing shoulder, thep.major, willalsogeneratesubstantialtorque et al.,1993),muscularactionbythelargest horizontalflexorofthe We proposethatwhentheforelimbismaximallycocked(Dillman during acceleration. reduce shoulderrotationangularvelocity, torque,powerandwork phase. Thisreductioninshoulderrotationworkshouldfurther amount ofnegativeworkdoneattheshoulderduringcocking predict thatusingabracetolimittorsorotationwillreducethe 2008a; Miyashitaetal.,2008b;Roach2013).We therefore external rotatormusclesandintothepassiverange(Miyashitaetal., rotation oftheshoulderbeyondactiveROMachievedby to lagbehindtheacceleratingtorso.Thiscausesfurtherexternal shoulder, increasingitsmomentofinertia,andcausingtheforelimb angular velocity, theforelimb’s massispositionedawayfromthe the throwarelargelygeneratedpassively Hypothesis 4:rapidelbowextensionandwristflexionattheend of energy attheshoulder Hypothesis 3:thepectoralismajoralsopowersstorageofelastic CD A Flexion (+) Towards target(+) Away fromtarget(–) Extension (–) External (–) B Extension (–) Flexion (+) Internal (+) (848±160 3).Theangularvelocityoftorsorotationpeaked (Fig. there waslittlevariationinkinematicpatternsacrosssubjects performance andthetimingdurationofthrowingphases, While considerablevariationexistsbetweensubjectsinoverall striking thetarget onaverage 0.3±0.2 27.7±3.8 During normalthrowing,themaximumballspeedwas shoulder internalrotationangularvelocitiesandwork. significant reductionsinwristflexion,elbowextension,and the durationoffinalaccelerationphasethrow, aswell restrict wristhyperextension,therewillbeasignificantdecreasein release trajectory. We thereforepredictthatwhenabraceisusedto continue toacceleratepriorreleaseandstillachieveanaccurate enable othermoreproximaljointactions(e.g.elbowflexion)to al., 1995;Hirashimaet2007).Thiswristhyperextensioncould rapidly flexesasthearmacceleratestowardstarget (Fleisiget while thearmiscocking,wristslowlyhyperextendsandthen Kinematic dataontheoverhandthrowingmotionhaveshownthat of negativework( opposing internalrotationtorque. Thisresultedinasustainedperiod was externallyrotatedwhilesimultaneouslygeneratinga large ( absorption duringacceleration,generatingnetnegative work phase. Thisopposingtorqueresultedinashortperiodofpower producing anopposingbrakingtorqueduringthebriefacceleration peak power(11,838±4170 Normal unrestricted Normal RESULTS elbow extensionmotionstoattainhigherangularvelocities the throwingmotion,enablingshoulderinternalrotationand Hypothesis 5:wristhyperextensionallowsreleasetooccurlaterin resulting inveryhighangular velocities (4290±1127 shoulder rotationtorqueand angular velocitybecamein-phase, phase beganwiththeinitiation ofinternalshoulderrotation,the cocking phase began andasamoderate flexion torquewas − 74±44 description isrelativetothethrowingside. rotation sensesaredependentuponhandedness,asthe directionality oftheangularvelocitiesandtorques.Note:torso in thediagramshowconventionusedtodescribe flexion/extension; (D)wristflexion/extension.The+and–senses study. Fig. J). Duringthecockingphaseatshoulder, thehumerus m deg
The JournalofExperimentalBiology(2014)doi:10.1242/jeb.103275 s
.Thefourcriticalupperbodymotionsexaminedinthis 2. − 1 s (A) Torso rotation;(B)shoulder(C)elbow − (mean ±s.d.ofallsubjectmeans),withtheball 1 ) duringthelatterhalfofcockingphase,before − 201±70 W). Theelbowcontinuedtoflex asthe J) attheshoulder. Astheacceleration
m fromthecenterorbullseye.
deg s − 1 2141 ) and
The Journal of Experimental Biology limited scapular protraction.Theclavicle sham producedno 2142 The claviclebracecraniallyrotated thescapula7±4 velocity ortorque(T were nosignificantreductionsintorsorotationpeakpower, angular brace, noshamconditionwaspossible.Contrarytoexpectations, there only thehiprotatorstorotatetrunk.Givendesignof torso intervertebral rotationbetweentheclaviclesandpelvis,allowing The torsorestrictionbraceprovidednear-complete restrictionof elbow begantoextendrapidly(–2434±552 produced. However, duringthelastquarterofcockingphase RESEARCH ARTICLE (1±2 oscillating powergeneratedasmall,netpositiveamountofwork near zeroandagainincreasedduringtheaccelerationphase.This 7±3 acceleration phase.A smallflexion momentwasproduced(peak: when thewristbegantorapidlyflex,continuingthrough sustained extensionoccurreduntiltheveryendofcockingphase, large amountsofnegativework( the opposingflexionmomentatelbowintensified,resultingin midway throughtheaccelerationphase.Duringthisrapidextension, Clavicle restriction Torso restriction ( expected, thereweresignificantreductionsinshoulderrotationpower torso rotationworkduringcocking( velocity ( P ball speeddroppedmoderately( hypothesized, whenthetorsorestriction bracewasapplied,maximum velocity, torque,powerorworkweremeasuredatthewrist. As − =0.004). A reductionalsooccurredinelbowextensionpeakangular
14±20%, Wrist Elbow Shoulder Torso –3000 –2000 –1000 2000 4000 1000 2000 Nm) attheendofcockingphase,whichthendroppedto 200 400 600 800 J) duringtheaccelerationphase. 0 0 STR STR STR STR 0 Angular velocity(degs 0 − Internal rotation(+) 6±7%, P Extension (–) =0.012), andworkduringthecockingphase( Flexion (+) 50% 50% 50% 50% P be1). able =0.001). Nosignificantreductionsinangular MER REL MER REL MER REL MER REL –1 However, therewasasignificantdropin –800 –400 Torque (Nm) ) 100 200 100 200 300 400 400 800 0 –2 STR STR STR STR 0 0 2 4 6 − 0 5±6%, − 246±63 Away fromtarget(–) Towards target(+) External rotation(–) Extension (–) Flexion (+) P − <0.001). 50% 50% 50% 50% 11±18%, J). Finally, atthewrist,a
deg MER REL MER REL MER REL MER REL P s
deg andalso − –12,000 =0.005). As 12,000 1 –4000 –8000 –4000 –4000 ), peaking 4000 8000 4000 8000 –100 100 200 STR STR STR STR 0 − 0 0 0 8±11%, oe W Work (J) Power (W) 50% 50% 50% 50% lengthened (38±56%, shortened (− ( reduction inmaximumball speed relativetotheshamtrials restriction wasemployed.The restrictedtrialscausedan8±6% condition, afurthersignificant reductionoccurredwhenthe P shortening ofthedurationaccelerationphase(6±10%, during thecockingphase( maximum ballspeed( During theshamtrials,therewerealsoslightreductionsin mean 11±7 However, theshoulderbracealsorestricted externalrotationby The shoulderbracereducedexternalrotationby24±9 duration (cocking reductions in:meanmaximumballspeed( perturbation ofthenormalthrowingmotionasevidentfrom 2)indicatesome However, datafromtheshamtrials(Table significant effects onjointmotionrelativetotheunbracedcondition. elbow extensionworkacceleration( P Shoulder restriction performance. No statisticallysignificantchangeswereobservedin wrist dropped by8±13%(P recorded relativetonormalvalues.Elbowworkduringacceleration P ( was added,maximumballspeeddroppedbyafurther3±6% rotation angularvelocity( rotation workacceleration( P P 005 al 3).Foreachsignificant changeinthesham =0.045; Table =0.010), torsorotationworkacceleration( <0.001) andworkduringcocking( <0.001). Thedurationofthecocking phaseoftherestrictedtrials =0.031). Reductionsinshoulderrotationpeaktorque( MER REL MER REL MER REL deg intheshamcondition,muchlikewearingatightjacket. MER REL –300 –200 –100 –200 200 200 400 600 The JournalofExperimentalBiology(2014)doi:10.1242/jeb.103275 0 0 0 2 0 1 9±14%, CA CA CA CA − 12±27%, − P <0.001) relativetothereducedshamvalues. 3±5%, P =0.013). Reductions intorsorotationwork =0.032), whiletheacceleration phase − throw. times relativetothenormalizedphasesof peak performanceoccurringatslightlydifferent Tables differ frommeanpeakvaluesreportedin the workplots.Note:peakvaluesshownhere (REL)] isshowninagrayfieldandlabeledA in acceleration phase[betweenMERandrelease labeled Cintheworkplots,while rotation (MER)]isshowninthewhitefieldand [between stride(STR)andmaximumexternal phase durationratio.Thearm-cocking proportional tothemeannormal,unrestricted length ratioofthetwophaseswaskept sampling eachthrowtoastandardlength.The each phase1000-foldandsubsequentlydown- individuals werestandardizedbyinterpolating lines. Differences inphasetimingbetween confidence intervalsareshownasdashed means areshownasboldlines,while95% throwing. the fourcriticaljointaxesduringnormal Fig. 11±12%,
.Jointkinematicandkineticdatafrom 3. − P −
56±25%, 1–4. Thisresultsfromeachsubject’s =0.026) andshoulderrotationwork P 9±13%, =0.028; acceleration Mean dataofallindividualsubject P − 10±17%, <0.001). Whentherestriction − P 9±10%, − P <0.001), andaslight 3±5%, <0.001) andshoulder − 42±42%, P <0.001), shoulder P P =0.029), phase =0.002) were − − P 16±27%, 13±31%, <0.001),
deg.
The Journal of Experimental Biology Shoulder rotation(+internal,–external) RESEARCH ARTICLE ( from shamconditions,while shoulderrotationpeakpower shoulder rotationpeakangularvelocity droppedby6±8%(P were notsignificantlydifferent fromtheshamcondition.Restricted ball speedandphasedurationfromnormalvalues,thesereductions Although therestrictedconditionproducedsignificantreductions in 4). reductions inthemeasuredperformancevariables(Table the wristrestrictionshamtrialsshowednumeroussignificant there wasnosignificantreductionintheshamcondition.However, The wristbracereducedextensionROMby62±7 were recordedforbothphases(cocking values, whileitalicvaluesindicateunexpectedchanges. that mettheP Given thatnoshamwaspossibleforthiscondition,restrictedvaluesstatisticallydiffer withasterisks(* fromnormal valuesareindicated Wrist flexion/extension(+flexion,–extension) Elbow flexion/extension(+flexion,–extension) Torso rotation(+throwarmtowardstarget,–awayfromtarget) Timing Performance measure Table Performance Wrist restriction reductions inelbowextensionangularvelocity( or workduringacceleration.Aspredicted,thereweresignificant occurred inshoulderrotationpeakangularvelocity, torque,power P during thecockingphasedroppedsignificantly( acceleration dropped by34±37% (P ( Restricted elbowworkduring accelerationdroppedby19±14% dropped relativetonormaland increasedrelativetoshamtrials. and elbowworkduringacceleration( acceleration phase( followed byasignificantincreaseinwristworkduring the reduction inwristworkduringthecockingphase( flexion peakangularvelocityremainedunchanged,butasignificant P P <0.001) fromnormalvalues,nofurthersignificantreductions Work –acceleration(J) ekpwr()22±93 2473±4498 357±121 2±27 2028±3983 392±116 Work –cocking(J) Peak power(W) Peak torque(Nm) Peak power(W) Peak angularvelocity(deg Work –acceleration(J) Peak angularvelocity(deg Peak angularvelocity(deg Work –cocking(J) Peak power(W) Peak torque(Nm) Peak angularvelocity(deg Duration ofacceleration(ms) Duration ofcocking(ms) Accuracy (mfrombullseye) Peak torque(Nm) Peak torque(Nm) Work –acceleration(J) Work –cocking(J) Work –acceleration(J) Work –cocking(J) Peak power(W) Max. ballspeed(m <0.001) fromshamlevels.The wrist flexionpeakangularvelocity <0.001) andworkduringacceleration values(
1. Kinematicandkineticperformancemeasuresforthefourcriticaljointaxesduringnormaltorsorestrictionconditions <0.05 threshold but did not survive multiple testing correction are indicated with §. Bold values indicate hypothesized reductions fromnormal <0.05 thresholdbutdidnotsurvivemultipletestingcorrectionareindicatedwith§.Boldvaluesindicatehypothesizedreductions − 41±57%,
s P − 1 =0.003). ) P <0.001) relative totheshamtrials,while
<0.001). Althoughshoulderrotationwork s s s s − − − − 1 1 1 1 ) ) ) ) − 20±21%, − − 14±20%, 21±10%, P P <0.001). Wrist P <0.001) both =0.020) was − P P 45±17%,
deg, but =0.006; <0.001) <0.001) 40±12 132±52 Normal 206±42 387±182 0.3±0.2 − 138±90 7±3 828±437 1±2 11,838±4170 27.7±3.8 1593±336 − 4290±1127 848±160 0.2±1 609±171 6207±2190 − − 246±63 2434±552 201±70 74±44 ( substantial ( torso rotationworkduringthecockingphasemaybedriven bya al., 2001;StoddenetWight etal., 2004).Thereductionin achieve highprojectilevelocityisgeneratedatthehips(Matsuo et that duringnormalthrowing,most(~90%)oftheworkrequired to and allothermeasuresremainedunchanged.Thisresultsuggests rotation workdecreasedsignificantlyonlyduringthecockingphase However, despitetherestrictionofintervertebralmotion,torso the vertebrae,measuresofthrowingperformancewoulddecrease. We proposed(H1)thatbyrestrictingrotationalmovementbetween acceleration ( wrist flexion/extensionpeakpower( rotation performance. Thedatafromthetorso restrictiontrials energy storageand,consequently, large reductionsin shoulder reductions intorsorotationperformance shouldresultinlesselastic storage mechanismattheshoulder (Roachetal.,2013),evenminor hypothesized (H2)thatiftorso rotationhelpspowertheelastic torso, theeffects ofthisbraceareamplifiedattheshoulder. We significant reductionsinangular velocity, torqueandpower atthe power. necessary todeterminewhichhiprotatormusclesgenerate this torso rotationworkperformedsuggestsotherwise.Furtherstudy is similar changesinphasedurationwithoutaffecting theamountof Hypothesis testing DISCUSSION P Although thetorsorestrictioncausedmostlyminor, non- =0.006). However, thefactthatotherbrace conditionsresultin The JournalofExperimentalBiology(2014)doi:10.1242/jeb.103275 − P 19±22%) reductioninthedurationofthisphase <0.001) increasedrelativetotheshamtrials. 37±12 Torso restriction 0.4±0.3 –218±53 155±109 6±3 − –2284±582 0.3±1 100±56 –184±73 9872±4005 178±42 303±122 26.3±4* 1645±280 3970±1226 835±158 − 773±424 536±149* 5968±2166 1±2 1±22 79±40 § § * * * * § P <0.001) andworkduring P <0.05); values 2143
The Journal of Experimental Biology Torso rotation(+throwarmtowardstarget,–awayfromtarget) hypothesized reductionsfromnormalvalues,whileitalicvaluesindicateunexpectedchanges. 2144 limiting scapular protractionatrelease.Whilereductions inshoulder the unloadedbracedidcause somerestriction,potentiallyby significant changesinperformance duringshamtrialssuggestthat shoulder. Althoughtheshamhadnoeffect onstaticshoulderROM, contributions fromtheinferior fiberstohorizontalflexionatthe change thismuscle’s majorlineofaction,effectively excluding shoulder complexinasuperiorly abductedposition,wesoughtto elastic energy storageatthe shoulder isthep.major. Byholding the the shoulderduringarm-cockingphase. torso rotationsignificantlycontributestoelasticenergy storagein results thereforeprovideadditionalsupportforthehypothesis that generated fortherapidinternalrotationofshoulder. These estimate thatthehiprotatorsaccountfor~30%ofpower/work dynamics inducedaccelerationdata(Hirashimaetal.,2008), we hips todownstreammotions,andcombiningourdatawithforward reductions thebracescausedreflectoverallcontributionof the velocity andpowerareachieved.Byassumingthattheperformance acceleration phasedurationwhenpeakshoulderrotationangular measures makethisunlikely. Furthermore,nochangeisseenin conditions inwhichthisphaseshortenedwithoutaffecting these again bepartlyresponsibleforthesechanges,datafromother the cockingphase.Whileareductioninphasedurationmay shoulder rotationpoweraccompanythisreductioninworkduring than 10%duringthetorsobracetrials.Furtherreductionsin cocking phase,aproxyforelasticenergy storage,decreasedbymore support thishypothesis.Negativeshoulderrotationworkduringthe the shamareshownwith‡.Values thatmetthe Restricted andshamvaluesthatstatisticallydiffer fromnormalvaluesareindicatedwithasterisks (* Wrist flexion/extension(+flexion,–extension) Timing Performance measure RESEARCH ARTICLE conditions Table Performance Elbow flexion/extension(+flexion,–extension) Shoulder rotation(+internal,–external) Peak angularvelocity(deg Peak power(W) Duration ofacceleration(ms) Work –acceleration(J) Work –cocking(J) Peak torque(Nm) Work –cocking(J) Peak power(W) Peak torque(Nm) Peak angularvelocity(deg Work –acceleration(J) Work –cocking(J) Peak power(W) Peak torque(Nm) Work –acceleration(J) Work –cocking(J) Peak power(W) Duration ofcocking(ms) Accuracy (mfrombullseye) Work –acceleration(J) Max. ballspeed(m Peak angularvelocity(deg Peak angularvelocity(deg Peak torque(Nm) The secondarysourceofpowerproposed(H3)tocontribute to 2. Kinematicandkineticperformancemeasuresforthefourcriticaljointaxesduringnormalclaviclebracerestriction
s − 1 )
s s s s − − − − 1 1 1 1 ) ) ) ) P <0.05 thresholdbutdidnotsurvivemultipletestingcorrectionareindicatedwith§.Boldvaluesindicate 40±12 1±2 138±90 7±3 828±437 Normal 392±116 132±52 0.2±1 609±171 6207±2190 2±27 2028±3983 27.7±3.8 1593±336 1505±255 − 4290±1127 848±160 862±144 870±155 206±42 − − 11,838±4170 387±182 − 0.3±0.2 2434±552 246±63 201±70 74±44 motion tobemore easily, effectively andconsistently produced. throwing poses.Suchreducedcomplexity wouldallowthethrowing wrist couldsimplifythedifficult neuralcontrolproblemthat rapid having multiplepassivecomponents intheshoulder, elbowand flexors ispossible.Giventhe brevityoftheaccelerationphase, at thewristsuggeststhatsome compensatoryactionbythewrist apply tothewrist,although lackofresponsetotherestrictions Hirashima etal.,2008;Putnam,1993).Thiskineticchainmay also transfer fromupstreamjoints(Feltner, 1989; Hirashimaetal.,2007; evidence thattheelbowislikelypoweredprimarilybykinetic seen attheelbow, butnotthewrist.Thesedatareinforceprevious rotation) wereaffected, significant performancereductionswere shoulder) inwhichproximaljointactions(torsoand/orshoulder Furthermore, whenexaminingallconditions(torso,clavicle and by passiveforcestransmittedfrommoreproximaljoints. are generatedlessbymusclescrossingeachdistaljoint,butrather either lowornegativeattheelbow. Thissuggeststhatbothmotions acceleration phasesofanormalthrowisverylowatthewrist and measures. superior rotationtoyieldalarge enougheffect ontheseperformance partially supported.Itispossiblethatthebracecausedtoolittle power andworkduringacceleration)leavesthishypothesisonly other performancemeasures(e.g.shoulderrotationangularvelocity, elastic elementsintheshoulder, thelackofsignificantshiftsin during accelerationconfirmtheroleofp.majorinloading rotation torqueandworkduringcockingelbowextension As hypothesized(H4),workduringboththecockingand The JournalofExperimentalBiology(2014)doi:10.1242/jeb.103275 P <0.05), whilerestrictedvaluesthatstatisticallydiffer from 6869±2617 1±1 113±80 6±2 580±167 631±1050 Clavicle sham 357±80 0.4±1 638±177 32±9* 4±21 27±4.2* − 180±38 –225±58 − 8431±4455 300±72* 54±35 –109±53 3852±1175 0.4±0.2 2326±517 188±60 * * * * § 6492±2159 630±1064 Clavicle restriction 1±1 107±73 6±2 588±240 336±84 0.3±1 607±174 34±11 5±22 –2220±517 –173±63 306±93 26.3±4.1 8958±4552 1510±276 –206±59 58±32 –107±63 3778±1126 169±37 0.4±0.2 * * § * ,‡ * * * * ,‡ ,‡ ,‡ * § §
The Journal of Experimental Biology RESEARCH ARTICLE the sham are shown with ‡. Bold values indicate hypothesized reductions from normal values, while italic values indicate unexpected changes. the shamareshownwith‡.Boldvaluesindicatehypothesizedreductionsfromnormalvalues,whileitalicunexpected Restricted andshamvaluesthatstatisticallydiffer fromnormalvaluesareindicatedwithasterisks (* Wrist flexion/extension(+flexion,–extension) Shoulder rotation(+internal,–external) Torso rotation(+throwarmtowardstarget,–awayfromtarget) Performance Performance measure conditions Table angular velocity, elbowextensionworkacceleration, andwrist effects relativetothewristshamwhereexpected(shoulder rotation finely tunedforpassiveaction. of inertiaduringthecriticalcocking phaseanddisruptasystem a changeinmasscouldsignificantly increasetheforelimb’s moment projectile ordistalforearmmass. Without posturaladjustments,such mechanism attheshouldercouldbequitesensitivetochanges in ball atthehand.Theseshamresultssuggestthatelasticstorage additional massmorethandoublesthepreviouslyaddedof the forelimb. Althoughthemassofbracewasonly~165 trials wereduetotheadditionofbrace’s masstothedistal Alternatively, itispossiblethattheeffects seenduringthe sham between braceandnon-braceconditions,whichwasnotthe case. proprioceptive perturbationtoalsoresultindifferences inaccuracy performance reductions.However, we would expectamajor at thehandandwrist,resultingintimingchangesacascade of possible thattheadditionofbraceitselfalteredproprioception measurable effect ofwrist ROM wasnotedwiththesham,itis segments analyzedduringthewristshamcondition.Giventhatno and severe.Significantperformancereductionswereseeninall conditions, theperformanceeffects ofthewristshamwerepervasive the shamtrials.Infact,unlikeresponsestootherbrace’s sham to thenormalcondition,thisreductiondoesnotdiffer fromthatof restriction didreducethedurationofaccelerationphaserelative of theproximaljointspriortorelease.Althoughwristbrace throwers todelayprojectilerelease,enablingadditionalacceleration Elbow flexion/extension(+flexion,–extension) Timing Peak power(W) Work –cocking(J) Peak power(W) Peak torque(Nm) Work –acceleration(J) Work –cocking(J) Peak power(W) Work –cocking(J) Peak torque(Nm) Work –cocking(J) Peak power(W) Peak torque(Nm) Work –acceleration(J) Peak angularvelocity(deg Peak torque(Nm) Work –acceleration(J) Peak angularvelocity(deg Work –acceleration(J) Peak angularvelocity(deg Duration ofacceleration(ms) Accuracy (mfrombullseye) Max. ballspeed(m Peak angularvelocity(deg Duration ofcocking(ms) The wristbracerestrictiondid causesignificantperformance We alsohypothesized(H5)thatwristhyperextensionallows
3. Kinematicandkineticperformancemeasuresforthefourcriticaljointaxesduringnormalshoulderbracerestriction
s − 1 )
s s s s − − − − 1 1 1 1 ) ) ) )
g, this 828±437 40±12 138±90 7±3 206±42 609±171 6207±2190 Normal 132±52 0.2±1 11,838±4170 − 2028±3983 27.7±3.8 − 1593±336 − 4290±1127 848±160 2±27 392±116 − 1±2 387±182 0.3±0.2 246±63 201±70 2434±552 74±44 for minortomoderate disruptionsoftheirnormal throwingmotion. ability ofthesubjects–allaccomplished throwers–tocompensate were relativelyminor(0.5–9%). Suchminorreductionshighlightthe speed relativetoboththeirsham andnormaltrials,thesereductions restrictions (exceptforthewrist) ledtosignificantreductionsinball 2007; Hirashimaetal.,2008). Additionally, althoughall brace contributions toprojectilevelocity areminimal(Hirashimaetal., only fromtheupperbody, aspreviousstudieshaveshownthatleg underlying mechanismsofpowergeneration.We alsocollecteddata bowls couldprovideimportantinsightsintodifferences inthe of otherthrowingkinematicpatternssuchaswindmill-typecricket style isknowntoproducethefastestthrows.However, furtherstudy subjects threwonlyoverhandbaseball-typepitches,asthisthrowing throwing motion,butthisapproachhaslimitations.Forexample, our different regionsoftheupper bodycontributetothecomplex Our experimentalapproachcanbeaneffective waytoaddresshow to addresstheeffects ofboth factorsonthrowingperformance. data onaddingmassatthewristwithoutusingabraceareneeded the outrightrejectionofwristhyperextensionhypothesis,further of compensationfortherestriction.Whilethesedatadonotleadto actually increasedrelativetotheshamvalues,potentiallybecause acceleration, wristpeakpowerandworkduringacceleration) because oftherestriction(shoulderrotationworkduring number ofperformancevariablesthatwerepredictedtodrop independent ofanychangeinphaseduration.Furthermore,a flexion angularvelocity).However, thesereductionsappeartobe Limitations The JournalofExperimentalBiology(2014)doi:10.1242/jeb.103275 P <0.05), whilerestrictedvaluesthatstatisticallydiffer from 827±404 587±152 6111±2036 Shoulder sham 12,145±4628 128±74 6±2 206±45 124±63 0.4±1 1549±490 4261±1106 859±161 − 1229±2050 27±4* − − − 3±20 355±88 38±14 392±167 1±2 0.4±0.3 236±58 181±63* 2341±505 78±42 * 5559±2000 890±453 Shoulder restriction 13,566±6141 127±70 6±2 198±45 4038±1141 833±156 138±58 513±154 –190±46 1180±2383 − –1923±471 –42±57 326±100 24.9±4* –0.1±1* 1515±332 4±24 55±27 354±196* 2±1* 0.4±0.3 113±57* ,‡ * ,‡ * ,‡ ,‡ ,‡ * * ,‡ ,‡ ,‡ ,‡ * ,‡ 2145
The Journal of Experimental Biology hypothesized reductionsfromnormalvalues,whileitalicvaluesindicateunexpectedchanges. Torso rotation(+throwarmtowardstarget,–awayfromtarget) Timing 2146 at theshoulder duringthecockingphaseand helpspowerelbow The p.majoralsocontributesto energy absorption(negative work) shoulder internalrotationandelbow extensionjustpriortorelease. then recoveredintheacceleration phase,resultinginfaster Much oftheenergy absorbedattheshoulderduringcocking is the elasticelementsinshoulder duringthecockingphase. Through akinetictransferofpower, torsorotationpassivelyloads the torsorotationpowerandworkproducedduringthrowing. al., 2013;Wilk etal.,1993).Thehiprotators accountformostof et al.,2008)andelasticenergy storageattheshoulder(Roachet 1979; Feltner, 1989;Fleisigetal.,1996;Higgins, 1977;Hirashima generation duringthrowingviaboththekineticchain(Atwater, The resultsofthisstudyconfirmtheimportancepower throwing motionwasmostlypreserved. patterns maintainedacrossallconditionsconfirmthatthenormal experimental drawbacks,theconsistentaccuracyandkinematic diminishing theeffects of therestrictions.Despitethese accurately aspossible,contributingtovariationamongtrialsand tended tofightthroughtherestrictionsinorderthrowasfastand hard aspossibleinallbrace-restrictedconditions,somesubjects motions reportedhere.Furthermore,evenwhentaskedtothrowas speed, buttheeffects ofthesebraceswerenotrestrictedtoonlythe experimental designtargeted keymotionsresponsibleforprojectile compensatory flexionactionatthewrist(shoulderbrace).Our limiting scapularprotraction(claviclebrace)orcausing Brace restrictionscanalsoleadtounintendedresponses,suchas the shamareshownwith‡.Values thatmetthe Restricted andshamvaluesthatstatisticallydiffer fromnormalvaluesareindicatedwithasterisks (* Wrist flexion/extension(+flexion,–extension) Elbow flexion/extension(+flexion,–extension) Shoulder rotation(+internal,–external) Performance Performance measure RESEARCH ARTICLE Table Conclusions Duration ofacceleration(ms) Peak torque(Nm) Work –cocking(J) Peak power(W) Peak power(W) Peak power(W) Peak angularvelocity(deg Duration ofcocking(ms) Accuracy (mfrombullseye) Work –acceleration(J) Work –acceleration(J) Work –cocking(J) Peak torque(Nm) Peak angularvelocity(deg Work –acceleration(J) Work –cocking(J) Peak power(W) Peak torque(Nm) Peak angularvelocity(deg Work –acceleration(J) Work –cocking(J) Peak torque(Nm) Peak angularvelocity(deg Max. ballspeed(m 4. Kinematic and kinetic performance measures for the four critical joint axes during normal and wrist brace restriction conditions 4. Kinematicandkineticperformancemeasuresforthefourcriticaljointaxesduringnormalwristbracerestrictionconditions
s − 1 )
s s s s − − − − 1 1 1 1 ) ) ) ) P <0.05 thresholdbutdidnotsurvivemultipletestingcorrectionareindicatedwith§.Boldvaluesindicate 40±12 828±437 387±182 0.3±0.2 609±171 6207±2190 Normal 1±2 138±90 7±3 392±116 132±52 11,838±4170 0.2±1 27.7±3.8 1593±336 − 4290±1127 − 848±160 − 2028±3983 − 206±42 2±27 2434±552 74±44 246±63 201±70 order tomaintain aflexedelbow, whichis vitaltoincreasethe external rotation(Burkhartet al., 2000;Burkhartet2003).In lesion/tear] likelyresultsfrom this highdegreeofpassivehumeral site [asuperiorlabrumextending fromanteriortoposterior(SLAP) al., 2008b).Damagetotheshoulder labrumatthebicepsattachment correlated withsuchinjuries(Miyashita etal.,2008a;Miyashita cocking phase(whenelastic energy isstored)known tobe amount ofpassiveexternalrotationattheshoulderduring arm- 1996; Jobeetal.,Meister, 2000;Rizio andUribe,2001).The Stennett, 2006;Fleisigetal.,2011; Fleisigetal.,1995; epicondylitis) (AltchekandDines,1995;Anzetal.,2010;Badia and labrum tearsandshoulderinstability)elbow(medial common injuriesinthrowingathletesoccurattheshoulder(shoulder well astheevolutionofhumanupperbody. Threeofthemost understanding boththeetiologyofcommonthrowinginjuries as Throwing mechanicsandpowergenerationhaveimplications for cloud interpretationoftheseresults. hyperextension, theunexpectedeffects ofaddingmassatthewrist unclear. Whiletherearesome performancebenefitsto effects ofwristhyperextensiononthethrowingmotionremain and elbowduringeitherthecockingoraccelerationphases.The are confirmedbythelackofpositiveworkproducedwrist et al.,2007;Hirashima2008;Putnam,1993).Theseeffects flexion motionsattheendofthrow(Feltner, 1989;Hirashima distal segmentsalsohelpdrivetherapidelbowextensionandwrist extension. Itislikelythatkineticpowertransfersfromproximalto Implications The JournalofExperimentalBiology(2014)doi:10.1242/jeb.103275 P <0.05), whilerestrictedvaluesthatstatisticallydiffer from 5488±1670 351±116 0.4±0.2 Wrist sham 34±9* 838±175 431±96 541±136 3534±1415* 0.5±1 24±28 26.1±3.9 309±72 − − –215±63 − 537±466 191±53 15±19* –3±2* 3±2* 33±27 1406±331 3799±1237 2308±587 69±42 181±66 * * * * * * * § * * § 5676±2149 0.4±0.2 831±188 Wrist restriction 409±101 0.5±0.4 311±95 33±10 − 550±155 4852±2614 354±178 185±53 –0.5±24 276±81 6±2† 47±29 25.8±4* –2261±588 − 881±243 3579±1217 –174±61 1±1 49±31 62±39 192±68 ‡ * * * ,‡ ,‡ * * § ‡ ,‡ * * * * § ,‡ ,‡ * § * ,‡ ,‡
The Journal of Experimental Biology functional explanationfortherelativeshorteningofforearmthat investigation. Ifsupported,selectionforthrowingwouldprovidea mechanism, reducingthrowingperformance,bearsfurther (e.g. viathewristbrace)perturbselasticenergy storage Additionally, thehypothesisthataddingmasstodistalforelimb 1972) mayhavesubstantiallyimprovedthrowingperformance. in Susman, 1983)andespeciallytheexpansionofgluteusmaximus RESEARCH ARTICLE Fig. musculature seenin These datasuggestthatthereorganization ofthepelvisandhip thus helpingtopowermanyoftherapidmotionsforelimb. the hiprotatorsinpoweringmuchoftorsorotationmotionand and throwingperformance.Thetorsorestrictiondataalsoimplicate cranially orientedshouldercomplexreduceselasticenergy storage the claviclebracerestrictionhighlightshowamoreape-like is vitaltogeneratingelasticenergy storageintheshoulder. Similarly, of apes(BrambleandLieberman,2004),showsthattorsorotation The torsobracerestriction,whichmimicsthereducedmobility affect theperformanceofeachmotionstargeted in thisstudy. rotation. restrictive garments(suchasacompressionshirt)topreventover Rizio andUribe,2001;Sabicketal.,2004)orwearingmildly 1986; Fleisigetal.,2011; Fleisigetal.,1996;Gainor1980; limiting thefrequencyofhigh-speedthrowing(FeltnerandDapena, storage, itmaybepossibletoprotectagainstsuchinjuriesby from forelimbpositioningnecessarytomaximizeelasticenergy ligaments tostoreelasticenergy. Whiletheseinjuriesdirectlyresult dislocation (Meister, 2000)]maybedrivenbyuseofthecapsular cause [e.g.anteriorligamentlaxity, increasedlikelihoodof Uribe, 2001).Similarly, shoulder instabilityandtheproblemsitcan repeated throws(Fleisigetal.,1995;Fleisig1996;Rizioand potentially leadingtopainfulinflammationortearingfrommany joint, stretchestheulnarcollateralligamentthatstabilizeselbow, This hightorque,whichisaligneddifferently fromtheplaneof 1995; Lofticeetal.,2004;SabickWerner etal.,1993). both thearm-cockingandearlyaccelerationphases(Fleisigetal., position alsoresultsinveryhighvalgustorquesattheelbowduring at thebiceps’ tendinousinsertiononthelabrum.Theflexedelbow external rotationofthehumeruscauseshighconcentrationsstress 2002). However, thecombinationofbicepsflexionandpassive 2013), thebicepsareactivatedduringcocking(Hirashimaetal., forelimb’s momentofinertiaforelasticenergy storage(Roachetal., different jointcentersforflexion/extensionand pronation/supinationintheelbow (Roachetal.,2013). joint centerofthe shoulder jointdefinedusingaconical motiontrial.RFA80 referstoanotherfunctional jointusedtosolve position ofasplit-fingerthrow. highlighted isthefunctional Thismasswasdroppedtozerointheanalyses aftertheballwasreleased.TheFuncShomarker the approximateball segments usedintheinversedynamics analysis.Theballsegmentwasanon-independentpointmassadded tothehandsegmentat markers (SupTorso, ContraTorso, InfTorso and ThrowTorso). A graykineticmodelshowsthe second rigid__Armclusterismissingfromthistrial.InB,thelight Finally, morphologicalshiftsknowntooccurinhomininsmay Homo erectus
.Reflective markers(A)andkineticmodel(B)usedindatacollection analysis. 4. (Lieberman etal.,2006;Marzke1988;Stern, Australopithecus A ContraAcro ___Torso ContraHip (e.g. Lovejoy, 1988;Sternand 7ThrowAcro C7 ScapMed ScapLat ThrowHip ElbMed (below) ElbLat WristLat WristMed MC2 MC5 Committees. University andMassachusettsGeneralHospitalHumanSubjects skeletal traitswasdeemedaheightenedbreastcancerriskbytheHarvard Female subjectswereexcludedfromthestudyasCT imagingofrelevant deviations awayfrommeanperformancemeasuresinallbraceconditions. excluded becausehiskinematicpatternsweremorethantwostandard opportunity towarmupandthenaskedthrowa144 4;supplementarymaterialTable torso (Fig. subject had21passivereflectivemarkerstapedonthethrowingarmand 3D infraredmotioncapturesystem(Vicon Inc.,Centennial,CO,USA).Each Kinematic datawerecollectedat1000 First, theyneededtobeablehita1×1 several predeterminedinclusioncriteriadesignedtoexcludepoorthrowers. Data werecollectedfrom21malesubjects(ages19–23)whofulfilled hypothesis that Walker, 1993;White,2002).Insum,thesedatasupportthe occurred inthegenusHomo condition employedaDonJoyDualTLSObackbrace(DonJoyInc.,Vista, both theshamandrestrictedportionsofeachcondition.Thetorsorestriction Subjects weregiven restriction (exceptforthetorsocondition,whichthiswasnotpossible). applied butnottightenedtotesttheeffect ofthebraceindependently restricted conditionswererepeatedwithshamtrialsinwhichthebracewas restricted, clavicleshoulderrestrictedandwristrestricted.All Five different experimentaltreatmentswereused:normalunrestricted,torso (v1.41) fromdigitalvideocollectedwitha30 Model 3600radargun,andaccuracywascalculatedusingImageJsoftware experimental conditions.BallspeedwasmeasuredusingaSportsRadar approximately 10–20baseball-typepitchesineachoffiverandomlyordered across allconditionshadtoreach22.4 side ofthedistalphalanxthirddigit. (Tekscan Inc.,Boston,MA,USA)collectingat1000 target. BallreleasewastimedusingasynchedFlexiForceA201forcesensor video camera(CanonInc.,Tokyo, Japan)recordingtheballimpacting radius target positioned10 22.4 years ago(Roach,2012;Roachetal.,2013). expand intonewhabitatsbothinandoutofAfricanearly2million and mayhaveusedthisabilitytohunt,protectthemselves Data collection Subjects MATERIALS ANDMETHODS Experimental treatments m B
s − RFA80 1 (50 Note: Themarkerslabeled__Torso arearigidclusteroffour FuncSho The JournalofExperimentalBiology(2014)doi:10.1242/jeb.103275 Ball mph) orhigherwithinfivetries.Inaddition,atleastonethrow H. erectus ad libitum could haveproducedfast,accuratethrows
m fromthesubject.Eachsubjectthrew practice throwstoacquaintthemselveswith (e.g. Richmondetal.,2002;Ruff and
Hz usinganeight-cameraVicon T10s atrackingproblem resultingfromthe
m squaretarget from10 m
s −
S1). Subjectsweregiventhe 1 Hz CanonVixia HV30digital or higher. Onesubjectwas
Hz tapedtothepalmar
g baseballata1 m awayat 2147
m
The Journal of Experimental Biology function. was instantaneous axisofrotation.TheCardansequencerotationsateachjoint angular velocities,momentsandpowerwerecalculatedusingeachjoint’s using massdistributionratiosfromDempster(Dempster, 1955).Joint Euler angleswerecalculatedandinversedynamicsanalysesperformed Winter, 1991).Markergapsofupto100frameswereinterpolated.Joint after aresidualanalysisofthedatawasconducted(Roachetal.,2013; condition arematchedpairs torso restrictionconditiondidnothaveasham,allreportedstatisticsforthis restricted) accountedforthesignificanceinmultivariatetests.Because matched pairs family andamaximumalphathresholdof<0.05(Holm,1979). the Holm–Bonferronimethodwitheachexperimentalconditiontreatedasa square, or MANOVA whenvarianceswerenotequal(Mauchley’s sphericitychi- compared acrossexperimentalconditionsusingrepeated-measuresANOVA Individual subjectmeansfromanumberofperformancemeasureswere 2148 http://jeb.biologists.org/lookup/suppl/doi:10.1242/jeb.103275/-/DC1 Supplementary material availableonlineat Department ofHumanEvolutionaryBiology. the AmericanSchoolforPrehistoricResearch, andtheHarvardUniversity This researchwasfundedbytheNational ScienceFoundation(BCS-0961943), N.T.R. wrotethepaper, andN.T.R. and D.E.L.editedthemanuscript. N.T.R. andD.E.L.designedthestudy, N.T.R. collectedandanalyzedthedata, The authorsdeclarenocompetingfinancialinterests. thoughtful commentsvastlyimprovedthispaper. for theuseoftheirequipmentandfacilities;twoanonymousreviewers,whose our subjectsforgenerouslygivingtheirtime;theWyss InstituteMotionCapturelab Emre, Wes Gordon,AdanmaEkeledoandAmandaLobellfortheirinvaluablehelp; Andrew Biewener, SusanLarson, MattVincent, George Karas,RandiGriffin, Gulus We thankMikeRainbow, MadhuVenkadesan, LeiaStirling,RichardWrangham, as positiveprojectilevelocityisgeneratedonlyduringthesephases(Fig. Statistical inquirywaslimitedtothearm-cockingandaccelerationphases second-order low-passfilterwithacut-off frequencyof25 exported toC-MotionVisual3D software(v4)foranalysis.A Butterworth Marker datawereidentifiedusingVicon Nexussoftware(v1.7.1)and dorsal handplateandpreventsthewristfromhyperextending. the extensionstopwasscrewedintoplace,plasticsleevecontactsa 0 Wrist brace(AllsportDynamicsInc.,Nacogdoches,TX,USA)withthe sleeve. ThewristrestrictionconditionemployedanAllsportDynamicsIMC strap wasaffixed fromtheventralsideofvesttodorsal external rotationofthehumerus,armwasinternallyrotatedandaVelcro elastic vestwithasingle,half-sleeveonthethrowingarm.To restrict used tolimitexternalrotationalROMattheshoulder. Thisbraceisatight, the shoulderrestrictioncondition,aDonJoyShoulderStabilizerbracewas shrug hisshouldersasthebracewastightened,preventingrelaxation.For and underthearmpits,joininginback.Thesubjectwasrequestedto rotated, ‘shrugged’ posture.Thisbracerunstwostrapsovertheshoulders DonJoy ClaviclePostureSupportbracetoholdtheshoulderinasuperiorly rotational motioninthetorso.Theclaviclerestrictionconditionuseda sides ofthetorsoandfixesasteelbaragainstclaviclestorestrict sacrum. Thisbracefastensrigidplasticplatestoboththedorsalandventral CA, USA)tolimitintervertebralmotionfromtheT2/T3vertebrae RESEARCH ARTICLE Supplementary material Funding Author contributions Competing interests Acknowledgements Statistics Analysis
deg extensionstopeitheremployed(restricted)orabsent(sham).When XYZ. JointworkwascalculatedinMATLAB (v7.11.0) usingthetrapz P <0.05). Correctionsformultiplecomparisonswereappliedusing t -tests wereusedtodeterminewhichcondition(shamand/or t -tests.
Hz wasapplied Post hoc
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