Development And Evaluation Of An Observational System For Goalball Match Analysis

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www.rbceonline.org.br

Revista

Brasileira

de

CIÊNCIAS

DO

ESPORTE

ORIGINAL

ARTICLE

Development

and

evaluation

of

an

observational

system

for

goalball

match

analysis

Márcio

Pereira

Morato

a,∗

_,

_Otávio

_Luis

_Piva

_da

_Cunha

_Furtado

b

_,

Diego

Henrique

Gamero

b

_,

_Thiago

_Pinguelli

_Magalhães

b

_,

_José

_Júlio

_Gavião

_de

_Almeida

b

a_Universidade_de_São_Paulo,_Escola_de_Educac_¸ão_Física_e_Esporte_de_Ribeirão_Preto_{(EEFERP-USP),}_Ribeirão_Preto,_SP,_Brazil b_Universidade_Estadual_de_Campinas,_Faculdade_de_Educac_¸ão_Física_{(FEF-Unicamp),}_Campinas,_SP,_Brazil

Received1April2016;accepted9August2016

KEYWORDS Performance indicators; Sportperformance; Paralympicteam sports; Visualimpairment

Abstract Ourpurposewastodevelopandevaluateanobservationalsystemforgoalballmatch analysis.Weusedanon-participantsystematicgameobservationmethodincludingeightelite games,videorecorded,andrandomlychosen.Observationalcategoriesandperformance indi-catorsweredeterminedforeachoffensive(i.e.,ballcontrol,attackpreparation,andthrowing) anddefensiveprinciples(i.e.,defensivebalance,throwreading,andblocking).The compre-hensivemethodofdevelopmentandtheidealreliabilitylevels(kappacoefﬁcientof0.81---1.00) ofthisprotocolensurethegenerationofquantitativeandqualitativeinformationforplayers andcoachesandtherigorrequiredforscientiﬁcuse.

©2016PublishedbyElsevierEditoraLtda.onbehalfofColégioBrasileirodeCiênciasdoEsporte. ThisisanopenaccessarticleundertheCCBY-NC-NDlicense(http://creativecommons.org/ licenses/by-nc-nd/4.0/). PALAVRAS-CHAVE Indicadoresde performance; Desempenho esportivo; Esportecoletivo paralímpico; Deficiênciavisual

Desenvolvimentoeavaliac¸ãodeumsistemadeobservac¸ãoparaanálisedojogo degoalball

Resumo Nossoobjetivofoidesenvolvereavaliarumsistemadeobservaçãoparaanálisedo jogonogoalball.Foiusadoummétododeobservaçãosistemáticanãoparticipante,incluindo vídeos de oito jogos de elite escolhidos aleatoriamente. Categorias de observação e indi-cadoresde desempenhoforamdeterminadaspara cadaprincípioofensivo(i.e., controlede bola,preparaçãodoataqueeefetivaçãodoarremesso)edefensivo(i.e.,balançodefensivo, leituradatrajetóriaeinterceptaçãodoarremesso).Oabrangentemétododedesenvolvimento

∗_{Corresponding}_author.

E-mail:[email protected](M.P.Morato).

http://dx.doi.org/10.1016/j.rbce.2016.08.002

CORE Metadata, citation and similar papers at core.ac.uk

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eosníveisdeconfiabilidadeideais(coeficientekappade0,81-1,00)desseprotocoloasseguram ageraçãodeinformaçõesquantitativasequalitativasparajogadores etreinadoreseorigor necessárioparausocientífico.

© 2016Publicado por Elsevier EditoraLtda. em nome de Colégio Brasileirode Ciênciasdo Esporte.Este éumartigoOpenAccesssobumalicençaCCBY-NC-ND(http://creativecommons. org/licenses/by-nc-nd/4.0/). PALABRASCLAVE Indicadoresde rendimiento; Rendimiento deportivo; Deportedeequipo paralímpico; Deficienciavisual

Desarrolloyevaluacióndeunsistemadeobservaciónparaelanálisisdeljuego delgoalball

Resumen Nuestroobjetivofuedesarrollaryevaluarunsistemadeobservaciónparaelanálisis deljuegodelgoalball.Seutilizóunmétododeobservaciónsistemáticanoparticipante,que incluíavídeosdeochojuegosdeéliteelegidosalazar.Sedeterminaronlascategoríasde obser-vaciónylosindicadoresderendimientodecadaprincipioofensivo(p.ej.,controldelbalón, preparacióndelataqueylanzamiento)ydefensivo(p.ej.,equilibriodefensivo,lecturadela trayectoriaeinterceptacióndellanzamiento).Elmétodocompletodeldesarrolloylos nive-lesdefiabilidadideales(coeficientekappade0,81a1,00)delpresenteprotocoloaseguranla generacióndeinformacióncuantitativaycualitativaparajugadoresyentrenadores,yelrigor necesarioparaelusocientífico.

Introduction

Inthecontextofteamsports,researchershaveassumedits inherentcomplexityandinstability,acknowledgingthemas systemsandbroadened theresearchfocus tothelogic of thegame anditspatterns(Bar-Yam, 2003;McGarryetal., 2002;ReedandHughes,2006;Travassosetal.,2013).This trendpresupposes thecreation of modelsableto charac-terize:therelationbetweenthequantitiesandqualitiesof thegameactions,theorganizationofthegame,thetypes of sequences that generate positive or negative results, thescenariosorgeometryof thegameintheevolutionof teamsinspaceandtime,theinteractionsorco-adaptation betweenattackersanddefenders(BarrisandButton,2008; Duarteetal.,2012;McGarry,2009;Passosetal.,2013;Vilar etal.,2012).

Research regarding Paralympic team sports, stillin its embryonicstage,hasnotconsistentlyaddressedthistrend ofmatchanalysistoadaptedsports,suchaswheelchair bas-ketball(Gómezetal.,2014;Wangetal.,2005),icesledge hockey(Moliketal.,2012),andalsogoalball(Amorimetal., 2010;Mora,1993).Goalballisanon-territorialinvasionteam sportcreatedexclusivelyforpeoplewithvisualimpairment, whichisbasedonhearing(ballwithbellsinside)andtactile (raisedlines)clues.Inthissport,twoteamwiththree ath-leteseachstaypositionedintheoppositeendsidesofacourt withdimension similar to a volleyball court(18m×9m), dividedintotwohalvesbyacenterline.Fromarestricted area,theattackingteamthrowsaballalongtheﬂoortoward the opponent’s goal. The defending team, positioned in an area with tactile markings, tries to block the thrown ball, usually by sliding on the ﬂoor (Gulick and Malone, 2011).

Assumingthe complexity ofteam sports, Moratoetal. (2012)identifiedtheself-organizingcycleofgoalballteams byusingsystematicvideoobservationofanelite competi-tion.Theseauthorspresentedthreeprincipleseachinthe offensive (ball control, attack preparation and throwing) anddefensive(defensivebalance,throwreadingand block-ing)dimensions.WhileTeam1attemptstocontroltheball afterinterceptingthethrowbyTeam2,thelatterassumes adefensivebalance,thatis,theteamreturnstoits tacti-calsystem andis attractedby theorigin of theopponent throwtoreconfigureitself,whilemovingasablockto ratio-nallyoccupythecourt(Fig.1).AsTeam1controlstheball, itcontinuespreparingitsattackinordertothrowtheball. Team2isstillfocusingonthedefensivebalanceprinciple, changingthefocustoread thethrowassoon astheTeam 1 thrower starts the run-up to throw the ball. When the attackerreleasestheball,Team2willinterpretthethrow, definingitstrajectoryandcategorizingitundertime pres-sureinordertointerceptiteffectively.Afterintercepting thethrow,Team2controls theball andpreparesthenext attackwhileTeam1movesfromtheoffensivetothe defen-sive dimension, focusing onthe defensiveprinciples until thethrownballisrecovered(seeVideo1).

Thus,agamesequenceincludesoneteam’sconﬁguration tocomplywiththeoffensiveprinciples,theconﬁgurationof theopponentteamtocomplywiththedefensiveprinciples inresponsetotheotherteam’sattack,andtheoutcomeof thisinteraction.Thesetofgamesequencesrepresentsthe goalballgame,meaningthehistoryofrelationsbetweenthe teams’oppositedimensions(Moratoetal.,2012).

Based on the offensive and defensive principles of goalball,ourpurposewastodevelopandevaluatean obser-vationalsystemforgoalballmatchanalysis.

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Opponent throw origin

T

a

ctical systems

Right Basic triangle Forward triangle Backward triangle Inverse triangle Stair Barrier Center Left LW CE RW LW LW LW LW LW CE CE CE CE CE RW RW LW CE RW RW LW CE RW RW LW LW LW LW LW LW LW LW CE CE CE CE CE CE CE CE RW RW RW RW RW RW RW RW RW LW CE RW LW CE RW

Figure1 Rationalcourtoccupationindifferenttacticalsystems.Whiteareasrepresentspacestobeoccupied,andgrayareas representlessdangerousareasforeachopponentthroworigin.Legend:LW,leftwing;CE,central;RW,rightwing.Adaptedfrom Moratoetal.(2012).

Methods

In this study, we useda non-participantsystematic game observationmethod(Anguera,1999;Thomasetal.,2011). Some basic principlesshould be followed in this method: elaborating an ad hoc instrument to record the cate-gories and indicators that are considered fundamental in thetheoreticalandspeciﬁcpracticalframework,preparing expertobservers,preservingthespontaneityofthesystem observed,focusingontheactual game/competition situa-tion,andmaintainingthetemporalcontinuity,sothat the patternscanbefoundamidstchangeableandrandom behav-iors(AngueraandHernández-Mendo,2014).Thestudywas conductedaccordingtotheDeclarationofHelsinkiandthe researchprojectwasreviewedandapprovedwithno restric-tionsbyaninstitutionalethicscommittee.

Goalballmatchanalysisinstrumentelaboration The observationalsystem is abasic matchanalysis instru-ment.Theobservershouldelaborateitbasedonthereality distinguished in his conception of the game and the the-oreticalframeworkthis realityis basedon,attemptingto answer questions about: who, when, where and how the actions are executed (Hughes and Bartlett, 2002; Wright etal.,2014).Thecategoriesformulatedshouldbe exhaus-tive(needtoclassifyallactionsofthegame)andmutually exclusive (each action should refer to only one of the indicators per category) (Anguera and Hernández-Mendo, 2014).

Therefore, Anguera and Hernández-Mendo (2013) con-siderthatit isfundamental todedicategreattimetothe creation,reformulationandestablishment ofeach model, withaviewtocoveringthefullspectrumofconstraintsthe observerconsidersfundamental.Theseauthorssuggest non-systematic,exploratoryobservationsessionsbeforestarting asystematicstudy,aimingtodelimittheresearchproblem; elaboratingtheadhocinstrument;trainingoftheobservers toreduce the occurrence of futureerrors;and collecting informationfor decision makingabout the research plan-ning.

Inthatsense,departingfromtheconceptionofthe goal-ball game proposed by Morato et al. (2012), the three offensive (ball control, attack preparation and throwing) and three defensive principles (defensive balance, throw readingandblocking)wereadoptedasthestructuralcriteria ofourobservationalsystem.Therefore,weobservedeight goalball gamesvideo recordedand randomly chosen from theIBSAWorldGames2007.

While observing the games, an open list of team con-ductswaselaboratedwhileperformingeachprinciple.Each principle was observed exhaustively, that is, until per-ceiving that all possible situations that represented the performanceindicatorshadbeenlisted.Afterobservingone principle, the next wasobserved until obtaining a list of eventsfor each ofthesix principles.With thelistof per-formanceindicatorsforeachprincipleinhand,athematic groupingprocess wasstarted,representing the identiﬁca-tionoftheobservationalcategories.

The nextstep was to present the matchanalysis pro-tocol, with its observational categories and respective

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Teams interaction flow Sequence 1 Outcome

Outcome

Ball control Preceding situation Thrower Offensive strategy Attack length Throw origin Throw target Ball type Ball time Defensive reaction Defensive balance Throw reading Blocking Tactical system Defender Body segment Ball blockage Attack preparation

Attack

Defense

Throwing Outcome Outcome

Sequence 2 Sequence 3 Sequence n

Team 1 Team 2 Team 1 Team 2 Team 2 Team 2 Team 1 Team 1 Team 2 Game start Game over

Team 1

Team 2

Figure2 Thegraphicrepresentationofagoalballgame.Theupperpartdisplaysamacro-viewofagoalballgamerepresented bytheteamsinteraction.Thelowerpartpresentsonegamesequenceandtheproposedobservationalcategoriesoftheoffensive anddefensiveprinciples.

performance indicators, to four experienced coaches (all havingatleast6yearsofcoachingclubteams;twoofthem coachingnationalteams).Performanceindicatorswere dis-cussedandtheselecteditemswereincludedintheprotocol. Following, clear operational deﬁnitions were established and agreed upon by the coaches involved in the process (Wrightetal.,2014).

Reliabilityassessment

Two expert observers (more than 2 years of experience as referees and goalball coaches) went through a learn-ing process of the instrument. Initially, they received a protocol with the observational categories and their per-formanceindicators.Next,twosupervisedtrainingsessions were performed on different days for the identiﬁcation of thedifferent indicators per categories in therecorded imagesandthepractical applicationofthedatarecording bycompletingtheadhocinstrument,elaboratedinan elec-tronicworksheet. As doubts emergedduring the training, theobserversreturnedtotheprotocoltoreachaconsensus. Thetrainingterminatedaftersolvingthedoubts.

Afterthetraining,theobserversstartedthevideo anal-ysis of two randomly selected goalball games from the Beijing 2008 Paralympic Games. This represented a sam-pleof 314 game sequences(attack/defense/results). The secondobservation ofthegamestookplace15daysafter theendoftheﬁrst.Wecalculatedtheinterandintra-rater reliabilitybyusingCohen’sKappacoefﬁcient(Fleissetal., 2013).

Results

InFig.2,weshowthegraphicrepresentationofagoalball game. Thismodel resultsfromthesystematic observation process of the offensive (ball control, attack preparation andthrowing)anddefensiveprinciples(defensivebalance, throwreadingandblocking)ofgoalball.

Basedonthisgoalballgamemodel,atleastone observa-tionalcategorywiththerespectiveperformanceindicators wasobtainedforeachprinciple(seeTables1---3).

Thereliability(Kappa)coefﬁcientsoftheproposedmodel arepresentedinTable4.

Discussion

Inthisstudywedevelopedandevaluatedanobservational systemforgoalballmatchanalysis.Theobservedcategories andtheperformanceindicatorsproposedintheinstrument representallpossibleactionsavailableinthegoalballgame (exhaustiveness) for each of the offensive and defensive principlesincludedinthemodel.Eachgame situationwas categorizedbyasingleindicator(mutualexclusivity), reduc-ing any observation bias (Anguera and Hernández-Mendo, 2014). This can beobserved in theKappa coefﬁcients,as demonstrated in Table 4, ensuringthat the instrument is rigorous enough for scientiﬁc use. For all observational categories,the intraand inter-raterreliabilityassessment showedhighagreementlevelsbetween0.81and1.00(Fleiss etal.,2013;LamesandMcGarry,2007).

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Table1 Offensiveprinciplestogoalballmatchanalysis:observationalcategories,performanceindicatorsanditsdescription. Principles

Observationalcategories Performanceindicators Ballcontrol

Attackingteam:Teamthatrecoverstheball Three-letterinitialsofthecountry

Precedingsituation:Linkwiththepreviousgamesequencetoindicatehowtheteamconqueredtheballpossession RB: Receivedballfromthemainrefereeatthebeginningoftheﬁrstorsecondhalfofthegame DE: Defenseofopponentthrow

OU: Outsidethrow BO: Blockout

IN: Infractionbytheopponent PE: Penaltybytheopponent DP: Defenseofpenaltyshot GA: Goalagainst

TTO: Teamtimeout OTO: Ofﬁcialtimeout SUB: Substitution Attackpreparation

Thrower:Identiﬁcationoftheplayerperformingtheattack 1---9: Jerseynumber

LW: Leftwing CE: Center RW: Rightwing

Offensivestrategy:Thestrategytheattackingteamusesforthethrow

RE: Regular:playerthrowstheballfromthesameorsurroundingsectorinwhich(s)hedefendedor receivedapass.Forexample,if(s)hedefendedthethrowinsector2,thethrowfromsector1,2or 3isconsideredregular(seeFig.3)

FL: Fluctuation:playerdefendstheballorreceivesapassand,beforethrowing,changesthesector beyondtheneighboringsectors.Example:(s)hedefendedinsector2andthrowfrom4,5or6(see Fig.3)

DB: Deliveredballpass:attackerreceivesahand-to-handpassingbeforethrowing

SP: Setpiece:organizedandpracticedmove,otherthanFLandDB.

CA: Counter-attack:attackisperformedwithinfoursecondsafterdefense

QA: Quickattack:subsequenttoaninterruption,attackisperformedwithintwosecondsafterreferee calls‘‘quietplease,play’’

SB: Safetyball:whentheplayerthrowstheballsoasnottocommitpenaltiesortoprioritizethe defensivebalance

SL: Slowball:strategyusedattheﬁnalmomentsofthegamesbytheleadingteamstospendthegame

timeleft

Attacklength:Timetheteamusestoperformtheattack

SH: Shortattack:upto4secondsafterdefense

ST: Standardattack:between4and7afterdefense

EX: Extendedattack:morethan7safterdefense

Throwing

Throworiginanthrowtarget:Categorizationofthethrowtrajectory,basedoncourtdivisionpresentedinFig.3 O1-6: Sectorinwhichtheballhadtheﬁrstcontactwiththegroundafterbeingthrownbytheattacker,

independentlyofhis/hermovementtoperformtheattack

T1-6: Theplacewheretheballthrownreachestheorientationareafrontlineoftheopponentteam

Balltype:Thrownballfeature

BO: Bouncing:ballbouncesatleastonceafterthehighballline

RO: Rolling:ballstraightandconstantlytouchingtheﬂoor

CU: Curve:rollingballwithsidespin

Balltime:Durationofthrownball

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Table2 Defensiveprinciplestogoalballmatchanalysis:observationalcategories,performanceindicatorsanditsdescription. Principles

Observationalcategories Performanceindicators Defensivebalance

Defendingteam:Teamthatmissestheballpossession Three-letterinitialsofthecountry

Tacticalsystem:Theteamconﬁgurationwhenwaitingfortheopponentattack(seeFig.1)

TR: Basictriangle

FT: Forwardtriangle

BT: Backwardtriangle

IT: Inversetriangle

ST: Stair

BA: Barrier

Throwreading

Defensivereaction:Defenderresponsetotheballsoundafteroppositethrow

ER: Earlyreaction:defenderreactstoosoontoanythrownballsoundbytheoppositeteam CR: Coherentreaction:defenderreactstimelytotheballsound

LR: Latereaction:defenderreactstoolatetotheballsound,remainingnotimetoﬁnishthedefensivetechnique NR: Noreaction:defenderdoesnotreacttotheballsound

Blocking

Defender:Identiﬁcationoftheplayerwhoperformstheﬁrstdefensiveinterception

1---9: Jerseynumber

LW: Leftwing

CE: Center

RW: Rightwing

Bodysegment:Bodypartusedbyplayertoblocktheball

UR: Upperregion:forhead,shoulders,arms,forearmsandhands CR: Centralregion:forchest,abdomen,hipsandthighs

LR: Lowerregion:forknees,legs,andfeet NC: Nodefensivecontactwiththeball

Ballinterception:Characterizationoftheblocking,referringtotheresultoftheapplicationofthedefensivetechnique NR: Norebound:defenderinterceptsandkeepstheballundercontrol

FR: Frontalrebound:theblockedballmovestowardsthecenterofthecourt LR: Lateralrebound:theballmovestowardsthelaterallinesafterthedefense BR: Backwardrebound:theballcontinuestowardsthegoalline

NC: Nodefensivecontactwiththeball

The use of this observational system to deal with performance analysis in goalball can help to evolve the base knowledge on technicaland tactical aspects of this particularsport.Thismethodisaninexpensivewayof pro-vidingquantitativeandqualitativefeedbacktoplayersand coachesof howindividualplayerscaninﬂuence team pat-terns(BarrisandButton,2008;HughesandBartlett,2002; Vilaretal.,2012).Uptonow,therehavebeenonlyafew studiestryingtocharacterizeparticularsituationsof goal-ball(Amorimetal.,2010;Mora,1993).Ourmodelexpands onthetheme, proposing means toassess all thekey ele-mentsoccurringinmaleandfemaleelitegoalballgames.We believetheinteractivewaytheinstrumentwascreated,by gatheringfeedbackthroughconstantexchangeofideaswith elitecoaches,ledustocomprehensivelydeterminewhich werethemostrelevantoffensive(howtheballiscontrolled; howtheattackisprepared;andhowthethrowisperformed) anddefensive(howtheteamispositionedonthecourt;how theathletesreactedtotheopponent’sthrow;andhowthe ballisblocked)aspectsofthegame.

Offensiveprinciples

The opponent’s throwing outcome is thestarting point to theballcontrolprinciple.Fromourexperience,this offen-siveprincipleismostcommonly notedasadefenseofthe opponent’s throw,as aball controlled aftera rebound or astheballreceivedfromthereferee.Differentpreceding situationswillinﬂuencetheoffensivestrategychoiceinthe followingprinciple(attackpreparation).Forexample,aball controlledwithout areboundor theonegivenbythe ref-ereeafteraball outwillallow lesstimepressuretobuild theattackwithinthetensecondsofballpossessionateam hastoattack.Ontheotherhand,theball controlledafter alongreboundorgivenbytherefereeafterablockoutwill reducetheavailabletimetothethrowing,hencereducing thepossibleoffensivestrategies.

Theattackpreparationprincipleisaimedtodetermine howthe attack is planned. The identiﬁcation of athlete’s position and roles on court can clarify the throwing fre-quency executed by wing and center players providing

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Table 3 Attack/defense interaction and game notes to goalball match analysis: observational categories, perfor-manceindicatorsanditsdescription.

Principles

Observationalcategories Performanceindicators Attack/defenseinteraction

Outcome:Resultoftheinteractionbetweenthe offensivedimensionofoneteamandthedefensive dimensionoftheother

DE:Defendingteamblockstheballwhich remainsinsidetheirhalfcourt BO: Ballpassesthelimitsofthecourtafter

beingblockedbythedefenders

OU:Ballthrownoutwithoutcontactwiththe defenders

IN: Aninfractionoccurs PE:Apenaltyoccurs GO:Attackingteamscores

PD:Defenderblocksthepenaltyshot PO: Attackerthrowsthepenaltyshotoutside PP:Throwercommitsapenaltyinapenalty

shot

PG: Penaltyshooterscores

Gamenotes:observationsforreferencesofeachgame sequence Gender F: Female M: Male Gameperiod 1: Firsthalf 2: Secondhalf Gamenumber

Accordingtothelistofgamesobserved

relevant informationfor training specificity. Forinstance, basedoneightgamesfromtheBarcelona 1992Paralympic Games,Mora(1993)showedthatwingplayerstendtoattack morefrequentlythancenters.Althoughthisisanimportant informationofthegamepatterns, theauthordidnottake intoconsiderationtheteams’tacticalsystems.Theathletes’ role and their spatial occupation on court is likely to be determinedby the tacticalsystem adopted by each team (Moratoetal.,2012),whichmayfurtherinfluencethe fre-quency ofattacks per players. When assessing theattack lengthonemayfindwhethershorteror longerattacksare moreeffectiveunderdifferentscenarios.Wealsobelieveit isveryimportanttoidentifyhowdifferentoffensive strate-gies(i.e.,regular,fluctuation,deliveredballpass,setpiece, counter-attack,quickattack,safetyball,orslowball) influ-encethedefensivebalanceofthedefendingteamandits respectiveoutcome.

Throwing,asthelastattackprinciple,isthoughtto char-acterizehowthethrowisperformedinagoalballgame.The efﬁcacyofball typeandballtimecanbedeterminedand itsrelation tothrow origin andthrow target canlater be established.Inpracticalterms,theinitialapplicationofour protocolallowed ustoinvestigatethe incidenceof differ-entballtypesandtheoriginandtargetthrowsinelitelevel

goalball.Among the identiﬁedthreetypes of ball seen in goalball (rolling, bouncing, and curve) we found that the rollingballsweremorecommoninfemaleswhencompared tomalesandthattherollingandbouncingballsweremore frequent than the curves balls for both genders (Morato etal.,2014).In anotherstudy,we detectedhigher occur-rence of throws from the wing sectors in both genders, similarto Amorim et al. (2010), and higher incidence of ballsarriving at thecentral sectorsof the opposingteam area(Moratoetal.,2013).

Defensiveprinciples

For the first defensive principle, defensive balance, we soughttoidentifyhowtheteamispositionedonthecourt (tactical system). The possible identification of throwing patterns,asdiscussed inthe offensiveprinciple, can con-tributetotheteams’organizationtoeffectivelycomplywith thedefensivebalanceprincipleconcept,movingasablock towardtheopponent’sthroworigin(Moratoetal.,2012).In addition,differencesinthedefensivetacticalsystems effec-tivenesscanbeidentifiedwithregardtotherationalspace occupation(seeFig.1).

Besides the spatial issue, the model also enables the recognitionof rhythms inherenttothe game.In thisway, intheseconddefensiveprinciple(throwreading)thefocus wastounderstandhowathletesreactedtotheopponent’s throwing(defensive reaction).According tothe observers whotookpartinthereliabilitytestingstageofthestudy,the subjectivitymayplaysomeroleinthisprinciplewhenone triestonoteanearly,coherentorlatedefender’sreaction toblocktheball.However,althoughamongthelowest val-uesofinter-raterreliability,agoodlevelofagreementwas achieved(Kappa0.82).Ingoalball, asthedefenders iden-tifytheopponent’sthrowtrajectoryunderatimepressure condition(Moratoetal.,2012),itisrelevanttounderstand ifdifferentrangesofattackballpossessionorthrowingball timeinterferein the defensiveefﬁcacy, asseem in other sports(Freestonetal.,2014;Wagneretal.,2012).

For the last defensive principle, blocking, our model permits tounderstand how the ball is blocked (defender number,defenderposition, bodysegment,and ball inter-ception).Traditionally,goalballteams assumeatriangular positioning,inwhich thecenter,moreadvancedoncourt, playtheprincipalroleofdefending,whilewings havethe mainroleofattacking(Moratoetal.,2012).However,this maynotbetruefortheallofthepossibledefensive tacti-calsystems,asproposedinFig.1.Anotherrelevantissueof investigationreferstowhichbodysegmentismoreandless efﬁcienttoblock theball. Fromourexperience,itseems reasonablethatdefendingtheballwiththebody extremi-tiesmaybelesseffectivetosecurelycontroltheballthan defendingit withthetrunk,hipandthigh,andtheuseof protocolcanhelptotestthishypothesis.

Possibleinteractionsbetweentheprinciples Inteamsportswithﬁeldinvasion,thegamepatternsderive from the continuous interaction between attackers and defenders,mainlyinatightspatialrelation.Bothteams con-stantlyre-organizetheirpositiononﬁeldaccording tothe

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Table4 Intraandinter-raterreliabilityofthegoalballobservationalcategories.

Principles Kappa

Observationalcategories Intra Inter

Observer1 Observer2 Observers

Ballcontrol Attackingteam 1.00 1.00 1.00 Precedingsituation 0.99 0.95 0.98 Attackpreparation Throwernumber 0.99 1.00 0.99 Throwerposition 1.00 1.00 1.00 Offensivestrategy 0.84 0.83 0.82 Attacklength 0.94 0.91 0.94 Throwing Throworigin 0.94 0.90 0.89 Throwtarget 0.95 0.91 0.90 Balltype 0.89 0.86 0.83 Balltime 0.89 0.81 0.81 Defensivebalance Defendingteam 1.00 1.00 1.00 Tacticalsystem 1.00 0.98 0.99 Throwreading Defensivereaction 0.89 0.95 0.82 Blocking Defendernumber 1.00 0.97 0.98 Defenderposition 1.00 0.97 0.99 Bodysegment 0.96 0.91 0.89 Ballinterception 0.87 0.92 0.85 Attack/defenseinteraction Outcome 0.99 0.98 0.99 Gamenotes Gender 1.00 1.00 1.00 Gameperiod 1.00 1.00 1.00 Gamenumber 1.00 1.00 1.00

Note:Akappacoefﬁcientof0.81---1.00indicatesalmostperfectagreement(LandisandKoch,1977).

opponent’sunpredictablebehaviors, dependingon spatial-time information from the game, which is clearly visual andacoustic(Passos etal.,2013).Ingoalball,where field invasion is not allowed, the temporal restriction is more noticeableinthedefensiveprinciplesofthrowreadingand blocking,whichexclusivelydependontheauditory percep-tiontoidentifythecharacteristic,rhythmandspeedofthe opponent’sthrow.Fromanotherperspective,providedthat theballiscontrolledeffectively,teamsintheoffensive sit-uationhavemorefreedomtopreparetheattacksequence. Therefore,changesinthegamestrategiesrepresent fluc-tuationsinthesystem(Moratoetal.,2012)andtheproposed protocolcanidentifythembyrecordingtheeventhistoryof eachgame.Withthisregisterinhand,themostappropriate statisticalmethodsstillneedtobeidentifiedtodefinethe secretsofthegoalballgame.Theuseofcomplex mathemat-icalmodelscancontributetotheidentificationofpredictive factorsof competitive performance ingoalball, positively

inﬂuencingthe teams’ preparationprocessin thetraining andchoiceofappropriatestrategicplansfor competitions (Duarteetal.,2012;Hughes,2004;MemmertandPerl,2009; Perl,2004).

Toinvestigatespatial-timeconﬁgurationsamongathletes and teams, differentmethods are available for the cine-maticanalysisofathletes incompetitivesituations(Barris andButton,2008;Bourboussonetal.,2010;Travassosetal., 2013;Vilaretal.,2014).Thesemethodsemploymanualor semi-automaticimagecapturinganddatatreatment tech-niques and, while promising for match analysis,they are costlytoolsthatwouldlimittheiruseinateamsportwith amateurcharacteristicsandlowbudget,whichisthecase ingoalball.Inthatsense,themodelhereproposedis demo-cratic,asanalystswhoarenovelinthissportcaneasilylearn it, besides thefact this is alow costtool. Usingan open software(e.g.,Kinovea)canfavormorereﬁnedanalysisof the game and provide consistent data when comparedto

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Orientation area Orientation area front line 18 meters 9 meters High ball line Landing area Neutral area

Figure3 Goalballcourtdiagramanditsorigin andtargetsectors.Theorigin sectorisdeterminedwhen thethrown ballﬁrst touchestheﬂoor intheorientationorlanding areas(sectors 1---6).Thetarget sectorisdeterminedwhen theballreachesthe orientationareafrontlineortouchesadefender.

theanalysisinloco(e.g.,balltimewithmanual chronome-terversusframe-by-framevideoanalysis).Inaddition,the real-world demands of an elite competition ensured that ecological validity was maintained to examine the game characteristics.

Conclusions

The observationalsystem for goalballmatchanalysishere presentedisthoughttorepresentallpossibleactions avail-ablein theoffensive (howtheball is controlled;howthe attack is prepared;andhow thethrow is performed) and defensive principles (how the team is positioned on the court;howtheathletes reacted totheopponent’s throw; andhowtheballisblocked)ofthesport.Thecomprehensive methodofdevelopmentanditsidealreliabilitylevelsensure thegenerationofquantitativeandqualitativeinformation forplayersandcoachesandtherigorrequiredforscientiﬁc use.Finally,weunderstandthisinnovativeandlowbudget toolisarareandimportantworkdedicatedtosystematically studygoalball(Fig.3).

Financial

support

ThisworkwassupportedbytheNationalCouncilofScientiﬁc andTechnologicalDevelopment(CNPq/Brazil).

Conﬂicts

of

interest

Theauthorsdeclarenoconﬂictsofinterest.

Appendix

A. Supplementary

data

Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.rbce. 2016.08.002.

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