Rev. Bras. Ciênc. Esporte vol.39 número4

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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

Availableonline13September2016

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.

PALAVRAS-CHAVE

Indicadoresde performance; Desempenho esportivo; Esportecoletivo paralímpico; Deficiênciavisual

Desenvolvimentoeavaliac¸ãodeumsistemadeobservac¸ãoparaanálisedojogo degoalball

Resumo Nossoobjetivofoidesenvolvereavaliarumsistemadeobservaçãoparaanálisedo jogonogoalball.Foiusadoummétododeobservaçãosistemáticanãoparticipante,incluindo vídeos de oito jogos de elite escolhidosaleatoriamente. Categorias de observação e indi-cadoresdedesempenho foramdeterminadasparacadaprincípioofensivo (i.e.,controlede bola,preparaçãodoataqueeefetivaçãodoarremesso)edefensivo(i.e.,balançodefensivo, leituradatrajetóriaeinterceptaçãodoarremesso).Oabrangentemétododedesenvolvimento

∗_{Corresponding}_author.

E-mail:mpmorato@usp.br(M.P.Morato).

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

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eosníveisdeconfiabilidadeideais(coeficientekappade0,81-1,00)desseprotocoloasseguram agerac¸ãodeinformac¸õesquantitativasequalitativas parajogadoresetreinadoreseorigor necessárioparausocientífico.

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 systemsand broadenedthe researchfocustothelogic of thegameanditspatterns(Bar-Yam,2003;McGarryetal., 2002;ReedandHughes,2006;Travassosetal.,2013).This trendpresupposes the creationof modelsable to charac-terize:therelationbetweenthequantitiesandqualitiesof thegameactions,theorganizationofthegame,thetypes of sequences that generate positive or negative results, thescenariosor geometryofthegameintheevolutionof teamsinspaceandtime,theinteractionsorco-adaptation betweenattackersanddefenders(BarrisandButton,2008; Duarteetal.,2012;McGarry,2009;Passosetal.,2013;Vilar etal.,2012).

Research regarding Paralympic team sports, still in 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 with dimension similar toa 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).

Assuming thecomplexity of teamsports, Moratoetal. (2012)identifiedtheself-organizingcycleofgoalballteams byusingsystematicvideoobservationofan elite competi-tion.Theseauthorspresentedthreeprincipleseachinthe offensive (ball control, attack preparation and throwing) anddefensive(defensivebalance,throwreadingand block-ing)dimensions.WhileTeam1attemptstocontroltheball afterinterceptingthethrowbyTeam2,thelatterassumes adefensivebalance,thatis, theteamreturnstoits tacti-calsystemand isattracted bythe originof theopponent throwtoreconfigureitself,whilemovingasablockto ratio-nallyoccupythecourt(Fig.1).AsTeam1controlstheball, itcontinuespreparingitsattackinordertothrowtheball. Team2isstillfocusingonthedefensivebalanceprinciple, changingthefocustoreadthethrowassoonastheTeam 1 thrower starts the run-up tothrow the ball. When the attackerreleasestheball,Team2willinterpretthethrow, definingitstrajectoryandcategorizingitundertime pres-sureinordertointerceptit effectively.Afterintercepting thethrow,Team2controlstheballandpreparesthenext attackwhileTeam1movesfromtheoffensivetothe defen-sive dimension,focusing onthe defensive principlesuntil thethrownballisrecovered(seeVideo1).

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

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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 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-participant systematic game observationmethod(Anguera,1999;Thomasetal.,2011). Some basic principles should befollowed in thismethod: 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,sothatthe patternscanbefoundamidstchangeableandrandom behav-iors(AngueraandHernández-Mendo,2014).Thestudywas conductedaccordingtotheDeclarationofHelsinkiandthe researchprojectwasreviewedandapprovedwithno restric-tionsbyaninstitutionalethicscommittee.

Goalballmatchanalysisinstrumentelaboration

Theobservational system isa basic matchanalysis instru-ment.Theobservershouldelaborateitbasedonthereality distinguishedin hisconception of the game and the the-oreticalframeworkthisreality isbased on,attempting to 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-sider thatitis fundamental todedicategreattimetothe creation,reformulation andestablishment ofeach model, withaviewtocoveringthefullspectrumofconstraintsthe observerconsidersfundamental.Theseauthorssuggest non-systematic,exploratoryobservationsessionsbeforestarting asystematicstudy,aimingtodelimittheresearchproblem; elaboratingtheadhocinstrument;trainingoftheobservers toreduce theoccurrence of future errors;and collecting information for decision making about 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 games video recordedand randomlychosen from theIBSAWorldGames2007.

While observing the games, an open listof team con-ductswaselaboratedwhileperformingeachprinciple.Each principle was observed exhaustively, that is, until per-ceiving that all possible situations that represented the performanceindicatorshadbeenlisted.Afterobservingone principle, the nextwas observed until obtaining a list of events for eachof thesixprinciples.Withthelistof per-formanceindicatorsforeachprincipleinhand,athematic grouping processwasstarted, representing the identifica-tionoftheobservationalcategories.

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Teams interaction flow Sequence 1

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 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 andtheir per-formanceindicators.Next,twosupervisedtrainingsessions were performed on different days for the identification of the differentindicators per categories in the recorded imagesandthepracticalapplicationofthedatarecording 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-ple of 314 game sequences (attack/defense/results). The second observationof thegamestookplace15 daysafter theendofthefirst.Wecalculatedtheinterandintra-rater reliabilitybyusingCohen’sKappacoefficient(Fleissetal., 2013).

Results

InFig.2,weshowthegraphicrepresentationofagoalball game.This modelresultsfromthe systematicobservation processof the offensive (ball control, attack preparation andthrowing)anddefensiveprinciples(defensivebalance, throwreadingandblocking)ofgoalball.

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

Thereliability(Kappa)coefficientsoftheproposedmodel arepresentedinTable4.

Discussion

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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

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 technical and tactical aspects of this particularsport.Thismethodisaninexpensivewayof pro-vidingquantitativeandqualitativefeedbacktoplayersand coachesofhowindividualplayers caninfluenceteam pat-terns(Barris andButton,2008;HughesandBartlett,2002; Vilaretal.,2012).Uptonow,therehavebeenonlyafew studiestryingtocharacterize particularsituationsof goal-ball(Amorimetal.,2010;Mora,1993).Ourmodelexpands onthe theme, proposingmeans to assessall the key ele-mentsoccurringinmaleandfemaleelitegoalballgames.We believetheinteractivewaytheinstrumentwascreated,by gatheringfeedbackthroughconstantexchangeofideaswith elitecoaches,ledustocomprehensivelydeterminewhich werethemostrelevantoffensive(howtheballiscontrolled; howtheattackisprepared;andhowthethrowisperformed) anddefensive(howtheteamispositionedonthecourt;how theathletesreactedtotheopponent’sthrow;andhowthe ballisblocked)aspectsofthegame.

Offensiveprinciples

The opponent’s throwingoutcome is the starting point to theballcontrolprinciple.Fromourexperience,this offen-siveprincipleismostcommonlynotedasadefenseofthe opponent’sthrow, asa ball controlledafter a rebound or astheballreceivedfromthereferee.Differentpreceding situationswillinfluencetheoffensivestrategychoiceinthe followingprinciple(attackpreparation).Forexample,aball controlledwithout arebound ortheonegivenby the ref-ereeafteraballoutwillallowlesstimepressuretobuild theattackwithinthetensecondsofballpossessionateam hastoattack.Ontheotherhand,theballcontrolledafter alongreboundorgivenbytherefereeafterablockoutwill reducetheavailabletimetothethrowing,hencereducing thepossibleoffensivestrategies.

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

Principles

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, basedoneightgamesfromtheBarcelona1992Paralympic Games,Mora(1993)showedthatwingplayerstendtoattack morefrequentlythancenters.Althoughthisisanimportant informationofthegamepatterns,theauthordidnottake intoconsiderationtheteams’tacticalsystems.Theathletes’ role and their spatial occupation oncourt is likely tobe determinedby thetactical system adopted byeach team (Moratoetal.,2012),whichmayfurtherinfluencethe fre-quencyof attacks perplayers. When assessing the attack lengthonemayfindwhethershorterorlongerattacksare moreeffectiveunderdifferentscenarios.Wealsobelieveit isveryimportanttoidentifyhowdifferentoffensive strate-gies(i.e.,regular,fluctuation,deliveredballpass,setpiece, counter-attack,quickattack,safetyball,orslowball) influ-encethedefensivebalanceof thedefendingteamandits respectiveoutcome.

Throwing,asthelastattackprinciple,isthoughtto char-acterizehowthethrowisperformedinagoalballgame.The efficacyofball typeandball timecan bedeterminedand itsrelation tothrow originand throw targetcan laterbe established.Inpracticalterms,theinitialapplicationofour protocolallowedustoinvestigatetheincidenceof 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).Inanotherstudy,wedetected higher occur-rence of throws from the wing sectors in both genders, similar to Amorim et al. (2010), and higher incidence of balls arrivingat the central sectorsof theopposing team area(Moratoetal.,2013).

Defensiveprinciples

For the first defensive principle, defensive balance, we soughttoidentifyhowtheteamispositionedonthecourt (tactical system). The possible identification of throwing patterns, asdiscussed intheoffensive principle,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 recognition ofrhythms inherent tothegame. Inthis way, intheseconddefensiveprinciple(throwreading)thefocus wastounderstandhowathletesreactedtotheopponent’s throwing (defensivereaction). According totheobservers 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 timeinterfere in thedefensive efficacy, asseem inother sports(Freestonetal.,2014;Wagneretal.,2012).

For the last defensive principle, blocking, our model permits to understand how the ball is blocked (defender number, defenderposition,body segment,and ball inter-ception).Traditionally,goalball teamsassumea triangular positioning,inwhichthecenter,moreadvancedoncourt, playtheprincipalroleof defending,while wingshave the mainroleofattacking(Moratoetal.,2012).However,this maynotbetruefortheallofthepossibledefensive tacti-calsystems,asproposedinFig.1.Anotherrelevantissueof investigationreferstowhichbodysegmentismoreandless efficienttoblockthe ball. Fromourexperience,itseems reasonablethatdefendingtheballwiththebody extremi-tiesmaybelesseffectivetosecurelycontroltheballthan defendingitwiththetrunk,hipandthigh,andtheuse of protocolcanhelptotestthishypothesis.

Possibleinteractionsbetweentheprinciples

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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(Passosetal.,2013).Ingoalball, wherefield 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 factors ofcompetitive performance in goalball, positively

influencingtheteams’ preparationprocessin thetraining andchoiceof appropriatestrategicplans forcompetitions (Duarteetal.,2012;Hughes,2004;MemmertandPerl,2009; Perl,2004).

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Orientation area

Orientation area front line

18 meters

9 meters

High ball line Landing area

Neutral area

Figure3 Goalballcourtdiagramanditsoriginandtargetsectors.Theoriginsectorisdeterminedwhenthethrownballfirst

touchesthefloorintheorientation orlandingareas (sectors1---6). Thetargetsector isdeterminedwhentheball reachesthe

orientationareafrontlineortouchesadefender.

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

Conclusions

Theobservational systemfor goalball matchanalysishere presentedisthoughttorepresentallpossibleactions avail-ableinthe offensive(howthe ballis controlled;howthe attackis prepared;and howthe throwis performed) and defensive principles (how the team is positioned on the court;howtheathletesreacted tothe opponent’sthrow; andhowtheballisblocked)ofthesport.Thecomprehensive methodofdevelopmentanditsidealreliabilitylevelsensure thegenerationof quantitativeandqualitative information 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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