TheBenefitsofExerciseWarm‐UponGripStrengthandFatigueTime

AlexFinn,AsiminaPappas,CamiloCampo,JoeHiggins,SethBraddock,RebeccaFrenz

Keywords:

BreathingRate(new)ExerciseEMGHeartRate(new)MuscleFatigue(new)PerformanceStrengthWarm‐Up(new)

Lab601

Group7

Abstract

Strengthandendurancearetwokeyfactorsinanyathlete’sabilitytoperform.This

experimentwasdesignedtomeasurethecorrelationbetweenanexercisewarmupand

gripstrengthandfatiguetime.Twogroups,acontrolandanexperimental,weretested.The

controlgroupsubjectsparticipatedintwoseparatesessionsoverthecourseofafew

weeks,neitherofwhichincludedanexercisewarmup.Theexperimentalgroupsubjects

participatedintwoseparatesessionsoverthecourseofafewweeks,thefirstofwhichwas

recordedasabaselinemeasurementandthesecondoccurredafterawarmupexercise.

Thepurposeoftheresearchgroup’sexperimentsistodeterminewhetherthereisa

positivecorrelationbetweenanexercisewarmupandanindividual’sstrengthand

endurance.

Introduction

Physicalfatigueisaloweredactualmuscularcontractileresponsecomparedtothe

anticipatedresponseofagivenstimulus(Fitts,1994).Thecausesoffatiguearenumerous;

althoughmanytheorieshavenotyetbeenproposed,itissuspectedthatanypointinthe

pathway‐‐fromspinalcordtomusclecell‐‐canleadtofatigue.Itissuspectedthatone

reasonforfatigueisareductionofneuraldrivetoworkingmusclecausedbya“spillover”

ofserotonin.Duringahighlevelofexercise,serotoninproductionincreases,causingitto

bind5‐HT1Areceptorsontheinitialsegmentofmotorneurons,andthus,inhibitingnerve

impulseinitiation(Coteletal.,2013).Similarly,anothercauseoffatigueistheinabilityofa

nervetomaintainahigh‐frequencysignalduringmaximummuscularexertion;thisfatigue

doesnotcausesoreness.Itcanbeovercomewithrepetitivetraininguntilthenerve

generatesmaximumcontractions(Robergs,2004).

Themostcommonmechanismsthoughttoexplainfatiguedealwiththemuscle

fiber;specifically,itisthoughtthatthedepletionofsubstratesortheaccumulationof

metabolicproductsinvolvedinmusclecontractionarethemainreasonsforfatigue.

DeficiencyinATP,creatinephosphateandglycogenreducesavailableenergy,hindering

contraction.Also,whenexerciseintensityincreases,moreATPisusedup,releasingmore

protons.TheincreasingneedforATPresultsintheneedforregenerationbynon‐

mitochondrialsources,furtherincreasingprotonrelease,causingacidosis(Robergs,2004).

Muscularfatiguecangreatlyaffectanathlete’sperformance;physicalandtechnical

abilitiesbecomeimpairedsincetechniqueandmotorskillexecutionisreduced.Decreased

throwingvelocities,kickingpower,mentalconcentration,andthrowingandshooting

accuracieshavebeenassociatedwithphysicalfatigue(Knickeretal.,2011).Understanding

somemechanismsinwhichfatiguecanbereducedoravoidedwouldgreatlybenefitnot

onlyprofessionalathletes,butalsoanyoneperformingphysicalactivity.

Extensiveresearchhasbeenconductedontheeffectsofwarmingupbeforeexercise

asitpertainstoincreasingthephysicalperformanceofathletes.Inastudythatassessed

theeffectsofwarminguponinjuryprevention,itwasfoundthatsoccerplayersincreased

theirstrengthandweremorelikelytopreventinjuryiftheywarmedupbeforehand.The

pre‐exercisewarm‐upincludedstrength,musclecontrol,balance,andrunningexercises

(Daneshjoo,2012).Similarly,anexperimenttoassesstheeffectsofadynamicwarm‐upon

powerandagilityperformancefoundthatstrengthandenduranceofthesubjectswho

incorporatedthedynamicwarm‐upimprovedincomparisontothosethatdidnot

(McMillianet.al,2006).Thewarm‐upsincorporatedintheseexperimentsproducedan

increasedbreathingrateandheartrate,andthesephysiologicalchangesresultinor

accompanyimprovedphysicalperformance.Anincreaseinbreathingrateduringexercise

leadstomoreoxygenintakebythebody,providingmoreoxygenformusclestowork

(Tatsuya,2004).Anincreasedheartrate,whichischaracterizedasmoreheartcontractions

perminute,increasestheamountofbloodthatcangettothemuscles,whichimproves

theirproductivity("BloodPressurevs.HeartRate,"2012).Thisalsohastodowiththe

amountofoxygenthatgetstothemusclesfromthelungs.Bothbreathingrateandheart

ratearerelated,andbothincreaseduringexercise.Theincreasesinthesevariablesarethe

presumedcausesofincreasesinstrengthandendurance,whichistherelationshipthatis

goingtobetestedinthisexperiment.

Theobjectofthisexperimentistodeterminehowmanipulatingtwovariables,heart

rateandbreathingrate,willaffectboththefatiguetimeandthemaximumgripstrengthof

thesubjects.However,theresultsofthisexperimentarenotintendedsolelyforthe

analysisofhandstrengthandfatiguetime—theresearchgroupintendstorelatethe

findingstooverallphysicalmuscularperformance.Withasuccessfulexperiment,the

researchgroupwillbeabletothenproposeanewhypothesis;thatanincreaseinheartrate

andbreathingratewillresultinanincreaseinoverallphysicalmuscularperformance.

Failuretorejectthehypotheseswillgivetheimplicationthatbywarmingupandelevating

anindividual’sheartrateandbreathingrate,theyarepreparingtoimprovetheirstrength

andendurance.Asidefrommeasuringgripstrengthandfatiguetime,theresearchgroup

willalsoobserveheartrateandrespiratoryrate.Manipulationofthesevariableswillbe

accomplishedthroughawarm‐upexerciseofbikingfor3minutes.

Thisstudywillbebasedontwohypotheses.Thefirsthypothesisisthatanexercise

warm‐up,definedbyanincreaseinheartrateandrespiratoryrate,willinduceasignificant

improvementingripfatiguetime.Thesecondhypothesisisthatanexercisewarm‐up,

definedbyanincreaseinheartrateandrespiratoryrate,willinduceasignificant

improvementingripstrength.

Methods

Inordertomeasurechangesinmusclefatigueandcontractilestrengthinducedafter

apre‐workoutwarm‐up,theresearchgroupfirstrecordedbasicinformationanddatafrom

eachparticipatingtestsubject.Participatingsubjectsweretakenfromthepoolofstudents

enrolledintheUniversityofWisconsin‐MadisonPhysiology435courseandincludedthe

researchgroupmembersaswell.Priortothecollectionofdataontheparticipants,a

consentformconcerningthedetailsofthestudywasgiventoparticipantstoreadandsign.

Theparticipantdatacollectionincludedbasicinformationabouteachsubjectsuch

astheirname,sex,age,weight,height,andhoursofphysicalactivityperweek,hoursof

sleep,breakfastconsumptionthemorningofthestudy,leftorrighthandedness,illnesses,

workoutstatus,alcoholandcaffeineconsumption,wristinjuries,andwhetherornotthe

participanthaspreviouslyusedanElectromyography(EMG)device.Thepurposeofthis

specificdatacollectionwastoprovidebehavioralorphysiologicalbasisforremovalof

statisticallydeterminedoutliers.

Oncethisinformationwascollected,theparticipantwasaskedtowearaBSL

RespiratoryEffortandaPulseOximeterinordertorecordtheirrestingbreathingrateand

restingheartrate,respectively.Therestingbreathingrateoftheparticipantwasrecorded

whiletheparticipantwascompletingtheirconsentformandquestionnaire.Toensurethat

theparticipantwasnotawareofwhentheirbreathingwasbeingmonitored,theywerenot

toldthattheirbreathingwasbeingrecorded.Theexperimentersalsodidnotspeakwith

theparticipantatthistime,sothatthebreathingratewouldnotbealteredbytheactionof

talking.Breathingratedatawasassessedbytakingtheaverageofthebreathsperminute

measuredforeveryinhale/exhalecycleina20‐secondtimeinterval.Theperiodsof

inhalationandexhalationwererepresented,respectively,byariseandfallofthegraph.To

calculatetheaveragebreathsperminute,theresearchgrouprecordedthevalues

designatedbythedistancebetweentroughsandusedthemtocalculatetheaverage

breathingrate.

ThePulseOximeterreading,whichmeasurednumberofheartbeatsperminute,

wasalsotakenandrecordedpriortotheuseoftheEMGdevice.Next,theparticipant

calibratedtheEMGdevicewithatwo‐secondsqueeze,whichwasimmediatelyfollowedby

theinvitationtosqueezetheEMGrecordingdevicewithalloftheirstrengthforaslongas

theycould.TheFatigueTimewasrecordedwhentheparticipant’sGripStrengthdropped

tohalfoftheirMaximumGripStrengthvalue,atwhichpointtheparticipantwastoldto

stopsqueezingandrelax.MaximumGripStrengthwasrecordedinkilogramsandFatigue

Timewasmeasuredinseconds.

Participantsfromthefirsttrialweresplitbysex,andeachsexwasthenassignedto

oneoftwogroupsbyrandomlydividingtheirconsentformsintoacontroland

experimentalpopulation.Thiswasaccomplishedbyshufflingtheconsentformsand

drawingthemoutofahat.Ofthethirteentotalmales,sixwereinthecontrolgroupand

sevenwereintheexperimentalgroup.Similarly,ofthefifteentotalfemales,eightwerein

thecontrolgroupandsevenwereintheexperimentalgroup.Theparticipantswereeach

calledbacktoperformanothertestaftertheircategorywasassigned.Theparticipants

werenotinformedofthereasonforthesecondtest,inanattempttoreducebias.

Participantsweretestedforthesecondtimeonetothreeweeksfollowingtheirinitialtest.

Again,eachparticipantwasaskedtofilloutthebasicinformationsurvey.Thecontrol

grouprepeatedtheinitialexperimentdescribedabove,inexactlythesamemanner.The

experimentalgroupperformedadifferentexperiment.

Theexperimentalgroup’sparticipants’heartrateandbreathingratewerefirst

measuredatrestwhilefillingoutthesamequestionnairesheetasthefirstweek.Then,the

participantswereplacedonastationarybike,whichconstitutedthepre‐workoutwarm‐up.

Theywereinstructedtopedalonthebikeforthreeminutes.Theparticipants’heartrates

andbreathingratesweremeasuredaftertheydismountedthebikeandweresittingdown.

Again,carewastakenbytheexperimentersnottoinfluencethebreathingrateofthe

participantswhentherecordingofthebreathingratewasbeingtaken(theBSLRespiratory

Effortwasnotremovedthroughouttheexperiment).

Afterthebreathingratewastaken,theparticipantswereaskedtorepeattheGrip

Strengthtest.DuringtheGripStrengthtest,GripStrengthandFatigueTimewererecorded

inthemannerpreviouslydescribed.Thetimeelapsedbetweentheendofthewarm‐upand

theGripStrengthtestwasminimized;itlastednomorethan2minutes.Thisreducedtime‐

lapseandensuredthatanyobservedeffectsonGripStrengthperformancewasduetothe

pre‐workoutwarm‐up.

StatisticalanalysiswasperformedusingMicrosoftExcel.Statisticalanalysis

comparedthetwopopulations,controlandexperimental,intermsofthechangein

individualfatiguetimeandthechangeinindividualgripforce.Thepercentchangein

individualfatiguetimewascalculatedbycomparingthevaluerecordedduringthesecond

seriesofmeasurementsfromthemeasurementrecordedatthefirstsession.Thesame

method,withtheappropriatedataset,wasusedtodeterminethepercentchangein

individualgripstrength.Eachdatasetwassubjectedtoaquantile‐quantileplotinorderto

determineifthedatawasnormallydistributed.Whenboththecontrolandexperimental

datasetsofthesamevariablewerefoundtobenormallydistributed,at‐testwas

performed.Thetypeoft‐testandthenumberoftailsweredeterminedbythestandard

deviationsandthecorrespondinghypothesis,respectively.Ap‐valuelessthan0.05was

consideredsignificant.

Furtherstatisticalanalysiswasperformedtotestforanyrelationshipsnotpredicted

andleftoutofthehypothesis.Linearregressionwasperformedinordertoobserve

relationshipsbetweenrespiratoryrate,heartrate,gripstrength,andfatiguetime.Data

pointsthreestandarddeviationsfromthemeanwereconsideredoutliersandomittedfrom

allfurtherstatisticalanalysis.

Materials

HandynamoSS25LA(BiopacSystems,Inc.,AeroCaminoGoleta,CA)

ElectromyographyII(BiopacSystems,Inc.,AeroCaminoGoleta,CA)

PulseOximeterModel9843(NoninMedical,Inc.,Minneapolis,MN)

BSLRespiratoryEffortXdcrSS5LB(BiopacSystems,Inc.,AeroCaminoGoleta,CA)

StationaryBicycle

SignaGel‐ElectrodeGel(BiopacSystemsInc.,Fairfield,NJ)

TheHandynamoSS25LAwasusedincooperationwiththeElectromyographyIIon

theBiopacprogramtomeasuregripstrengthinkilograms.ThePulseOximeterModel9843

wasusedtomeasureheartrate.Thedeviceworksbyhavingthesubjectplacetheirindex

fingerintoaslotthatisprogrammedtorecordtheheartrate.TheBSLRespiratoryEffort

XdcrSS5LBwasusedtomeasurebreathingrate.Thisdeviceconsistedofanelasticband

witharecordingunitthatwasplacedaroundthetorsoofthesubject.

Timeline

Week1&2Controlgroup/Week1ExperimentalGroup

Figure1–Themeasurementsthatweretakenfromparticipantsoveratimeperiodoffiveminutes;thisisaccordingtothecontroltrial.

Figure2–Themeasurementsthatweretakenfromparticipantsoveratimeperiodofsevenminutes;thisisaccordingtotheexperimentaltrial.Results

Overthetwoseparateoccasionsthatparticipantswereevaluated,statistical

analysisofthecontrolgroupreportedameanpercentchangeforthegripstrengthand

fatiguetimeof+3.0%and‐1.9%,respectively.Apositivemeanpercentchangeforgrip

strengthindicatesthatonaverage,thecontrolsubjectsshowedasmallincreaseingrip

strength.Anegativemeanpercentchangeinfatiguetimeindicatesthatonaverage,the

controlsubjectsshowedasmalldecreaseinfatiguetime.

Overthetwoseparateoccasionsthatparticipantswereevaluated,statistical

analysisoftheexperimentalgroupreportedameanpercentchangeforgripstrengthand

fatiguetimeof+23.3%and+42.7%.Apositivemeanchangeof23.3%forgripstrength

indicatesthatonaverage,theexperimentalgroupshowedadramaticincreaseingrip

strengthfromthebaselinemeasurementsrecordedinthefirstweektothemeasurements

recordedafterexerciseinthefollowingevaluation.Apositivemeanchangeof42.7%for

fatiguetimeindicatesthatonaverage,theexperimentalgroupshowedadramaticincrease

infatiguetimefromthebaselinemeasurementsrecordedinthefirstweektothe

measurementsrecordedafterexerciseinthefollowingevaluation.

Aonetailedtype2T‐Testcomparingthecontrolandexperimentalgroupsfor

fatiguetimereportedap‐valueof0.009404.Thisvalueindicatesthattheresultsare

statisticallysignificantandtheresearchgroupfailtorejectthefirsthypothesis,which

statesthatanexercisewarm‐up,definedbyanincreaseinheartrateandrespiratoryrate,

willinduceasignificantincreaseinfatiguetime.

Aonetailedtype2T‐Testcomparingthecontrolandexperimentalgroupsforgrip

strengthreportedap‐valueof0.002601.Thisvalueindicatesthattheresultsare

statisticallysignificantandtheresearchgroupfailtorejectthesecondhypothesis,which

statesthatanexercisewarm‐up,definedbyanincreaseinheartrateandrespiratoryrate,

willinduceasignificantincreaseingripstrength.

Graphsindicatingthebestindividualchangeforallvariablesforboththe

experimentalandcontrolsubjectsareshownbelow,alongwithgraphsindicatingthe

summaryofthemeanpercentchangeforallindividualsforboththeexperimentaland

controlsubjects.

Figure3–TwentyeightstudentsinPhysiology435wereseparatedintocontrolandexperimentalgroupsandtestedinaseriesofweeksfromFebruarytoApril2014.Thepercentincreaseinstrengthwascalculatedasthemeanofindividualchangesinstrengthfromweekonetoweektwo.Theexperimentalandcontrolgroupwereshowntobesignificantlydifferent(t‐test,pcalc>0.05).Errorbarsare+/‐onestandarddeviation.

Figure4–TwentyeightstudentsinPhysiology435wereseparatedintocontrolandexperimentalgroupsandtestedinaseriesofweeksfromFebruarytoApril2014.Thepercentincreaseinfatiguetimewascalculatedasthemeanofindividualchangesinfatiguetimefromweekonetoweektwo.Theexperimentalandcontrolgroupwereshowntobesignificantlydifferent(t‐test,pcalc>0.05).Errorbarsare+/‐onestandarddeviation.

Figure5–Valuesofweeklymeasurementsofanexperimentalindividual’sheartrate,breathingrate,gripstrength,andfatiguetime.

Figure6–Valuesofweeklymeasurementsofacontrolindividual’sheartrate,breathingrate,gripstrength,andfatiguetime.

Figure7–Percentchangeofweeklymeasurementsofanexperimentalindividual’sheartrate,breathingrate,gripstrength,andfatiguetime.

Figure8–Percentchangeofweeklymeasurementsofacontrolindividual’sheartrate,breathingrate,gripstrength,andfatiguetime.

Discussion

Theresultsfailedtodisproveeitherofthehypothesesbecause,asthep‐values

indicate,themaximumgripstrengthandfatiguetimeoftheparticipantsincreasedin

responsetothewarm‐up.Additionally,thecollectionofdatawassuccessfulbecauseofthe

efficiencyandconsistencyoftheresearchgroup’smethods.Thatis,theprotocolwas

consistentforeachparticipantinbothgroups.

Anumberofoutsideinfluencesmayhavecausedpotentialchangeswithinthe

experimentandthecollecteddata.Includedinthesepotentialinfluencesarethephysical

stateandwellbeingoftheparticipantsandtheplacementandmechanicalintegrityofthe

measuringdevices.Forexample,factorssuchastheamountofsleepobtainedbyeach

participant,iftheparticipantworkedoutintherecentpast,generalhealthstatus,and

overallphysicalfitnessoftheparticipantpriortoeachtestmayhaveaffectedtheamountof

forcetheyareabletoexertontheHandDynamometer.Inaddition,mechanicalfactorssuch

astheaccurateplacementoftheelectrodesfortheEMG,efficiencyofthemeasuring

devices,andcorrectplacementoftheBSLRespiratoryEffortcouldhavehadunprecedented

effectsonthedata.

Implicationsoftheresultscanbenefitpeoplelookingtoimprovetheirathletic

performance.Morespecifically,athleteslookingtoincreasetheirmaximumstrength

outputaswellasthetimeduringwhichthisstrengthisexertedshouldconsider

incorporatingasimilarwarm‐upintotheirworkoutroutine.Asthedatasuggests,

increasingheartrateandbreathingratewerebeneficialtotheparticipants'performance.

Althoughtheexactreasonsfortheparticipants’increasesinfatiguetimeandforceexerted

areunknown,possibleexplanationshaverisen.Mechanismssuchasaccumulationofacidic

wasteproducts,depletionofenergy,reductionofneuraldrivetoworkingmusclecausedby

aserotonin“spillover,”andtheinabilityofanervetomaintainahigh‐frequencysignal

wereallpossiblecausesoffatiguethattheresearchgroupmentionedintheintroduction.

Althoughtheinabilityofthenervetomaintainhigh‐frequencysignalingduringmaximum

muscularexertioncanbeacauseoffatigue,itshouldnotbethemechanismunderlyingthe

resultsinthisstudybecausenotenoughexercisewasperformedbythesubjectstochange

this.Itcanbethat,sincetheexperimentaldataafterthe3‐minutewarm‐upwascollected

afterspringbreak,participantsmayhaveworkedoutortrainedmore,andthatwasnot

controlledbythestudy.

Theimprovementinperformancecouldalsobeduetotheincreasedflowof

oxygenatedbloodtomuscle,duetoanincreaseinstrokevolumeinducedbythe

sympatheticnervoussystemwhichisachievedwhilewarmingup.Increaseinblood

temperatureresultingfromexerciseisalsocrucialtothereleaseofoxygentothetissuesas

impliedbytheoxygen‐hemoglobindissociationcurve.Increasedbloodflowcouldhave

clearedmetabolitebuild‐upassociatedwithfatigueinmusclefibers.Additionally,another

possibletheoryexplainingtheincreaseinstrengthandfatigue‐timewithwarm‐upcanbea

delayedadrenalglandinfluenceofthesympatheticnervoussystemonthebody.Warming

upforafewminutesbeforetheexperimentcouldhavegiventhesubjectsenoughtimefor

theepinephrinesecretedintothebloodstreamtoreachtargetorgans(Raff,Levitzky2011).

Althoughtheerrorproducedintheexperimentwasasminimizedaspossible,itwas

notabsent.Themainsourceoferrorinthisexperimentwashumanerror.Thebreathsper

minutewerecalculatedbyhandbytheexperimentersbecausetherewasnotasystemto

calculatethisonthecomputer.Thisledtovaryingresultsbasedonhoweachspecific

breathpeakwasmeasured,althoughcarewastakentobeaspreciseaspossible.An

additionalsourceofhumanerroroccurredwhiletheparticipantwasperformingthe

experiment.Iftheparticipantspokewhiletheirbreathingratewasbeingmeasuredthe

outcomeofbreathpeaksonthegraphgeneratedbytheBSLrespiratoryeffortwerealtered.

Speakingwiththeparticipantsduringthisparticulardatacollectionwasdiscouraged;

however,theparticipantsweresometimesspokento.Thiserrorcouldeasilybecorrected

byensuringsilenceduringthesubject’sbreathmeasurements.Toremovebias,careshould

betakeninthefuturetonotletthesubjectknowwhentheirbreathingrateisbeingtaken,

andtonotaltertheirresultsbytalkingtothem.Inaddition,someoftheparticipantswere

alreadyfatiguedfrompriorexperimentsinthedayatotherlabstations,thus,potentially

skewingthedata.Thiswasoutofthecontroloftheparticipantsandtheexperimenters.

ThefinalsourceofhumanerrorwastheplacementoftheelectrodesoftheEMG

Device.Eventhoughelectrodeswereplacedascloseaspossibletothedesignatedpositions

asindicatedbythemachine,humanerrorcouldhaveplayedaroleinputtingtheminless

thanidealplaces.Equipmentinaccuraciesalsooccurredthroughouttheexperiment.The

equipmentthatwasused(theexercisebike,theBSLRespiratoryEffort,PulseOximeter,

andEMGDevice)wasusuallyaccurate,butdidshowsomesignsofbeinginaccurate.

Ideally,morepreciseequipmentcouldbeusedifthereisameanstoattainit.

FutureDirection

Experimenterslookingtoconductasimilarstudyshouldincorporatethesame

sequenceofeventsforthecontrolandexperimentalprocedures.Theorderinwhichthe

datawascollectedallowedforminimalinfluencefromoutsidesources.Additionally,the

variablesthatconstitutedthepre‐workoutwarm‐upshouldbekeptthesame,astheseare

inaccordancewiththeliterature.

Futureexperimentscouldincludemoreexplicitpre‐workoutwarm‐up.For

example,insteadofhavingparticipantsbikeforthreeminutes,futureexperimentscan

haveparticipantsbikeforthreeminutesatapacethatwillincreasetheirheartrateby

50%.Thisallowsstrongercomparisonstobemadebetweenindividualsandthe

correlationbetweentheirincreasedbloodflowandmaximumstrengthoutput.Future

experimentscouldalsomeasuretheeffectsofincreasedoxygenintake,asthiswould

separatetheeffectsofthewarm‐upontheheartandonrespiration.Additionally,amore

precisecontrolwouldbetohavetheparticipantssitonthebikeforthreeminutes.This

wouldtakeintoaccounttheeffectsofsittingonthebike,holdingthehandlebars,etc.on

theirheartrateandbreathingrate.

Finally,experimenterslookingtorepeatthisstudycouldmeasuretheheartrateand

breathingrateoftheexperimentalgrouptenminutesaftertheydothewarm‐upin

additiontobeforethewarm‐up.Presumably,theparticipant’sheartrateandbreathingrate

wouldreturntotheirbaselinevaluestenminutesafterthewarm‐up.Thisallowsfor

confirmationoftheeffectsofthewarm‐upontheexperimentalresultsbyensuringthatthe

gripstrengthandfatiguetimeweremeasuredwhiletheparticipanthadanelevatedheart

rateandbreathingrate.

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