KINEMATICANALYSISOFPEAKVELOCITIESINTHEBREASTSTROKE

ASAFUNCTIONOFTHETIMINGOFTHEKICK

ATHESISSUBMITTEDTOTHEGRADUATEDIVISIONOFTHEUNIVERSITYOFHAWAI‘IATMĀNOAINPARTIALFULFILLMENTOFTHEREQUIREMENTSFORTHE

DEGREEOF

MASTEROFSCIENCE

IN

POST-PROFESSIONALATHLETICTRAINING

MAY2018

By

SusanM.Ward

ThesisCommittee:

Dr.CrisStickley,ChairpersonDr.JanPrinsDr.YukiyaOba

Dr.BretFreemyer

ii

AbstractThepurposeofthisstudywastodeterminetheeffectsofthetimingofthe

Breaststrokekickonintra-cyclicvelocityfluctuations.Researchersexaminedpeak

hipvelocitiesofBreaststrokeswimmerstodetermineanysignificantvelocitydrop-

offsandmagnitudeofvelocityregainedbetweendifferentkickingtechniques.

Subjectsperformedswimmingtrialswiththreedifferentkickprotocols:a

conventionalstroke,alatekick,andadelayedlatekick.Videoanalysiswasusedto

analyzepeakandminimumhipvelocitieswithinoneBreaststrokecycleforeach

trial.DatawasanalyzedusingANOVArepeatedmeasuresanalysis.Majorfindingsof

thisstudywerethatduetosmallerpercentagesofhipvelocitydrop-off,higher

swimmingvelocitiesmaybeachievedwhenthekickisinitiatedduringtheinsweep

orearlyrecoveryarmphasesandthatvideoanalysisandverbalcueingareviable

toolstohelpswimmersimprovetheirregularstroketechnique.

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TABLEOFCONTENTSABSTRACT………………………………………………………………………………………………………......ii

LISTOFTABLES…………………………………………………………………………………………………...v

LISTOFFIGURES…………………………..…………………………………………………………………….vi

LISTOFABBREVIATIONS………………………………………………………………………………..….vii

ARTICLEMANUSCRIPT……………………………………………………………………………………..viii

CHAPTER1:INTRODUCTION……………………………………………………………………………….1

Introduction……………………………………………………………………………………………...2

Statementoftheproblem…………………………………………………………………………..3

NeedfortheStudy……………………………………………………………………………………..3

OperationalDefinitions……………………………………………………………………………...3

Delimitations………………………………………………………………………………………….....4

Limitations………………………………………………………………………………………………..4

CHAPTER2:LITERATUREREVIEW……………………………………………………………………....5

HistoricalDevelopmentoftheBreaststrokeTechnique……………………………….6

ThePhasesoftheBreaststrokePull…………………………………………………………...6

PropulsiveKickPhasesoftheBreaststroke………………………………………………...8

TheGlidePhaseintheBreaststroke…………………………………………………………...9

HeadPositionsintheBreaststroke…………………………………………………………….9

iv

Arm-LegCoordinationintheBreaststroke………………………………………………..10

KinematicFactorsRelatingtotheTimingoftheBreaststroke……………………11

Velocity-VideoAnalysisValidation…………………………………………………………...12

CHAPTER3:METHODS………………………………………………………………………………………13

StudyObjectives……………………………………………………………………………………...14

ResearchDesign………………………………………………………………………………………14

Participants…………………………………………………………………………………………….14

PerformanceSite……………………………………………………………………………………..15

Instruments…………………………………………………………………………………………….15

KinematicDataCollectionProcedures……………………………………………………...16

StatisticalAnalysisofData……………………………………………………………………….17

Results……………………………………………………………………………………………………19

ComparativeSignificantDifferences………………………………………………20

Discussion……………………………………………………………………………………………….21

PracticalApplications………………………………………………………………………………25

APPENDIXA:CONSENTFORM……………………………………………………………………………27

REFERENCES……………………………………………………………………………………………………..29

v

LISTOFTABLES

1 AnthropometricMeasurements…………………………………………………………..19

2 ComparisonofBreaststrokeBiomechanicswithDifferentKickTechniques………………………………………………………………………………………...20

3 Univariatetestsfordependentvariables……………………………………………..21

vi

LISTOFFIGURES

1 Synchronizedframesofthethreecameraanglesusedtofilmswimmingtrials…………………...…………………………………………………………….15

2 Time-velocitygraphusedtoanalyzevelocitiesoftheBreaststroke………18

3 MaximalkneeflexionanglecalculatedinTemplo………………………………...18

4a Protocol1:Closeupofhandpositionduringtheearlyinsweep……………22

4b Protocol1:Coincidentkneekick…………………………………………………………22

5a Protocol2:Closeupofhandpositionduringthelateinsweep……………...23

5b Protocol2:Coincidentkneekick…………………………………………………………23

6a Protocol3:Closeupofhandpositionduringtheearlyrecovery…………...24

6b Protocol3:Coincidentkneekick…………………………………………………………24

vii

LISTOFABBREVIATIONS

%VDO PercentageVelocityDrop-off

%VR PercentageofVelocityRegained

ANOVA AnalysisofVariance

C100 ConventionalStroke100-yardsprintpace

CFD ComputationFluidDynamics

CI ConfidenceInterval

DU1 LateKick

DU2 DelayedLateKick

LED Light-EmittingDiode

MKF MaximalKneeFlexionAngle

NCAA NationalCollegiateAthleticAssociation

PAV MaximumHipVelocityGeneratedbytheArms

PLV MaximumHipVelocityGeneratedbytheLegs

SD StandardDeviation

SPSS StatisticalPackagefortheSocialSciences

TCK TimetoCompleteKick

UH UniversityofHawai‘iatMānoa

viii

KINEMATICANALYSISOFPEAKVELOCITIESINTHE

BREASTSTROKEASAFUNCTIONOFTHETIMINGOFTHE

KICK

IntroductionTheBreaststrokecanbebrokendownintothreephases,theKick,thePull,

andtheGlide.Whenthesethreephasesarecompletedinsuccession,aswimmer

hascompletedonefullcycleoftheBreaststroke.Thevariationsintheoverall

swimmingvelocitythroughoutoneBreaststrokecycleareagoodindicatorofthe

swimmer’sstrokeefficiency;themoreefficientaswimmer’sstrokeis,thebetter

theywillperform(Takagi,Sugimoto,Nishijima,&Wilson,2004).Anumberof

currentstudieshaveexaminedthecoordinationofthearmsandthelegsduringthe

Breaststrokecycle(C.D.D'AcquistoLJ,1998;Leblanc,Seifert,&Chollet,2009;van

Houwelingen,Roerdink,Huibers,Evers,&Beek,2017).Theearlierstudiesmainly

focusonperiodsofpropulsionprovidedbyeachphaseandhowtheyaffectthe

accelerationanddecelerationoftheentirecycle.Themostrecentstudybyvan

Houwelingenetal.notedswimmersarecapableofmanipulatingtheirarm-leg

coordinationresultinginintra-cyclicvelocityvariations.However,theirresults

wereinconclusive.

Duringthe2016Olympics,BritishswimmerAdamPeatywonthemen’s100-

meterBreaststrokeraceinworld-recordfashionusingakicktechniquethat

performsthekickphaseoftheBreaststrokelaterthanitisconventionallytaught.

Toourknowledge,thereiscurrentlynoresearchthatexamineshowthetimingof

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theinitiationofthekick,whenoccurringduringdifferentphasesofarmpullcan

affectthepropulsion,acceleration,andconsequentlyintra-cyclicvelocityofthe

Breaststroke.

ThelackofresearchregardinganalysisofthetimingoftheBreaststrokekick

islikelyduetherelativelynewnatureofthistechnique.However,giventhe

surprisingeffectthistechniquehashadonAdamPeaty’sgold-medal,world-record

performanceatthe2016Olympicgames,itisclearthatthistechniqueshouldbe

investigatedtodetermineifhisperformancesweretheresultoftraining,or

improvedtechnique.

Kinematicanalysisprovidesinvaluableinformationforbothswimmersand

coaches;videoplaybackallowsthemtoimmediatelyreviewaswimmer’stechnique

andobtainfeedbackformakingcorrections,anddigitalanalysisallowsaswimmer’s

strokeefficiencytobeformallyevaluatedandimproved(Costaetal.,2010;C.D.

D'AcquistoLJ,1998;C.D.D'AcquistoLJ,GehtsenGM,Wong-TaiY,LeeG,1988;

Jaszczak,2011;Strzałaetal.,2012).Thehiphasbeenvalidatedasthemostreliable

anatomicallandmarktouseformeasuringintra-cyclicvelocityanditschanges

withinastroke;theframe-by-frameanalysisthatcanbeutilizedinaccompaniment

withtherecordedintra-cyclicvelocityfluctuationsallowsresearcherstopinpoint

whichaspectsofthetechniquearecontributingtothefluctuationsinordertomake

improvements(Costaetal.,2010;C.D.D'AcquistoLJ,1998;C.D.D'AcquistoLJ,

GehtsenGM,Wong-TaiY,LeeG,1988;Jaszczak,2011;Strzałaetal.,2012;van

Houwelingenetal.,2017).

x

NeedfortheStudy Currentlytherearenopublishedstudiesthatexaminetheeffectsofthe

timingoftheBreaststrokekickduringspecificpullphasesonintra-cyclicvelocity

fluctuations.Theexpectationisthatthisresearchcanleadtoimprovedstroke

efficiencyandconsequentlyfasterswimmingtimes.

StatementoftheProblem Thepurposeofthestudyistodeterminetheeffectsofthetimingofthe

Breaststrokekickonintra-cyclicvelocityfluctuations.Theexpectationisthat

throughthisinvestigationitcanbedeterminedifthetimingassociatedwitha“late

kick”canprovidehigheroverallswimmingspeedsthanthe“conventionalkick”

technique.

MethodsStudyObjectives

Thepurposeofthisstudywastodescribetheresultsofakinematicanalysis

ofthe“conventional”vs.“late”Breaststrokekick,usingselectedvariablesofthese

twotypesofkickpatterns.Thestudywasdividedintotwoelements,eachposing

thefollowingquestions:

Question1:Isthereasignificantdifferenceinpeakhipvelocitydrop-offsbetween

thetwotechniques(conventionalvs.late)ofBreaststrokekicking?

Hypothesis1:Therewillbeasignificantdifferencebetweenthetwotechniquesof

kicking–therewillbelessofadrop-offinpeakhipvelocityforthesubjectswho

utilizethelatekicktechnique.

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Question2:Isthereasignificantdifferenceinthepercentageofvelocityregained

duringthepropulsivephaseofthekickrelatedtothemagnitudeofvelocity

percentagedrop-offduringkickdeceleration?

Hypothesis2:Therewillbeasignificantdifferenceinthepercentageofvelocity

regainedduringthepropulsivephaseofthekickrelatedtothemagnitudeofvelocity

percentagedrop-off–thesmallerthepercentagevelocitydrop-off,thegreaterthe

percentageofvelocityregainedwillbe.

ResearchDesign

Thisstudyutilizedasingle-subjectdesignbyexaminingtheeffectsonpeak

velocityduringtheBreaststrokewiththreedifferenttrialsofexecutingthekick

duringdifferentphasesofthestroke.Theindependentvariablewasthetimingof

thekick(conventional,late,ordelayedlate)andthedependentvariableswere

maximalkneeflexionangle,peakarmvelocity,peaklegvelocity,timetocomplete

kick,percentageofvelocitydrop-off,andpercentageofvelocityregained.

Participants

SubjectswererecruitedfromanNCAADivisionIswimmingteam(4males&

5females).n=9subjects(G*Powerapriorianalysis:ANOVArepeatedmeasures,

withinfactors;effectsizef=0.5;p=0.05;power=0.8;numberofgroups=1;number

ofmeasurements=3;correlationamongrepeatedmeasures=0.5;non-sphericity

correction=1)

Inclusionarycriteria:Breaststrokemustbeoneoftheirprimarycompetitiveevents;

theymusthavereachedNCAADivisionIlevelsofcompetitiveexperience.

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Exclusionarycriteria:Non-experiencedcompetitiveswimmers;injurythatprevents

swimmerfromswimmingwithnormaltechnique;Breaststrokeisnotaprimaryrace

eventfortheswimmer.

PerformanceSiteThisstudywasperformedattheDukeKahanamokuAquaticComplex,onthe

campusoftheUniversityofHawai‘i–Mānoa.

Instruments

• Three high-speed digital cameras (Baumer Model HXG with CMOS sensors),

installed in custom housings (The Sexton Company, Salem, Oregon).

• All 3 housings were attached to custom-designed mounting frames and positioned

so as to provide the three required fields of view (Figure 1).

Figure1.Synchronizedframesofthethreecameraanglesusedtofilmswimmingtrials.

• Camera 1 was used for recording the frontal, or head-on view, of the subject’s

progress and was mounted on a vertically oriented frame. The camera was

positioned at a depth of 0.48 meters (1.57 feet).

• Camera 2 was mounted on a horizontal platform that rested on the bottom of the

pool at a depth of 2.13 meters (7 feet). The camera was aligned vertically, i.e.

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pointing upwards to the surface and provided a transverse view of the subject’s

progress.

• Camera 3 was mounted on a laterally positioned frame that was bolted to the

concrete deck of the pool. The camera was positioned at a depth of 0.48 meters

(1.57 feet), similar to the depth of Camera 1. The lateral orientation of Camera 3

provided the data for the progress of the subject in the longitudinal plane of

motion.

• Thedistancethesubjectwasrequiredtocoverineachtrialvariedbetween

11.89and13.71meters(39to45feet).Thisdistancewasdeterminedby

placingthecamerathatwasusedforrecordingthefrontal,orhead-onview

ofthesubjectatadistanceof13.71meters(45feet)yardsfromthesideof

thepoolfromwhichthesubjectwasrequiredtopush-offatthestartofeach

trial.Subjectswereinstructedtoswimdirectlytowardsthiscamera,

approachingitascloseaspossiblewithoutcollidingwiththecamera.

• Thecameraswerecontrolledviadual9.14meter-long(30feet)Gigabit

(GigE)Ethernetcables connected to a desktop computer located on the pool

deck. Each camera had two cables - one cable was assigned to camera control

and another cable was used for frame synchronization. Unlike the limitations

relating to maximum functional lengths inherent when using Firewire cabling,

GigE cabling does not have a length restriction, which allowed for optimum

placement of the underwater cameras in the pool.

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• Rotational joint segments were identified using a custom-designed string of light

emitting diodes (LED’s), housed in waterproof housings. The LED’s were duct

taped to the body and powered by a battery pack attached to a belt worn by the

subject at the waist.

• Templo (Contemplas, Kempten, Germany) motion capture software was used for

capturing and recording the video data.

• A second software package, Motus, (Contemplas, Kempten, Germany), was used

for digitizing, data analysis, and generating “reports”. This software included a

“Multi 2-D” (M2-D) feature, which enabled multiple cameras to be synchronized.

Each sequence was digitized using a combination of auto-tracking and manual

modes.

• IBM Statistical Package for the Social Sciences (SPSS) version 23 was used to

run statistical analysis.

KinematicDataCollectionProcedures

AfterobtainingapprovalforthestudyfromtheUniversityofHawai‘iat

MānoaUniversityInstitutionalReviewBoardfortheStudyofHumanSubjects,

BreaststrokesubjectswererecruitedfromtheUniversityofHawai‘iatMānoa

IntercollegiateSwimmingTeam.Subjectsreportedtothepoolatascheduledtime,

andsignedaconsentform.Priortovideotaping,eachsubjectwasshowna

previouslydigitizedswimtrialsoastofamiliarizethemwiththeoutcomeofthe

videotapingandresulting“report.”Followingtherecordingofeachsubject’s

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anthropometricdata,theLEDlightsweretapedontospecificanatomiclandmarks

(bilateralfingers,wrists,elbows,shouldersandrighthip).Thesubjectwas

providedwithsufficienttimetoswimafewwarmuplapstogetaccustomedto

swimmingwiththetapedLEDlightstrings.

Thesubjectperformedatotalofthreetrialsof3specifiedswimming

protocols.

Thethreeprotocolsconsistedofthefollowing:

ProtocolOne(ConventionalStroke):Thesubject,whileswimmingtheBreaststroke,

wasrequiredtousetheirregulartechnique,ataneffortthatcorrespondedtothe

pacetheywouldcompletea100-yardracesprint.Inallexceptasinglecase,the

subject’s“conventionalstroke”consistedoftheinitiationofthekickcoincidingwith

thebeginningstageoftheinsweep,calledthe“earlyinsweep.”

ProtocolTwo(LateKick):Thesubject,whileswimmingtheBreaststroke,was

requiredtotimetheinitialdraw-upofthekicktocoincidewiththeperiodduring

whichthehandswereinthefinalstageofthesecondphaseoftheBreaststrokepull

pattern(theinsweep),calledthe“lateinsweep.”

ProtocolThree(DelayedLateKick):Thesubject,whileswimmingtheBreaststroke,

wasrequiredtotimetheinitialdraw-upofthekicktocoincidewiththeperiod

duringwhichthehandswerebeginningthe“recovery”phase,i.e.handsmoving

forwards.

Subjectswereaskedtorepeatatrialiftheydidnotmeetthecriteriafora

givencondition,withamaximumofthreetrialspercondition,andweregiventime

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torestbetweentrialsinordertoeliminatefatigueasaconfoundingvariableduring

thesecondandthirdtrials.

Thevideodatawasthenuploadedtothedigitizingsoftware,whereitwas

digitizedandthefootagewassynchronizedtoproducedynamicpeakvelocity-time

graphstoanalyzethefluctuationsinpeakvelocities.Thetrialswerecomparedto

eachothertorecordtheresultingdifferencesbetweenthepeakvelocity,the

minimumvelocityrecordedduringtheeffort,andthevelocityregainedasthenext

strokewasinitiated.

StatisticalAnalysisofData

Eachsubject’sstrokewasdigitizedandanalyzedusingtheMotusandTemplo

software.Thepercentagedrop-offinpeakvelocity,percentageofthevelocity

regained,maximumhipvelocitygeneratedbythearms,andmaximumhipvelocity

generatedbythelegswereseenthroughtheuseoftime-velocitygraphs(Figure2).

Figure2.Time-velocitygraphusedtoanalyzevelocitiesoftheBreaststroke.

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Maximumkneeflexionangleandtimetocompletekickweremeasuredby

usingTemplo’sanglemeasurefunctiononatime-stampedvideo(Figure3).

Figure3.MaximalkneeflexionanglecalculatedinTemplo.

Duetothesingle-subjectdesignofthisstudy,eachsubject’sowntrialswere

analyzedagainsteachothertonoteanysignificantdifferenceinthetimingofthe

Breaststrokekickonpeakvelocity(notedifferenceindrop-off/regained);for

example,subject1’sProtocol1trial,Protocol2trial,andProtocol3trialwereall

comparedagainsteachother,butsubject1’sProtocol1trialwasnotcompared

againstsubject2’sProtocol1trial.Foreachdependentvariable,allofthedata

varianceforeachsubjectwascomparedagainstrespectivedatavarianceforthe

othersubjectsforalltrials;forexample,subject1’smaximalkneeflexionanglefor

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Protocol1trialwascomparedtosubject2’smaximalkneeflexionangleforProtocol

1trial.ThesignificantdifferenceforeachprotocolwasdeterminedusingANOVA

repeatedmeasuresanalysiswithasignificancelevelsettop=0.05(Field2009).

Mauchly’stestofsphericitywasruntovalidatetheparametersoftheANOVA

repeatedmeasuresanalysiswithasignificancelevelsetatp=0.05(Field2009).

Greenhouse-GeisserandHuynh-FeldtcorrectionswereusedwiththeMauchly’s

test;Huynh-Feldtcorrectionwasusedforpeakhipvelocitygeneratedbythelegs,

andGreenhouse-Geissercorrectionwasusedforallotherdependentvariables

(Field2009).

Results

Subjectsinthisstudyweren=9NCAADivisionIswimmers.Anthropometric

datacollectedforthesesubjectsincluded:age,height,weight,bodymassindex,and

wingspan.Thedataisdisplayedintable1.

Table1.Anthropometricmeasurements.

Variable Mean SDAge,years 20.67 1.32Height,in. 70.34 3.81Weight,lb. 158.34 16.96Bodymassindex,kg/m2 22.49 1.56Wingspan,in. 71.11 5.73SD=StandardDeviation

Followingthestatisticalanalysisoftheirtrials,themeans,standard

deviations,and95%confidenceintervalsforallvariableswerecalculatedandare

reportedintable2.Alsocalculatedintable2arepairwisecomparisonsofdatato

demonstratesignificancebetweenthethreedifferentkicktechniquesforeach

dependentvariable.

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Table2.ComparisonofBreaststrokeBiomechanicswithDifferentKickTechniques.

Measure

C100 DU1 DU2

Mean±SD CIp-value

Mean±SD CIp-value

Mean±SD CIp-value

DU1 DU2 C100 DU2 C100 DU1%VDO 91.2±4.9 91.3±3.8 0.02 0.01 86.8±5.0 86.8±3.8 0.02 0.03 82.5±5.2 82.5±4.0 0.01 0.03%VR 91.1±11.8 91.1±9.1 0.02 0.01 96.3±11.6 96.4±9.0 0.02 0.39 97.3±10.2 97.3±7.9 0.01 0.39MKF,O 36.1±5.1 36.1±4.0 0.22 0.03 33.7±6.8 33.7±5.2 0.22 0.03 31.6±6.1 31.6±4.7 0.03 0.03PAV,m/s 2.2±0.5 2.2±0.4 0.10 0.06 1.9±0.3 2.0±0.3 0.10 0.23 1.9±0.4 1.9±0.4 0.06 0.23PLV,m/s 2.0±0.4 2.0±0.3 0.42 0.27 1.9±0.3 1.9±0.3 0.42 0.43 1.8±0.4 1.8±0.3 0.27 0.43TCK,s 0.6±0.1 0.7±0.1 0.02 0.05 0.7±0.1 0.7±0.1 0.02 0.36 0.7±0.1 0.7±0.1 0.05 0.36

%VDO=PercentageVelocityDrop-off;%VR=PercentageofVelocityRegained;MKF=MaximumKneeFlexionAngle;PAV=PeakHipVelocityGeneratedbytheArms;PLV=PeakHipVelocityGeneratedbytheLegs;TCK=TimetoCompleteKick;C100=ConventionalStroke100-ydsprintpace;DU1=LateKick;DU2=DelayedLateKick;SD=StandardDeviation;CI=ConfidenceInterval

ComparativeSignificantDifferences

Whencomparing“ConventionalStroke”andthe“LateKick,”significantdifferenceswereseeninthefollowingparameters:

a) Timetakentocompletekick.

b) Percentageofhipvelocitydrop-off.

c) Percentageofvelocityregained.

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Whencomparing“ConventionalStroke”andthe“DelayedLateKick,”significant

differenceswereseeninthefollowingparameters:

a) Maximalkneeflexionangle.

b) Timetakentocompletekick.

c) Percentageofhipvelocitydrop-off.

d) Percentageofvelocityregained.

Whencomparingthe“LateKick”tothe“DelayedLateKick,significantdifferences

wereseeninthefollowingparameters:

a) Maximalkneeflexionangle.

b) Percentageofhipvelocitydrop-off.

ToensurethevalidityofthesignificancefoundintheANOVArepeated

measuresanalysis,Mauchly’stestofnon-sphericitywasrun.Huynh-Feldtcorrection

wasusedforpeakhipvelocitygeneratedbythelegs,andGreenhouse-Geisser

correctionwasusedforallotherdependentvariables.Partialetasquaredwasalso

calculatedtodeterminehowmuchofthechangeseenineachvariablecouldbe

attributedtotheconditionalone.Changesinkickprotocolaccountfor11-56%of

thedifferenceseenforeachdependentvariable.Thisdataisshownintable3.

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Table3.Univariatetestsfordependentvariables.

Peakhipvelocitygeneratedbythearmswastheonlyvariablefound

significantintheMauchly’stestofnon-sphericity(p=0.04);Greenhouse-Geisser

correctionwasusedtodeterminesignificanceforthisvariable(p=0.07).Therefore,

allthesignificantvaluesfoundintheANOVArepeatedmeasuresanalysiscanbe

consideredvalid.

Discussion

Thepurposeofthisstudywastodescribethekinematicsoftheconventional

versusthelateBreaststrokekicktechniqueusingselectedvariablestodetermine

theefficiencyofeachtechnique.Currently,onlyonestudyexiststhatexaminesthe

effectsofthetimingoftheBreaststrokekickonintra-cyclicvelocity.However,this

singlestudybyvanHouwelingenetal.usedsubjectsthatwereof“average”

competitiveexperience,andconsequentlynotclassifiedascompetingattheelite

levels.Theirconclusionswerelimitedtostatingthat“average-levelswimmersare

capableofadjustingtheirleg-armcoordinationwithacousticcueingandthat

differenttimingofthekickdoesaffectintra-cyclicvelocityvariation”.(van

Houwelingenetal.,2017)Unfortunately,thisstudydoesnotspecificallyaddressleg-

MeasureMauchly’s Greenhouse-Geisser Huynh-Feldt

Sig. W Sig. PartialEtaSq. Sig. PartialEtaSq.%VDO 0.05 0.435 0.01 0.558 0.01 0.558%VR 0.28 0.695 0.01 0.516 0.00 0.516MKF,O 0.08 0.489 0.05 0.354 0.05 0.354PAV,m/s 0.04 0.411 0.07 0.331 0.06 0.331PLV,m/s 0.11 0.531 0.36 0.110 0.36 0.116TCK,s 0.06 0.447 0.04 0.379 0.04 0.379

MKF=MaximumKneeFlexionAngle;PAV=PeakHipVelocityGeneratedbytheArms;PLV=PeakHipVelocityGeneratedbytheLegs;TCK=TimetoCompleteKick;%VDO=PercentageVelocityDrop-off;%VR=PercentageofVelocityRegained

xxii

armcoordination,howtoreplicatethestudy,norweretheyabletoexplainhow

thesefindingscouldbeappliedbycoacheswhentrainingswimmers.

Consequently,ourstudyisthefirsttohavedefinedparameterstoclassify

leg-armcoordinationandincorporatethemintoaspecificvariationofthe

Breaststrokeswimmingtechnique.

Inordertobedesignatedasa“ConventionalStroke”,“LateKick”ora

“DelayedLateKick”,thetimeatwhichthekickreached160degreesofflexionwas

matchedwiththephaseatwhichthepullingactionofthehandscoincidedwiththis

positionoftheknee.

Duringtheprotocolwherethesubjectswererequiredtoswimusingtheir

“ConventionalStroke”,thedistinguishingfeaturewasthattheinitiationofknee

flexiontookplaceduringtheearlystagesofthesecondphaseoftheBreaststroke

armpull.Thisphaseistermedthe“earlyinsweep”ascomparedtothe“late

insweep”whichisthelaterstageandconcludingportionofthepropulsivephaseof

theBreaststrokepull(Figures4aand4b).

Figure4a.Protocol1:Closeupofhandpositionduringtheearlyinsweep.

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Figure4b.Protocol1:Coincidentkneekick.The“LateKick”wasthetimethehandswerecompletingthe“lateinsweep”

(Figures5aand5b)and“DelayedLateKick”coincidingwiththepositionofthe

handswhentheywerestartingtobethrustforwardsintotherecoveryphase

(Figures6aand6b).

.

Figure5a.Protocol2:Closeupofhandpositionduringthelateinsweep.

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Figure5b.Protocol2:Coincidentkneekick.Figure6a.Protocol3:Closeupofhandpositionduringtheearlyrecovery.

xxv

Figure6b.Protocol3:Coincidentkneekick.Allninesubjectsofthisstudywereelite-levelswimmerswhowereallableto

performeachspecifiedkicktechniquewithonlyverbalcueing.Theanalysisofeach

subject’strialsrevealedthatthesmallestpercentagesofvelocitydrop-offwereseen

duringthe“delayedlatekick”technique.Thatis,whenthethreeprotocolswere

compared,thethirdprotocol,whenthesubjectswaiteduntiltheirhandsstartedto

beextendedforwards,weobservedthesmallestdrop-offinoverallhipvelocities.

Thesecondphaseof“leastdrop-off”wastheprotocoldesignated“LateKick”,when

thehandswereapproachingthebody,duringthe“insweep”phaseofthearmpull.

Thegreatestamountofvelocityregainedwasinthelatekicktechniqueand

thedelayedlatekicktechnique.Thisindicatesasmallervelocityvariationwithin

onestrokecycle,whichindicatesamoreefficientBreaststroketechniquethanthe

subject’snormaltechnique.Thesefindingsareinagreementwiththeconclusions

xxvi

reachedbytwoearlierpublishedmanuscripts(C.D.D'AcquistoLJ,1998;van

Houwelingenetal.,2017).

Therewerenosignificantdifferencesinpeakhipvelocitygeneratedbythe

armsorpeakhipvelocitygeneratedbythelegsbetweenthesubjectswhenusing

eitherofthethreeprotocols.However,thefastestoverallswimmingvelocitieswere

achievedinthesubjects’regularBreaststroketechniquetrialsbeforetheywere

askedtomakeadjustmentstotheirstrokes.Theseresultswereexpectedbecause

allsubjectstestedwerecurrentlyin,orrecentlyconcluded,intensetraining,and

wereinstinctivelyswimmingattheircurrenttrainingvelocities.

Maximalkneeflexionangleandtimetocompletekickaretwovariablesthat

havenotyetbeenstudiedasitrelatesarm-legcoordinationoftheBreaststroke

techniqueandintra-cyclicvelocityvariations.Maximalkneeflexionwas

significantlydifferentbetweentheregularBreaststroketechniqueandthedelayed

latekicktechnique,butnotbetweentheregularBreaststroketechniqueandthelate

kicktechnique.Whatwasobservedwasthatthesubjectstendedtoincreasethe

degreeofkneeflexion,thelatertheywereaskedtokickintheirstroke.These

changesmaybeattributedtotheperceptionoftheoverallstrokecycletakingmore

time,therebyallocatingmoretimetoincreasetheamountofkneeflexion.As

expected,thisalsoincreasedthetotaldurationsofthe“LateKick”and“DelayedLate

Kick”whencomparedtothedurationsofthesubjects’kickwhenswimmingtheir

“ConventionalStroke”.

Inregardstotheresearchquestionsposedforthisexperiment,itcanbe

concludedthatthereisasignificantdifferencebetweenhipvelocitiesasafunction

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oftheinitiationofkneeflexionandhandpositionsduringtheBreaststrokepull

phase.Itcanbeconcludedthatthereislessofadrop-offinhipvelocities,and

highervaluesforregaininghipvelocities,accompanyinglaterdurationsofthepull

phase.

PracticalApplications

Theconclusionsderivedfromthisstudyareinagreementwiththecurrent

trendincompetitivesprintBreaststroketechnique.Althoughthetimingoftheleg

draw-upduringthelongestcompetitivedistance,the200meters,stillshows

relativelyearlydraw-upofthekick,thefindingsofthestudyshowscleardifferences

whenthereisadelaybeforetheinitiationofthekickwhenswimmingtheshorter

competitivedistances.

Thisstudyrevealedthatbyvirtueofsmallerdecreasesintheperiodsof

velocity“drop-off”,higherswimmingvelocitiesmaybeachievedwhenthekickis

initiatedduringtheinsweeporearlyrecoveryarmphases.Thisstudyalsoproves

thatvideoanalysisandverbalcueingarebothviablefeedbacktoolsthatcanbeused

tohelpswimmerslearntomakeadjustmentstotheirregulartechniquestobecome

moreefficientinthewater.

CHAPTER1:INTRODUCTION

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Introduction

TheBreaststrokecanbebrokendownintothreephases,theKick,thePull,andtheGlide.Whenthesethreephasesarecompletedinsuccession,aswimmerhascompletedonefullcycleoftheBreaststroke.ThevariationsintheoverallswimmingvelocitythroughoutoneBreaststrokecycleareagoodindicatoroftheswimmer’sstrokeefficiency;themoreefficientaswimmer’sstrokeis,thebettertheywillperform(Takagi,Sugimoto,Nishijima,&Wilson,2004).AnumberofcurrentstudieshaveexaminedthecoordinationofthearmsandthelegsduringtheBreaststrokecycle(C.D.D'AcquistoLJ,1998;Leblanc,Seifert,&Chollet,2009;vanHouwelingen,Roerdink,Huibers,Evers,&Beek,2017).Theearlierstudiesmainlyfocusonperiodsofpropulsionprovidedbyeachphaseandhowtheyaffecttheaccelerationanddecelerationoftheentirecycle.ThemostrecentstudybyvanHouwelingenetal.notedswimmersarecapableofmanipulatingtheirarm-legcoordinationresultinginintra-cyclicvelocityvariations.However,theirresultswereinconclusive.

Duringthe2016Olympics,BritishswimmerAdamPeatywonthemen’s100-

meterBreaststrokeraceinworld-recordfashionusingakicktechniquethatperformsthekickphaseoftheBreaststrokelaterthanitisconventionallytaught.Toourknowledge,thereiscurrentlynoresearchthatexamineshowthetimingoftheinitiationofthekick,whenoccurringduringdifferentphasesofarmpullcanaffectthepropulsion,acceleration,andconsequentlyintra-cyclicvelocityoftheBreaststroke. ThelackofresearchregardinganalysisofthetimingoftheBreaststrokekickislikelyduetherelativelynewnatureofthistechnique.However,giventhesurprisingeffectthistechniquehashadonAdamPeaty’sgold-medal,world-recordperformanceatthe2016Olympicgames,itisclearthatthistechniqueshouldbeinvestigatedtodetermineifhisperformancesweretheresultoftraining,orimprovedtechnique. Kinematicanalysisprovidesinvaluableinformationforbothswimmersandcoaches;videoplaybackallowsthemtoimmediatelyreviewaswimmer’stechniqueandobtainfeedbackformakingcorrections,anddigitalanalysisallowsaswimmer’sstrokeefficiencytobeformallyevaluatedandimproved(Costaetal.,2010;C.D.D'AcquistoLJ,1998;C.D.D'AcquistoLJ,GehtsenGM,Wong-TaiY,LeeG,1988;Jaszczak,2011;Strzałaetal.,2012).Thehiphasbeenvalidatedasthemostreliableanatomicallandmarktouseformeasuringintra-cyclicvelocityanditschangeswithinastroke;theframe-by-frameanalysisthatcanbeutilizedinaccompanimentwiththerecordedintra-cyclicvelocityfluctuationsallowsresearcherstopinpointwhichaspectsofthetechniquearecontributingtothefluctuationsinordertomakeimprovements(Costaetal.,2010;C.D.D'AcquistoLJ,1998;C.D.D'AcquistoLJ,GehtsenGM,Wong-TaiY,LeeG,1988;Jaszczak,2011;Strzałaetal.,2012;vanHouwelingenetal.,2017).

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StatementoftheProblem ThepurposeofthestudyistodeterminetheeffectsofthetimingoftheBreaststrokekickonintra-cyclicvelocityfluctuations.Theexpectationisthatthroughthisinvestigationitcanbedeterminedifthetimingassociatedwitha“latekick”canprovidehigheroverallswimmingspeedsthanthe“conventionalkick”technique.NeedfortheStudy CurrentlytherearenopublishedstudiesthatexaminetheeffectsofthetimingoftheBreaststrokekickduringspecificpullphasesonintra-cyclicvelocityfluctuations.Theexpectationisthatthisresearchcanleadtoimprovedstrokeefficiencyandconsequentlyfasterswimmingtimes.OperationalDefinitions

IndependentVariablesMeasured

• ConventionalStroke:Thekickistimedtoinitiatewiththeearlyinsweepofthehands

• LateKick:Thekickistimedtoinitiatewiththelateinsweepofthehands• DelayedLateKick:Thekickistimedtoinitiatewithearlyarmrecovery• BreakinRhythm:Thekickistimedtoinitiatewiththeendofthearm

recovery

DependentVariablesMeasured

• MaximumHipVelocityGeneratedbytheArms(PAV):Thehipvelocityspeed(m/s)obtainedbyswimmerasmeasuredattheanatomicalmarkerplacedatthehipduringpeakspeedofarmpull

• MaximumHipVelocityGeneratedbytheLegs(PLV):Thehipvelocityspeed(m/s)obtainedbyswimmerasmeasuredattheanatomicalmarkerplacedatthehipduringpeakspeedoflegkick

• TimetoCompleteKick:Thetime(s)elapsedfrominitiationofkick(kneeflexionangle160O±3O)toterminationofkick(returnaftermaximalkneeflexionto160O±3O)

• MaximumKneeFlexion:Theangle(degrees)measurebetweenhip-knee-anklewhenthesubjects’legshavereachedthemaximalflexionpointofthekick

• %Drop-off:Thepercentageofvelocitylostfrommaximumhipvelocitygeneratedbythearmstominimumvelocityduringlegdeceleration

• %Regained:Thepercentageofvelocityregainedfromminimumvelocityduringlegdecelerationtomaximumhipvelocitygeneratedbythelegscomparedtomaximumhipvelocitygeneratedbythearms

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Delimitations

1. Subjectsinthisstudywere9healthyswimmers(4maleand5female),withaprimarystrokefocusofeitherBreaststrokeorIndividualMedley.AllsubjectsweremembersofanNCAADivisionIVarsitySwimTeam.Thissubjectpoolwasselectedtoensuresimilarlevelsofcompetitiveexperience.

2. Measuringhipvelocityhelpedtoensurethemostaccuratevelocitymeasurementswererecordedduringtheswimtrials.

3. Eachsubjectwasconsideredtheirowncontrol;eachoftheirtrialswereonlycomparedagainsttheircurrentstroketechnique.

4. Variablesweremeasuredagainstthesubject’sowndatapoints;datafromeachsubjectwerethencomparedtoeachother.

Limitations

1. Thesubjectswereaskedtomakemodificationstotheirnormalstroketechnique.Becausethisstudyrequiredvariationsbemadetoeachindividual’skickmechanics,itwasanticipatedthatthesechangesmightaffectstrokeperformanceinawayotherthanthefactorsstudied,forexample,thelikelihoodofthesubjectslowingdowntheirnormalcadencesoastoperformtherequestedvariation.

2. Usingarepeated-measuresdesignintroducedthepossibilitythatthesubjectsmightmodifytheirtechniquebasedontheprevioustrials.Subjectswereaskedtoperformonemodificationatatime,buteachtrialmayhavehadaninfluenceonsubsequenttrials.

3. Theresultsofthisstudywerelimitedtothesubjectpopulationused.

CHAPTER2:LiteratureReview

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HistoricalDevelopmentoftheBreaststrokeTechnique

Breaststrokeisoneofthefourcompetitiveswimstrokes;asastroke,ithasdevelopedfromitsorigin,asaskillusedforlifestyleactivitiessuchashunting,fishing,andmilitarypurposes,toitscurrentcompetitivetechnique(Trendafilov,2015).Whenthemoderntechniquewasfirstdeveloped,swimmersperformedthekickingactionusingwhatwastermedthe“wedgekick”.Thebeliefwasthatattheconclusionofthekick,whenthelegsapproachedeachotherinbi-lateraladduction,topushawedgeofwaterbetweentheirlegstoachieveforwardpropulsion,andusedanunderwaterhandscoopmotionbacktotheshoulderlinetocreateforwardmovementfromthearmpull(Trendafilov,2015).

Later,thekickwaschangedtoresemblea“circularpushingmotion”focusing

onnarrowingthegapbetweenthefeet,asthiswasfoundtoproducelessdragwhilestillproducingtheforwardpropulsion(Trendafilov,2015).Whenanalyzingthetechnique,thekickandthepullcaneachbebrokendownintospecificphases;otherkinematicfactorsanalyzedfortheBreaststroketechniqueinclude:velocity,drag/resistance,propulsion,buoyancy,andpitch.ThePhasesoftheBreaststrokePull

Researchersdisputethenumberofphasesintowhichthearmpullmaybebrokendown;Takagi,Sugimoto,Nishijima,andWilson(2004)andMartensandDaly(2012)breakthearmpulldownintofourphases,whileSeifertandChollet(2005)breakdownthearmpullintofivephases.Takagietal.(2004)breaksdownthearmpullintotherecoveryphase,theglidephase,theoutsweepphase,andtheinsweepphase;MartensandDaly(2012)breakthearmpulldownintotwotranslationalphases–theoutsweepandtheinsweep–andtworotationalphases–pronationandsupinationoftheforearm.SeifertandChollet(2005)breakthearmpullintothefivephasesofarmglide,armpropulsion,elbowpush,upperlimbpropulsion,andrecovery.

InthestudyofTakagietal.(2004),armrecoverywasdefinedastheperiod

startingatmaximumelbowflexionunderthebreastuntilthearmsarefullyextendedinfrontoftheface;theglidestartsattheendofthearmrecoveryandendswhenthefirstlateralmovementofthearmsisobserved;theoutsweepstartswiththefirstlateralarmmovementandendswhenthehandsarefirstseenmovingdownandbackwards;andtheinsweepistheperiodstartingattheendoftheoutsweep,andendingwhenthehandscometogetherfortherecoverymotion.InthestudyofSeifertandChollet(2005),the“armglide”istheperiodbetweenfullarmextensionandthestartofthebacksweepofthehand;thearmpropulsionisthephasebetweenthebeginningandtheendofthebacksweepofthehand;theelbowpushisthetimestartingattheendofthebacksweepofthehandandthebeginningoftheforwardhanddriveandtheendofthebackwardinsweepoftheelbowpush;theupperlimbpropulsionisthesumofthearmpropulsionandelbowpushphases;andthe

7

recoveryphasestartswiththeendoftheelbowpushandendswiththearmsinfullextension,stretchedoutinfrontoftheface.

TherehasbeenmuchdebateaboutwhetherthearmpulloftheBreaststrokeisapullingactionorascullingaction.WhileNewton’sLawofaction/reactioncanbeappliedtoforcesonland,itcannotbeappliedtoswimmingstrokesbecausethewaterisnotasolidobjecttobeactedupon;however,inordertoapplythisformofpropulsion,“propulsivedrag”forceswouldbethedominantforce.

TheearlyschoolofthoughtonBreaststrokepropulsionwasthatpropulsion

inthestrokewascreatedfromliftduetotheBernoullieffect(Maglischo,2013a,2013b).However,Maglischo(2013)notesthattheBernoulliTheoremrequireslaminarflowtoproducelift,anddiscreditsthistheoremasameansofpropulsionbyprovingthatwatermovesoveraswimmer’shandsduringtheBreaststrokeinturbulentflowinstead.Thethree-dimensionalmotionoftheBreaststrokearmpull,createdbythecurvilinear,semicircularpathofthehands,thesimultaneousupanddownmotionofthehands,andshoulderadductioncauseittoinsteadbeaformofpropulsiondominatedbydragratherthanlift,thoughliftisstillproduced(Maglischo,2013a,2013b).Aslongasthearmsandhandsaremovingbackwardstosomeextent,thebackwardforceexertedbytheswimmerwillacceleratetheirbodyforward(Maglischo,2013a,2013b).Consequently,Maglischo(2013)presentsastrongargumentthatthearmstrokeisindeedapull.TheargumentispresentedonthebasisthattheBreaststrokearmmotionisadrag-dominatedpropulsivepullratherthanascullingmotion(Maglischo,2013a,2013b).

Whencomputationfluiddynamics(CFD)wereusedinasimulationofturbulentflowwaterconditionsoverasimulatedforearmandhandtofurtheranalyzetheBreaststrokearmpull,maximumpropulsionwasfoundtooccurwhenthehandswerefacingdirectlybacktowardthefeet,evenwhilethehandswerestrokingdiagonallythroughthewater(Maglischo,2013a,2013b).Thebodywasacceleratingwhenthehandswereinthediagonal-backwardspointintheoutsweepanddecelerationofthebodybeganwhenthehandsstartedmovingforwardduringtheinsweep(Maglischo,2013a,2013b).

Basedonthesefindings,Maglischo(2013)hadseveralrecommendations

aboutthebesttechniquefortheBreaststrokearmpull,including:thearmsshouldmovebackinalargesideward,shoulderadducting,semicircularsweep;thepropulsivephaseoftheinsweepshouldterminateandtherecoveryshouldbeginaftertheswimmerhascompletedabouttwo-thirdsoftherecovery;andthattheelbowsshouldtravelbeyondtheshouldersinordertolengthenthepropulsivephaseoftheinsweep.

FindingsfromaCFDanalysisofaswimmer’sarmandhandduringaBreaststrokepullperformedbyRiewaldandBixler(2001)alsosupportedtherecommendationsofMaglischo(2013).Theirstudyfoundaccelerationanddecelerationofthehands,haveagreatereffectondragthanonlift,andalsofound

8

thattheyaffectthearmdragtwiceasmuchasthehanddrag(RiewaldS,2001).Theyalsoconcludedthatmaximumhandpropulsiveforceisachievedwhenthepalmofthehandisfacingdirectlytowardsthefeet,evenifthepullitselfismovingdiagonally(RiewaldS,2001).TheirrecommendationsforthebesttechniquefortheBreaststrokearmpullinclude:keepingthearmsandhandsacceleratingasmuchaspossible,becauseevenaslightdecelerationcanresultinasignificantreductionofpropellingforce;thehandshouldbeinapositiontomaximizedragduringtheaccelerationpartofthestroke;placingmorefocusonthearm,asitplaysalargerroleinpropulsionthanpreviouslythought;andmaximizingpropulsionduringthephasesofthearmpullwherethepalmsarefacingtowardsthefeet(RiewaldS,2001).

MartensandDaly(2012)notethattheBreaststrokepullisresponsibleforthesecondlargestvelocityincreaseduringaBreaststrokestroke(kickisresponsibleforlargestvelocityincrease).Theynotethatduringthearmpull,theswimmermovesfromtheirmosthydrodynamicposition,thestreamlinedpositionwhentheirarmsarestretchedoutinfrontofthemattheendoftherecoveryphase(Costaetal.,2010;Martens&Daly,2012)totheleasthydrodynamicposition,whentheylifttheirheadtobreathe(Martens&Daly,2012).ContrarytoMaglischo(2013),theyconsidertheBreaststrokepullasproducingmoreofascullingmotion,andpositthattheinsweepscullingismorepropulsivethantheoutsweepsculling(Costaetal.,2010).

Whenspecificallyexaminingthemotionofthehands,theynotethattheoptimalhandpositionforcreatingmaximumpropulsionishavingthefingersclosedandthethumbfullyabducted,andusingacuppedhandwithstraightfingersisbetterthannaturallybentfingers(Costaetal.,2010).TheirotherkeyfindingsregardedswimmerswhoperformtheBreaststrokewithanundulatingmotion,ratherthanswimmingflatBreaststroke.TheyreportthatundulatingBreaststrokeswimmersbenefitmorefromalongerhandpaththanflatBreaststrokeswimmersandthatduringthefirstpartofthearmpulltheyalsoacceleratemore(Costaetal.,2010).PropulsiveKickPhasesoftheBreaststroke

Researchersdisputethenumberofphasesinthelegkick;whileTakagietal.(2004)separatethelegkickintothreephases,SeifertandChollet(2005)analyzetheBreaststrokekickbybreakingitdownintofivephases.ThethreephasesdescribedbyTakagietal.(2004)includethesweep,theliftandglide,andtherecoveryphases;thefivephasesdescribedbySeifertandChollet(2005)includethesephases,buthaveaddedtwomorephases:legpropulsion,leginsweep,legglide,recoverypartone,andrecoveryparttwo.Legpropulsionisthephaseofthekickthatbeginswiththefirstbackwardmovementofthefeetandendswhenthelegshavereachedfullextension(Seifert&Chollet,2005).Leginsweepreferstothephaseofthatstartswhenthelegsreachfullextensionandendswhenthelegsare

9

joinedtogether(Seifert&Chollet,2005).Legglideisthephaseofthekickthatbeginswhenthelegsarejoinedtogetherandendswhenthelegsbegintobeflexedforward(Seifert&Chollet,2005).Legrecoveryreferstothephase(s)thatbeginswiththeendoflegglideandendswiththeterminationoftheforwardmovementofthefeet(Seifert&Chollet,2005).

ThesephasescombinetocreateoneBreaststrokekick,whichcausesthe

largestvelocityincreaseduringaBreaststrokestroke(Martens&Daly,2012).Thefirstlargeincreaseinvelocityisduetheextensionofthelegswiththefeetpronated–thelegpropulsionphase(Martens&Daly,2012;Seifert&Chollet,2005).Asecond,slightlysmallerincreaseinvelocityisseenasthelegpropulsionphaseendsandthelegsfinishthecircularkickingmotionduringtheleginsweep,duringwhichthefeetshouldsupinatetocontinuetoprovideforwardpropulsionfortheswimmer(Martens&Daly,2012;Seifert&Chollet,2005).Duringthismoment,asthelegsfinishextending,theswimmer’smaximummomentofinertiaduringthestrokeoccurs;however,theminimummomentofinertiaoccursquicklyafterwhenthelegsbecomefullyflexedattheendoftherecoveryphase(Cohen,Cleary,Harrison,Mason,&Pease,2014).TheGlidePhaseintheBreaststroke

Ashasalreadybeennoted,thearmandlegphaseseachhavetheirownrespectiveglidephases;however,thereisaoverall“glidephase”thatisincludedaspartoftheBreaststrokestroke(Seifert&Chollet).Theglidephaseisaperiodofdecelerationinthestroke.Inorderfortheswimmertominimizetheirdeceleration,theyattempttomaintainastreamlinedpositionduringtheglidephaseofthestroke(Seifert&Chollet)sincethestreamlinepositionisthemosthydrodynamicbodyposition(Costaetal.,2010).

Aswimmermayvarytheamountoftimetheyspendintheglidephaseofthestrokedependingonthedistanceoftherace;200mswimmerstendtooptimizetheirstrokeeconomybylengtheningtheglidephaseanddecreasingthestrokerate(Strzałaetal.,2012).InastudybyTakagietal.(2004),itwasnotedthatthenon-propulsivephaseofthestoke,theglide,maybemoreimportantforhigherperformancethanthepropulsivephase.Theystatedthatacharacteristicofbetterperformingswimmerswasthelesserreductioninvelocityduringthenon-propulsivephase–essentially,alowerdrop-offbetweenintra-cyclicpeakvelocities(Takagietal.,2004).HeadPositionsintheBreaststroke

AstudybyStallman,Major,Hemmer,andHaavaag(2010)analyzedtheBreaststrokefromasurvivalperspective,andintheirstudyitwasnotedthatswimmingthestrokewiththeheadupandoutofthewaterdisplacesthecenterofgravityofthebodyfurtherbackwardsfromthecenterofbuoyancyoftheswimmer,

10

whichleadstoanincreaseintheamountoffrontalresistancetheswimmerencounters.SwimmingBreaststrokewiththeheadoutofthewaternotonlyincreasedtheresistance,butconsequentlycausedgreatermuscularexertionandearlierfatigueoftheswimmers;swimmingwithanormalbreathingpattern,wheretheheadissubmergedforpartofthestroke,wasfoundtobetheoptimalwaytobreatheduringtheBreaststroke(Stallman,Major,Hemmer,&Haavaag,2010).However,currentliteratureissparseinregardtotheoptimaltimetakentolifttheheadtobreatheduringtheBreaststroke.

Arm-LegCoordinationintheBreaststrokeAswimmer’ssuccessinthewatercanlargelybeattributedtotheirabilityto

effectivelyapplypropulsiveforcesinthewater(C.D.D'AcquistoLJ,1998).Thoughthearmpullandthelegkickcaneachbebrokendownintotheirownphases,theyareperformedsimultaneouslyduringtheBreaststrokestrokeandthestrokeitselfhasitsownphases(C.D.D'AcquistoLJ,1998;Leblancetal.,2009).Leblanc,Seifert,andChollet(2009)breaktheBreaststrokedownintothefollowingphases:simultaneousrecoveryofthearmsandlegs;thelegkick;theglide;andthearmpullandinsweep.

Thelegkickprovidespropulsion,however,thelegrecoveryproducesadecelerationinvelocity;duringthistimethearmpullalsoprovidespropulsion(Leblancetal.,2009).SimilarfindingsaresupportedbythestudyofD’AcquistoandCostill(1998),whobreaktheBreaststrokedownintofourphases–twophasesofaccelerationandtwophasesofdeceleration.Thefirstphaseofaccelerationisthelegkick,followedbythefirstphaseofdecelerationcomposedofthecompletionofthearmrecoveryandtheoutsweepofthehands,whichisthenfollowedbythesecondphaseofaccelerationwhenthearmsprovidepropulsiveactionsthroughtheirinsweepmotion,andendingwithasecondphaseofdecelerationwhenthelegsrecoverandthehipsandkneesbecomeflexed(C.D.D'AcquistoLJ,1998).

ThevelocityvariationsfoundwithinoneBreaststrokestrokecyclecanbeagoodindicatoroftheefficiencyoftheswimmer’stechnique(C.D.D'AcquistoLJ,1998;vanHouwelingenetal.,2017);strokeindexcanalsobeusedtoevaluatetheefficiencyofaswimmer’sstroke(Barbosa,Marinho,Costa,&Silva,2011;Seifert&Chollet,2005).SeifertandChollet’s(2005)studyexaminingthestrokeindexforBreaststrokealsoconfirmsthattherecoveryandglidephasesoftheBreaststrokestrokearephasesofdeceleration,andthatthetimethebodyisspentinastreamlinedpositionistheperiodwhenactivedragislimitedandvelocityisbestmaintained.AccordingtoastudyperformedbyJaszczak(2011),asymmetricallegmovementscanresultinanincreaseinasymmetricalhandmovementaswell.Poorbodyalignmentcanleadaswimmertoexperienceincreaseddragforces,whichmayhindertheirabilitytoswimfaster(Strzałaetal.,2012);incontrast,properbodyalignmentwhileswimminghelpstheswimmertoreducethedragforcestheyexperienceandincreasetheirspeed(Sandersetal.,2015).

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AstudyperformedbySandersetal.examinedasymmetriesofanelite-levelBreaststrokeswimmerinordertoidentifythecausesofmisalignmentsinthestroke(2015).Theyfoundthatdifferentlevelsoftorqueproducesmisalignmentsduringvariouspartsofthestroke;positivetorqueduringtheoutsweep,therecoveryoftheupperlimbs,andduringthekickandnegativetorqueduringtheinsweepandpriortothekickwereallidentifiedcauses(Sandersetal.,2015).KinematicFactorsRelatingtotheTimingoftheBreaststroke

ThereareseveralkinematicfactorsthataretobeexaminedwhenevaluatingoptimalefficienttechniqueoftheBreaststroke.Sincethemaingoalofcompetitiveswimmeristoincreasespeedthroughefficientstrokemechanics,velocityisthebestvariabletouseforassessingstrokeperformance(Barbosaetal.,2011).Velocitycanfurtherbebrokendownintotwocomponents:strokerate,referringtohowquicklyafullcycleoftheBreaststrokestrokeisperformed,andstrokelength,whichreferstothedistancecoveredbyafullcycleoftheBreaststrokestroke(Barbosaetal.,2011).Strokerateandstrokelengthworktogetherinaninverserelationship;aswimmerwithhighstrokeratewillhavealowerstrokelength,andviceversa(Barbosaetal.,2011).

Ahigherstrokeratecoupledwithalowerstrokelengthisfoundtoproducegreaterspeed,andisthetechniquehighlyfavoredbyBreaststrokersintheshorterdistanceraces(50meterand100meterevents);alowerstrokeratewithahigherstrokelengthisusedtooptimizetheeconomyoftheglidephaseandisthetechniquemorefavoredbyswimmersinlongerdistanceBreaststrokeraces(200meterevents)(Strzałaetal.,2012).InBreaststroke,thetimingbetweenthemovementsofthearmsandthelegsisalsoamajorconcern(Barbosaetal.,2011).Ithasbeensuggestedthathigherswimvelocitiesmaybeachievedbyreducingthetimespentduringtheglidephaseinthestroke,andbyincreasingthepartialduration,andthepropulsiveforceduringthefinalactionsoftheunderwatercurvilineartrajectoriesofthearms(Barbosaetal.,2011).

Horizontalvelocityandintra-cyclicvariationshavebeendeemedthemost

importantbiomechanicalvariablesincompetitiveswimming.HorizontalvelocitiesoftheBreaststrokeatthehipinthelongitudinalplaneofmotionarethemostcommonlymeasured(Barbosaetal.,2011;vanHouwelingenetal.,2017).InBreaststroke,thehorizontalvelocityischaracterizedbyabi-modalprofile,withonepeakrelatingtotheactionsofthearmsandtheotherpeakrelatingtotheactionsofthelegs(Barbosaetal.,2011).Alowintra-cyclicvariationofthehorizontalvelocityleadstogreaterswimtechniqueefficiencyfortheswimmer(Barbosaetal.,2011).

Theotherkeyvariablethatisexaminedispropulsion.Thecontributionsofliftanddragforcestooverallpropulsionarestillwidelydebated(Barbosaetal.,2011).InthestudyofBarbosaetal.(2011)theynotethatthereisalargeamountofpropulsiongeneratedbythearms,andthatdifferentpositionsoffingerspreading

12

canchangetheamountofpropulsionthatisproduced.Dragisdefinedas“anexternalforcethatactsintheswimmer’sbodyparallelbutintheoppositedirectionofhismovementdirection”(Barbosaetal.,2011).Theresistiveforcesthatdragproducescanbeinfluencedbyanyoneofseveralfactors.Theseinclude:anthropometriccharacteristicsoftheswimmer;characteristicsoftheequipmentusedbytheswimmer;physicalcharacteristicsoftheswimmingfield;andtheswimmer’stechnique(Barbosaetal.,2011).Barbosaetal.(2011)alsonotedthatitisimportanttolookatactivedrag,andnotjustpassivedrag,becausethevariablespertainingtodragforcescanchangewhenthesubjectinthewaterisactivelymoving,incontrasttobeingtowedthroughthewater.Velocity-VideoAnalysisValidation

Manystudiesusethevelocity-videosystemandviewitasareliablewaytoanalyzethestrokemechanicsoftheBreaststroke,andoftensometypeofmarkersareplacedontheswimmeratspecificanatomicallandmarksbeforethetrialbegins,andthesemarkersareusedtohelpdigitizeandanalyzethefilmafterithasbeenrecorded(Costaetal.,2010;C.D.D'AcquistoLJ,1998;C.D.D'AcquistoLJ,GehtsenGM,Wong-TaiY,LeeG,1988;Jaszczak,2011;Strzałaetal.,2012).

AstudyperformedbyD’Acquisto,Costill,Gehtsen,Wong-Tai,&Lee(1988)

setouttovalidateavelocity-videosystemforuseinanalyzingBreaststrokeeconomy,skill,andperformance.Theswimmersintheirstudywerefilmedusingthevelocity-videosystemaswellasanotherbiomechanicalanalysissystemthathadpreviouslybeenvalidated;afterusingacomputerprogramtodigitizethefilmandanalyzethestrokemechanics,acomparisonofthetwoanalysesprovedthevelocity-videosystemtobeavalidsystemtouseintheanalysisofswimstrokemechanics(C.D.D'AcquistoLJ,GehtsenGM,Wong-TaiY,LeeG,1988).Usingthevelocity-videosystem,thefilmoftheswimmerwasabletobedividedintopropulsiveandnon-propulsivevelocitydata.Distanceperstroke(strokelength),thepeakminimumandmaximumvelocitiesachievedwithinthestrokecycle,andthetimespentanddistancetravelledpereachstrokeweremeasured(C.D.D'AcquistoLJ,GehtsenGM,Wong-TaiY,LeeG,1988).Thismethodwasfoundtobeareliablewaytodeterminehorizontalstrokevelocity,andwhenvelocitytimegraphsweresynchronizedwiththefilmoftheswimmer’strial,itprovidedaquickandreliablefeedbackforswimmersandtheircoaches(C.D.D'AcquistoLJ,GehtsenGM,Wong-TaiY,LeeG,1988).

CHAPTER3:Methods

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StudyObjectives

Thepurposeofthisstudywastodescribetheresultsofakinematicanalysisofthe“conventional”vs.“late”Breaststrokekick,usingselectedvariablesofthesetwotypesofkickpatterns.Thestudywasdividedintotwoelements,eachposingthefollowingquestions:Question1:Isthereasignificantdifferenceinpeakhipvelocitydrop-offsbetweenthetwotechniques(conventionalvs.late)ofBreaststrokekicking?Hypothesis1:Therewillbeasignificantdifferencebetweenthetwotechniquesofkicking–therewillbelessofadrop-offinpeakhipvelocityforthesubjectswhoutilizethelatekicktechnique.Question2:Isthereasignificantdifferenceinthepercentageofvelocityregainedduringthepropulsivephaseofthekickrelatedtothemagnitudeofvelocitypercentagedrop-offduringkickdeceleration?Hypothesis2:Therewillbeasignificantdifferenceinthepercentageofvelocityregainedduringthepropulsivephaseofthekickrelatedtothemagnitudeofvelocitypercentagedrop-off–thesmallerthepercentagevelocitydrop-off,thegreaterthepercentageofvelocityregainedwillbe.ResearchDesign

Thisstudyutilizedasingle-subjectdesignbyexaminingtheeffectsonpeakvelocityduringtheBreaststrokewiththreedifferenttrialsofexecutingthekickduringdifferentphasesofthestroke.Theindependentvariablewasthetimingofthekick(conventional,late,ordelayedlate)andthedependentvariablesweremaximalkneeflexionangle,peakarmvelocity,peaklegvelocity,timetocompletekick,percentageofvelocitydrop-off,andpercentageofvelocityregained.Participants

SubjectswererecruitedfromanNCAADivisionIswimmingteam(4males&5females).n=9subjects(G*Powerapriorianalysis:ANOVArepeatedmeasures,withinfactors;effectsizef=0.5;p=0.05;power=0.8;numberofgroups=1;numberofmeasurements=3;correlationamongrepeatedmeasures=0.5;non-sphericitycorrection=1)Inclusionarycriteria:Breaststrokemustbeoneoftheirprimarycompetitiveevents;theymusthavereachedNCAADivisionIlevelsofcompetitiveexperience.Exclusionarycriteria:Non-experiencedcompetitiveswimmers;injurythatpreventsswimmerfromswimmingwithnormaltechnique;Breaststrokeisnotaprimaryraceeventfortheswimmer.

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PerformanceSite

ThisstudywasperformedattheDukeKahanamokuAquaticComplex,onthecampusoftheUniversityofHawai‘i–Mānoa.Instruments

• Three high-speed digital cameras (Baumer Model HXG with CMOS sensors), installed in custom housings (The Sexton Company, Salem, Oregon).

• All 3 housings were attached to custom-designed mounting frames and positioned

so as to provide the three required fields of view (Figure 1).

Figure1.Synchronizedframesofthethreecameraanglesusedtofilmswimmingtrials.

• Camera 1 was used for recording the frontal, or head-on view, of the subject’s progress and was mounted on a vertically oriented frame. The camera was positioned at a depth of 0.48 meters (1.57 feet).

• Camera 2 was mounted on a horizontal platform that rested on the bottom of the pool at a depth of 2.13 meters (7 feet). The camera was aligned vertically, i.e. pointing upwards to the surface and provided a transverse view of the subject’s progress.

• Camera 3 was mounted on a laterally positioned frame that was bolted to the

concrete deck of the pool. The camera was positioned at a depth of 0.48 meters (1.57 feet), similar to the depth of Camera 1. The lateral orientation of Camera 3 provided the data for the progress of the subject in the longitudinal plane of motion.

• Thedistancethesubjectwasrequiredtocoverineachtrialvariedbetween11.89and13.71meters(39to45feet).Thisdistancewasdeterminedbyplacingthecamerathatwasusedforrecordingthefrontal,orhead-onviewofthesubjectatadistanceof13.71meters(45feet)yardsfromthesideofthepoolfromwhichthesubjectwasrequiredtopush-offatthestartofeach

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trial.Subjectswereinstructedtoswimdirectlytowardsthiscamera,approachingitascloseaspossiblewithoutcollidingwiththecamera.

• Thecameraswerecontrolledviadual9.14meter-long(30feet)Gigabit

(GigE)Ethernetcables connected to a desktop computer located on the pool deck. Each camera had two cables - one cable was assigned to camera control and another cable was used for frame synchronization. Unlike the limitations relating to maximum functional lengths inherent when using Firewire cabling, GigE cabling does not have a length restriction, which allowed for optimum placement of the underwater cameras in the pool.

• Rotational joint segments were identified using a custom-designed string of light

emitting diodes (LED’s), housed in waterproof housings. The LED’s were duct taped to the body and powered by a battery pack attached to a belt worn by the subject at the waist.

• Templo (Contemplas, Kempten, Germany) motion capture software was used for

capturing and recording the video data. • A second software package, Motus, (Contemplas, Kempten, Germany), was used

for digitizing, data analysis, and generating “reports”. This software included a “Multi 2-D” (M2-D) feature, which enabled multiple cameras to be synchronized. Each sequence was digitized using a combination of auto-tracking and manual modes.

• IBM Statistical Package for the Social Sciences (SPSS) version 23 was used to

run statistical analysis.

KinematicDataCollectionProcedures

AfterobtainingapprovalforthestudyfromtheUniversityofHawai‘iatMānoaUniversityInstitutionalReviewBoardfortheStudyofHumanSubjects,BreaststrokesubjectswererecruitedfromtheUniversityofHawai‘iatMānoaIntercollegiateSwimmingTeam.Subjectsreportedtothepoolatascheduledtime,andsignedaconsentform.Priortovideotaping,eachsubjectwasshownapreviouslydigitizedswimtrialsoastofamiliarizethemwiththeoutcomeofthevideotapingandresulting“report.”Followingtherecordingofeachsubject’santhropometricdata,theLEDlightsweretapedontospecificanatomiclandmarks(bilateralfingers,wrists,elbows,shouldersandrighthip).ThesubjectwasprovidedwithsufficienttimetoswimafewwarmuplapstogetaccustomedtoswimmingwiththetapedLEDlightstrings.

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Thesubjectperformedatotalofthreetrialsof3specifiedswimmingprotocols.

Thethreeprotocolsconsistedofthefollowing:

ProtocolOne(ConventionalStroke):Thesubject,whileswimmingtheBreaststroke,wasrequiredtousetheirregulartechnique,ataneffortthatcorrespondedtothepacetheywouldcompletea100-yardracesprint.Inallexceptasinglecase,thesubject’s“conventionalstroke”consistedoftheinitiationofthekickcoincidingwiththebeginningstageoftheinsweep,calledthe“earlyinsweep.”ProtocolTwo(LateKick):Thesubject,whileswimmingtheBreaststroke,wasrequiredtotimetheinitialdraw-upofthekicktocoincidewiththeperiodduringwhichthehandswereinthefinalstageofthesecondphaseoftheBreaststrokepullpattern(theinsweep),calledthe“lateinsweep.”ProtocolThree(DelayedLateKick):Thesubject,whileswimmingtheBreaststroke,wasrequiredtotimetheinitialdraw-upofthekicktocoincidewiththeperiodduringwhichthehandswerebeginningthe“recovery”phase,i.e.handsmovingforwards.

Subjectswereaskedtorepeatatrialiftheydidnotmeetthecriteriaforagivencondition,withamaximumofthreetrialspercondition,andweregiventimetorestbetweentrialsinordertoeliminatefatigueasaconfoundingvariableduringthesecondandthirdtrials.

Thevideodatawasthenuploadedtothedigitizingsoftware,whereitwasdigitizedandthefootagewassynchronizedtoproducedynamicpeakvelocity-timegraphstoanalyzethefluctuationsinpeakvelocities.Thetrialswerecomparedtoeachothertorecordtheresultingdifferencesbetweenthepeakvelocity,theminimumvelocityrecordedduringtheeffort,andthevelocityregainedasthenextstrokewasinitiated.StatisticalAnalysisofData

Eachsubject’sstrokewasdigitizedandanalyzedusingtheMotusandTemplosoftware.Thepercentagedrop-offinpeakvelocity,percentageofthevelocityregained,maximumhipvelocitygeneratedbythearms,andmaximumhipvelocitygeneratedbythelegswereseenthroughtheuseoftime-velocitygraphs(Figure2).

MaximumkneeflexionangleandtimetocompletekickweremeasuredbyusingTemplo’sanglemeasurefunctiononatime-stampedvideo(Figure3).

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Figure2.Time-velocitygraphusedtoanalyzevelocitiesoftheBreaststroke.

Figure3.MaximalkneeflexionanglecalculatedinTemplo.

Duetothesingle-subjectdesignofthisstudy,eachsubject’sowntrialswereanalyzedagainsteachothertonoteanysignificantdifferenceinthetimingoftheBreaststrokekickonpeakvelocity(notedifferenceindrop-off/regained);forexample,subject1’sProtocol1trial,Protocol2trial,andProtocol3trialwereallcomparedagainsteachother,butsubject1’sProtocol1trialwasnotcompared

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againstsubject2’sProtocol1trial.Foreachdependentvariable,allofthedatavarianceforeachsubjectwascomparedagainstrespectivedatavariancefortheothersubjectsforalltrials;forexample,subject1’smaximalkneeflexionangleforProtocol1trialwascomparedtosubject2’smaximalkneeflexionangleforProtocol1trial.ThesignificantdifferenceforeachprotocolwasdeterminedusingANOVArepeatedmeasuresanalysiswithasignificancelevelsettop=0.05(Field2009).Mauchly’stestofsphericitywasruntovalidatetheparametersoftheANOVArepeatedmeasuresanalysiswithasignificancelevelsetatp=0.05(Field2009).Greenhouse-GeisserandHuynh-FeldtcorrectionswereusedwiththeMauchly’stest;Huynh-Feldtcorrectionwasusedforpeakhipvelocitygeneratedbythelegs,andGreenhouse-Geissercorrectionwasusedforallotherdependentvariables(Field2009).

Results

Subjectsinthisstudyweren=9NCAADivisionIswimmers.Anthropometricdatacollectedforthesesubjectsincluded:age,height,weight,bodymassindex,andwingspan.Thedataisdisplayedintable1.Table1.Anthropometricmeasurements.

Variable Mean SDAge,years 20.67 1.32Height,in. 70.34 3.81Weight,lb. 158.34 16.96Bodymassindex,kg/m2 22.49 1.56Wingspan,in. 71.11 5.73SD=StandardDeviation

Followingthestatisticalanalysisoftheirtrials,themeans,standarddeviations,and95%confidenceintervalsforallvariableswerecalculatedandarereportedintable2.Alsocalculatedintable2arepairwisecomparisonsofdatatodemonstratesignificancebetweenthethreedifferentkicktechniquesforeachdependentvariable.

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Table2.ComparisonofBreaststrokeBiomechanicswithDifferentKickTechniques.

Measure

C100 DU1 DU2

Mean±SD CIp-value

Mean±SD CIp-value

Mean±SD CIp-value

DU1 DU2 C100 DU2 C100 DU1%VDO 91.2±4.9 91.3±3.8 0.02 0.01 86.8±5.0 86.8±3.8 0.02 0.03 82.5±5.2 82.5±4.0 0.01 0.03%VR 91.1±11.8 91.1±9.1 0.02 0.01 96.3±11.6 96.4±9.0 0.02 0.39 97.3±10.2 97.3±7.9 0.01 0.39MKF,O 36.1±5.1 36.1±4.0 0.22 0.03 33.7±6.8 33.7±5.2 0.22 0.03 31.6±6.1 31.6±4.7 0.03 0.03PAV,m/s 2.2±0.5 2.2±0.4 0.10 0.06 1.9±0.3 2.0±0.3 0.10 0.23 1.9±0.4 1.9±0.4 0.06 0.23PLV,m/s 2.0±0.4 2.0±0.3 0.42 0.27 1.9±0.3 1.9±0.3 0.42 0.43 1.8±0.4 1.8±0.3 0.27 0.43TCK,s 0.6±0.1 0.7±0.1 0.02 0.05 0.7±0.1 0.7±0.1 0.02 0.36 0.7±0.1 0.7±0.1 0.05 0.36

%VDO=PercentageVelocityDrop-off;%VR=PercentageofVelocityRegained;MKF=MaximumKneeFlexionAngle;PAV=PeakHipVelocityGeneratedbytheArms;PLV=PeakHipVelocityGeneratedbytheLegs;TCK=TimetoCompleteKick;C100=ConventionalStroke100-ydsprintpace;DU1=LateKick;DU2=DelayedLateKick;SD=StandardDeviation;CI=ConfidenceInterval

ComparativeSignificantDifferences

Whencomparing“ConventionalStroke”andthe“LateKick,”significantdifferenceswereseeninthefollowingparameters:a) Timetakentocompletekick.b) Percentageofhipvelocitydrop-off.c) Percentageofvelocityregained.

Whencomparing“ConventionalStroke”andthe“DelayedLateKick,”significantdifferenceswereseeninthefollowingparameters:

a) Maximalkneeflexionangle.b) Timetakentocompletekick.c) Percentageofhipvelocitydrop-off.d) Percentageofvelocityregained.

Whencomparingthe“LateKick”tothe“DelayedLateKick,significantdifferenceswereseeninthefollowingparameters:

a) Maximalkneeflexionangle.b) Percentageofhipvelocitydrop-off.

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ToensurethevalidityofthesignificancefoundintheANOVArepeatedmeasuresanalysis,Mauchly’stestofnon-sphericitywasrun.Huynh-Feldtcorrectionwasusedforpeakhipvelocitygeneratedbythelegs,andGreenhouse-Geissercorrectionwasusedforallotherdependentvariables.Partialetasquaredwasalsocalculatedtodeterminehowmuchofthechangeseenineachvariablecouldbeattributedtotheconditionalone.Changesinkickprotocolaccountfor11-56%ofthedifferenceseenforeachdependentvariable.Thisdataisshownintable3.

Table3.Univariatetestsfordependentvariables.

PeakhipvelocitygeneratedbythearmswastheonlyvariablefoundsignificantintheMauchly’stestofnon-sphericity(p=0.04);Greenhouse-Geissercorrectionwasusedtodeterminesignificanceforthisvariable(p=0.07).Therefore,allthesignificantvaluesfoundintheANOVArepeatedmeasuresanalysiscanbeconsideredvalid.Discussion

ThepurposeofthisstudywastodescribethekinematicsoftheconventionalversusthelateBreaststrokekicktechniqueusingselectedvariablestodeterminetheefficiencyofeachtechnique.Currently,onlyonestudyexiststhatexaminestheeffectsofthetimingoftheBreaststrokekickonintra-cyclicvelocity.However,thissinglestudybyvanHouwelingenetal.usedsubjectsthatwereof“average”competitiveexperience,andconsequentlynotclassifiedascompetingattheelitelevels.Theirconclusionswerelimitedtostatingthat“average-levelswimmersarecapableofadjustingtheirleg-armcoordinationwithacousticcueingandthatdifferenttimingofthekickdoesaffectintra-cyclicvelocityvariation”.(vanHouwelingenetal.,2017)Unfortunately,thisstudydoesnotspecificallyaddressleg-armcoordination,howtoreplicatethestudy,norweretheyabletoexplainhowthesefindingscouldbeappliedbycoacheswhentrainingswimmers.

MeasureMauchly’s Greenhouse-Geisser Huynh-Feldt

Sig. W Sig. PartialEtaSq. Sig. PartialEtaSq.%VDO 0.05 0.435 0.01 0.558 0.01 0.558%VR 0.28 0.695 0.01 0.516 0.00 0.516MKF,O 0.08 0.489 0.05 0.354 0.05 0.354PAV,m/s 0.04 0.411 0.07 0.331 0.06 0.331PLV,m/s 0.11 0.531 0.36 0.110 0.36 0.116TCK,s 0.06 0.447 0.04 0.379 0.04 0.379

MKF=MaximumKneeFlexionAngle;PAV=PeakHipVelocityGeneratedbytheArms;PLV=PeakHipVelocityGeneratedbytheLegs;TCK=TimetoCompleteKick;%VDO=PercentageVelocityDrop-off;%VR=PercentageofVelocityRegained

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Consequently,ourstudyisthefirsttohavedefinedparameterstoclassifyleg-armcoordinationandincorporatethemintoaspecificvariationoftheBreaststrokeswimmingtechnique.

Inordertobedesignatedasa“ConventionalStroke”,“LateKick”ora

“DelayedLateKick”,thetimeatwhichthekickreached160degreesofflexionwasmatchedwiththephaseatwhichthepullingactionofthehandscoincidedwiththispositionoftheknee.

Duringtheprotocolwherethesubjectswererequiredtoswimusingtheir

“ConventionalStroke”,thedistinguishingfeaturewasthattheinitiationofkneeflexiontookplaceduringtheearlystagesofthesecondphaseoftheBreaststrokearmpull.Thisphaseistermedthe“earlyinsweep”ascomparedtothe“lateinsweep”whichisthelaterstageandconcludingportionofthepropulsivephaseoftheBreaststrokepull(Figures4aand4b).

Figure4a.Protocol1:Closeupofhandpositionduringtheearlyinsweep.

Figure4b.Protocol1:Coincidentkneekick.

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The“LateKick”wasthetimethehandswerecompletingthe“lateinsweep”

(Figures5aand5b)and“DelayedLateKick”coincidingwiththepositionofthehandswhentheywerestartingtobethrustforwardsintotherecoveryphase(Figures6aand6b).

.

Figure5a.Protocol2:Closeupofhandpositionduringthelateinsweep.

Figure5b.Protocol2:Coincidentkneekick.

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Figure6a.Protocol3:Closeupofhandpositionduringtheearlyrecovery.Figure6b.Protocol3:Coincidentkneekick.Allninesubjectsofthisstudywereelite-levelswimmerswhowereallableto

performeachspecifiedkicktechniquewithonlyverbalcueing.Theanalysisofeachsubject’strialsrevealedthatthesmallestpercentagesofvelocitydrop-offwereseenduringthe“delayedlatekick”technique.Thatis,whenthethreeprotocolswerecompared,thethirdprotocol,whenthesubjectswaiteduntiltheirhandsstartedtobeextendedforwards,weobservedthesmallestdrop-offinoverallhipvelocities.Thesecondphaseof“leastdrop-off”wastheprotocoldesignated“LateKick”,whenthehandswereapproachingthebody,duringthe“insweep”phaseofthearmpull.

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Thegreatestamountofvelocityregainedwasinthelatekicktechniqueand

thedelayedlatekicktechnique.Thisindicatesasmallervelocityvariationwithinonestrokecycle,whichindicatesamoreefficientBreaststroketechniquethanthesubject’snormaltechnique.Thesefindingsareinagreementwiththeconclusionsreachedbytwoearlierpublishedmanuscripts(C.D.D'AcquistoLJ,1998;vanHouwelingenetal.,2017).

Therewerenosignificantdifferencesinpeakhipvelocitygeneratedbythe

armsorpeakhipvelocitygeneratedbythelegsbetweenthesubjectswhenusingeitherofthethreeprotocols.However,thefastestoverallswimmingvelocitieswereachievedinthesubjects’regularBreaststroketechniquetrialsbeforetheywereaskedtomakeadjustmentstotheirstrokes.Theseresultswereexpectedbecauseallsubjectstestedwerecurrentlyin,orrecentlyconcluded,intensetraining,andwereinstinctivelyswimmingattheircurrenttrainingvelocities.

Maximalkneeflexionangleandtimetocompletekickaretwovariablesthathavenotyetbeenstudiedasitrelatesarm-legcoordinationoftheBreaststroketechniqueandintra-cyclicvelocityvariations.MaximalkneeflexionwassignificantlydifferentbetweentheregularBreaststroketechniqueandthedelayedlatekicktechnique,butnotbetweentheregularBreaststroketechniqueandthelatekicktechnique.Whatwasobservedwasthatthesubjectstendedtoincreasethedegreeofkneeflexion,thelatertheywereaskedtokickintheirstroke.Thesechangesmaybeattributedtotheperceptionoftheoverallstrokecycletakingmoretime,therebyallocatingmoretimetoincreasetheamountofkneeflexion.Asexpected,thisalsoincreasedthetotaldurationsofthe“LateKick”and“DelayedLateKick”whencomparedtothedurationsofthesubjects’kickwhenswimmingtheir“ConventionalStroke”.

Inregardstotheresearchquestionsposedforthisexperiment,itcanbe

concludedthatthereisasignificantdifferencebetweenhipvelocitiesasafunctionoftheinitiationofkneeflexionandhandpositionsduringtheBreaststrokepullphase.Itcanbeconcludedthatthereislessofadrop-offinhipvelocities,andhighervaluesforregaininghipvelocities,accompanyinglaterdurationsofthepullphase.PracticalApplications

TheconclusionsderivedfromthisstudyareinagreementwiththecurrenttrendincompetitivesprintBreaststroketechnique.Althoughthetimingofthelegdraw-upduringthelongestcompetitivedistance,the200meters,stillshowsrelativelyearlydraw-upofthekick,thefindingsofthestudyshowscleardifferenceswhenthereisadelaybeforetheinitiationofthekickwhenswimmingtheshortercompetitivedistances.

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Thisstudyrevealedthatbyvirtueofsmallerdecreasesintheperiodsofvelocity“drop-off”,higherswimmingvelocitiesmaybeachievedwhenthekickisinitiatedduringtheinsweeporearlyrecoveryarmphases.Thisstudyalsoprovesthatvideoanalysisandverbalcueingarebothviablefeedbacktoolsthatcanbeusedtohelpswimmerslearntomakeadjustmentstotheirregulartechniquestobecomemoreefficientinthewater.

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AppendixA:ConsentForm

University of Hawai‘i Consent to Participate in Research Project:

Kinematic Analysis of Peak Velocities in the Breaststroke as a Function of the Timing of the Kick

My name is Susan Ward. I am a graduate student at the University of Hawai‘i at Mānoa

in the Department of Kinesiology. I am doing a research project as a requirement for earning my graduate degree. The purpose of my project is to evaluate the effectiveness of different stroke timing variations in the kick for Breaststroke swimming. I am asking you to participate because of your participation as a Breaststroke specialist on the U.H. swim team between the 2017 and 2018 intercollegiate swimming seasons. Activities and Time Commitment: I am asking for your permission to use video filming to record and analyze your Breaststroke technique. This research will require a one-session commitment of approximately 1.5-2 hours. You will be one of nine people who will be filmed and analyzed for this study. I will measure your wingspan before the start of the session, as well as height and weight (if not known). LED lights will then be fixed to the fingers, wrist, elbows, shoulders, and hips with duct tape to hold the markers in place in the water. You will then be filmed while swimming 12 Breaststroke trials with different technique variations. Filmed will be analyzed to measure changes of velocity within one stroke cycle to determine stroke efficiency. You will be contacted to review your individual results upon the completion of their analysis if you wish to review them. Your film may be used, as video or as still photos taken from the video, to present the results of this research study. Potential Risks/Benefits: Potential risks of the study include all the risks involved with swimming – fatigue, cramping, and drowning. To ensure the participants’ safety, they will be allowed as much time as they need to rest between trials, there will be a lifeguard present during filming, and filming will be performed in the shallow end of the pool, where the participants will be able to touch the bottom of the pool while having their heads out of the water. Another potential risk is feeling discomfort from having the LED lights taped on – as the lights are taped on, the swimmers will be asked to perform the motions of their normal technique to help the researcher affix the lights in a manner that will allow the swimmer to perform the trials with comfortable swimming technique. The swimmers will be allowed to swim a few trials as warm-up trials to become accustomed to the feel of swimming with the lights on their body. If the lights become uncomfortable while performing the trials, the researcher will be available to re-tape the lights in a more comfortable position before continuing on with the study. Potential benefits of the study include the possibility of definitively discovering at which point in the Breaststroke cycle a swimmer should begin their kick in order to perform with the greatest amount of stroke efficiency – which in turn would lead to faster performances. Though this study offers no direct benefit to the swimmer, indirectly they may also be able to increase the efficiency of their stroke. Privacy and Confidentiality: I will keep all information in a safe place on a password-protected computer in a locked office. Only my University of Hawai‘i advisor and I will have access to the information. Other agencies that have legal permission have the right to review research records. The University of Hawai‘i Human Studies Program has the right to review research records for this study. When I report the results of my research project, I will not use your name. I will not use any other personal identifying information that can identify you, unless you give your consent. If you choose to give consent to use your film (video/still picture) when the research is

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published you can designate that on this form. If you do not consent to have your film used, you will not be included in the study. I will report my findings in a way that protects your privacy and confidentiality to the extent allowed by law. Voluntary Participation: Your participation in this project is completely voluntary. You may stop participating at any time. If you stop being in the study, there will be no penalty or loss to you. If you agree to participate in this project, please sign and date this signature page and return it to:

Susan Ward, Principal Investigator at: [susan37@hawaii.edu, 910-585-1098]

An Independent Institutional Review Board (IRB) has approved this voluntary consent form and study. You may contact the UH Human Studies Program at (808) 956-5007 or uhirb@hawaii.edu to discuss problems, concerns and questions; obtain information; or offer input with an informed individual who is unaffiliated with the specific research protocol. Please visit https://www.hawaii.edu/researchcompliance/information-research-participants for more information on your rights as a research participant. Signature: I have read and understand the information provided to me about being in the research project, Kinematic Analysis of Peak Velocities in the Breaststroke as a Function of the Timing of the Kick My signature below indicates that I agree to participate in this research project. Printed name: ______________________________ Signature: _________________________________ Date: ______________________________ My signature below indicates that I agree to allow use of my film when publishing research. (No names will be disclosed). Signature: __________________________________

You will be given a copy of this consent form for your records.

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Strzała,M.,Krężałek,P.,Kaca,M.,Głąb,G.,Ostrowski,A.,Stanula,A.,&Tyka,A.(2012).Swimmingspeedofthebreaststrokekick.JournalOfHumanKinetics,35,133-139.doi:10.2478/v10078-012-0087-4

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