stretching Scientific

8/6/2019 stretching Scientific

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JournalofHumanKineticsvolume192008,165176

EditorialCommitteeofJournalofHumanKinetics

165

Warmup:ACaseStudyonMaximalOxygen

ConsumptionasitRelatestoAcuteStretching

by

BekirYuktasir1

The aim of this study was to determine the acute effects of static and Pro-

prioceptive Neuromuscular Facilitation (PNF) stretches on maximal oxy-

gen consumption (VO2 max). Ten physically active men (mean SD,23.80 1.54 years, 70.60 9.70 kg, 1.74.60 5.23 m), who were healthy

students volunteered to take part in the study. The participants were sub-

jected to Static and PNF stretching exercises. After the interventions, the

Bruce treadmill protocol was applied to measure VO2 max values. The

expired gases were collected and analyzed continuously using the Cortex

Metalyzer II. Analysis of variance showed significant main effects for in-

terventions (F(2,18)=10.74, p


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166 Warmup:Acasestudyonmaximaloxygenconsumptionasitrelatestoacutestretching

Introduction

StaticandProprioceptiveNeuromuscularFacilitation(PNF)stretchingexer

cises are largely used in sports activities and rehabilitation as a part of the

warmup routine with the principal intent to prevent injuries and improve

muscularperformance.Staticstretchingisperformedbytheapplicationofgen

tle stretchesof aparticularmuscleormusclegroup.This technique involves

slowlyelongatingthemuscletoatolerancepointwherethemuscleisstretched

toitsgreatestallowed,andthustoleratedlength,andheldinthatpositionfora

period of time.Through thisprocess a stress relaxation occurs,with a static

tension alsobeing placed on themuscletendon,which in turn activates the

golgitendonorgan.Autogenicinhibitionistherebygeneratedonthestretched

muscle (Bandyand Irion,1994;MooreandHutton1980;MagnussonandRen

strom, 2006).Like static stretching,PNF is a common techniqueusedduring

sports activities and rehabilitation. The contractility of themuscle supplies

flexibilityofthemusclebychangingitsviscoelasticproperties.Autogenicand

reciprocal inhibitionmechanisms occur during the PNF stretching technique

application.AnisometriccontractionofstretchedmuscleduringPNFstretching

causes an inhibition of themusclesautogenic inhibitionmechanism, thereby

reducingmuscle tension through the stimulationofGolgi tendonorgans. In

addition, tension during a maximum isometric contraction of the stretched

muscleresultsinlessresistancetolengthchangesinthesamemuscle(Prentice,

1983;MooreandHutton,1980;EtnyreandAbraham,1986).Recentstudieshave

shownthatacutestaticandPNFstretchingofmusclesmayincreasetherange

ofmotion (ROM) (Magnusson et al., 1995;McNair and Stanley, 1996; Hal

bertsmaetal.,1996;Felandetal.,2001).Bothmechanicalandneuraladaptation

mechanismsare responsible for thesechangesduringstretching (Guissardet.al.,2004).AlthoughacutestaticandPNFstretchingexerciseshavebeenshown

tobeeffectiveinenhancingROM,theymayalsoresultinthereductionofthe

rateofforceproduction,poweroutput,maximalvoluntarycontraction (MVC)

andjumpperformance(Poweretal.,2004;Wallmannetal.,2005;Fowlesetal.,

2000;Churchetal.,2001).Despitethewelldocumentedfactsoftheacuteeffects

ofstaticandPNFstretchingonpower,torque,andMCV,theefficacyofstatic

andPNFstretching techniqueonaerobicperformance isstillquestionedwith

itsongoingdebatesinthescientificcommunity.VO2 maxisreportedasoneof

theprimaryindicatorsofaerobicperformance.Itisdefinedasameasureofthe

highestrateatwhichoxygencanbeusedbythebodyduringexercisepermin

ute (Billatetal.,1996;Bangsbo,2000;Vellaetal.,2006). Limitednumbersofstudies have shown, although inconclusively, stretching to cause changes in


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byB.Yuktasir 167

favorofaerobicperformance(StewartandSleivert,1998;Guidettietal.,2007).

But the reportedarticleson thissubjecthavenotassessed theacuteeffectsof

static andPNF stretchingonmaximaloxygenuptake.Hence, thepurposeof

thisstudywastofurtherinvestigatetheacuteeffectsofstaticandPNFstretches

onmaximaloxygenuptake.

Material and Method

Ten physicallyactivemen (meanSD,23.801.54years,70.609.70kg,

1.74.605.23m),whowerehealthystudentsataSchoolofPhysicalEducation

andSports,volunteeredtotakepartinthestudy.Theparticipantswereallwell

accustomedtotheexperimentalprocedureandhadnosignsofanyneurologi

cal, orthopedic or systemic complications or disorders.All participantswere

informed about the experimental procedures.Written consentwas obtained

fromtheparticipantsafterwhichtheywereinformedofthepurpose,procedure

andrisksofparticipatinginthestudy.Theywerealsoinformedthattheycould

withdrawfromthestudyatanytime.The total intervention timewas seven daysper participant. Inparticular,

theywereexposed toa test schedulewhich involveda48hours rest interval

betweeneachintervention.Alldatacollectiontookplaceunderlaboratorycon

ditions.Ambient atmospheric conditions of the laboratory included tempera

tureof25o1oCandpressureof9191mbar.Thefirstintervention(Int1)was

a treadmill test (Bruceprotocol) inorder todetermine theVO2maxvalueof

eachparticipant.Afterthefirstrest intervalperiod,inthesecondintervention

(Int2),theparticipantsunderwentan18min.passivestaticstretchingoflower

extremities,followedbythesametreadmilltest(Bruceprotocol).Afterthelast

rest intervalperiod, theparticipantswent throughan18min.holdrelaxPNF

stretchingoflowerextremities(Int3),followedagainbytheBruceprotocol.TheBruceprotocol, whichisavalidatedtestforestimatingVO2 maxfromamaxi

malperformance,wasperformedonatreadmill(h/p/cosmosmercury;0 22.0

km/hrspeed,0 24%angleof inclination,150cmx50cmrunningsurface).The

test started at a speedof 2.74km/hrat a 10%degreeof inclination.At three

minute intervals thedegree of inclinationon the treadmill increasedby 2%,

reaching amaximum inclinationof 22%.The treadmill speed also increased

progressively in thefollowingsequence:4.02,5.47,6.76,8.05,8.85,9.65km/hr.

(MaudandFoster,1995).Duringtheexercisetest,expiredgaseswerecollected

and analyzed continuouslyusing theCortexMetalyzer II (CortexBiophysik,

Leipzig,Germany).CortexMetaLyzer II, isacardiopulmonaryexerciseappa

ratususedforpulmonarygasexchangemeasurementsinastationaryenvironment.During theexperimental testsparticipantsworeasmallfacemask,and


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breathedoutthroughavolumetransducerfixedtothefacemask.Directmeas

ureofgasexchange includedO2,CO2concentrationofexpired / inspiredair,

ambienttemperatures,andpressure. Beforethetestingsession,thegasanalyz

erswerecalibratedagainstaprecisionanalyzedgasmixture (Reference /cali

bration

gas

from

cortex

calibration

kit

or

span

gas

with

4

6

%

CO2

,

14

16

%

O2

,

bal.inN2).

PassiveStaticStretchingAtthebeginningofthestretching,theparticipantswereinformedaboutthe

stretchingtechniques.Inthepassivestaticstretchingexerciseseachofthesub

jects lower extremitymuscles, including thehips (Gluteusmaximus,gluteus

medius, gluteus minimus, illiopsoas, sartorius, tensor faciase latae), thighs

(quadriceps, hamstrings, gracilis), and calves (gastrocnemius, soleus, tibialis

anterior)werestretchedbyatrainedassistant.Thefollowingwerepassivestatic

stretchingexercisesdonebefore thesecond intervention;1.Hamstringstretch

foreachleg(3x30secforoneleg)2.Quadriceps stretchforeachleg(3x30sec

foroneleg)3.Calvesstretchforeachleg(3x30secforoneleg)4.Groinstretch

(3x30sec)5.Lying lowerbackstretch (3x30sec.)6.Lyingglutestretch for

eachleg(3x30secforoneleg)7.Lyinghipflexorstretchforeachleg(3x30sec

forone leg).Stretchingexerciseswereperformedat themaximumpain toler

atedby theparticipants.Foreach leg, thestretchingwasrepeated three times

witharestperiodof10secondsbetweenstretches. Inthisstudy,staticstretch

ingvolumerefersto18min;30sec.hold(BandyandIrion,1994;Cornwelletal.

2002;McNealandSands,2003)andcomfortlevelnotexceeding5onastandard

Visualanaloguescale(VAS).

HoldRelaxPNFStretchingFortheholdrelaxstretchingexercisesthesubjectslowerextremitymuscles

(asmentionedabove)werestretched.Holdrelax techniquebeganwithapas

siveprestretching that isheld at a tight sensation for 10 seconds (Holcomb,

2002).Following10seconds, theparticipantsmaintainedamaximal isometric

tensionagainstamanual resistance (appliedby the sameassistant) for5 sec

onds.Then,eachsubjectwasaskedtorelaxandapassivestretchwasdonefor

15 seconds.PNF stretching exerciseswereperformed at themaximum range

toleratedby the participants. For each leg (3 x 30 seconds for one leg), the

stretching was repeated three times with a rest period of 10 sec between

stretches. Like the static stretching exercise procedure, the hold relax PNF

stretchingexercisewasalsoconductedoveratotalperiodtimeof18min.


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byB.Yuktasir 169

StatisticsDescriptivestatisticalmethodswereused tocalculate themeansandstan

darddeviationof thevariables involved in this study.RepeatedMeasuresof

ANOVAwasappliedtotestsignificantlevelsofdependentvariables.Thistest

examined theeffectivenessofstaticandPNFstretchingonVO2 max.TheRe

peatedMeasuresincludedthefollowingpoints:baseline(int1),staticstretching

(int2), and hold relaxPNF stretching (int3). For statistically significantmean

differences,aPaired Sample ttestwasrun.Thealpha levelwassetat .05for

thisstudy.

Results

DescriptivestatisticsforVO2 maxandtimetoexhaustionwererepresented

inTable1andFigure1respectively.Table1depictsasummaryofdescriptive

statisticsforall three interventionsonVO2 max,including thetime toexhaus

tion inminutes.RepeatedMeasuresofANOVAanalysisshowedasignificant

maineffectwithinsubjectsforVO2 max(F(2,18)=10.74,p


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Fig1.

DescriptivestatisticsoftheinterventionsonVO2

maxvalues

Table2

Pairedt testresultsforallinterventionsonVO2Max(ml.kg1.min1)

MeanSD Mean SD t df P

Intervention1

Intervention2

50.904.67

55.006.844.10 4.04 3.20 9 .01*

Intervention1

Intervention3

50.904.67

56.706.705.80 4.73 3.87 9 .001*

Intervention2

Intervention3

55.006.84

56.706.701.70 3.30 1.62 9 .13

*P


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byB.Yuktasir 171

swimming, stretching).A number of studies havedemonstrated that aerobic

performancedidnotchangeaftersometypesofwarmupwithdifferentinten

sities:

GenovelyandStamford(1982)determinedtheeffectsofprolongedwarmup

exercise(withpedallingtheMonarckcycleergometer)atabove(68%)andbe

low(40%)anaerobicthreshold.Attheendofthestudy,theyfoundthatneither

aboveanaerobic threshold(AT)warmupnorbelowATwarmupcontributed

toan improvedmaximalperformance.Thiswasattributed toglycogendeple

tionoffasttwitchmusclefibers.

Moreover,inastudybyTeubesetal.(1992)differentwarmupprotocols(40

%,57%,and67%ofVO2max,respectively)wereexamined.Theirresultsindi

cated thatvarying intensityanddurationofwarmupdidnotcauseasignifi

cantdifferenceonVO2.

Similarly,Bishopetal.(2001)examinedtheeffectofthreedifferentwarmup

intensities (i.e.,warmupfor15minataerobic threshold,anaerobic threshold,

anda intensitybetweenaerobicandanaerobic threshold)onkayakergometer

performance.Nosignificantdifferenceswereobservedonaveragepower,peak

VO2, totalVO2, totalVCO2,andaccumulatedoxygendeficit. Itwasconcluded

thatdespitethedegreeofmetabolicacidosis,itmightbenecessarytoincrease

O2kinetics;howeverifthewarmupistoointense,itmayspoilsupramaximal

performanceby reducing anaerobic energy contribution and affectingmuscle

contractileprocess.Itshouldbenotedthatthedifferencesbetweenthefindings

reportedaboveandthefindingsofthepresentstudymaybeduetothediffer

ences inemployedmethodologicaldesigns.Additionallydifferences in the in

tensityofthewarmuptechniquescouldplayasignificantrolein thediscrep

ancy of our results. This study utilized low intensity stretching techniques,

whereastheabovestudiesapplieddifferenthighintensitywarmuptechniques.

Ontheotherhand,somestudiesreportedthataerobicperformancewasim

provedbyactivewarmupactivities.

Ingjer andStromme (1978) found a significanthigheroxygenuptake, and

lowerlactateconcentrationwhentheworkwasprecededbyactivewarmupas

comparedwithpassiveornowarmup.

GrayandNimmo(2001)foundthattotaloxygenconsumptionduringthe30

s exerciseboutwas signicantly greater after the activewarmup, causing an

elevationinmuscletemperature (consistingofcyclingat40%maximalpower

output for5min. then15s sprintsat120% maximalpoweroutput).Active

warmup also resulted in a decreased blood lactate response during high


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intensityexercise.ThisfindingissimilartothatprevioulyreportedbyRobergs

etal.(1991),whoshowedagreatincreaseinaerobiccontributiontoastandard

high intensity exercisebout after an activewarmup. Themajorityof these

effectswere reported as a result of elevation inmuscle temperaturewhich

indicated

a

potential

blood

flow

to

active

muscles

(Robergs

et

al.,

1991;

Takizavaand Ish,2006).Furthermore, findingsbyTakizavaand Ish (2006)

pointedoutsignificantchangesinoxyHb/MbanddeoxyHb/Mbduetowarm

upexercises,whichinturn,mayimprovehighintensityaerobicperformance.

Only a limited number of studies have examined the effects of different

typesofshorttermstretchingonrunningeconomyandmaximaloxygencon

sumption: Below, the results of ourpresent study are comparedwithprevi

ously, relevant studies reported in the literature.Stretchingprior tomaximal

exerciseinthepresentstudyincreasedaerobicperformanceinagreementwith

thefollowingstudies:

Godgesetal.(1989)examinedtheeffectofincreasedhipflexibilitybyusing

static

stretching

and

soft

tissue

mobilization

with

PNF

on

gait

economy

and

submaximaloxygenconsumption.Godgesetal.foundthattherewasasignifi

cantincreaseingaiteconomyat40%,60%,and80%VO2maxfollowingthe

staticstretchingexercise.Theseresultssuggestedthatincreasesinperformance

were related to increases in thebalanceofmuscleand fasciaabout thepelvis

hip.

StewartandSleivart(1998)examinedanaerobiccapacity(time tofatigueat

13km/hrand20percentgrade)afterawarmup(15minrunningat60,70,or80

percentVO2max,followedbyalowerlimbstretch).Theirresultsshowedthata

15minwarmupatanintensityof6070percentVO2maxenhancedanaerobic

performance.

Similarly

Guidetti

et

al.

(2007)

reported

that

in

dance

exercises

preceded

by

warmup, the contribution of anaerobicmetabolismdecreased,while aerobic

energysources increased (from26 to39%,p


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byB.Yuktasir 173

exercisesmaybeexplainedbyanincreasedbloodflowtoactivemuscle,ade

creasedmusclelactateconcentrationandmuscletemperaturerelatedfactors.

Conclusions

Themain result of this study showed thatboth static andPNF stretchingexercises improved VO2 max values. These findings encourage the use of

stretchingexercisesasawarmupinsportsandrehabilitationactivitiesnotonly

to prevent possible sports related injuries as it is commonly used today.

Moreover,anincreasedVO2maxvaluewillresultinpostponingfatiguethereby

improving the overall sport performance. However, further studies should

attempttoprovidefurtherevidenceastowhichstretchingtechniquemightbe

mostadvantageousinsportsandexercisesettings.Hence,theimportantanceof

determing the most efficient and effective stretching technique to achieve

desiredoutcomes,needsfurtherresearch.

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Corresponding author:

YuktasirBekir

AbantIzzetBaysalUniversity,Bolu,Turkey,

Email:[email protected]

Telephone:+903742541000

Fax:+903742534506

Authorssubmitedtheircontributionofthearticletotheeditorialboard.

AcceptedforpintinginJournalofHumanKineticsvol.19/2008onMarch2008.

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