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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.
iii
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
xviii
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.
xix
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.
xxiii
Figure4b.Protocol1:Coincidentkneekick.The“LateKick”wasthetimethehandswerecompletingthe“lateinsweep”
(Figures5aand5b)and“DelayedLateKick”coincidingwiththepositionofthe
handswhentheywerestartingtobethrustforwardsintotherecoveryphase
(Figures6aand6b).
.
Figure5a.Protocol2:Closeupofhandpositionduringthelateinsweep.
xxiv
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
2
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
14
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
28
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
Takagi,H.,Sugimoto,S.,Nishijima,N.,&Wilson,B.(2004).DifferencesinStrokePhases,Arm-LegCoordinationandVelocityFluctuationduetoEvent,GenderandPerformancelevelinBreaststroke.SportsBiomechanics,3(1),15-27.
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