cardiovascular response to simulated real and non -real

Cardiovascular response to simulated real and non-real life

stressors - A comparative case study using heart rate

variability and personality traits in a physically trained group

¹Remya George, ²Biju Bahuleyan, ³K. Meenakshy

¹Department of Electrical and Electronics Engineering, Govt. Engineering college, Thrissur, Kerala, India.

corresponding e-mail: remya- [email protected].

²Dept. Physiology, Jubilee Mission Medical College and Research Institute, Thrissur, Kerala, India.

email: [email protected]

³Dept. Applied Electronics and Engineering, Govt. Engineering College, Calicut, Kerala, India.

email: [email protected]

Abstract

Heart ratevariability (HRV)is oftenusedas a reliable,noninvasive, objective measure of

acuteandchronicpsychologicalstress.Studieson acutestressresponse

usuallyinvolvetheapplication of a stressor for inducingstressandthen

assessingthechangesin HRVof theparticipants. Forthispurpose, laboratorysimulated, real

life stressors andnon-reallife stressors are commonly used in different contexts. The

suitability of various stressors in inducing remarkable stress response in different

categories of participants is not well addressed. Similarly, whileenoughattention

hasbeenpaidtopatient population andnormaladults, studieson stressresponsecharacteristics

in physically trained groupsis notmuchundertaken. Thisstudy examined thecardio-

vascular responseto an acutenon real life stressanda simulated real life stressin a groupof

physically conditioned femaleparticipants, who haveundergoneninemonths of

aerobicconditioning.Theobjective wastoidentifythe better stressor in termsof elicitingthe

stressresponse in a physically elite group.The stressors used were Stroop’scolor

wordtest(SCWT) anda modifiedversionof Trier’s social stresstest(TSST). Further

theassociation of Eysenck’spersonalitytraits andthevulnerability tostressis also

investigated in thesame group.Results revealedthat therewasnegligible physiological

responsein therecruits withthenon-reallife stressor.Ontheother hand,noticeable

responsewas elicitedby thesimulated real life stressor. Also, theself-reported extraversion

personality trait showed significant negative association withthestressresponseas

measured by RMSSD(ρ = -0.376, p = .042), SDHR (ρ = -0.566, p = .003), correlation

dimensionD2 (ρ = -0.314, p = .077) andSampleentropy SampEn (ρ =-0.416, p = .027).The

results established the supremacy of TSST as an acute psycho-social stressor in

physically trained subjects. Further, the recruits who were sociallyconfident exhibited

least vulnerability to the acutesimulated real-life stressor. Results have the potential of

influencing the decision making in selection and training of recruits in high stress

profession.

Keywords: Heart rate variability, linear and nonlinear features, psycho-social stress

response, personality.

1. Introduction Stressinallformshasbeenrecognizedastheleadingcauseofmortalityworld-

wide(WorldHealthOrganization,2011) and is manifested as a decreased ability to organize

resources to meet the demand put on an individual.Psychologicalstressculminatesin

cognitivedisorder,cardiovasculardysfunction[1,2]andisoneofthefirstcauseofpoorperformancesonth

eworkplaceandindailylife[3].Mentalstress

disturbstheAutonomousNervousSystem(ANS),whichcontrolsourabilityto

respondtointernalandexternalchallenges[4].Majorityoftheobjectivestudies

International Journal of Pure and Applied MathematicsVolume 119 No. 12 2018, 12575-12591ISSN: 1314-3395 (on-line version)url: http://www.ijpam.euSpecial Issue ijpam.eu

12575

onpsychologicalstressiscarriedoutbyexternallydistressingtheparticipant

andthenanalyzingthephysiological stressresponse such as heart rate variability (HRV), Skin

conductance (SC), Blood pressure regulation etc.Lowreactionstoinducedstressare

generallyfoundassociatedwithlowerriskforstress-relateddiseases[5,6].It

isobviousthattheeffectivenessofeachstressinductionmethodsrequiresspecialattention,especiallyw

henphysicallytrainedsubjectsaremonitored,as

physicallyconditionedsubjectsarebelievedtoberesilienttoacutementalstress [7,8,9].

Apersonalfactorthathasreceivedcontinued,albeitmodest,attentionin

exerciseandhealthpsychologyacrosstheyearsis personality.Stressis ahighly

personalizedprocess,notasimple,stimulus-responsereaction.Duringexposure

toanacutestressor,thereexistsaninteractionbetweentheindividualandthe

environment,involvingsubjectiveperceptionsandassessmentofthestressor.

Specificinheritedcharacteristics,lifeexperiencesandlearnedcognitivepredispositionsmakeindividu

alsmoreorlesssusceptibletotheeffectsofstressors.

Whileanumberofstudieshaveattemptedtoelucidatethepathwaysofpersonalityandstressreaction,ther

esultsareinconsistentandthefindingss t i l l notgeneralized.

1.1Mental stress and Heart rate variability

TheANSplaysamajorroleinmodifyingtheheartrateaccordingtothevariousdemandsputuponah

ealthyindividual,whilemaintaininghomeostasis. Amongthetwobranchesof

ANS,theparasympatheticdivisionisprimarilyinvolvedinrelaxation,helpingthebodytorestandrecov

er.Thesympathetic divisionpreparesthebodytofightorflyinresponsetostressbyaccelerating

bodilyfunctions.Bothphysicalandmentalstressarephysiologicallymanifested

innormalpeopleasanincreaseinsympatheticcardiaccontrol,adecreasein

parasympatheticcontrol,orboth.Asaresultofthestressreaction,theflexibilityofANSisdisturbed,resul

tingintheincreasedrateandforceofcontraction

oftheheart.Thisinturnreducesthevariabilityorthecapacityofthecardio-

vascularsystemtoadapttothechangingenvironment.Itiswellknownthat,

generalhealthisaffectednegativelybylong-lastingsympatheticactivationand

slowrecoveryofthestresssystems[10].

Heartratevariability(HRV)isanon-invasivetoolfortheassessmentofvariationsinthebeat-to-

beatcardiaccontrolofautonomicnervoussystem(ANS).

HRVhasextensivelybeenstudiedinregardstoexercise[11,12]andstress[13].

Uusitaloetal.[13]reportslowerworkrelatedstressinworkerswithhighHRV.

SystematicreviewsonacutementalstressassessmentviashorttermHRVanalysesinhealthyadulthuman

samplesupportthefactof distinctHRVprofilesin differentstatesof theANS[6].Anumberof

researchershaveevensuccessfully

attemptedtodiscriminatethestatesofANSinstressfulstatesfromrelaxed

states[14,15,16].Reportsonhealthdisparitiesinpopulationsthatarecon-

frontedwiththerecurringstressofeverydaylife[17]highlightsreducedHRV asoneofthebio-

markersofthisproblem. IncreasedHRVhasbeenrelatedto

reducedriskofthecardiovascularsystemsandgreateradaptationtoaerobic

training[18].Regularphysicalactivityisalsofoundassociatedwithgreater

emotionalresiliencetostress[19].Theliteratureunanimously emphasizethat

physicalconditioningpotentiallyenhancesHRVcontrolonstressresponse[20].

HRVisusuallyevaluatedintimedomainandfrequencydomaintoestimat

e thelinearcomponentsofvariability.Morethan70variablescanbecalculated

fromHRVanalysis[21,22],outofwhichthevariablesofinterest

inpsychophysiologicalresearch[23]areshowninTABLEI.ThetimedomainmeasuresofHRV

arebasedoneitherstatisticalorgeometricalanalysisoftheHRVsignal.Frequencydomainmeasuresusual

lyestimatethespectralpowerinvariousbandsof

interest.Asetofnonlinearfeaturesarealsocalculatedinspecificapplications

todescribethecomplexityoftheHRVsignal.Approximateentropy(ApEn)

International Journal of Pure and Applied Mathematics Special Issue

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developedbyPincus[24]andsampleentropy(SampEn)developedbyRichman

andMoorman[25]aretwopopularnonlinearcomplexityindexusedtoquantify

therandomnessorirregularityoftheHRVtime-series.Detrendedfluctuation

analysis(DFA)isanothertechniqueusedtodeterminetheshortterm(dfa1)

andlongterm(dfa2)correlationswithintheHRVsignal.Italsoquantifiesthe

nonlinearfractalscalingpropertiesofHRVtimeseries.SD1andSD2asobtainedfromPoincareplotquantif

ytheshortandlongrangevariabilityofthe

HRVsignal[26].Thefactord2isameasureofthedimensionalityofasetofrandompointsthatoccupythesp

ace.

Table 1:SummaryofHRVfeaturesused

Domain No: Feature Description

Time

1

HRVTRI

HRVindexfromNNinterval histogram

2 MeanHR (bpm) MeanHeart Rate (bpm)

3 MeanRR (ms) Meaninterval between QRSpeaks

4 NN50 CountofNormal RRintervals (NN)>50

5 pNN50(%) ProportionofNN50divided bytotal number ofNNs

6 RMSSD(ms) RootMeanSquare oftheSuccessiveDifferences

7 SDHR(bpm) Total variabilityinheart rate

8 SDNN(ms) Total variabilityinNNinterval

9 TINN TriangularinterpolationindexofNNintervals

Frequency

10

pHF

Powerofhighfrequencyband(0.15 Hz-0.4Hz)(ms2)

11 pLF Poweroflowfrequencyband(0.04 Hz-0.15Hz)(ms2)

12 LF/HF Sympathovagalratio

13 TP Total poweroftheFFT spectrum(ms2)

Nonlinear

14

ApEn

Approximateentropy

15 d2 Correlationdimension

16 dfa1 Detrendedfluctuationshort term scalingexponent

17 dfa2 Detrendedfluctuationlongtermscalingexponent

18 SampEn Sampleentropy

19 SD1(ms) Poincare plotshort term variabilitydimension

20 SD2(ms) Poincare plotlongterm variabilitydimension

1.2Mentalstressandpersonalitytraits Someindividualsareinherentlyhypo-orhyper-

reactivetogeneralformsofstressors[27,28].Peoplehighlyreactivetomentalstressappeartobehighlyrea

ctive tophysicalstressalso[29].Resilienceandvulnerabilitytostressorsaswellas

intensityofstressresponsearegreatlydependableonthenumerouscharacteristicsofpersonality.Forcan

didatesvulnerabletostress,prolongedstresswith

insufficientrecoveryleadtothedevelopmentofadversepsycho-physiological

healthoutcomesinfuture,throughthedefinedphysiologicalpathwaysrelated

tocardiacregulationbytheautonomicnervoussystem[30].Personalityand

heartratevariability(HRV)areeachstrongpredictorsofpsycho-physiological

stress,cardiachealthandlongevity.Thereisevidencethathighextraversion

andlowneuroticismareimportant

personalitycharacteristicstoworkandperformwellunderstressfulconditions[31,32].Systematicands

ignificantassociationsbetweenpersonalitytraitsandHRVatbaselinearereportedinliterature

[33].Thisassociationisexpectedthroughthemodulatoryinfluenceofbrain

structuresimplicatedinpersonality.Eysenck,whodevelopedtheinfluential extraversion-

neuroticismmodel,hypothesized neuroticismtobelinkedtohigh


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sympatheticandlowparasympatheticactivity leadingtolowthresholdsfor emotionalresponses[34,

35].Thusindividualshighinneuroticismareproneto

experiencestress.Extraversion,ontheotherhand,ishypothesizedtobelinked

tolowactivationandhighthresholdsinthelimbicsystem,leadingtoattenuated

responsestoemotionalchallenges[36,34].Althoughprogresshasbeenmade

inestablishingthebiologicalbasesofpersonality[37], studiesonphysiological

correlatesofpersonalityarestillscarceandinconclusive[69].

1.3Mechanismsofinducingpsychologicalstress

A deep probingintothestressresearchhas revealedthat, real life, simulated real life andnon-

real life stressorsare commonlyemployedto studythestress response.Fernandez et al.used simulated

vehicle drivingsituation for evoking stressresponse.WhereasHealy et al.[38]

studiedcognitivestressresponsein vehicle driversengagedin real-worlddrivingusing

HRVandmultiplephysiological signals.Few otherHRV based studiesemployed non real time

cognitive stressors such as Stroop’s color word test(SCWT). Examplesare studies by Salai etal.

[14], Karthikeyan etal. [39], Lambiaseetal. [40] andRoemmichet al. [41].Stroop’scolourwordtestis

aneffective nonreal-timestressstimuli frequentlyused in the laboratory stress research[42, 9].

Authorslike Salai et al. [14] obtained significant change in majority of time and frequency

domainHRV features.Karthikeyan et al. [39] reports79.17% discrimination accuracybe- tween

stress and relaxed statesusing time and frequency domainHRV features. In SCWTstudies on

patient population, the low HRV groups represented a low degree of neuro-visceralintegration

[43].

FewotherslikeMelilloetal.[15]andTarionitetal.[44]haveusedacademic examinationasreallife

stressinductionmethod.Anumberof studieshavealso

usedpsychosocialstresstestsuchasTrier’ssocialstresstest(TSST)alongwith

heartrate(HR)andHRVaspsychophysiologicalindicesofstressandvagal

influenceonstressreaction[45].Trier’ssocialstresstest,extremelymodifiable

totheneedsoftheresearcher,withstrongneuro-physiologicalstressreactions isawell-

recognizedlaboratorystressorwithreallifecharacteristics[46,47].

An overallreductionofHRVhavebeenreportedforacutestressorssuchasmentalarithmetic,

reactiontimetasks,Stroopinterferencetask,orspeechstress[48,49,50],real-

lifeacutestressorssuchascollegeexaminations[51]androaddrivingtests in general population.But

veryfewstudieshavesystematicallyattemptedtocomparetheeffectofmore thanonestressorinwell

t rained healthyparticipants.While different mechanisms ofinducing stress in individuals are

reported in the literature,the suitabilityofaparticularstressor indifferentcategories of

participantsare not addressed well. Comparable effectsinlaboratorysimulated

socialstresstestandreal-lifestresshasbeendemonstratedbyRajcanietal.

[52].Theyfoundanalogicalfindingsinstressfuldaysduringevery-daylifeto

laboratorystressprotocol.Theyalsodemonstratedstrongereffectof simulated real-

lifestressthanreallifestress.Tothebestofourknowledge,exceptfor

theabovementionedstudy,aquantitativeanalysisusingreliableandobjective markersof

stressontheeffectivenessof aninducedstressor,inaphysicallywell-

conditionedgroupisnotcarriedoutsofar.

1.4Objectivesofthestudy

Itiscomparativelyeasytoinduce

stressinunhealthysubjects.Healthyindividuals,whoaresupposedtohave

highvagaltoneandhighlyadaptiveANS,canbluntthestressresponseand

producelittleornoeffect,ifthestressorisnotadequate.WhiletheSCWTis

widelyusedtomeasurecognitivestress;itis rarelyseeninreallife.TSSTonthe

otherhandisastandardizedsimulated real life-likepsychosocialstressor.Them a i n


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objectiveofthepresentstudyistotesttheadequacyofthetwowell-

knownstressors,theSCWTandTSST,inasampleofhealthy andphysicallywell

trainedsubjectsusingmeasuresofHRV.Theotherobjectiveistoelucidatethe

associationbetweentheEysenck’sthreefactorpersonalitytraitswiththestress reactivity.

2 Methodologies

2.1Sample

Theparticipantswere27womencandidates.Themeanheightandweightof

theparticipantswere58.4Kgand159cmrespectively.Theaverageageofthe

participantswas27.Allofthemhavecompletedrigorousphysicaltrainingofaerobictype,uniformlyfor

durationof3hoursweekly,exceptonSundaysfort hepreviousninemonths.Thedeliberatetrainingwasun

dertakenin

thetrainingcampofKeralaPoliceacademy,undercloseobservationofprofessionaltrainersandsuperior

officers.Noneoftheparticipantsweresuffering

withmedicalconditionssuchasdiabeticmellitus,hypertension,cardiovascular

abnormalitiesorpsychiatricdepression.Alltheparticipantswereinstructedto

befreefromallsortsofhardcorephysicalactivitiesfor36hourspriortothe experiments.

2.2Experimentaldesign

Theobjectivesandproceduresofthestudywereexplainedtotheparticipants

clearly.Voluntarywritteninformedconsentwasalsocollectedfromallparticipants.Theprocedureshad

beencarriedoutinaccordancewithTheCodeof

EthicsoftheWorldMedicalAssociation(DeclarationofHelsinki)forexperimentsinvolvinghumans.Th

eEthicalclearanceforthestudywasobtainedfrom

JubileeMissionMedicalCollegeandResearchInstitute,Trissur, Kerala.The

dataacquisitionconditionssuchastimeofthedayandthesequenceinwhich

theparticipantsturnupfortheinductionofstressweremaintainedthesameforbothstressors.Recruitswe

reinformedtorefrainfrom drinkingcoffeeandengaginginhardphysicalactivitybeforethestresstests.

PreparationsforECGacquisition:Recruitswerecalledupontotherecordingroominturn.They

werecomfortablyseatedinrestfor30minutesand

disposableECGelectrodeswereattachedtothelimbsofthesubjectsinleadII

configuration.ECGwasrecordedfor5minutesunderspontaneous breathing

conditionbeforeandduringthestressinduction.ECGsignalswereacquiredby

VernierEKGsensorunit.ThesensorunitwasinterfacedwithamyRIOTM(NationalInstruments).Thisr

e-programmable hardwareunitwassoconfiguredto

collectdatafromtwoanaloginputchannelssimultaneouslyatasamplingrate

of500Hz.Thustworecruitsweremonitoredsimultaneously,soastosavethetotal

experimentduration,withonewaitingforthestressorandotherunderstress.

Thesetworecruitswerephysicallyseparatedfromeachotherbythewallsofthe

waitingroomandtestingroom.

Inductionofnon-real lifestress: SCWTisaquickandeasytoadminister

stressstimuliwithhighvaliditybutrarelyseeninreallife.Immediatelyafter

theawaitingperiodthesubjectswereprovidedwithacomputerizedversionof5

minuterunofSCWT.TheParticipantsweregivencolorwordswrittenincolor

andareaskedtoindicatethecoloroftheword(notitsmeaning)orallyasfastas

theycanwithoutmakingerrors.Thetestdisplayscongruentandin-congruent color-

wordcombinationsrandomlyinthecomputer monitor.Fortheserandom trialsofcolor-

words,anobserverhadtohitappropriatekeysinthecomputer

keyboard.Thisensuredmusclenoisesfromhandmovementoftheparticipants


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areabsentintheECGsignals.Simultaneouswiththetest,ECGwasrecorded

andmeanreactiontimeandperformanceofthesubjectswerenoteddownafter

thetest.Meanreactiontimeistheaveragetimeelapsedforeachrecruitbefore

hittingthecorrectkeyinresponsetotheSCWT.

Inductionofsimulatedreal-lifestress:AmodifiedversionofTSSTwas

employedtoevokethesocialinteractionstressandsocialevaluationthreat

amongtherecruits.Thetestcomposedof5minutesforrelaxationand5minutes

foraspeechsessionandamentalarithmetic task.Uponarrivaltoaninterview

panelcomprisedof5superiorofficers(3membersanonymoustothetrainees),

theyweredemandedtointroducethemselvesandsupport withfactsabouttheir

suitabilityforthelawenforcementprofession.Oncehalfthetesttimeisover

theyweregivenamentalarithmeticproblemofserialsubtractionwhichthey

hadtorepeatfrombeginningifamistakeismade.ECGwasrecordedandthe

performancewasevaluatedforeachsubject.

Personalityprofilingoftheparticipants:Themostpopularandhighly established,modelof

personalityistheEysenck’sthreefactormodel.Itincludesneuroticism(ie,tendencytobeemotionallyuns

table,anxious,self-consciousandvulnerable),

extraversion(ie,tendencytobesociable,assertive,energetic,seek excitement

andexperiencepositiveaffect)andpsychoticism(ie,risktaking,impulsiveness,irresponsibility,manipu

lativeness,sensationseeking,toughmindednessandpragmatism)traitstodescribethevariousdimensi

onsofpersonality.

PersonalityassessmentviatheEysenck’spersonalityinventoryconsistingof90itemswithabinaryscalei

sausualprofilingmechanismemployedinthe

policetrainingacademiesinKerala.WehenceusedtheEysenck’sinventory

forassessingthepersonalitytraitsoftheparticipants.Thescoresoverthethree

scaleswerethenstandardizedandtabulatedforfurtheranalyses.

2.3Signalanalysis

TheECGsignalsobtainedforthetwosessionswereclearedofbaselinewander

andothernoiseinterferenceforQRScomplexdetection.Theintervalbetween

eachQRScomplexwasverifiedformanagingasystole,extra-

systolesormisplacedheartbeatsusinga20%filter.ThefilterremovedrelativeRRintervals

whichdifferatleast20%.TheHRVsignalwasthenderivedfrombeatoccurrenceinstancesofsuccessivenor

mal-normalQRScomplexes.TheTaskForce

oftheEuropeanSocietyofCardiologyandNorthAmericanSocietyofPacing

ElectrophysiologyrecommendsanalyzingHRVsignalintime,frequencyand

complexdomains[53].ToinvestigatetheHRVinthefrequencydomain,each

tachogramwasinterpolatedtoobtainequallyspacedsamples,whichwerethen re-

sampledatarateof4Hz.RRintervalsignalscontainbaselinewandering,

whichresultsininaccuratefrequencyanalysis.TheHRVsignalwashencede-

trendedusingdb06waveletdenoisingtechniqueandremovedthetrendbelow0.015Hz.Welch’speriodogr

amwithaHammingwindow(N=512)and50% overlapwasusedfortheestimationof

powerspectraldensity.Therangesof the spectralcomponentsusedwere:HFcomponent0.15-

0.4HzandLFcomponent0.04-0.15Hz.

Allthepre-processingoftheECGsignalswerecarriedoutusingtheECG

FeatureExtractorVIandtheHRVanalysisiscarriedoutusingHRVanalyzer

applicationoftheNILabVIEW2015.

2.4Statisticalanalysis


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Pairedsamplet-testwasusedforthecomparisonofmeanstressresponsesin

eachcase.Asafirststep,thetestfornormalitywascarriedoutforallmeasures

ofHRVtoqualifythefeaturesfort-test.Thefeatureswerefoundnormally

distributedexceptfrequencydomainmeasures.Thefrequencydomainparameterswerehencetransfor

medtothenaturallogscale. Thepersonalitytraits alsoexhibitednon-

normaldistribution.Hencetheassociationofpersonality

andstressresponsewereevaluatedwithSpearman’scorrelation(ρ)analysis.

Analphalevelof.05wasusedforalltheanalyses.

3 Resultsanddiscussion

TABLE IIshowstheresultsof physiologicalresponseinSCWT andTSST. The levelofsignificance in

mean difference ofHRV parametersat pre-stress and during stressisalsotabulated.

TABLEII:Descriptive statisticsofHRVparametersofb o th stress

sessions(mean ±S.E)

Pre TSSTTSST Sig Pre SCWTSCWT Sig

MeanHR 77.5±2.854 88.968±3.575 0.001 69.629±7.73 74.785±8.753 0 MeanRR 808.415±29.337 711.865±30.833 0.009 881.51±101.358 821.734±98.058 0.767 NN50 109.875±14.209 79.584±12.898 0 123.643±56.482 116.965±62.117 0 pNN50 33.388±5.061 22.114±4.355 0.331 37.738±19.3 33.355±19.68 0.096 RMSSD 74.944±10.342 55.259±7.849 0.028 67.804±32.055 65.55±33.208 0.439 SDHR 7.03±0.986 6.853±0.432 0.019 5.369±2.596 5.362±1.516 0.29 SDNN 61.79±6.589 49.063±5.317 0.005 54.882±21.564 54.337±20.551 0.038 TINN 348.125±30.313 222.114±4.355 0 345.472±32.514 467.583±48.325 0.61 HRVTRI 13.075±1.2 79.584±12.898 0 12.19±2.23616.68±4.1 0.055 pHF 2042.538±613.998 1149.243±362.875 0.013 1793.274±895.509 1690.573±738.645 0.6 pLF 1614.501±316.83 994.819±177.703 0.001 1514.653±664.987 1360.472±396.325 0.509 LF/HF 1.632±0.279 1.443±0.171 0.587 1.307±0.973 1.351±0.814 0.316 TP 849.472±941.427 2255.954±526.525 0.2 3503.323±4440.517 3151.529±3542.693 0.891 ApEn 1.157±0.019 1.173±0.017 0.028 1.161±0.057 1.178±0.073 0.75 SampEn1.67±0.047 1.543±0.063 0.743 1.843±0.218 1.806±0.258 0.3 d22.515±0.38 2.004±0.318 0.732 2.949±1.601 2.56±1.837 0.585 dfa1 0.937±0.051 0.995±0.049 0.11 0.88±0.182 0.896±0.222 0.906 dfa2 0.408±0.035 0.423±0.027 0.17 0.322±0.099 0.281±0.084 0.376 sd1 53.076±7.327 39.129±5.561 0.265 48.018±22.706 46.417±23.521 0.909 sd267.739 ±6.281 55.82 ±5.535 0.458 60.411±21.852 60.465±19.518 0.076

3.1StressresponseinTSST

DuringTSST,HRincreases,variabilityintimeandfrequencydomainsisreducedandcomplexityo

ftheHRVtimeseriesisreducedincomparisonwiththe pre-

stressperiod.Thereissignificantchangeinalltime(except

pNN50)andgeometricalindices.Theobservationofincreasedheartrateisinagreementwith

otherstudieswhousedTSSTasastressinductionmethod[54,55].Inthefrequencydomain,exceptTPand

LF/HF,theothervariablesdiffersignificantly.

InthefrequencydomainHRVparameters,vagalwithdrawalduringstresshas

leadstoasignificantreductionofpowerinboththebands(p=0.013forpLFand

0.001forpHF).SimilarresultsareobtainedbyTharionetal.[44],Papousek

etal.[56]andT.MarcelloandA.Cataldo[57].LF/HFratioisgenerallyseen

increasedduringstress,butitisnoticeablethatthesympathovagalbalanceasmeasuredbyLF/HFisfoun

ddecreasedinourresults.Butthereductionin

LF/HFhasnotdiffereduptoalevelofstatisticalsignificanceunderstress.Althoughashiftinautonomicba

lanceisobserved,itisnotremarkableenough.

Regardingthenonlinearindices,noneoftheHRVmetricexhibitedasignificant

reduction.Eventhoughadirectcomparisonisnotmeaningful,duetothedifferencesinthemethodologyan

dparticipantcharacteristics,Vuksanovicetal.


12581

[58]haveobservedsignificantreductioninSampEnandsignificantincrement

indfa1inamentalarithmetictaskofserialsubtraction.Melilloetal.alsoobtainedsignificantreductioni

nthecomplexityofHRVsignalsduringreallife examination

stress[15].Boththestudiesdonotreportaboutthephysicalcharacteristicsoftheparticipants,exceptthat

theyarehealthy.Henceitturnsout

thatphysicalactivitylevelalsocouldbeanimportantfactortobeconsidered

instressinductionmethods.

3.2Stressresponse inSCWT

OveralltheresultsofSCWTsuggestparasympatheticdominanceintherecruits

evenunderstress.ExceptforMeanHR,NN50andSDNN,noneofthetime

HRVmetricsatstressshowedasignificantchangefromrest.Similarly,noneof

thefrequencydomainfeaturesornonlinearfeaturesshowedasignificantchange.

Theresultsareinobjectionwiththemuchreported resultsofSCWTongeneral

samples.Oneofthereasonsforthecontradictoryfindingcouldbethewell-

conditionedANSoftheparticipantsduetothephysicaltraining.

ThemeanRTfortheparticipantstorespondtothecongruentandin-

congruenttrialsofSCWTisalsoanalyzed, astherearereportssuggesting

possibleassociationbetweenHRV,workingmemory,performanceandresponse

control[9,59,60].Thereactiontime(RT)isthetimethatelapsesbetween acolor-

wordstimulusandthemotorresponsetohittheresponsekey.Itis

usuallyontheorderof200ms[61].ThemeanRTinourcaseturnedoutto

be127.85ms,muchbetterthanthegeneralaverage.Butourstudy,irrespectiveofshowingan

i n s i g n i f i c a n t suppressioninHRV, didnot

revealanyrelevantbivariateassociationswithmeanRT.Butitisnoteworthy

thattheassociationswereintheexpecteddirection,withhighHRVconnected withlowmeanRTandvice-

versa.These different resultsonreactiontimealso couldbeduetothephysiologicalmodificationof

theANSduetophysicaltraining.Toreinforcethecurrentknowledge,furtherstudiesaretobetakenup,in

cross-sectionaldesignusingtrainedanduntrainedparticipants.

Itistobenotedthat,asitishardandextrastressfultoperformbothattentionandspeechtaskswithrespir

ationcontrolledsimultaneously[62],breath

rateoftheparticipantswasnotcontrolled.Dependingonthebreathingpat-

tern,numericalvaluesofpHFmaybedifferent.Butcorrectingforrespiratory

frequencyinhealthysubjectsdoesnotappeartogiveabetterestimateof vagal

activity[63,64].Alsootherstudies[65]havedemonstratedthatrespirationis

notrelatedtoHRVatrestinhealthyparticipants.Duringboththesessions

ofstressinduction,therateofrespirationisassumedtobeafunctionofthe

appropriatelyperceivedstress.SothepHFresultsaretobeinterpreted, keeping this aspect in mind.

3.3 Comparisonofstressresponsein bothstressors

Acomparison ofthestressresponseinboththestressorsistabulatedinTABLE III.Thetable

showsthepairedmeandifferenceofthestressresponseinSCWT and TSST alongwiththe 95%upper

and lowerconfidenceinterval and significanceofthedifference. Asitcanbeseen,TSST

couldincreasethemeanHR of theparticipantsmoreby15bpm, than SCWT. ThemeanRR

islowerinTSST by 121.602ms. In TSST, the other HRV time domain parameterssuch as NN50is

lowerby39.540,pNN50is lowerby12.522,SDHRlowerby1.278 bpm, HRVTRIN

lowerby60.124,andTINNlowerby321.602.All thesetimedomain indicesaresignificantlylow

compared tothestressresponseinSCWT. Further, TSST couldreducethecomplexity

ofcardiovascularneuralcontrolsignificantly betterthan SCWT (SD1, SD2,ApEn, SampEn, D2).

This clearly showsthe increasedstressinductioncapabilityofTSST inphysicaly conditioned

subjects compared to SCWT. While this istrue forthe above saidfeatures, the other


12582

timedomainfeaturessuchas RMSSD,SDNNandthefrequencydomainfeatures couldnot exhibit

asignificantly betterstress response inTSST than SCWT.

TABLEIII:Paired mean differenceofHRVparametersofboth stress

sessions(mean ±S.E)

HRV FeatureMean ±SE Lower Confidenceinterval Upper Confidenceinterval t Sig(2-tailed)

meanHR -15.00843±4.45023 -24.26320 -5.75367 -3.373 .003 meanRR 121.60294±41.14939 36.02811 207.17778 2.955 .008 NN50 39.54545±20.03392 -2.11737 81.20828 1.974 .062 Pnn50 12.52270±6.42904 -.84722 25.89262 1.948 .065 RMSSD 10.91977±11.42337 -12.83643 34.67598 .956 .350 SDHR -1.27831±.56304 -2.44922 -.10741 -2.270 .034 SDNN 5.56495±7.63591 -10.31479 21.44469 .729 .474 HRVTRIN 60.12400±10.23000 18.23300 48.25900 -2.260 .035 TINN 321.60294±28.14939 26.05463 277.17355 2.955 .008 pLF 207.33159±275.88802 -364.82515 779.48832 .752 .460 pHF 519.34340±723.40841 -980.91383 2019.60062 .718 .480 TP 705.82430±975.91847 -1318.10673 2729.75532 .723 .477 LF/HF -.11779±.24815 -.63241 .39683 -.475 .640 SD1 2.11256±7.85597 -14.22482 18.44995 .269 .791 SD2 .45845±6.63524 -13.34029 14.25719 .069 .946 ApEn .01516±.02257 -.03178 .06210 .672 .509 SampEn .25182±.07947 .08655 .41709 3.169 .005 D2 1.08851±.42865 .19707 1.97994 2.539 .019 dfa1 -.08249±.06100 -.20934 .04437 -1.352 .191

dfa2 -.13542 ±.03004 -.19789 -.07295 -4.508 .000

Eventhen, pLF,pHFandTParealllowerinTSST(207.331ms2,519.343ms2, 705.824ms2

respectively),indicating theclearadvantageofitoverSCWT. All nonlinear indices,

butdetrendedfluctuationparameters(dfa1 and dfa2) also indicate the superiorityofTSST

inreducing the flexibility ofANS.Further, theseresultsareinaccordancewithKlaperskietal.

[54]andRimmeleetal. [55] who observedhighlyactivewomenandmenshowinglowestheart

ratereactivity and sedentaryreporting highest reactivityinresponse topsychological stress. Figure

1showsthe Box-Whisker plots ofthe features whichshowedsignificant differenceinstress response

forthe both the stressors. The response inTSST isremarkablyhigherthan theSCWT session.

Figure1:Box-Whiskerplotsofthefeatureswithsignificantchangeinresponse

duringSCWTandTSST(inappropriateunits)


12583

3.4Associationofpersonalitytraitsandstressresponse

ThescoresobtainedforeachoftheEysenck’spersonalityfactoraregiveninTable4.

Table4:Eysenck’spersonalityprofileoftherecruits

Trait Mean Score Std. Score

Extraversion

35

14.166

-2.892

Neuroticism 9.663 -1.1721

Psuchoticism 4.22 -1.794

Thenon-parametriccorrelationanalysis between thestressresponsesδ(the

differencebetweenpreSCWTandTSST HRVfeatures) andtheEysenck’straits of

personalityareillustratedinTable5.Itcanbeseenthat theassociation of

extraversionwiththestressresponseisnegative formajorityoftheHRVfeatures. The result indicates

thatextraverts,whoconverselypossessthe tendency tobe sociable,assertive, energetic, and

experience positive affect,perceived the lowestreaction inresponsetothe acute psycho-social stress.

Those high on extraversion experienced the lowest reduction in variability factor of heart rate

during TSST. Infact,the measures ofparasympatheticmodulationsuchasRMSSDand

SDHRshowsignificant weak and moderate associations

withtheextraversioncharacteristicsoftheparticipants.

Table 5:Association ofstressresponseandpersonalitytraits

Extraversion Psychoticism Neuroticism

δmeanRR -.019 -.323 -.300

δMEANhr .091 .174 .179

δSDNN -.266 -.225 .039

δsdHR -.566** .144 .325

δRMSSD -.376* -.214 .010

δNN50 -.326 -.150 .112

δPNN50 -.291 -.237 .003

δpLF .080 .024 -.150

δpHF -.134 .001 .042

δpTP .017 -.075 .153

δLFHF .162 .112 -.251

δSD1 -.279 -.091 .183

δSD2 -.268 -.315 .080

δApEn .294 .151 -.171

δsampEn -.314 .188 .233

δD2 -.416* -.224 -.101

δdfa1 .061 -.257 -.245

δdfa2 -.503** .280 -.144

Psychoticism -.105 - - Neuroticism -.126 .257 -

Note: **ρsignificantatp≤0.01,*significantatp=0.05(two-tailed).

The results are inaccordance with the other studies, where people

withlowextraversionscoreshowedhighstressresponseindifficultmental tasks and mildelectrical

shocks[34,66,67].Additionally,the longrange correlation asmeasured

bythedetrendedfluctuationanalysis dfa2andcorrelationdimensionD2alsoshowmoderatenegative

association withextraversion.That means, the complexity of cardiac control of the ANS


12584

experienced the lowest reduction for people high on extraversion. Extraverts still maintain the

dynamic complexity of HRV even under stress. Itis worthy tonote that bothpsychoticism

andneuroticism traits arenotsignificantlyassociatedwiththestressresponse in our study.

Thisisinlinewithotherstudieswhichfailedto findavalidrelation between neuroticism

andcardiovascularreactivity[68,69]. Even then, theconnection

ofphysiologicalstressresponseandthesetwopersonalitytraits inphysically conditioned

groupsstillneedtobeestablished with more samples and cross-sectional study designs.

4. Conclusions PA and exercisehave beendemonstratedtopromote positive changes inone’s mental health

and ability to cope with stressful encounters. In lightofthe results furnished from the stress tests,

it isclear thatphysically welltrained participantsofthis study exhibited stress bufferingeffectonthe

non- realtime cognitive stressor. Itistobenoted thatthe obtained result is contrarytothe

findingsofothers whohaveusedthesamestressor. At the same time, it is to benoted also that, these

studies have notreportedonthephysical activity levelofthe participants. Compared to SCWT,

noticeable response above the resting leveliselicited byTSST. The results have further proved the

efficiencyofTSST asastressor inphysically conditioned subjects. The cardiac control ofautonomic

nervous system during both stressors waswellbalanced, indicating

thebufferingroleofphysicalfitnessinstressresponse.

Theresultsshowlightsintothebenefitsofexercisetrainingintransformingthe recruits tohandle

psycho-physiological stress inhighstress occupations. Thus highlyactive lawenforcementtrainees,

whoconversely possesshigher physical fitness,arefoundtobemoreresilienttonon-

reallifecognitivestress. Thisneeds tobeestablishedwithcomparativestudies incrosssectional

designontrained and sedentarygroupsinlargesize. Inthis study, weonly found an association inthe

expected direction between extraversionand stress reaction asdefinedbyHRV. TSST

ledtoastronger reduction in baselineHRVamonglowextraversion individuals compared

tohighextraversion. HRVbased physiological measures may beavaluable addition tothe

questionnairetoolstoestablish anindividual’spersonalitydimensions

suchasextraversionandvulnerabilitytostress, in policeselection procedures. The results pointout

thatpersonality traitsand physical activitylevelaretwoimportantfactors tobeconsidered in stress

research.

Acknowledgment

TheauthorswouldliketothanktheofficialsofKeralaPoliceAcademy,Thrissur,

especiallyDr.JayeshK.Joseph(Criminologist,KEPA),forsupervisingthe

conductofthestudy,andSri.RajeshP.(Asst.Professor,Dept.Economics,

Govt.Engg.College,Thrissur)forsupportingthestatisticalanalysisofdata.

References

[1]Crowley,O.V., McKinley,P. S.,Burg,M.M.,Schwartz,J.E., Ryff, C.D., Weinstein,M.,Seeman,T.

E.andSloan,R. P., 2011.Theinteractiveeffectof

changeinperceivedstressandtraitanxietyonvagalrecoveryfromcognitivechallenge.InternationalJou

rnalofPsychophysiology,82(3), pp.225–232.

[2]Kofman,O.,Meiran,N . , Greenberg,E.,Balas,M.andCohen,H., 2006.Enhanced

performanceonexecutivefunctionsassociatedwithexaminationstress:Evidencefromtask-

switchingandstroopparadigms.Cognition&Emotion, 20(5),pp.577–595.

[3]Hjortskov,N.,Rissen,D.,Blangsted,A.K.,.Fallentin, A.,Lundberg, U. and Søgaard, K.,2004.

Theeffectofmentalstressonheartratevariabilityandblood

pressureduringcomputerwork.Europeanjournalofappliedphysiology, 92(12),pp.84–89.


12585

[4]Pan, R. L.C. andLi,J. K.-J. ,2007Anoninvasiveparametricevaluationof

stresseffectsonglobalcardiovascularfunction.CardiovascularEngineering,7(2)pp.74–80.

[5]Chida, Y.andSteptoe,A., 2010. Greatercardiovascularresponsestolaboratory

mentalstressareassociatedwithpoorsubsequentcardiovascularriskstatus.Hypertension55(4),pp.10

26–1032.

[6]Castaldo,R.,Melillo,P.Bracale,U., Caserta,M.Triassi,M. andPecchia, L.,

2015.AcutementalstressassessmentviashorttermHRVanalysisinhealthy

adults:Asystematicreviewwithmeta-analysis.BiomedicalSignalProcessingandControl,18, pp.370–

377.

[7]Raglin,J.,Wilson, G.,andGalper,D.,2007. Exerciseanditseffectsonmental

health.Physicalactivityandhealth,1,pp.247–257.

[8]Scully,D.,Kremer,J.,Meade,M.M.,Graham,R., andDudgeon, K., 1998.Physical

exerciseandpsychologicalwellbeing:Acriticalreview.BritishJournalof SportsMedicine, 32(2),

pp.111–120.

[9]Hansen,A.L., Johnsen, B.H., andThayer, J.F., 2003. Vagalinfluenceonworking

memoryandattention.International Journalof Psychophysiology,48(3),pp.263–274.

[10]Chrousos, G.P., 2 0 0 9 . Stressanddisordersof thestresssystem.Naturereviews

endocrinology,5(7),pp.374–381.

[11]Boullosa,D.A.,Abreu,J . L.,Tuimil,L . a ndLeicht,A.S.,2012.Impactofasoccer

matchonthecardiacautonomiccontrolofreferees.Europeanjournalof

appliedphysiology,112(6),pp.2233–2242.

[12]Buchheit,M.,Mendez-Villanueva,A.,Quod, M.J.,Poulos,N, andBourdon, P.,

2010.Determinantsofthevariabilityofheartratemeasuresduringacompetitiveperiodinyoungsoccerpl

ayers.Europeanjournalof appliedphysiology,109(5),pp.869–878.

[13]Uusitalo, A . ,Mets,T.,Martinmaki,K,Mauno,S.,.Kinnunen, U.,and Rusko,H., 2011.

Heartratevariabilityrelatedtoeffortatwork.AppliedErgonomics,vol.42,no.6,pp.830–838.

[14]Salai,M.Vassanyi,I. andKosa, I., 2016. Stressdetectionusinglowcostheart ratesensors.

Journalofhealthcareengineering, 2016.

[15]Melillo,P.,Bracale,M., andPecchia,L., 2011. Nonlinearheartratevariability featuresforreal-

lifestressdetection.casestudy:Studentsunderstressdue

touniversityexamination.Biomedicalengineeringonline,10(96).

[16]Pereira,T.,Almeida,R.P.,Cunha,J. P.,andAguiar, H., 2017. Heartratevariabilitymetricsforfine-

grainedstresslevelassessment.ComputerMethods andProgramsinBiomedicine, 148,pp.71–80.

[17]Djuric,Z.,Bird,C.E.,Furumoto-Dawson,A.,Rauscher,G.H.,RuffinIV,M.T,Stowe,R.P.,

Tucker,K.L.andMasi,C.M., 2008. Biomarkersof

psychologicalstressinhealthdisparitiesresearch.Theopenbiomarkersjournal,1,p.7.

[18]Kiviniemi,A. M., Hautala,A. J.,Kinnunen,H.,Nissila,J.,Virtanen, P.,Karjalainen,J.

andTulppo,M.P., 2 0 1 0 . Dailyexerciseprescriptiononthebasis of

HRvariabilityamongmenandwomen.Medicine&ScienceinSports& Exercise,vol.42,no.7,pp.1355–

1363.

[19]Childs, E.,andWit,H., 2014. Regularexerciseisassociatedwithemotional

resiliencetoacutestressinhealthyadults.Frontiersinphysiology,5.


12586

[20]Tonello,L., Rodrigues,F.B.J.W.,Campbell,S.,Leicht,A.S.andBoullosa,D.A., 2014.

Theroleofphysicalactivityandheartratevariabilityfor thecontrolofworkrelatedstress.

Frontiersinphysiology, 5.

[21]Bravi,A.,Longtin,A., andSeely,A.J., 2 0 1 1 . Reviewandclassificationofvariabil-

ityanalysistechniqueswithclinicalapplications.Biomedicalengineering online,10(1)pp.90.

[22]Smith,A.L.,Owen,H., andReynolds,K.J., 2013.Heartratevariabilityindices forveryshort-

term(30beat)analysis.Part2:Validation.Journalofclinicalmonitoringandcomputing,27(5),pp.577–

585.

[23]Laborde,S.Mosley, E.,andThayer,J. F.,

2017.Heartratevariabilityandcardiacvagaltoneinpsychophysiologicalresearch:

Recommendationsfor

experimentplanning,dataanalysis,anddatareporting.Frontiersinpsychology, 8.

[24]Pincus,S.,1995. Approximateentropy(apen)asacomplexitymeasure.Chaos:

AnInterdisciplinaryJournalofNonlinearScience,5(1),110–117.

[25]Richman,J. S. andMoorman,J. R., 2000. Physiological time-seriesanalysis

usingapproximateentropy andsampleentropy.American Journalof Physiology-

HeartandCirculatoryPhysiology,278(6),pp.H2039– H2049.

[26]M.Brennan,M.Palaniswami,andP.Kamen,Doexistingmeasuresof

poincareplotgeometryreflectnonlinearfeaturesofheartratevariability?,

IEEEtransactionsonbiomedicalengineering,vol.48,no.11,pp.1342–

1347,2001.

[27]P.A.Deuster,J.S.Petrides,A.Singh,G.P.Chrousos,andM.Poth,En- docrineresponsetohigh-

intensityexercise:dose-dependenteffectsofdex- amethasone,

TheJournalofClinicalEndocrinology&Metabolism,vol.85, no.3,pp.1066–1073,2000.

[28]P.A.Deuster,J.S.Petrides,A.Singh,E.B.Lucci,G.P.Chrousos,

andP.W.Gold,Highintensityexercisepromotesescapeofadrenocor-

ticotropinandcortisolfromsuppressionbydexamethasone:sexuallydi-

morphicresponses,TheJournalofClinicalEndocrinology&Metabolism, vol.83,no.9,pp.3332–

3338,1998.

[29]A.Singh,J.S.Petrides,P.W.Gold,G.P.Chrousos,andP.A.

Deuster,Differentialhypothalamic-pituitary-adrenalaxisreactivityto

psychologicalandphysicalstress,TheJournalofClinicalEndocrinology&Metabolism,vol.84,no.6,pp.

1944–1948,1999.

[30]S.K.Crowley,L.L.Wilkinson,L.T.Wigfall,A.M.Reynolds,S.T.Muraca,S.H.Glover,N.R.Wooten,X.S

ui,M.W.Beets,J.L.Durstine,etal.,Physicalfitnessanddepressivesymptomsduringarmybasiccombat

training,Medicineandscienceinsportsandexercise,vol.47,no.1,p.151,

2015.

[31]E.-R.Saus,B.H.Johnsen,J.Eid,andJ.F.Thayer,Whobenefitsfrom

simulatortraining:Personalityandheartratevariabilityinrelationto

situationawarenessduringnavigationtraining,Computers inHumanBe-

havior,vol.28,no.4,pp.1262–1268,2012.

[32]T.R.Schneider,T.A.Rench,J.B.Lyons,andR.R.Riffle,Theinfluence

ofneuroticism,extraversionandopennessonstressresponses,Stressand Health,vol.28,no.2,pp.102–

110,2012.

[33]S.Koelsch,J.Enge,andS.Jentschke,Cardiacsignaturesofpersonality,PloSone,vol.7,no.2,p.e31441,

2012.


12587

[34]A.-M.Brouwer,M.G.VanSchaik,J.H.Korteling,J.B.vanErp,and A.Toet,Neuroticism,

extraversion,conscientiousnessandstress:Physio-

logicalcorrelates,IEEEtransactionsonaffectivecomputing,vol.6,no.2, pp.109–117,2015.

[35]H.J.Eysenck,Biologicalbasisofpersonality,Nature,vol.199,no.4898, pp.1031–1034,1963.

[36]M.FredriksonandA.Georgiades,Personalitydimensionsandclassical

conditioningofautonomicnervoussystemreactions,PersonalityandIn-

dividualDifferences,vol.13,no.9,pp.1013–1020,1992.

[37]J.Ormel,A.Bastiaansen,H.Riese,E.H.Bos,M.Servaas,M.Ellenbo-

gen,J.G.Rosmalen,andA.Aleman,Thebiologicalandpsychological

basisofneuroticism:currentstatusandfuturedirections,Neuroscience

&BiobehavioralReviews,vol.37,no.1,pp.59–72,2013.

[38]J.A.HealeyandR.W.Picard,Detectingstressduringreal-worlddriv-

ingtasksusingphysiologicalsensors,IEEETransactionsonintelligent

transportationsystems,vol.6,no.2,pp.156–166,2005.

[39]P.Karthikeyan,M.Murugappan,andS.Yaacob,Analysis ofstroop colorwordtest-

basedhumanstressdetectionusingelectrocardiography and

heartratevariabilitysignals.,ArabianJournalforScience&Engineering

(SpringerScience&BusinessMediaBV),vol.39,no.3,2014.

[40]M.J.Lambiase,H.M.Barry,andJ.N.Roemmich,Effectof asimulated

activecommutetoschooloncardiovascularstressreactivity,Medicineand

scienceinsportsandexercise,vol.42,no.8,p.1609,2010.

[41]J.N.Roemmich,M.Lambiase,S.J.Salvy,andP.J.Horvath,Protec-

tiveeffectofintervalexerciseonpsychophysiologicalstressreactivityin

children,Psychophysiology,vol.46,no.4,pp.852–861,2009.

[42]A.R.JensenandW.D.RohwerJr,Thestroopcolor-wordtest:areview,

Actapsychologica,vol.25,pp.36–93,1966.

[43]J.F.ThayerandR.D.Lane,Amodelofneurovisceralintegrationinemo-

tionregulationanddysregulation,Journalofaffectivedisorders,vol.61, no.3,pp.201–216,2000.

[44]E.Tharion,S.Parthasarathy,andN.Neelakantan, Short-termheartrate

variabilitymeasuresinstudentsduringexaminations.,NationalMedical JournalofIndia,2009.

[45]B.M.Kudielka,N.C.Schommer,D.H.Hellhammer,andC.Kirschbaum,

Acutehpaaxisresponses,heartrate,andmoodchangestopsychosocial

stress(tsst)inhumansatdifferenttimesofday,Psychoneuroendocrinol- ogy,vol.29,no.8,pp.983–

992,2004.

[46]J.U.Frisch,J.A.Hausser,andA.Mojzisch,Thetriersocialstresstestas

aparadigmtostudyhowpeoplerespondtothreatinsocialinteractions,

FrontiersinPsychology,vol.6,pp.14–14,2014.

[47]S.S.DickersonandM.E.Kemeny,Acutestressorsandcortisolresponses:

atheoreticalintegrationandsynthesisof laboratoryresearch.,Psycholog-

icalbulletin,vol.130,no.3,p.355,2004.

[48]J.DelaneyandD.Brodie,Effectsofshort-termpsychologicalstresson

thetimeandfrequencydomainsofheart-ratevariability,Perceptualand

motorskills,vol.91,no.2,pp.515–524,2000.

[49]J.W.HughesandC.M.Stoney,Depressedmoodisrelatedtohigh- frequencyheartratevariability

duringstressors,Psychosomaticmedicine, vol.62,no.6,pp.796–803,2000.


12588

[50]D.Jain,T.Joska,F.A.Lee,M.Burg,R.Lampert,andB.L.Zaret,Day- to-

dayreproducibilityofmentalstress-inducedabnormalleftventricular

functionresponseinpatientswithcoronaryarterydiseaseanditsrelation-

shiptoautonomicactivation,JournalofNuclearCardiology,vol.8,no.3, pp.347–355,2001.

[51]D.Lucini,G.Norbiato, M.Clerici,andM.Pagani,Hemodynamicand autonomicadjustmentstoreallife

stressconditionsinhumans,Hyperten- sion,vol.39,no.1,pp.184–188,2002.

[52]J.Rajcani,P.Solarikova,D.Turonova,andI.Brezina,Heartratevari-

abilityinpsychosocialstress:Comparisonbetweenlaboratoryandreal-life

setting,ActivitasNervosaSuperior,vol.58,no.3,2016.

[53]A.J.Camm,M.Malik,J.Bigger,G.Breithardt,S.Cerutti,R.Cohen,

P.Coumel,E.Fallen,H.Kennedy,R.Kleiger,etal.,Heartratevariabil-

ity:standardsofmeasurement,physiologicalinterpretationandclinical

use.taskforceoftheeuropeansocietyofcardiologyandthenorthamer-

icansocietyofpacingandelectrophysiology,Circulation,vol.93,no.5, pp.1043–1065,1996.

[54]S.Klaperski,B.vonDawans,M.Heinrichs,andR.Fuchs,Doesthelevel of

physicalexerciseaffectphysiologicalandpsychologicalresponsestopsy-

chosocialstressinwomen?,PsychologyofSportandExercise,vol.14, no.2,pp.266–274,2013.

[55]U.Rimmele,R.Seiler,B.Marti,P.H.Wirtz,U.Ehlert,andM.Heinrichs,

Thelevelofphysicalactivityaffectsadrenalandcardiovascularreactivity

topsychosocialstress,Psychoneuroendocrinology,vol.34,no.2,pp.190–

198,2009.

[56]I.Papousek,K.Nauschnegg,M.Paechter, H.K.Lackner,N.Goswami,and

G.Schulter,Traitandstatepositiveaffectandcardiovascularrecovery

fromexperimentalacademicstress,BiologicalPsychology,vol.83,no.2, pp.108–115,2010.

[57]E.M.MEDICA-TORINO,Effects.ofanxietyduetomentalstressonheart

ratevariabilityinhealthysubjects,MinervaPsichiatr,vol.52,pp.227–31,

2011.

[58]V.VuksanovicandV.Gal,Heartratevariabilityinmentalstressaloud,Medicalengineering&physics,vol

.29,no.3,pp.344–349,2007.

[59]B.H.Johnsen,J.F.Thayer,J.C.Laberg,B.Wormnes,M.Raadal, E.Skaret,

G.Kvale,andE.Berg,Attentionalandphysiologicalchar-

acteristicsofpatientswithdentalanxiety,Journalofanxietydisorders, vol.17,no.1,pp.75–87,2003.

[60]H.Middleton,A.Sharma,D.Agouzoul,B.Sahakian,andT.Robbins,

Contrastsbetweenthecardiovascularconcomitantsoftestsofplanning

andattention,Psychophysiology,vol.36,no.5,pp.610–618,1999.

[61]Wong,A.L.,Haith,A.M.andKrakauer,J. W., 2015.

Motorplanning.TheNeuroscientist,21(4),pp.385–398.

[62]QuintanaD.S.andHeathers,J. A.,2 0 1 4 .Considerationsintheassessmentof

heartratevariabilityinbio-behavioralresearch.Frontiersinpsychology, 5.

[63]Houtveen,J. H.,Rietveld,S. andGeus,E.J., 2002. Contributionoftonicvagal modulationof

heartrate,centralrespiratorydrive,respiratorydepth,and

respiratoryfrequencytorespiratorysinusarrhythmiaduringmentalstress

andphysicalexercise.Psychophysiology,39(4),pp.427–436.


12589

[64]Grossman,P. andTaylor,E.W., 2007. Towardunderstandingrespiratorysinus

arrhythmia:relationsto cardiacvagaltone,evolutionandbio-behavioral

functions.Biologicalpsychology,74(2),pp.263–285.

[65]Denver,J. W.,Reed,S.F.andPorges,S.W., 2007. Methodologicalissuesin

thequantificationofrespiratorysinusarrhythmia.Biologicalpsychology, 74(2),pp.286–294.

[66]Pearson, G. L. andFreeman,F. G., 1991. Effectsofextraversionandmental arithmeticonheart-

ratereactivity.PerceptualandMotorSkills,72(3),pp.1239–1248.

[67]Jonassaint,C.,Why,Y.,Bishop,G.,Tong,E.,Diong,S.,Enkelmann, H.,Khader, M.andAng,J., 2009.

Theeffectsofneuroticismandextraversionon

cardiovascularreactivityduringamentalandanemotionalstresstask.

InternationalJournalofPsychophysiology,74(3),pp.274–279.

[68]SchwebelD.C.andSuls,J.,

1999.Cardiovascularreactivityandneuroticism:Resultsfromalaboratoryandcontrolledambulator

ystressprotocol.Journal ofPersonality67(1),pp.67–92.

[69]Brumbaugh, C.C.,Kothuri,R.,Marci,C.Siefert,C . andPfaff,D.D., 2013.

Physiologicalcorrelatesofthebig5:Autonomicresponsestovideopresentations.

Appliedpsychophysiologyandbiofeedback38(4),pp.293–301.


12590

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