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Original article

Effects of unstable shoes on chronic low back pain in health professionals: A randomized controlled trial

Stéphane Armand

^a,b,∗

, Ziva Tavcar

^a

, Katia Turcot

^a,b

, Lara Allet

^c,d

, Pierre Hoffmeyer

^b

, Stéphane Genevay

^e

aWillyTaillardLaboratoryofKinesiology,GenevaUniversityHospitalsandUniversityofGeneva,4,rueGabrielle-Perret-Gentil,1211Geneva14, Switzerland

bDivisionofOrthopaedicsandTraumaSurgery,GenevaUniversityHospitalsandUniversityofGeneva,Geneva,Switzerland

cUniversityofAppliedSciencesofWesternSwitzerland,Physiotherapy,Geneva,Switzerland

dHealthCareDirectorate,GenevaUniversityHospitalsandUniversityofGeneva,Geneva,Switzerland

eDivisionofRheumatology,UniversityHospitalsofGeneva,Geneva,Switzerland

a r t i c l e i n f o

Articlehistory:

Accepted18May2014 Availableonline28June2014

Keywords:

Lowbackpain Shoes Walking

Randomizedcontrolledtrial

a b s t r a c t

Objective:Theaimofthisstudywastoevaluatetheeffectivenessofunstableshoesinreducinglowback paininhealthprofessionals.

Methods: Ofavolunteersampleof144participants,40withnonspeciﬁcchroniclowbackpainwere eligibleandenrolledinthisstudy.Participantswererandomizedtoaninterventiongroup,whowore unstableshoes(modelMBTFora),oracontrolgroup,whoworeconventionalsportsshoes(modelAdidas Bigroar).Theparticipantshadtowearthestudyshoesduringtheirworkhours,andatleast6hours perworkday,overaperiodof6weeks.TheprimaryoutcomewaslowbackpainassessedonaVisual AnalogScale.Thesecondaryoutcomeswerepatientsatisfaction,disabilityevaluatedusingRoland-Morris questionnaireandqualityoflifeevaluatedusingEQ-VAS.

Results: Theinterventiongroupshowedasigniﬁcantdecreaseinpainscorescomparedtothecontrol group.Therateofsatisfactionwashigherintheinterventiongroup(79%)comparedtothecontrolgroup (25%).TherewasnosigniﬁcantdifferencefortheRoland-Morrisdisabilityquestionnairescoreandthe EQ-VASscale.

Conclusions:Theresultsofthisclinicaltrialsuggestthatwearingunstableshoesfor6weekssigniﬁcantly decreaseslowbackpaininpatientssufferingfromchroniclowbackpainbuthadnosigniﬁcanteffecton qualityoflifeanddisabilityscores.

1. Introduction

Lowbackpain(LBP)isaverycommonhealthproblem[1].LBPis alsoaverycommoncomplaintamonghospitalworkersandhealth- careprofessionals[2].Theannualprevalencehasbeenreportedto bebetween40and50%amongnurses[3]andtwothirdsofhospital employeescomplainedofspinalpainduringthepreviousyear[4].

PheasantandStubbsobservedthathealthprofessionalswhosuf- ferfrombackpainhave30%higherrateofabsenteeismfromwork comparedtotherestoftheworkforce[5]resultinginanimportant societalburden[4,6].Numerousinterventionstrategiesexistfor

∗ Correspondingauthorat:WillyTaillardLaboratoryofKinesiology,GenevaUni- versityHospitalsandUniversityofGeneva,4,rueGabrielle-Perret-Gentil,1211 Geneva14,Switzerland.Tel.:+41223727827;fax:+41223727799.

E-mailaddress:stephane.armand@hcuge.ch(S.Armand).

themanagementofLBPamongwhichdrugs,spinalmanipulation, rehabilitationexercises,andsurgeryarethemostwidelyused[7,8].

Exercisetraining tostrengthenspinemusclesisfrequentlypre- scribedforLBPandiswidelyrecommended[9].However,arecent systematicreviewontheeffectivenessofphysicalandrehabilita- tioninterventionsforchronicnonspeciﬁclowbackpainshoweda limitedimprovementintheinterventiongroupcomparedtocon- trolgroup[7].Themaincriticismsagainstconventionalexercise trainingstudiesaretherateofnon-complianceduetotimecommit- ments,theavailabilityofequipmentandthepersonalhighdegree ofmotivationrequiredtosustainthetrainingsessions[10].

Unstableshoes(shoesincorporatingaroundedsoletoincrease instabilityintheanterior–posteriordirection)havebeenadvocated bythebrandMasaiBarefootTechnology(MBT)since1996toreduce LBP,toimprovepostureandbalance,andtoincreasemuscleactiv- ity.Niggetal.arguedthattheseunstableshoescouldbeanoptimal solutionforexerciseinterventionastheyarenottimeconsumingto http://dx.doi.org/10.1016/j.jbspin.2014.05.006

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useanddonotrequireanyequipmentapartfromtheshoesthem- selves,andcanbeusedindailylifeactivities[11].Moreover,ina non-randomizedcontrolledtrialNiggetal.showedasigniﬁcant reductionofLBPamonggolferswearingthesetypesofshoes[11].

Biomechanical studies investigating the effects of unstable shoesduringstanding,showedagreaterexcursionscenterofpres- sureduringstanding[12,13],anincreasedmuscleactivityofankle muscles[12–14].During walking,studiesreportedanincreased dorsiflexion angle at initial contact [12,15], an increased spine movement[16],ashiftinpressuretowardsthefrontofthefoot [17],anincreasedmuscleactivityofanklemuscles[15]andlow backmuscles[16].Therefore,asunstableshoesmodifybiomechan- icalgaitandpostureparametersatthelowerlimbandspine,and couldreduceLBPingolfers,wehypothesizedthatemployeeswitha nonspecificLBP,wearingunstableshoeswouldsignificantlyreduce thelevelofLBPandrelatedfunctionaldisability.Therefore,theaim ofthisstudywastoevaluatetheeffectivenessofunstableshoesin reducingLBPinhealthprofessionals.

2. Methods

2.1. Standardprotocolapprovals,registrations,andpatient consents

Thisstudyprotocolwasapprovedbytheethicalcommitteeat GenevaUniversityHospitalsandregisteredinJune2011atClin- icalTrials.gov(NCT01384071).Allsubjectsgavewritteninformed consentaccordingtotheethicalstandardssetforthinthedeclara- tionofHelsinki(1983).

2.2. Participantsandrecruitmentprocedure 2.2.1. Enrolmentprocedure

Recruitment was done through internal hospital announce- ments,viaaninstitutionalwebsiteandvianoticeboards.

2.2.2. Eligibilitycriteria

Tobeincluded,participantshadtobeagedbetween30and65- years-old,toworkinthehospitalforatleast80%ofthetimeand toworkina positionthatrequiredtowalkortobestandingat least50%ofworkingtimeandtosufferofchronicLBP(≥3/10VAS –averagepainofthelastweek).Participantswithdisablingpainin anyotherbodyparts,orrecentspineorlowerlimbsurgerywere excluded.Wefurtherexcludedsubjectswithlumbarradiculopa- thy,neurologicalororthopedicproblemsaffectingthelowerlimbs, gaitandbalancedisturbances.Finally,participantswereexcluded iftheywalkedwithanassistive deviceorwereunabletowalk morethan100meters.Inadditionparticipantswhoalreadywore unstableshoeswereexcludedfromthisstudy.

2.2.3. Testingprocedureforparticipant’sinclusion

All interested participants were screened for inclusion and exclusioncriteria viaa ﬁrsttelephonecall.Followingthis,each eligibleparticipantwasinvitedfora clinicalexaminationinthe laboratory. During this examination, an experienced clinician performeda basic neurological examination toexclude lumbar radiculopathy.Eachparticipantevaluatedtheaveragepainlevel overthelastweekonaVAS.Eligibleparticipantswereincludedin thestudy.

2.3. Randomizationandgroupallocation

Eligible participants were randomized via a computer- generatedlistintotwogroups:

Fig.1.Interventionshoes(a)andcontrolshoes(b).

•aninterventiongroup(IG)thatworeunstableshoes;

•acontrolgroup(CG)thatworeconventionalsportsshoes.

Theallocationwascentrallygeneratedandconcealed.Tolimita placeboeffect,participantswerenotawareofthestudyhypothesis andtheirgroupallocation(controlorintervention).Allparticipants wereinformedthatbothtypesofshoescouldhaveapositiveeffect ontheirbackpain.Bothgroupswererequiredtoweartheshoes everyworkdayforatleast6hours/dayaftertheﬁrstweek,overa periodof6weeks.

2.4. Samplesize

Apreviousstudyongolfershowedareductionofbackpainof 17.5(SEM:3.03)ona0to100VASpainafter6weeksofwearing unstableshoes[11].Basedonthisresultandtobeconservative,we calculatedthata10(SD:10)pointsdifferencebetweentreatment andcontrolgroupswouldrequire40patientstohave80%chance todetectadifferenceinLBP,withanalphaerrorof0.05%,including a20%dropout.

2.5. Intervention

Attheﬁrstevaluation,bothgroupsofparticipantsreceiveda newpairofshoesaccordingtotheirallocation.Participantsinthe IG(n=20)receivedunstableshoes(modelMBTFora,athleticcollec- tionSS2010,MasaiBarefootTechnology,Switzerland)(Fig.1a)and participantsintheCG(n=20)receivedconventionalsportsshoes (modelAdidas,Bigroar,Germany)(Fig.1b).Anexpertinstructed allofparticipantsduring15minuteshowtousetheshoescorrectly andadvisedpatientstoprogressivelyincreasethetimewearingthe shoes,startingwith2hoursperdayandincreasingthedurationby 1houreveryday.After1week,participantswereaskedtowearthe shoesforaminimumof6hoursadayduringtheirtimespentat work.

2.6. Testingprotocolandmeasurements

The outcome measures were assessed at baseline and after 6weeksbythesameevaluator.Moreovertheparticipantsfulﬁlleda diarylogbooktoindicatethelevelofLBPandtoreportanyincidents suchasfallsorexperiencedinstability.

2.6.1. Primaryoutcome

The pain intensity at the pre- and post-intervention was recordedontheVAS.Thescaleisdeterminedwithalineof10cm, withextremitiesofminimum(0)tomaximum(10).AsLBPﬂuctu- atesduringaperiodoftime[18],LBPwasassessedwithdifferent scores.Firstly,eachparticipantreportedthemeanintensityofLBP forthelast24hours.Secondly,painwasassessedduringgaitanal- ysisinthelaboratorywhilewalkingbarefootandwhilewalking withallocatedshoes.Finallyapaindiarywasprovidedandpar- ticipantswereinvitedtoratetheirpainattheendoftheworkday basedontheaverageamountofpainduringtheworkday.Wealso predeﬁnedrespondersasparticipantswhoachievedareductionof

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Assessed for eligibility(n=144)

Excluded (n=104)

Not meeting inclusion criteria (n=86) Declined to participate (n=12) Other reasons (n=6)

Randomized (n=40)

Allocated to intervention group (n=20) Allocated to control group (n=20)

Lost to follow-up (n=4) ankle injury (n=1) foot pain in shoes (n=3) Lost to follow-up (n=1)

ankle injury (n=1)

Analyzed (n=19) Analyzed (n=16)

Follow-UpAnalysisAllocationEnrollment

••

•

••

•

Fig.2.Flowchartwithdetaileddescriptionofrecruitment.

atleast2points[19]foreachpainscale(painduringlast24h,pain whilewalkingwithshoes,painwhilewalkingandpainreportedin thedailylogbook).

2.6.2. Secondaryoutcomes

Functionaldisabilitiesrelated toLBPwereassessedwiththe validatedFrenchtranslation[20,21]oftheRoland-Morrisdisabil- ityquestionnaire(RMDQ)[22].RMDQisa24itemsquestionnaire (yes/noanswer)exploring24activitieslimitationduetoLBP.The scorerangesfrom0 (nolimitation) to24 (fulldisability). Qual- ity of life was assessed with EQ-VAS scales, which represents healthstatusfor themomentofevaluationintherangefrom0 (extremelybad)to100(excellentqualityoflife)[23].A5-point Likert scale satisfaction question regarding the efﬁcacy of LBP treatmentusingshoes wasgiventotheparticipantsat thelast evaluation.

2.7. Dataanalysis

StatisticalanalyseswereperformedusingStatistica10.0(Stat- Soft Inc., Tulsa, OK, USA). Means and standard deviations of variableswerecalculatedfordescriptivestatisticsandalldatawere checkedfor normality usingthe Kolmogorov–Smirnovtest and forequalvarianceusingtheLevenetest.Themeanchangeinthe IGwascomparedwiththemeanchangeintheCGtodetermine the effect of unstable shoes on LBP (t-test or equivalent non- parametrictest:Mann-Whitney Ufor non-normally distributed outcomes).Differencesinproportionsbetweengroupswerecom- pared withthe Fisher exact test. The level of signiﬁcance was setatP<0.05.Anintentiontotreatanalysiswithimputationby lastobservationcarriedforwardwasperformedwhendropouts occurred.

3. Results

Atotalof144subjectsshowedaninterestinparticipatingin thisstudy,ofwhich40wererandomized.Participantshadsimilar baselinecharacteristicsinbothgroupsforpain,professionaland physicalactivitiescharacteristics(Table1).

Aflowchart(Fig.2)summarizestherecruitmentandtheeval- uationprocess.Duringthe6-weekinterventionperiod,therewere fivedropouts,oneintheinterventionandfourintheCG.Onein eachgroupwasrelatedtoankleinjury(malleolusfracture),occur- ringduringleisuretimeactivities,thusnotrelatedtothestudied shoes;andthreedropoutsintheCGwererelatedtoafootpainin theexternalpartofshoes.After6weeks,35participantsreached theendoftheinterventionandunderwentthefollow-upevalua- tioninthe7thweek.Therewerenosignificantdifferencesinpain scoresobtainedatbaselinebetweendropoutsandotherpartici- pants(P>0.05).Themedianandquartilerangewererespectively fordropoutsandotherparticipantsforthedifferentpainscores:

24hours4.8[1.9]vs.3.9 [2.7],in-laboratorypainwhilewalking barefoot4.0[4.0]vs.2.2[4.0]andwithshoes3.0[2.0]vs.1.5[2.5].

3.1. Primaryoutcome

Table2andFig.3presentdifferentLBPpainscoreassessments (duringtheprevious24hours,in-laboratorypainwhile walking barefootand withshoes,painreportedin thedailylogbook)at inclusionandfollow-upvisit.Averagepaininthelast24hourswas assessedforallparticipants.Therewerethreemissingdatasetsfor painduringwalking.Thecompliancerateforthepaindiarywas77%

(27of35participants,5participantsintheIGand3participantsin theCGdidnotfulﬁllcorrectlythediarylogbook).

TheIGshowedagreaterimprovementthantheCGforallpain scores.Thedifferencebetweenbaselineandfollow-upforthepain scores:in-labwakingbarefoot,in-labwalkingwithshoesandin

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Table1

Descriptionofparticipants’characteristicsatbaseline.

Interventiongroup (n=20)nor Mean±SD(range)

Controlgroup (n=20)nor Mean±SD(range) Generalcharacteristics

Gender(female) 19 17

Age(years) 44.5±7.9(31–58) 46.8±8.8(32–62)

Height(cm) 162.1±9.1(144–180) 164.8±7.8(155–187.7)

Weight(kg) 66.2±11.3(50–90) 71.6±13.7(52.5–106)

Bodymassindex(kg/m²) 25.1±3.9(20.1–32.5) 26.5±5.5(19.1–40.8)

Pain

Painlast24h 4.2±1.9(1.0–7.4) 4.1±1.8(0.6–7.6)

In-labpainduringwalkingwithshoes 1.9±1.6(0–5) 2.3±1.6(0–5)

In-labpainduringbarefootwalking 2.3±1.9(0–6) 2.7±2.1(0–7)

Painkillersintake(n) 7 7

NSAIDs(n) 7 6

Musclerelaxants(n) 1 1

Opioids(n) 0 2

Lowbackpainbeforethisepisode(n) 20 18

Painduration(currentepisode)

<7weeks(n) 4 5

7weeks–3months(n) 1 3

3months–6months(n) 5 2

6months–18months(n) 4 4

>18months(n) 6 6

Employmentstatus

Percentofemployment(%) 92±8.9(80–100) 95±8.2(80–100)

Earliersicknessleaveduetolowbackpain(n) 5 11

Workingatnight(n) 7 9

Employmenttype

Medicaldoctor(n) 0 1

Nurses(n) 6 6

Nursesassistants(n) 8 5

Midwifes(n) 1 4

Administrativestaff(n) 1 0

Technicalstaff(n) 4 4

SD:standarddeviation;NSAIDs:non-steroidalanti-inﬂammatorydrugs.

Table2

Lowbackpainintensities,functionaldisabilityandqualityoflifeatbaselineandfollow-upfortheinterventionandcontrolgroup.Statisticaltestcomparisonsbetween groupswereperformedonchangesovertimefrombaselinetofollow-up.

Interventiongroup Mean±SD Controlgroup Mean±SD Pvalues(t-test)

n Baseline Follow-up n Baseline Follow-up

Pain

Last24h(VAS0–10) 20 4.3±1.9 2.8±2.3 20 4.1±1.8 3.5±2.2 0.199

In-labwalkingbarefoot 18 2.3±2.0 0.8±1.1 19 2.7±2.1 2.4±2.0 0.037

In-labwalkingshoes 18 1.9±1.6 0.3±0.8 19 2.3±1.6 2.4±1.6 0.001

Dailylogbook 14 3.7±2.3 1.8±1.7 13 3.5±1.4 3.8±1.9 0.005

Functionaldisability

Roland-Morris(0–24) 20 7.5±3.2 5.1±4.9 20 7.6±3.1 6.3±3.5 0.287

Qualityoflife

EQ-VAS(0–100) 20 79.0±12.7 81.4±15.5 20 76.6±13.4 79.8±8.4 0.867

SD:standarddeviation;VAS:VisualAnalogScale.

0 1 2 3 4 5 6 7

W1 W2 W3 W4 W5 W6

Pain level (VAS 0-10)

Control Intervenon

Fig.3.Lowbackpainassessedfor6weekswithadailylogbook.

the diary showed a statistically signiﬁcant difference (P<0.05) betweenthetwo groups(IG and CG).Onlythepain scoredur- ing the last 24h was not signiﬁcant between the two groups (P=0.199).

Althoughallparticipantshad a meanpain scorefor thelast week≥3atinclusion,asrequiredintheeligibility criteria,they could have other pain score (e.g. in-lab pain while walking barefoot)lowerthan2.Inlinewiththepredefineddefinitionof responders(adecreaseofatleast2points),computationofrespon- ders’ rate had thus tobe limited to participantswith baseline score≥2forthisspecificscore.Thepercentageofresponderswas higherintheIGcomparedtotheCGforallpainscores(paindur- inglast24h:56.25%[9/16]vs.33.3%[6/18]P=0.16;painwhile

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Fig.4. Painmanagementsatisfactionoftheparticipantsatthefollow-up.

walkingwithshoes80%[4/5]vs.27.3%[3/11],P=0.08;painwhile walkingbarefoot100%[8/8]vs.27.3% [3/11],P=0.002andpain reported in the daily logbook: 77.8% [7/9] vs. 7.8% [1/13], P= 0.001).

3.2. Secondaryoutcomes

Comparingbaselineandfollow-upevaluations,theRMDQscore reducedinbothgroups(1.3pointsforCGand2.4pointsinIG).How- ever,nobetweengroupdifferencecouldbedetected(P=0.287) (Table 2). Therewas no signiﬁcant difference in EQ-VAS scale betweenthemeanchangeintheIGandthemeanchangeinthe CG(P=0.867).

SatisfactionresultisillustratedonFig.4.Therateofsatisfaction (satisﬁedandverysatisﬁed)was79%intheIGcomparedto25%in theCG(P=0.002).

4. Discussion

TheobjectiveofthisRCTwastoevaluatetheeffectofunstable shoesamongworkinghealthprofessionalssufferingfromchronic LBP.Thegroupwearingunstableshoesfor6weeksshowedasupe- riorreductioninpaincomparedtoparticipantswearingcontrol shoes.Thedifferencewasstatisticallysignificantforself-reported painin a diary logbookandpain duringwalkingwithunstable shoesandbarefoot.Atrendwasobservedformeanpaininthelast 24hoursbutthisresultwasnotstatisticallysignificant.Inaddition, theproportionofresponders(predefinedasaclinicallymeaning- fulreductionof2pointsinVASpainscores)forallthepainscores and“satisfactionwiththepainmanagement”werehigherintheIG comparedtotheCG.Thisisthefirststudythatshowedasignifi- cantreductionofLBPinhealthprofessionalsbywearingunstable shoes.IngolferswithchronicLBP,inanon-controlledstudy,Nigg etal.reportedasimilaramountofpainreduction(1.75/10points) after6weeksofusingunstableshoes[11].Ourresultsarepromis- ing compared to those reported in recent reviews on physical and rehabilitationinterventions forLBP [7].They reportedthat mostof thestudiesdid notreacha differencebetween IGand CGlargerthan10%.Ourresultsshowedadifferencegreaterthan

20%inallthepainscores,whichisdeﬁnedasaclinicallyrelevant reduction[7].

TheinitialproposedmechanismforthisdecreaseinLBPisthe modificationofpostureduringstandingandwalking[11,15,24]and morespecificallyatthepelvisandtrunklevel[16].Futureresearch should investigate mechanisms of action of unstable shoes for chronicLBPbyidentifyingposture,gaitandmusclesactivitymod- ificationsthatcouldexplainreductionofLBP.Thepresentstudy foundnoeffectonfunctionaldisabilityandonqualityoflifeafter theintervention.Theabsenceofapositiveeffectcouldberelatedto theshorttimeoffollow-up(6weeks).Whynesetal.reportedthat qualityoflife(EQ-5Dindex)islessresponsivethaninstruments specifictopainmeasurement[25].Therewerehoweverimpor- tantdifferencesbetweenthe2groupsintherateofsatisfaction.

Themoststrikingdifferencewastheabsenceof“verysatisﬁed”

participantintheCGwhereasitwasexpressedbyhalfofthepar- ticipantsintheunstableshoesgroup.Inaddition,there wasan absenceof“verydissatisﬁed”intheCGcomparetotwointheunsta- bleshoesgroup.Itisapparentthatunstableshoesseemtoinduce amoreextremereaction(whethersatisﬁedornot)comparedto usualshoes.

Asobesityhasbeenidentiﬁedasariskfactoroflowbackpain [26],apost-hocanalysiswasconductedtoexploreifobesepartic- ipantshadadifferentevolutionthannon-obeseparticipants.Two obeseparticipants(BMI>30)wereincludedineachgroup.Dueto smallnumbers,astatisticalanalysiscouldnotbeperformed.How- ever,anincreaseinthedifferentpainscoreswasreportedforthe twoparticipantsintheCGwhileadecreasewasreportedforthe twoparticipantsintheIG.Studieswithalargernumberofobese patientsshouldbeconductedtoconﬁrmthesepreliminaryresults.

ThemajorstrengthofthisstudywastheuseofaRCTdesign toassesstheeffectsofunstableshoesona chronicLBPpopula- tion.However,thisstudyhasalsosomelimitations.Asformost trialsthat donot investigatedrugs,doubleblindingdesign was impossible.Albeitparticipantswerenotawarethat onetypeof shoeswasconsideredascontrolshoesandgreatcarewastaken topresentthe“control”shoesinthesamewayastheinterven- tionshoes,we cannotfullyexcludethatsomeofthem guessed whethertheywereallocatedtoaninterventionoracontrolgroup.

In addition,as thestudy wasconductedin a singleinstitution, thereis apotentialforacontamination,withsomeparticipants exchangingtheiropinionwithothersonanobservedeffectrelated totheshoestheywerewearing.However,asmore than11,000 individualsareworkingintheinstitutiontheriskisrelativelylow.

Thereisalsoalackofgeneralizabilityasthisstudywasconducted in a singleinstitution;and onprofessionals that spentmostof theirworkingtimewalkingorstanding.Thisstudyisasaproof ofconceptstudy.Thelengthoffollow-upwaschosenbasedona previousstudyshowingthataneffectcouldalreadybedetected after6weeks[11].However,aswithanychroniccondition,addi- tionalstudieswithlongerfollow-uparerequiredbeforedeﬁnite conclusioncanbedrawn.Lastly, thecomplianceofusingshoes (control or intervention) and the compliance with instructions (progressivewearingtime,onlyatwork)wereonlyassessedwitha logbook.

Insummary,wefoundthatthegroupwearingunstableshoes for6weeksshowedasuperiorreductioninpaincomparedtopar- ticipantswearing controlshoes. The reduction of painwas the mosteffectiveduringwalkingwiththeunstableshoes.Addition- ally,therateofsatisfactionforpainmanagementandthenumber ofresponderswerehigherinthegroupwearingunstableshoes.

However,theinterventionhad noeffectonfunctionaldisability andonqualityoflifeona periodof6-week.Futurestudiesare neededtodeterminetheeffectofunstableshoesonalongerperiod, onotherand largerpopulationsandtodeterminetheproﬁleof responders.

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Disclosureofinterest

ThecompanyMasaiBarefootTechnologyhasofferedtheshoes foralltheparticipants.MasaiBarefootTechnologyhasnotinany wayinﬂuencedthestudydesign,themeasurementprocedures,the dataanalysis,ortheinterpretationoftheresults.

ThisprojectwassupportedbyagrantfromtheGenevaUniver- sityHospitals(PRD10-II-8).Thefundershadnoroleinstudydesign, datacollectionandanalysis,decisiontopublish,orpreparationof themanuscript.

Acknowledgments

TheauthorsthankCharlotteElsworthandAxelFinckhforcritical reviewofthemanuscript.

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