Taiji practice attenuates psychobiological stress reactivity - A randomized controlled trial in healthy subjects
Marko Nedelj kovic a,*, Brigitte Ausfeld-Hafter
a,Konrad S treitberger
b,Roland Seiler c, Petra H. Wirtz d
a University of Bern, Institute of Complementary Medidne KIKOM, lmhoof·Pavillon, lnse/spital, CH-3010 Bern, Switzerland
b lnselspital Bem, University Department of Anesthesiology and Pain Therapy, CH-3010 Bern, Switzerland
c University of Bern, Institute of Spart Sdence, Alpeneggstrasse 22, CH-3012 Bern, Switzerland
d University of Bern, Department of Psychology, Biological and Health Psychology, Alpeneggstrasse 22, CH-3012 Bern, Switzerland
KEYWORDS Taiji;
Psychosocial stress;
Salivary cortisol;
Salivary a-amylase;
Heart rate
Summary
Background: Stress reducing effects of Taiji, a mindful and gentle form of body movement, have been reported in previous studies, but standardized and controlled experimental studies are scarce. The present study investigates the effect of regular Taiji practice on psychobiological stress response in healthy men and women.
Methods: 70 partidpants were randomly assigned to either Taiji classes or a waiting list. After 3 months, 26 (8 men, 18 women) persons in the Taiji group and 23 (9 men, 14 women) in the waiting control group underwent a standardized psychosocial stress test combining public speaking and mental arithmetic in front of an audience. Salivary cortisol and a-amylase, heart rate, and psychological responses to psychosodal stress were compared between the study groups. (ClinicalTrials.gov number, NCT01122706.)
Results: Stress induced characteristic changes in all psychological and physiological mea.sures.
Compared to controls, Taiji partidpants exhibited a significantly lower stress reactivity of cortisol (p = .028) and heart rate (p = .028), as well as lower a-amylase levels (p = .049). They reported a lower increase in perceived stressfulness (p = .006) and maintained a higher level of calmness ( p = . 019) in response to psychosodal stress.
Conclusion: Our results consistently suggest that practidng Taiji attenuates psychobiological stress reactivity in healthy subjects. This may underline the role of Taiji as a useful mind-body practice for stress prevention.
• Corresponding author. Tel.: +41 31 632 9758; fax: +41 31 632 4162.
E-mail address: marko.nedeljkovic@kikom.unibe.ch (M. Nedeljkovic).
Konstanzer Online-Publikations-System (KOPS) URL: http://nbn-resolving.de/urn:nbn:de:bsz:352-0-276658
1. Introduction
Theharmfulimpactofstressonhealthhasbeendocumented repeatedly(Rozanskietal.,1999;Ehlertetal.,2001;Brot- man etal.,2007; Shonkoff etal.,2009). Stress reactivity researchsuggeststhatadverseconsequencesofpsychosocial stresson physicalandmentalhealth mayrelateto stress- inducedactivationofdifferentstress-responsivephysiologi- cal systems (Ehlert etal., 2001; Lovallo and Gerin, 2003;
RaisonandMiller,2003;Brotmanetal.,2007).Large-magni- tudephysiologicalreactionstoacutestressorsinparticular, oftencombinedwithdelayedrecovery,couldbeidentifiedas stress-relatedriskfactorsforcardiovasculardisease(Steptoe etal., 2006; Chida and Hamer, 2008; Chida and Steptoe, 2010).Moreprecisely,stress-inducedhyperreactivityofthe two main human stress systems, the hypothalamus—pitui- tary—adrenal(HPA)axiswithitsend-productcortisolandthe sympatheticnervoussystem (SNS)mayincreasecardiovas- cularrisk,eitheraloneand/orbyinducingadversechangesin intermediate biological risk factors for cardiovascular dis- ease such as coagulation activity, inflammation, or lipids (Rosmond and Bjorntorp, 2000; von Kanel et al., 2001;
Lovallo and Gerin, 2003; Rozanski et al., 2005; Brotman et al., 2007; Steptoe et al., 2007; Chida and Steptoe, 2010;Hameretal.,2010).
Thesefindingsunderlinetheimportanceofinvestigating stresspreventiveinterventionsandtheireffectsonpsycho- biological stress reactivity. By now, cognitive behavioural stressmanagementhasbeenrepeatedlyshowntomarkedly decrease psychological and biological reactivity towards psychosocialstressin healthysubjects (Gaab etal.,2003;
Hammerfaldetal.,2006).Incontrast,theeffectivenessof mind—body interventions for reducing psychosocial stress reactivity so far has only been examined for compassion meditation, showing a dose dependent effect on immune andpsychologicalstressresponses(Paceetal.,2009).
Mind—bodypracticesarecharacterizedasmethodsfocus- ingon the interactions among the brain,mind, body,and behaviour,withtheintentofusingthemindtoaffectphysical functioningandpromotinghealth(U.S.NationalInstitutesof Health, 2010). In fact, an increasing amount of scientific evidencesuggeststhatmind—bodypractices,suchasTaiji, might contributeto improvementsin physical and mental health(KleinandAdams, 2004;Jahnkeetal.,2010;Wang etal.,2010a,b).Taiji—variablyspelledTaijiquan,TaiChior TaiChiChuan—isamindfulandgentleformofslowbody movements with roots in ancient Chinese martial arts.
Becauseofits integrationofnumerousphysical,cognitive, andcontextualcomponentswhichpotentiallyhaveindepen- dentaswellassynergistictherapeuticvalue,Taijihasbeen describedasacomplexmulti-componentmind—bodyprac- tice(WayneandKaptchuk,2008).
AfewstudiessuggestthatTaijimayhavestressreducing effects.TwostudiessuggestthatpracticingTaijihasshort- andlong-termeffectsonthebasalactivityoftheHPA-axis.In hispioneeringresearchwork,Jin(1989)foundthatpracti- cingTaiji for60min reduced cortisol levels after Taiji as comparedtobefore.Similarly,resultsfromanon-controlled pilotstudyfoundreducedsalivarycortisollevelsinhealthy subjects, bothimmediately and 4weeks after they com- pletedaTaijibeginnerscourse(Eschetal.,2007).Hitherto,
studiesexploringthesuitabilityofTaijiasastressmanage- mentinterventionarescarce.Intermsofstressasmeasured bypsychologicalmeasuresonly,adecreaseofself-reported stress was observedin healthy youngadults as wellas in elderlysubjectswithcardiovasculardiseaseriskfactorsand personswithHIVdisease(Robinsetal.,2006;Taylor-Piliae etal.,2006;Eschetal.,2007).Todate,onerandomized- controlledstudyassessedtheeffectof60minofTaijiprac- ticeonthepsychobiologicalrecoveryofsubjectsafterthey wereexposedtoanon-validatedstressorintendedtoinduce mentalandemotionalstressbyhavingthemwatchstressful moviesandperformmentalarithmeticundertime—pressure andnoise (Jin, 1992). Adecrease of salivary cortisol was measuredafterTaijiaswellasafterthreedifferentinter- ventions(reading,briskwalking,meditation).However,due tolimited saliva sampling andmissing pre-stressbaseline measurement,findingsfromthisstudyremaininconclusive.
Taken together, studies measuring self-reported psycho- metricparametersconsistentlysuggestthatTaijimayserve asaneffectivestressmanagementinterventiontechnique, but its effects on physiological reactivity to acute stress remainunclear.
Tothebestofourknowledge,randomizedcontrolledtrials examiningtheeffectsof Taijion physiologicalandpsycho- logicalreactivitytostandardizedpsychosocialstressorshave notyet beenreported. Wethus setoutto investigatethe effectsofTaijion psychobiologicalreactivityto astandar- dizedandwell-validatedstressor,theTrierSocialStressTest (TSST).Werepeatedlyassesseddifferentmeasuresofinde- pendent stress responsive systems such as self-reported stressfulness,mood,andcalmness,aswellasthephysiolo- gical stress indicators salivary cortisol, salivary a-amylase levelsandheartrate.WehypothesizedthatpracticingTaiji wouldbeassociatedwithlowerpsychobiologicalstressreac- tivity.
2. Methods
2.1. Participantsanddesign
The ethics committeeof the Canton of Bern, Switzerland formallyapproved theresearchprotocol.Recruitmentwas carried outfromApril2010 toAugust2010 throughadver- tisementofthestudyonpinboardsandonthewebsitesofthe UniversityofBernandtheUniversityHospitalinBern.
Throughtelephonescreening,healthysubjectsagedfrom 18 to 50years and fluent in Germanwere included ifthe followingexclusioncriteriadidnotapplywithinthe6months priortothescreening(yes/no):regularoroccasionalintake of any medication, any self-reported acute or chronic somaticormentaldisorders,smokingmorethanfivecigar- ettes/day,consumptionofmorethantwoalcoholicdrinks/
day, consuming anykind ofaddictive substances,any pre- vious participationin stress researchprojects (in order to ensurethatsubjectsincluded werenaı¨ve totheTSST pro- tocol),morethan1weekofpredictableabsenceduringthe interventionperiod,anypreviouspracticalexperiencewith Taiji exercises. Women who were using hormonal contra- ceptives, were pregnant or planning to become pregnant duringthestudywerealsoexcluded.Theincludedsubjects receivedcompletewrittenandoraldescriptionsofthestudy.
Informedwrittenconsentwasobtainedbeforeparticipating.
Afterbaselineexaminationwascompleted,theparticipants were randomly assigned to either the Taiji group or the waitingcontrolgroup.Theallocationratiowas1:1.Alloca- tion concealmentwas achievedbyusingsequentially num- bered, opaque and sealed envelopes. An independent researchassistantgeneratedtherandomallocationsequence by sealing,mixing andsubsequently numbering80 opaque envelopes. Theywere opened individually by the primary investigator(MN)foreacheligiblesubjectwhohadagreedto participate in thestudy andcompleted baseline examina- tion.TSSTexaminationwascompletedonlyonsubjectswith compliance to start andtest instructions. The participant inclusionprocessisdepictedinFig.1.
2.2. Taijiintervention
The Taiji course being offered to the intervention group started in September 2010 and lasted for 12weeks. The training sessions of 60min took place twice a week. Taiji classesdifferedincomposition(participantschose2—6poten- tialtrainingtimepointsperweek)andsize(5—15participants persession).Participantswhomissedaclasswere askedto attendamake-upclass.Theinterventiongroupwasencour- agedtopracticeTaijiathomeinadditiontotheclasses.The averagenumberofhomepracticesessionswasassessedretro- spectivelyusingabriefself-reportquestionnaireattheendof thecourse.Participants’classattendancewasjournalizedby the Taiji teacher. All classes were held by the same Taiji teacher. Hewas trainedinChina aswell asin Europe,has 10yearsofTaijiexperience,andisacertifiedTaijiteacheras
awardedbytheSwissSocietyforQigongandTaijiquan(Schwei- zerischeGesellschaftfu¨rQigongundTaijiquan—SGQT).
IntheTaijicourse,participantsweretaughtthefirst18 sequencesofthe37ChenMan-Ch’ingYang-StyleTaijishort form.AnadaptationoffivesimplifiedTaijimovementsfrom thisformhasbeenpreviouslyusedinTaijitrialsonpatients with chronicheart failure (Yehetal.,2004,2011). Asour studyparticipantswereallhealthy,wedecidednottosim- plifytheformbuttoteachthefirst18movementsconsecu- tively, as recommended by Robinson (2006). The main reasonsforchoosingthisformarethefollowing:(1)inclusion ofthebasicTaijiprinciplessuchasextension,relaxationand alignmentofthebody,aswellasholisticandmindfulbody movements (Wolf et al., 1997), (2) feasibility given the moderateteachingandpracticingtimeof2hperweekfor 3months,(3)enhancedembodimentofbasicTaijiprinciples thanksto frequentrepetitionsenabledbytheshortness of the18sequences.Moreover,theChengMan-Ch’ingform is widely taught in Switzerland and subjects interested in learningtheremainingpartofthisformafterthestudywould easily find asuitable Taiji-school.Each Taijisession began withwarm-upexercises(15min)followedbypracticingTaiji movementsandreviewingtheunderlyingprinciples(35min) and concluded with Taijirelated breathing andrelaxation exercises(10min).
Priortogroupallocationparticipantsofbothstudygroups wererequestednottotakepartinanynewphysicalexercise or mind—bodyprogrammeduringtheirstudyparticipation.
Allparticipantsagreedwiththisrequest.Afterthetermina- tionofthestudy,anequivalentTaijitrainingwasofferedto allsubjectsparticipatinginthecontrolgroup.
Figure1 Flowdiagramfortheprogressthroughthephasesoftherandomizedtrial(basedontheconsolidatedstandardsofreporting trials[CONSORT]recommendations).Documentationofthesubjectinclusionprocess.
2.3. Assessment ofpotentiallyconfounding variables
2.3.1. PotentialTaiji-relatedconfoundingvariable Weassessedparticipants’previousregularpracticalexperi- ence(inmonths)withself-applicablemind—bodypractices (i.e.meditation,Feldenkrais,AlexanderTechnique,Qigong, Yoga, Pilates, guided imagery, deep breathing exercises, progressivemusclerelaxationandReiki)atbaselinetorule outanon-Taijirelatedinfluenceofpriormind—bodypractice experienceontheparametersunderstudy.
2.3.2. Potentialconfoundersofphysiologicalstress reactivity
Wecontrolledforage(Kudielkaetal.,2004),aswellasfor menstrualcyclephase(lutealvs.follicularphase,seebelow) andgenderassalivarycortisolreactivityinhormonalcontra- ceptive-freefemalesubjectsisbluntedduringthefollicular phaseanddiffers from cortisolreactivity in male subjects (Kirschbaumetal.,1999).Weaskedallfemaleparticipantsto fillouta questionnaireassessing duration(days) andregu- larityofthemenstrualcyclephase(yes/no),aswellasthe datesofonset ofmenstruationbefore andafterthestress testexamination.Lutealphasewasdefinedasthetimespan of14daysbeforeonsetofmenstruation(Lentonetal.,1984).
Additionally,wecontrolledforthecardiovascularriskfactors smoking(number of cigarettessmoked per day) andbody massindex(BMI,kg/m2,seeTable1),aswellasforregular physicalactivity(averagehoursperweek)duringtheinter- vention period (Rohleder and Kirschbaum, 2006; Rimmele etal.,2007;Bensonetal.,2009).
2.4. ProcedureoftheTrier SocialStressTest (TSST)examination
Theexperimental sessionswereconductedduringthefirst 3weeksafterterminationofthe12weekTaijiintervention between1300h and 1800h. The timing of the stress test
performancewasbalancedbetweenmalesandfemalesand betweenparticipantsinthetwo studygroups.Participants weretoldto refrainfrom eatinganddrinkinganythingbut waterfor 2hand from intense physical activity,caffeine, nicotine,andalcoholduringthe24hbeforetheexperiment.
Participants’ compliance to preparatory instructions and absenceoftheexclusioncriteriawasverified;non-compliant participants were excluded from the TSST. Next,the ECG recordingequipment was attached and the recordingwas started.WeusedtheTrierSocialStressTest(TSST)combining a 10min preparation phase followedby a5min mock job interview,anda 5min mentalarithmeticexercise (Kirsch- baumetal.,1993).Bothtaskswereperformed2minfrontof twoevaluativepanelmembersdressedinwhitelaboratory coats,andaconspicuousvideocameraandmicrophone.The socio-evaluative character of this performance task was further underlined by presenting the panel members (a retired male finance manager and a female psychologist) as experts inevaluationof nonverbal behaviour.The TSST reliably activates HPA-axis and the sympathetic nervous system(DickersonandKemeny,2004).Duringrecovery,sub- jectsremainedseatedinaquietroomfor60min.
2.5. Outcomemeasures
All outcomes of interest were measured during the TSST- examinationsessions.Physiologicalaswellaspsychometric measureswereevaluated.Stressreactivityofrepeatedsali- varycortisollevels(i.e.theinteractiongroup-by-stress)was definedasthemainoutcomemeasure.Secondarymeasures includedrepeateda-amylase,heartrate,anddifferentpsy- chometricassessmenttools.
2.6. Physiologicalmeasures
Salivasamples (Salivette1;Sarstedt AG,Sevelen,Switzer- land) were obtainedfor determination of salivary cortisol (10min( 20min)and1min( 10min)priortotheTSSTand
Table1 Demographic,Taiji-related,andpsychometricgroupcharacteristicsofthe49subjectsunderstudywhocompletedthe TrierSocialStressTest(TSST).
Groupcharacteristics Taijigroup(n=26) Controlgroup(n=23) p
Agea(years) 35.771.61 35.741.31 .99
Gender(male/female) 8/18 9/14 .56
MenstrualcyclephaseatTSSTexaminationday (femalesubjectsinlutealphase/infollicularphase)
9/9 4/10 .29
Bodymassindex(kg/m2) 23.47.67 23.51.79 .97
Education(with/withouthighschooldegreei.e.Swiss‘‘Matura’’) 20/6 17/6 1.00
Occupationalstatus(fullorparttimeworkers/students) 24/2 23/0 .49
Smoking(nonsmokers/lightsmokersb) 21/5 18/5 1.00
Sportiveactivity—duringtheintervention(h/week) 2.40.37 2.98.52 .37
Previousexperiencewithmind—bodypractices (monthsofregularpractice;preintervention)
15.626.03 29.1310.68 .26
Depressiveaffect(ADS-Kscore) 10.881.35 11.041.45 .94
Perceivedstress(PSSscore) 17.461.03 17.911.22 .78
Taijiclassesattended(incl.%-value) 20.65.59(86%) — —
Taijipracticeathome(numberofsessions/week) 1.69.33 — —
aContinuousdataareexpressedasmeanS.E.M.
b Smokinglessthan5cigarettesperday.
immediately(+1min)aswellas10,20,30,45and60minafter stress cessation) anda-amylase levels ( 20min, 10min, +1min,+10min,+20min,+45min).Sampleswerestoredat 208C until assaying. After thawing, saliva samples were prepared for biochemical analysis by centrifuging at 3000rpm for 5min to produce a clear supernatant of low viscosity.Estimationofsalivaryfree cortisolwasperformed usingachemiluminescenceimmunoassaywithhighsensitivity of0.16ng/ml(IBLHamburg,Germany).Levelsofa-amylase were determined following previously described methods (RohlederandNater,2009).Bothsalivarycortisolandsalivary a-amylasewereanalyzedinacommerciallaboratory(Dresden LabServiceGmbH,Dresden,Germany).Inter-andintra-assay coefficientsofvariationwerebothbelow8%(cortisol),and10%
(a-amylase),respectively.Asingle-channelelectrocardiogram (ECG,standardlead) wasrecordedcontinuouslyat 4036Hz throughouttheexperimentalsessionusing aportableheart rate(HR)monitoringdevice(MedikorderMK3,TOM-Medical, Graz,Austria).HRdatawasaggregatedto5minHRsegments.
Thefirst5minHRsegment( 10min)wasdefinedasbaseline.
HR segments measured before ( 5min), during (+5min, +10min)and after thestress task (+15min,+20min)were consideredinstatisticalanalyses.
2.7. Psychometricmeasures
Baseline group characteristics included assessment of per- ceived stress and depression symptoms. Perceived stress wasassessedbytheGermanversionofthePerceivedStress Scale(PSS)(CohenandWilliamson,1988).This10-itemself- report questionnaire measures subjects’ evaluation of the stressfulnessofthesituationsexperiencedinthepastmonth oftheirlives.ItemsinthePSSweredesignedtoassesshow predictable,uncontrollableandoverloadingparticipantscon- sidertheirlives.Goodinternalconsistencyisreported(Cron- bach’s a=.78). Depressive affect and negative thought patternswere measured by usingthe ‘‘Allgemeine Depres- sionsskala-Kurzform’’(ADS-K)questionnaire(Hautzingerand Bailer,1993),theGermanversionofthe‘‘CenterforEpide- miologicalStudiesDepressionScale’’(CES-D)(Radloff,1977).
Thisquestionnairewasdevelopedforresearchinthegeneral populationand has showngoodinternal consistency (Cron- bach’sa=.90).WemeasuredpsychologicalTSSTstressreac- tivityatbaselineandimmediatelyafterstresscessation:the MultidimensionalMood Questionnaire(MDMQ) assessesself- reportedmoodandcalmnesswithgoodinternalconsistencies (‘‘mood’’—Cronbach’sa=.75—.87;‘‘calmness’’—Cronbach’s a=.77—.83)(Steyeretal.,1997).Psychologicalevaluationof perceived stressfulness during the TSST examination was obtainedbycompletionofavisualanaloguescale(VAS)ranging from0to10with0indicatingnostressexperiencedatall.
2.8. Statisticalanalysis
Datawereanalyzedusing SPSS(version 18)statisticalsoft- warepackageforMacintosh(IBMSPSSStatistics.Somers,NY, USA).Thecalculationof theoptimaltotalsamplesizehas been conducted using the statistical software G-Power (Buchneretal.,1997).Basedonpriorresearch oncortisol stressresponsesreportingeffectsizesrangingfromf2=.28—
.35(Gaabetal.,2003;Storchetal.,2007),theoptimaltotal
sample sizeof N=64was calculated a priori to detect an expectedmediumtolargeeffectsizeoff2=.25withapower .85 anda=.05 (effect size conventions:f2: .02=small, .15=medium, .35=large; see Cohen, 1988). Effect size parameters (f)werecalculatedfrom partialh2-valuesand arereportedwhereappropriate(effectsizeconventions:f: .10=small,.25=medium,.40=large;seeCohen,1988).All analysesweretwo-tailed,withthelevelofsignificancesetat p<.05andthelevelofborderlinesignificanceat p<.10.
Unlessindicated,allresultsarepresentedasmeanstan- standarderrorofmeans(S.E.M.).Priortostatisticalanalyses alldataweretestedfornormaldistributionandhomogeneity ofvarianceusingaKolmogorov—SmirnovandLevenetest.As cortisol levels were skewed we log-transformed (log10) cortisoldataandobtainedanormaldistribution.Log-trans- formedcortisoldatawereusedinstatisticalanalysesbutfor reasonsofclarityuntransformeddataaredepictedinFig.2a.
Group characteristics were analyzed by x2-analysis for categorical data, andindependent samples t-test for con- tinuous data. Group differences in TSST related baseline valueswerealsotestedbyt-tests.
Torevealpossibletimeandconditioneffects,repeatedly measured physiological and psychological data were ana- lyzed by using two way ANCOVAs with repeated measure- mentswithgroupastheindependentfactor(Taijigroupvs.
controlgroup)andcortisol,heartrate,a-amylase,perceived stressfulness,mood,andcalmnessdataasrepeateddepen- dent factors. We applied Huynh—Feldt correction where appropriate.
Topreventovercontrollinggivenoursamplesize(Babyak, 2004),we performedatwo-stepprocedureforanalysesof physiologicalparameters.Inthefirststep,representingthe mainanalysisfortheprimaryoutcomemeasurecortisol,we calculated repeatedcortisol ANCOVAswhilecontrolling for cortisolbaselinelevels,priorexperiencewithself-applicable mind—bodypractices,age,menstrualcyclephase,andgen- der asa priori definedcovariates. Significanteffectswere furthertestedinasecondstep,whereweadditionallycon- trolled for smoking and BMI, as well as regular physical activityduringtheinterventionperiod.Analysesfora-amy- laseandheartratewerecalculatedaccordingly.Inanalyses of repeated psychological data, we controlled for prior mind—bodypracticeexperienceasacovariate.
Posthoctestingofsignificanteffectsinthemainanalyses includedseparaterecalculationofthepreviouslydescribed ANCOVAanalysesforeachoftherepeatedtimepoints.
3. Results
Ofthe112subjectswhounderwentatelephonescreening, 40 subjects did not fulfil selection criteria. Reasons for exclusion anddrop-out aredocumented in Fig.1. Of the remaining74subjects,70successfullyunderwentbaseline examinationandwererandomlyassignedtoeithertheTaiji group (N=35)or thewaitingcontrolgroup (N=35).TSST examination wascompletedby26subjects fromthe Taiji group(meanage35.771.61;69%female)andby23sub- jectsfromthecontrol group(meanage 35.741.31; 61%
female)as21subjectsdroppedoutbeforetheTSSTordidnot fulfilinclusioncriteriafortheTSST(Fig.1).Since95%ofall dropouts have not attended the TSST examination, an
intention-to-treatapproachisnotapplicabletothisstudy design.Thereforeonly subjectscompletingtheTSSTwere includedindataanalysis.Wehadnomissingdata.Noadverse effectsoftheTaijitrainingwereobservedorreported.
3.1. Groupcharacteristics
The two study groups did notsignificantly differ in group characteristic(Table1)anddrop-outrate(p=.603).Drop- out subjects did not significantly differ from the subjects completing the study in any group characteristic (p’s>.415),except BMI(21.17.49 (drop-outgroup) vs.
23.49.51(finalstudygroup);p<.001).
3.2. Physiologicalstressreactivity
At baseline,the studygroups didnotdiffer incortisol, a- amylase, or heart rate. The TSST induced significant increases in all physiological measures under study (main effectsofstress:p’s<.001).Whencontrollingforconfoun- ders considered in the main analyses, a significant main effect of stress was observed for cortisol (p<.001) and heartrate(p=.027),butnotfora-amylase(p=.91).
3.2.1. Cortisol
TheTaijigroupshowedanattenuatedcortisolstressreactiv- ityascomparedtothecontrolgroupwhilecontrollingforthe firstsetofconfounders(i.e.physiologicalbaselinelevel,age, gender,menstrualcyclephase,andpriormind—bodyprac- tice experience) [interaction group-by-stress: F(2.92/
122.50)=3.16,p=.028,partialh2=.07,f=.27;maineffect of group: F(1/0.79)=2.99, p=0.091; Fig. 2a]. Additional controllingforthesecondsetofconfounders(i.e.smoking status,BMI,andphysicalactivity)didnotsignificantlychange results(p=.044,resp. p=.122).Posthoctestsrevealeda trendtowardslowercortisollevels10min[F(1/0.22)=3.80, p=.058],30min [F(1/0.20)=2.96,p=.093],45min[F(1/
0.20)=3.71,p=.061]and60minafterstresscessation[F(1/
0.20)=3.80,p=.058]intheTaijigroup,suggestingalower increase and a faster recovery of salivary cortisol in the interventiongroup(seeFig.2a).
3.2.2. a-Amylase
Comparedtocontrols,participantsoftheTaijigroupshowed significantlower a-amylaseactivitybeforeandafterstress whilecontrollingforthefirstsetofconfounders[maineffect ofgroup:F(1/100795.10)=4.12,p=.049,partialh2=.089, f=.31;Fig.2b].Nosignificantgroupdifferencewasfoundfor a-amylase stress reactivity [interaction group-by-stress:
p=.16]. After additional consideration of the second set ofconfoundersthemaineffectofgroupremainedsignificant (p=.040) and a trend towards reduced a-amylase stress reactivity in participants of the Taiji group was revealed [interaction group-by-stress: p=.086]. Post hoc testing showed significantly lower a-amylase levels 10min [F(1/
40874.38)=6.63, p=.014], 20min [F(1/23952.02)=4.03, p=.051] and 45min after stress cessation [F(1/
41612.24)=8.66, p=.005] in the Taijigroup as compared to the control group, indicating a faster recovery (see Fig.2b).
Figure2 Valuesare meansS.E.M.WecalculatedANCOVAs withrepeated measuresofphysiological stress parametersas dependentvariables andgroup(Taijivs.control)astheinde- pendentvariable.Wecontrolledforphysiologicalbaselinelevel, age,gender,menstrualcyclephaseand priorexperiencewith mind—body practices as covariates. The Taiji group showed attenuated cortisol stress reactivity (p=.028; a), a-amylase levels(p=.049;b),aswellaslowerheartratestressresponses (p=.028; c). Significance levels are: 8p<.1; *p<.05;
**p<.01.
3.2.3. Heartrate
Themainanalysisrevealedasignificantlybluntedheartrate stressreactivity intheTaijigroupcomparedtothecontrol group [interaction group-by-stress: F(2.55/173.76)=3.34, p=.028, partial h2=.087, f=.31; Fig. 2c]. Furthermore, theparticipantsoftheTaijigroupshowed atrendtowards lowerheartratelevelsbeforeandafterthestressprotocol [maineffectofgroup:F(1/750.01)=3.15,p=.083;Fig.2c].
Additionalcontrollingforthesecondsetofconfoundersdid notsignificantlychangeresults.Posthoctestsrevealedthat participantsoftheTaijigroupexhibited significantlylower heartratelevelsduringthefirst5min[F(1/559.40)=5.93, p=.019], and the second 5min [F(1/569.63)=4.33, p=.044]oftheTSSTascomparedtocontrols(seeFig.2c).
3.3. Psychologicalstressreactivity
Atbaselinesubjectivemeasuresofperceivedstressfulness, mood,andcalmnessdidnotdifferbetweenstudygroups.The TSST significantly increased perceived stressfulness, wor- senedmood,andreducedcalmnessinallstudyparticipants (main effects of stress: p’s<.001). Controlling for prior experience with self-applicable mind—body practices did notsignificantlychangefindings.
Comparedtothecontrols,participantsintheTaijigroup reported significantly less stressfulness [F(1/16.37)=8.48, p=.006,partialh2=.156,f=.43],maintainedahigherlevel of calmness [F(1/21.79)=5.87, p=.019, partial h2=.113, effectsizef=.36]andtendedtowardsalowerdecreaseof mood[F(1/17.78)=3.43,p=.070]in reactionto theTSST (seeTable2).
4. Discussion
This is the first randomized-controlled study to explore effectsofTaijion measuresof adrenocortical,autonomic, andpsychologicalresponsestoastandardizedandvalidated psychosocialstresstaskinhealthyTaijibeginners.Wefound forthefirst timemarkedlyreduced psychobiologicalstress responses in Taijipractitioners as compared to anon-Taiji controlgroup,i.e.attenuatedcortisolandheartratestress reactivity,lowera-amylaselevels,aswellaslowerperceived stressfulnessandbettermaintenanceofcalmnessinresponse to the stress task. Baseline values did notdiffer between
groups and stress induction proved to be successful, as indicatedbytheexpectedsignificantincreasesinallphysio- logicalmeasuresunderstudyinthetotalsample.
Thepresentresultsextendpreviousresearchbysuggest- ingan overallstress-buffering effect ofTaijipracticeon a broad array of measures representing different stress- responsive systemswith effect sizes rangingfrom medium tolarge.Notably,werecruitedTaijibeginnersandourTaiji intervention lasted for 12weeks. As Taiji is thought to improveitsbeneficialeffectswithincreasingpracticeskills over years (Cheng, 1982), it can be speculated that the observedeffectsmaybeevenmorepronouncedinadvanced Taijipractitioners.
In contrast to stress management interventions (Gaab et al., 2003; Hammerfald et al., 2006; Storch et al., 2007), the Taiji course in our study was neither designed nortaughtasaformofstressmanagement.Itwasconcep- tualizedtoconveyanembodimentofbasicTaijiprinciplesby applying aguidedintrospectiveteachingapproach.Wedid nottrainanyspecificcopingstrategy(e.g.cognitiverestruc- turing) nor did we use role-plays or psychodrama course elements as often used in cognitive behavioural (Gaab etal.,2003;Hammerfaldetal.,2006)andresourceactivat- ingstressmanagementprogrammes(Storchetal.,2007).In contrasttoourTaijicourse,trainingelementsofsuchstress managementprogrammes may,inadditiontotheirspecific effectsonstressappraisal,havemoresimilaritiestotheTSST situation andtherefore might additionally preparefor the stresstestitself.Consideringthelackingemphasisonstress management in the Taiji intervention, the incongruence between the training environment and the TSST setting, and the focus on developing Taijirelated bodyawareness and body mechanics, we feel that the stress protective effectsofTaijiobservedinourstudyarelikelytoresultfrom amindfulembodimentofeffortlessstabilityandcalmnessin motion. Thisreasoning is further supported byour finding that,similarlytotheTaijieffect,thecontrolvariable‘‘prior experiencewithmind—bodypractices’’(otherthanTaiji)was significantlyassociatedwithbluntedcortisolstressreactiv- ity, lower a-amylase levels, as well as lower perceived stressfulness andbettermaintenance of moodin response tothestresstask(p’s<.040).
Priorresearchfurthersupportsthattheobservedattenua- tion of psychobiologicalstressreactivity in ourTaijigroup mayrelatetomind—bodyinteractioneffects.Anincreased Table2 PsychologicalreactivityinresponsetotheTrierSocialStressTest(TSST).a
Variables Taijigroup(n=26) Controlgroup(n=23) pc
PreTSST PostTSST Stresschangeb PreTSST PostTSST Stresschangeb Self-reported
stressfulness(VAS)d
1.22.19 3.47.45 2.25.39 1.01.20 4.91.48 3.90.41 .006 Calmness(MDMS)e 16.47.46 12.78.62 -3.69.54 16.25.49 10.64.66 5.61.57 .019 Mood(MDMS)e 17.30.44 14.23.74 -3.07.64 17.19.47 12.39.79 -4.80.68 .070
aAlldataareexpressedasmeanS.E.M.
bStresschange postTSSTvalueminuspreTSSTvalue.
c p-ValuesrefertorepeatedmeasuresANCOVAswithpriormind bodypracticeasacovariate.
dVAS visualanaloguescalerangingfrom0 ‘notstressfulatall’to10 ‘extremelystressful’.
eMDMS multidimensionalmoodscalerangingfrom5to20withhigherscoresindicatingahigherdegreeofcalmnessandamorepositive mood.
bodyawarenessinducedbyregularTaijipracticehasbeen reportedinpreviousstudies(Gyllenstenetal.,2010;Uhlig etal.,2010)andislikelyto enhancearesource activating embodiment.Maintainingresourceactivatingembodimentin turnhasbeenshowntoreducecortisollevelsunderresting conditions(Carneyetal.,2010).Moreover,copingstrategies includingembodimentwereanintegratedpartofaresource activatingstressmanagement programmefoundto attenu- atethereactivity of theHPA-axis inresponse to the TSST (Storchetal.,2007).AsparticipantsdidnotreportanyTaiji- participationinducedincrease insocialcontacts (datanot shown),itseemsunlikelythattheobservedstress-buffering intheTaijigrouprelates to atraining-induced increasein socialsupport.However,itmaybespeculatedthatsubjects intheTaijigroup,becauseoftheirparticipationintheactive studygroup,mighthaveexpectedtobebetterpreparedfor theirupcomingperformancetaskandthusachievedgreater emotionregulationduringtheTSST.Toclarifythepotential contributionofsuchanexpectancyeffect,futureresearchis needed,preferablybyincludinganadditionalactivecontrol groupwithaninterventionraisingsimilarexpectations.
Our studyhas severalstrengths. First, we used a well- validatedstandardizedacutepsychosocialstresstask(Kirsch- baumetal.,1993;DickersonandKemeny,2004).Second,we usedanon-Taijicontrolgroupwithrandomizedassignment.
Third,weassessedmultipleparametersindicatingreactivity ofdifferentindependentstressresponsivesystems.Fourth, baselinecharacteristicswerethoroughlycollectedandboth studygroupswerehomogenousregardingtheirdemographic andpsychometricparameters,indicatingasuccessfulrando- mization of subjects. Finally, both groups had moderate scores in questionnaires assessing baseline levels of per- ceivedstressanddepressiveaffect.Itthereforeseemsunli- kelythatthereportedresultsareinfluencedbypre-existing group differences or selection bias related to increased pronenesstostress.
Thefollowinglimitationsneedtobeconsidered.First,our resultsarerestrictedtoagroupofhealthyandwell-educated young to middle-aged men and women. They cannot be generalizedto other groupswith lessadvantageous health conditionsorsocialbackgrounds.Second,theretrospectively assessedaveragenumberofTaijihomepracticesessionsper week,theaveragetimespentonsportiveactivitiesperweek duringtheinterventionperiod,andthedeterminationofthe menstrualcyclephasewerebasedonself-report.Third,our resultsare restrictedto Taijinovices.The effectsoflong- termTaijipracticeonpsychobiologicalstress-reactivitystill needtobeinvestigated.Fourth,ourpsychobiologicalassess- mentapproachdoesnotincludeassessmentoffurtherstress- responsivephysiological systems such as theimmune, the lipid, or the coagulation system. Also, HPA axis measures otherthancortisolsuchascorticotropinreleasinghormone (CRH),oradrenocorticotrophichormone(ACTH)stillneedto be examined. Fifth, because of habituation of cortisol responses in the majority of people repeating the TSST (Schommeretal.,2003),itwasnotpossibletoassesscortisol stressresponsesbeforeandaftertheintervention,norinthe controlgroupaftercompletionoftheirTaijicourse.Sixth, ournon-significanteffectsofTaijiona-amylasestressreac- tivityshouldbeinterpretedwithcareaswecannotruleouta typeIIerror.Futurestudies,preferablywithahigherpower, areneededtoconfirmournon-significanteffectsofTaijion
a-amylase stress reactivity as well as the overall stress- reducingeffectsontheothermeasuresunderstudy.Finally, duetoourrestrictiveexclusioncriteriawe hada drop-out rateof30%.However,thisrateiscomparabletoapriorTSST studyexaminingmind-bodypractices(Paceetal.,2009)and doesnotseemunusualinstudiesexaminingTaijieffectson psychologicalwell-being(Wangetal.,2010a).
Inconclusion,ourresultsconsistentlysuggestthatpracti- cingTaijiattenuatespsychobiologicalstressreactivity.This mayunderlinetheroleofTaijiasausefulmind—bodyprac- ticeforstresspreventionwhichmaycontributetoenhance healthinthegeneralpopulation.Clinicalimplicationsremain tobeelucidated.
Role of funding source
FundingforthisstudywasprovidedbyStiftungfu¨rKomple- menta¨rmedizin,GottfriedundJuliaBangerter-RhynerStiftung and Parrotia Stiftung (to M.N.) and by the Swiss National FoundationGrantPP00P1 128565/1(toP.H.W.).Thefunding sourceshadnofurtherroleinstudydesign;inthecollection, analysis and interpretation of data; in the writing of the report;andinthedecisiontosubmitthepaperforpublication.
Conflict of interest
Allauthorsdeclarethattheyhavenoconflictsofinterest.
Acknowledgements
We thankBarbara Schwab, Christina Bu¨rgler, Tina Camen- zind,Marina Haller andNikola Nedeljkovic for their assis- tance in conducting the study, and Dr. Ursula Wolf and Dietrich von Bonin for their technical support andhelpful advises.
Appendix A. Supplementary data
Supplementary dataassociated with thisarticle can be found, in the online version, at doi:10.1016/j.psy- neuen.2011.12.007.
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