ValidationofRunningSymmetryUsingTrunkMounted
Accelerometry:ClinicalTrialandCaseStudy
DavidJosephSaba
SubmittedtotheGraduateFacultyofVirginiaPolytechnicInstituteandStateUniversityin
partialfulfillmentoftherequirementsforthedegreeof
MastersofScience
in
HumanNutrition,Food,andExercise
CommitteeMembers:
JayWilliams
MadlynFrisard
AlfredWicks
ValidationofRunningSymmetryUsingTrunkMountedAccelerometry:
ClinicalTrialandCaseStudy
Abstract
Trunk-mountedmonitoringequipmentlikeGPSportsSPIHPUunitsaredesignedtouse
globalpositioning(GPS),accelerometerandheartratemonitoringtoevaluatethephysical
demandsofanactivity.Amedicalstaffmightalsoconsidermarkerssuchasrunning
symmetryinevaluationofinjuryoccurrenceandrehabilitation.Arunningsymmetryisa
ratioofthesynchronizationoftherightandleftlowerlimbsduringthegaitcycle.An
asymmetrydueto,apathologyormusculoskeletalinjury,resultsinabnormalloadingon
thefootthatmaybedetectedbytrunk-mountedaccelerometry.Theaimofthisstudyisto
evaluatetheabilityofSPIHPUunitstodetectrunningasymmetry.Subjectsworethe
HPISPUunits(100Hz,16gtri-axialaccelerometer,50Hzmagnetometer)whileengagedin
variousrunningactivities.Inthefirststudy,artificiallyinducingaleglengthdiscrepancy
ledtoadifferencebetweenrunningsymmetryscores.Thisdiscrepancywasconfirmed
usingindividualaccelerometersattachedtothelowerlegnearthefoot.Next,varying
runningspeeddidnotresultindifferencesinrunningsymmetry.However,theSPIHPU
unitsdiddetectarunningasymmetrybetweenfatiguedandnon-fatiguedconditions.
Finally,twocasestudiesshowedthattheunitscouldidentifyasymmetryimmediatelyafter
alowerleginjuryandduringrehabilitationofanteriorcruciateligamentreconstruction
surgery.TheresultsofthisstudyshowthattheHPUSPIunitscanbereliablyusedto
monitorrunningsymmetryandtodetectasymmetricalgaitpatterns.
TableofContents
ABSTRACT.............................................................................................................................................ii
TABLEOFCONTENTS........................................................................................................................iii
CHAPTER1:PurposeandSignificance.........................................................................................1
CHAPTER2:LiteratureReview....................................................................................................10
CHAPTER3:Methods.......................................................................................................................28
CHAPTER4:Results..........................................................................................................................34
CHAPTER5:Discussion...................................................................................................................47
Chapter1
PurposeandSignificance
1
Introduction:
Withthegrowthoftechnologyandanalyticsprograms,sportsscienceisina
positionwheremorequantitativedatacanbecollectedandinterpretedonaday-to-day
basis[1].Wearealsoinatimewhereprofessionalathletesaresomethehighestearning
professionalsinoursociety.Theircontractsaregivenintheexpectationtheywillmake
certaincontributionstothecommongoalofwinningateamchampionship.Christiano
Ronaldoearnedapproximately$53millionduringthe2015-2016season.Duringthistime,
heplayedin48matchesforRealMadridFC[2].Thismeansthathemadeover$1million
foreverygameheplayed,showingjusthowvaluableoneathletecanbetoanorganization.
ThisfinancialimpactcanbefurtheranalyzedusingthecaseofWayneRooney.By
multiplyinggameslosttoinjury(GLI)andsalaryowedperweek.Duringa9-month
windowRooneywasinjuredoffandonfor3monthsandmissed36%ofmatchesplayed
duringthisperiod.DuringthatsametimeRooneywasmaking£250,00perweekgrossing
£7.5millionoverthe9-monthwindow[3,4].Therefore,ManchesterUnitedpaid£2.7
million,or36%of£7.5million,toaplayerwhowasphysicallyunabletoperform(PUP).
LukeShaw,making£70,000perweek,missedover7months,86%,ofthesame9-month
window[3,4].ThetimeonthePUPlistcosttheteamonly£1.8million.Thisexampleshows
howplayerswithlargersalariescanimpactthefinancialaspectofperformancemorethan
GLIalone.GLIisjustthebeginningofthefinancialburdenplacedonanorganizationwhen
aplayerisunfittoparticipateinteamactivitiesasadditionalcostsareincurredformedical
treatmentsandrehabilitation,lostticketsalesandpotentialpost-seasonparticipation.
Afterinjury,itisalmostguaranteedthatsomerehabilitationprogramwillbe
establishedwhichmaybeextensiveifsurgeryisrequired[5].Withonesessionofphysical
2
therapycostingaround$250,a2-weeksessioncouldcostthousandsinadditionalexpenses
[6].Specialistsmaybeoutsourcedtoadministeralternativetreatmentslikecryotherapy,
addinganothercosttotheathletewhoisunabletoprovidehisorherskillsettothe
organization.Thekeytomaximizing“profit”oftheathleteistominimizethetimespent
awayfromtheirjobputtingafocusonquickrehabilitationtime.Iftherehabprocessis
rushedproperhealingmaynottakeplaceleadingtore-injuryandadditionaltimePUP[7].
Inadditiontominimizinginjuriesteamsareinterestedinquantifyingasmany
variablesaspossibleandturningtoanalyticstoidentifystrongandweakaspectsofthe
roster.ThemovieMoneyballgaveagoodrepresentationofhowsportsanalyticscanbe
utilizedtomaximizeallthepiecesofateamandreachtheultimategoalofwinningthe
championship[8].Theuseofhigherlevelsanalyticsasshownbythe2002OaklandA’sin
whichtheteamwasabletoeliminatemajorcontractsandfillthelossofproductivitywith
cheapercontractscanleadtogreatbenefitsforanorganization.Thesesmallercontracts
allowedtheA’stocorrectadditionaldeficienciesandseebeyondstatslikehittingand
homerunsalone.Thekeytoalloftheirsuccesswasbeingabletocalculatetrendsinteam
performanceandidentifysolutionstomaximizeperformancewhileremaininginthelimits
ofaleaguesalarycap[8].
Asweprogressthroughthisperiodoftechnologicalrevolution,productionof
smallerandmoreaccuratemonitoringdevicesarebeingmadeavailabletothepublic
sector,creatingastrongermarketforwearabletechnology[9].TechnologieslikeGlobal
PositioningSystem(GPS)andaccelerometrycanbeutilizedinmanyfieldsrangingfrom
phoneappstoexternalsystemssuchasthoseproducedbycompanieslikeGPSportsand
Catapult[10,11].
3
Thesetypesofequipmentaccuratelyandreliablycollectquantitativevariableslike
totaldistanceorbodyimpacttobeanalyzed[12,13].GPSportsnewestwearable,SPIHPU
unit(Figure1),isgrowinginpopularityamongstmajorsportsteamsincludingseveral
EnglishPremierLeague(soccer),NFL(football)andNBAteams(basketball)[14].These
smallcompactunitsallowforthedailycollectionofover100variablesdescribingthe
trainingloadexertedonaspecificindividualinanon-invasivemanner.Theunitutilizesan
externalheartratestrap,wornbelowthexiphoidprocess,GPS,accelerometer,and
magnetometer.
Inadditiontocollectingvelocityandheartratevariables,thistechnologyallowsthe
usertoutilizeaccelerometryvariables,likeimpactforce,runningorgaitsymmetryand
bodyload,asametricforevaluatingtotaltrainingload.Gaitsymmetryisdefinedasthe
equalvaluesofgaitvariableonbothsides,suchasaccelerationorgroundreactionforce
[15,16,17].Equalpeakgroundreactionforcesexperiencedduringrightandleftfootstrike
isconsidered“symmetrical”whereasdifferencedonfootstrikeforcesisdescribedas
“asymmetrical”.Gaitsymmetryisalsoreferredtoasrunningorwalkingsymmetry.An
asymmetricalgaitmayalsobereferredtoawalkingorrunningimbalance.Usinga
symmetryindexallowsforleftandrightgaitdatatobequantifiedintoapercentdifference.
Inthismethodologyascoreofzerowouldrepresentperfectsymmetrywhilevaluesabove
andbelowzerowouldrepresentasymmetryintherightorleftdirectionwherehigher
scoresrepresentmoreasymmetry[18,19].
Utilizinggaitsymmetry,onecanmonitorimproperloadingofthebodyandidentify
whentheseabnormalitiesoccur.Studieshaveshownthatassubjectsarefatiguedchanges
ingaitoccur,whichincreasesone’sriskofinjurybyreducingstability[20,21].Ifasituation
4
arisesinwhichanathleteisshowingabnormalgaitsymmetry,physicianscanact
proactivelytoadministertreatmenttorestoregaitfunctionbeforeinjurymayoccur.Risk
ofmajorinjuriestothejointsofthelowerextremitiescanbereducedviathereductionof
abnormalloadingforcesseeningaitasymmetry[22,23].Lowerleginjuryoftenresultsin
gaitasymmetrywhichisreducedduringrecoveryandrehabilitation.Thus,thismetric
couldalsobeusedtomonitorinjuryrecoveryandmake“returntoplay”determinations.
Therehavebeenstudiesthatexaminedaccelerometersandtheircapacityto
quantifyhumangait[24,25,26].Allofthesestudiesutilizedgroundreactionforcefroma
forceplateorvideoderivedaccelerationstovalidateaccelerometerdata.Trunk-mounted
accelerometryhasonlybeenusedinafewstudieswithforceplateorvideomonitoring
usedtovalidatethefindingsofthesestudies.Themainissuethatariseswhenusingsuch
validationtoolsisthelackofapplicabilityinarealworldsetting.Byrequiringasubjectto
performexerciseonaninstrumentedtreadmillortohavecompletefootstrikesonan
individualforceplatesomedeviationfromthenaturalgaitpatterncanoccur[27].
Inadditiontotheperturbedgaitthesemonitoringtoolsarelargeandrequireateam
ofresearcherstoconductdatacollectioninalaboratorysetting[28,29].Thisrequiresan
athletetotakeadditionaltimetohavetheirgaitsymmetrytestedoutsideofthenatural
environment[30].Anotherlimitisthatonlyonesubjectcouldbeevaluatedatatime
whetherthatbebyinstrumentationinthelaborviavisualexamintheclinic[31].One
studylookedathowrunningkinematicschangedduringlongdistancerunningand
concludedthatassubjectsbecamefatiguedverticalaccelerationofthetibiaincreasedat
heelstrike[32].Thisincreasedaccelerationwouldcauseanincreasedforcetobedelivered
5
upthekineticchainrequiringthebodytodissipatesuchforcesinanabnormalmanner,
leadingtoanincreasedinjuryrisk.
Anexperimentaldesignthatvalidatestrunk-mountedaccelerometersinamanner
directlytranslatabletofield-basedsportsandclinicalsettingdoesnotexistcurrently.Thus,
thisstudyfocusesontheaccelerationsenduredbetweenthefootandgroundinareal
worldsettingbyutilizinganon-invasivemonitoringsystemthatcanbeusedonaday-todaybasisduringeverydayactivitiesperformedoutsideofthelaboratory.
StatementoftheProblem:
Currentmethodologyusedtoquantifyrunningsymmetryoutsideofthelaboratory
isvisualinspectionofanathletebyaphysician.Insidethelaboratoryclinicianstypically
instrumentathletesandconductshortboutsoflocomotioninheavilycontrolledsettings.
Byutilizingtrunkmountedaccelerometry,gaitsymmetrycanbeassessedinavarietyof
real-worldconditions.AlthougharunningsymmetrycanbeidentifiedviatheGPSportsSPI
HPUtechnology,thesevalueshavenotbeencomparedagainstlowerlimbmounted,bilateralaccelerometry.Thisisproblematicasaccelerationdataobtainedfromatrunkmountedaccelerometerisinfluencedbythedampingeffectsofknee,hipandvertebral
columnflexionandextension(e.g.dampening).Inaddition,therearenodatashowing
changeinrunningsymmetrywithvariedexerciseintensityorduringarehabilitation
program.Thus,thethreeaimsofthisprojectareprovidedinthebelowsection.
6
SpecificAims:
Aim1:DeterminetheabilityoftheGPSportsSPIHPUtrunk-mountedunitstodetect
runningasymmetryduringartificiallyinducedrunningimbalanceandcomparethose
valuestoankle-mountedsensors.
Hypothesis:Anklemountedaccelerometersandtrunkmountedunitswillshow
similarchangesingaitsymmetryunderconditionsofanartificiallyinducedasymmetry.
Objective:Showthatbyapplyingpeakaccelerationstoasymmetryequation,a
runningsymmetryscoreisproducedthatissimilartothoseproducedbytheGPSports
proprietoralgorithm.
Aim2:Identifyhowexerciseintensity(i.e.runningvelocity)andfatigueaffect
runningsymmetry.
Hypothesis:Moreintenseexerciseprescriptionswillresultinthedevelopmentof
anincreasedgaitasymmetrywhencomparingthefirst100mtothefinal100mofa1600m
effort.
Objective:Confirmthatrunningsymmetryisaffectedbyvaryingworkout
intensitiesduetofatigue.
Aim3:Usecasestudiesonknownlowerleginjuriestoverifythatinjury-induced
gaitasymmetriescanbedetectedwiththetrunkmountedaccelerometer.
Hypothesis:Anathletesufferinganacutelowerleginjuryandanathleteundergoing
rehabilitationfollowinganteriorcruciateligamentreconstructionsurgerywillshowgait
asymmetriesduringrunning.
7
Objective:Adaptcodeusedinpreviousexperimenttocalculatearunningsymmetry
duringanexerciseprescriptionandcomparetoexistingrunningimbalance
Significance:
Byutilizingtrunk-mountedaccelerometerdataandasymmetryindex,gait
symmetrycanbequantifiedunderreal-worldsettinglikethefieldofplayorclinical
environment.Trunkmountedaccelerometryprovidesanon-invasivemeansto
quantitativelyevaluatearunningsymmetry.Ratherthanarbitrarilyidentifyinga“limp”,
practitionerscouldquicklyandreliablyquantifyanasymmetryandmonitorhowitchanges
asrehabprogresses.Ifusedinasportssetting,teamscouldidentifywhenasymmetries
developinsubjectsasthetrainingperiodprogresses.Physicianscancomparegait
symmetryacrossagiventimeline,allowingforevaluationofrehabilitationordevelopment
ofpathology.Trunkmountedsystemsalsoallowforcollectionofmultiplesubjectsatthe
sametime,amajorlimitationofinlabtesting.
Assumptions:
Subjectsarelimitedtomale,collegeathletes(soccer).Itisimpossibletoassure
subjectswillbefreeofbothmentalandphysicalfatigue,whichcaninfluencegait
symmetry.Theinductionofrunningasymmetryislimitedtobi-anduni-lateralshod
conditionsandexerciseprescriptionsof1600matvaryingintensities.Althoughdatawas
collectedundersimilarweatherconditions,factorsliketemperatureandhumiditycould
influenceeffortofathletes.Forthecasestudy,itislimitedtoonesubjectrecoveringfrom
ACLreconstructionandonesubjectrecoveringfromafootinjury.Lastly,subject’sdietary
8
intakecouldnotbenormalizedforthisstudy.Malnourishedordehydratedsubjectswould
notonlyaffectexerciseperformanceviathelackofsubstratetoproduceATPbutcouldalso
influencespatialcognition.
9
Chapter2
LiteratureReview
10
HumanGait:
Humanlocomotionrequiresthebodytosynchronizemusclecontractionsina
mannerthatisbothsafeandenergyefficient.Overmillenniaofevolutionhumanshave
adaptedtomaintainastablebase,allowingtheupperbodytomoveforwardoverthelower
limbs,preciseneuromuscularcoordination,andefficientabsorptionanddissipationof
forces[33].Theresultingmotionisacyclicalpatternoftheleftandrightlowerlimbs,
defininganindividual’sgait.Currentpracticeforevaluatinganindividual’sgaitrequires
thephysiciantobreakeachstrideinto4sections;weightacceptance,stance,forward
progression,andswing[31,33,34].Weightacceptancephase(0-10%)includesinitial
contact(IC)andtheloadingresponse(LR)andwhenthefootcomesincontactwiththe
groundandbearstheweightofthebody.Stancephase(10-50%)includesmidstance(MSt)
toterminalstance(TSt),thebodiescenterofmass(COM)isshiftingoverthefootto
preparefortoe-off.Theforwardprogressionphase(50-60%)encompassestheterminal
stanceandpre-swing(pSw)wherethebodyispropelledforwardandbeginstopreparefor
theswingphase.Theswingphaseisbrokendownintoinitial(ISw),middle(MSw),and
terminalswing(Tsw).Duringtheswingphasethefootisnotincontactwiththeground
andispreparingitselfforthenextweightacceptancephase.Onegaitcycleisdefinedasone
fullprogressionofallfourofthesephases.Generally,thisisbrokendownfromheel-strike
toheel-strikeina0-100%asshowninFigure2[33].
Normalgaitwouldbeasituationwherealloftheseportionsofthegaitcyclecome
togetherinasymmetricalandharmoniousmanner[35].Pathologicalgaitentailsany
deviationfromthisnormalgaitpattern.Pathologycanarisefromdeformitylikea
discrepancyinleglengthorissueswithjointmobilityasseeninACLreconstructionorjoint
11
replacementprocedures[36,].Muscleimbalances,issueswithneuromuscularfunction,and
paincanalsoresultinpathologicalgait[34].Pathologicalgaitrequiresthebodyto
compensateacrossalllowerbodyjoints:ankle,knee,andhip[33].Thiscausesmusclesto
beutilizedthatwouldnottypicallybeneededforagivenmotionlikewalkingorrunning.
Anexampleofhowpathologyleadstoincreasedenergyexpenditureandfurther
pathologywouldbeindividualswho“hike”theirhips.Individualswithlimitedhip
flexibilitymusthikeorraisetheirhipresultinginacircumductionofthelowerlimb.Not
onlydoesthisinterferewithgaitcycletiming,italsorequiresnovelmusclegroupsto
compensateleadingtoanabnormalloadappliedtothelowerlimb[37].Thisabnormal
loadincreasesthetotalworkthatcompensatorymusclesareperformingleadingto
increasedenergyexpenditure.Aswellasrequiringmoreworktobeperformedbynovel
musclesthiscircumductionofthehipappliesabnormalloadtothejointsofthelower
extremities.Abnormalwearingofthejointcapsulemayleadtootherissuessuchas
arthritisorosteoporosis.Consideringthatpathologyresultsinanasymmetricalgaitit
shouldbenosurprisethatthemonitoringofgaitisimportantindiagnosisandtreatmentof
manypathologies[38].
MonitoringGait:
Traditionallyresearcherscollectedgaitdatabyusingacombinationofforceplates
andvideomonitoringsystems[39,40].Forceplatesareplatformsthatareabletoconverta
changeinvoltageintoaforcevalueorgroundreactionforce(GRF)[41].Whenan
individualmakescontactwiththeforceplate,thereisadeflectionthatcreatesachangein
voltageandthroughaseriesofmathematicalconversionsproducestheGRF.ThisGRF
12
allowsforquantificationofdynamiceventssuchaslandingorrunningforcesinsixdegrees
offreedom,forcesandmomentsintheX,Y,andZcoordinate[41].Itcanalsobeusedto
calculatecenterofmass(COM),animportantvariableforquantifyingbalance[41].
Limitstousingsuchtechnologyincludetheneedofacontrolledenvironmentand
needformultipleplatforms[27-30].Videomonitoringisagreattooltocalculatejoint
anglesandhowtheychangeduringvaryingactivities.Byusingreflectivemarkersanda
roomequippedwithmultiplecamerasresearcherscancalculatehowajointismoving,
velocity,andthenpredictforcesexertedonsaidjointbyintegratingtodetermine
accelerationandutilizingNewton’ssecondlawofmotion,forceequalsmassmultipliedby
acceleration[41].Thisrequiresaroomofagivenareasetupwithuptoeightinfrared
cameraslimitingthecapacitytocapturereal-worlddata.Asbroughtupearliertheforce
plateneedsagroupofresearcherstocalibratethesystembyfirstensuringtheplateis
firmlyattachedtoalevelsurface.Duetotheintricaciesofcalibratingtheplatestheyare
ofteninstalledonceandnotmovedrestrictingtheoutoflabutilization[41].
Anotherlimittoforceplatesisthatfullfootcontactisrequiredforaccurate
measurementofGRF[42].Ifoneweretoonlystriketheplatewithhisorhersheelaforce
wouldbegeneratedbuttheportionofthefootoffoftheplatewouldalsoexertaforcethat
wouldnotbecaptured.Sinceaskingasubjecttostriketheplatewouldaltergait
researchersmustinstallmultipleplatestoincreasetheoddsofcapturinganentirefoot
strike.
Withthemainlimitationofbothtoolsbeingthattheyrequirealabsettingan
alternativeisneededtoconductdataintherealworld.Inertialmeasuringunits(IMU)
provideananswertothisproblem.AnIMUisacombinationofaccelerometer,gyroscope,
13
ormagnetometer[43].AccelerometersmeasurelinearaccelerationsintheX,Y,andZ
planeswhilegyroscopesmeasureangularvelocitiesalongtheX,Y,andZplanes.
Magnetometersareabletodetectmagneticnorththusallowingthesystemtoorientitself
toacommonpoint.BasedonNewton’ssecondlaw,F=ma,datacollectedfrom
accelerometrycanbecomparedtoforcedatalikeGRF.Onestudythatdirectlycompared
forceplatedatatoaccelerometrydatawasastudyconductedbySeimetzetal.Inthisstudy
theywantedtolookathowaccelerometryandforceplatedatacomparedwhenmeasuring
posturalstability[44].Stabilogramsandswayprofilesweregeneratedfromforceplateand
sternum-mountedaccelerometerrespectively.Subjecthadbothvisualandproprioceptive
systemsperturbedinordertoseehowforceplateandaccelerometerwereabletodetecta
changeinCOM.Thefindingsofthestudywerethatthetwotechnologieswerenotdirectly
comparablebutshowedsimilartrends.ThiswasshownbyincreasedCOMareaonthe
stabilogramandincreaseswayprofilewhenthebodiesvisualandproprioceptivesystems
wereperturbed.
Theuseofaccelerometershasbeenusedinsciencesfordecadesbutisonlyrecently
beingintroducedonlargescaleinteam-basedsports(12,13).Byutilizingaccelerometry
estimationsofforcesandhowtheyaredistributedacrossthebodyasawholecanbe
obtained[24,25,26].AstudyperformedbyTorrealbaetal.[45]identifiedsignificant
landmarksingaitdatacollectedfromaccelerometers.Thesignificantfindingsofthisstudy
weretwonegativeaccelerationsthatoccurredduringthegaitcycle.Thelargeracceleration
wasassociatedwithheelstrikeandthelesserpeakbeingassociatedwithtoe-off.The
authorsusedthegaitcycleandfoundthetoe-offoccurredapproximately61%intothegait
cycle,whichissupportedbyvideomonitoringsystemslikeVicon[45,46].
14
Zhangetal.[47]lookedtoidentifyhowaccelerometerattachmentsiteaffected
accelerations.Subjectsattachedaccelerometersabovethemedialandlateralmalleolusand
performedawalkwherethefootstruckaforceplate.Accelerometerdatafromboth
attachmentsiteswerewellcorrelatedwithforceplatedatabutlateralattachmentwas
morehighlycorrelated.Thehypothesisontheseresultswasthatbyattachingsensors
closertothepointofcontacttheforceexertedontheunitwouldbehigher.Thisbrings
lighttoanimportantpointthatthebodyhasbuiltindampersliketheankle,knee,andhip
jointcapsule.Thesedampersincludeskeletalmuscle,ligaments,tendons,andcartilage.As
thesedampersdeteriorategaitwillbealteredinordertoaccommodate.Ifdataweretobe
collectedfurtherfromthepointofcontactvaluesmaydifferbuttrendsshouldremain.
GaitSymmetry:
Therearenumerousstudiesexaminingabnormalitiesingaitsymmetryincluding
detectinganasymmetryincerebralpalsy,stroke,andtheelderlytoassessriskoffalling
[19-23,48-50].Variableofinterestincludedvariationinstridedistance,GRF,peak
acceleration(PA),andCOM.Fewstudiesutilizedtrunk-mountedunits,likeGPSports
(SPIHPU)units,forcollectionofaccelerationdata.Carpesetal.[19]conductedareview
lookingatlegpreference,whichincludedanalysisofavarietyofsymmetryequations.All
equationscomparedvariablefromtherightlimbtoleftlimb.Fromtheirstudyandothers,
themostcommonmethodologytoevaluatesymmetryistotaketheabsolutevalueofright
(Xr)minusleft(Xl)dividedbyonehalfright(Xr)plusleft(Xl)asshowninFigure3
[19,39,40].Carpesetal.[19]foundthatbyusingthisformulaasymmetrypercentage
(ASI%)canbeproducedallowingfortheidentificationofsymmetryinasubject’sgait[19].
15
Itwasimportanttoidentifypossiblesourcesoferrorwhencollectingsymmetry
data.Basedontheproprietor’sinformationandcurrentliteraturefoursourcesarose
includingvelocity,runningsurface,footwear,andattachmentsite.Croweetal.[51]looked
athowgaitvariableswereinfluencedbyvaryingwalkingspeeds.UsingGRFdata
researchersfoundthatasvelocityincreasesgaitcycleduration,timefromrightheelstrike
tonextrightheelstrike,andforceintheYplane,mediolateral,decreasedwhileforceinthe
X,anterior-posterior,andZ,vertical,planeandstridelengthincreased.Thesefindings
showthevariabilityinforcesasvelocitychangesmakingvelocityanimportantfactorto
considerwhiletestinggaitparameters.TheXandZGRFdatawashighlycorrelated
showingarelationshipbetweentheforcesatwhichthefootstrikes,weightacceptance
phase,theplatetotheforcegeneratedtopropelthebodyforward,toe-off.Theseincreased
forcesrequirethebodytoincreasetherateatwhichgaitcycleoccurstobe
biomechanicallyefficient.
Giandolinietal.[52]conductedandexperimentwheretheyutilizedaccelerometers
toidentifydifferencesbetweendownhillandlevelgroundrunning.Basedonprevious
studies,theystatethatdownhillrunninginduceshigheraccelerationsatthetibiaequating
increasedforces.Findingsofthisstudywerethatdownhillrunningpromotedrear-foot
strikeandfoot-strikepatterninfluencedshockintensity.Specifically,theyfoundthat
forefootstrikeproducedlessforcethanrear-footstrike.Theanklecanbemodeledasa
first-classleverwheretheloadisappliedtothefoot,thetalocruraljointactsasthefulcrum
allowingforforcestobedistributedtothemusclesofthecalfandviceversa.Intheforefoot
strikethedistancebetweenourfulcrumandsiteofforceapplicationisincreasedwhereas
inarear-footstrikerthisdistanceisreducedleadingtoanincreasedforcesentthroughthe
16
talocruraljointandupthekineticchain.Althoughsubjectsmaynaturallyberear-foot
strikersbyensuringaflatsurfaceweareminimizingtheeffectsofanunevensurfaceon
accelerations.
Ourthirdsourceoferroristhatfootwearcanaffectgaitsymmetry.Hoerzeretal.
[53]testedhowshodvsunshodinfluencedGRFdata.Theirfindingsweresimilartoother
studiesthatshodrunningreducedrunningasymmetry.Theyproposedthatshoesalter
sensoryinformationfromtheplanterand/orthedorsalportionofthefoot.However,some
subjectsdidshowanincreasedgaitasymmetrygivingsupportforhowvariablehumangait
is.Thisvariabilitycanarisefromthevariationinafferentfeedbackoftheneuromuscular
systemeffectingproprioception[53,54].
Lastly,accelerometerplacementwillaffectthecollectionofaccelerometerdata.Two
aspectstoplacementisassuringtheunitissecurelyattachedandunderstanding
placement.Thefirstpointisintuitiveinthatiftheunitisnotsecurelyattachedtothebody
theaccelerationcancomefromtheunitmovingindependentlyoftheattachedlimb.To
reducetheseeffects,researchersuseathletictape,Velcro,or2-sidedtapetofirmlyattach
unitstothebody.Asmentionedpreviouslythebody’sjointandmusculoskeletalsystem
dispersesforceasittravelsupthekineticchain.Thisideaissupportedbyastudy
conductedbyZhangetal.[47]Theyidentifiedhowwellaccelerometerdata,peak
acceleration,wascorrelatedtoGRFwhenattachingunitstothedistaltibiaandlateral
malleolus.AlthoughbothattachmentsiteswehighlycorrelatedtoGRFdata,lateral
malleolusattachmentwasmorehighlycorrelated.Thisattachmentwasalsosupportedby
studiesconductedbyManninietal.[55]andLeMoyneetal.[56].
17
WearableTechnology:
Recentlyseveralcompanieshavedevelopedwearableunitsdesignedtomeasure
variableslikevelocity,heartrate,acceleration,andrunningsymmetry.TheSPIHPUisan
80gtrunk-mountedunitthatincorporatesGPS,accelerometer,andmagnetometerhoused
ina74mmx42mmx16mmwaterproofcase,Figure1.Thetrunk-mountedunitis
positionedbetweentheathlete’sscapula,nearvertebraeT4andT5,byavestprovidedby
manufacture,Figure4.Inadditiontothetrunk-mountedunitheartratedataiscollectedvia
polarheartratestrap.Alldatafromthefourinstrumentsisstoredontheunituntil
downloadedtothedockingstationandinterpretedusingproprietarysoftware.TheGPS
unitrecordsat15Hzandcollectsposition,speed,anddistancevariables.Theaccelerometer
recordsimpacts,accelerations,anddecelerationsupto16gatarecordingfrequencyof
100Hz(Figure5).Themagnetometerisstrictlyusedtotrackmovementprofilesandused
inconjunctionwiththeaccelerometertoestablishorientation.Utilizingthesefour
separatetechnologiesallowstheproprietorssoftwaretogeneratevisualizationsofhow
variablesinteractwitheachother.Figure6showshowvelocityandheartrateofan
individualtrackoverthecourseofanexercisebout.
Theincreasedlevelofmonitoringproduceslargedatasetscomprisedofover150
variablesallowingforamorequantitativemeasureofthetotaltrainingload(TL)endured
bytheindividual[57].Trainingloadcanbedefinedasbothexternal(thevolumeand
intensityofworkbeingperformed)andinternal(thephysiologicalandmechanical
responsetotheexternalload).Anathlete’sTLisimportanttomaximizingperformance
gainsaswellasreducingtheriskofinjury.Gabbettetal.[58]modelTLbytakingtheratio
ofacutevs.chronicloadandmaintainingitbetweenaspecificrange,0.8-1.3au.[58].Using
18
thisscaleundertrainingandovertrainingarerepresentedbelow0.8auorabove1.3au
respectively.Acuteandchronicloadcanbeanyslidingwindowofdata,1-6dayaverage
versus10-18dayaveragerespectively[59].ThiswayofanalyzingTLmakestheobserver
moreconcernedaboutthesimilaritybetweenexerciseboutsratherthanlookingateach
exerciseboutasanindividualstress.TherateatwhichTLvariesismoreimportantthan
theindividualsessionsthemselves.ModelingTLinsuchamannerwecancomparehowwe
areperformingnowversushowwewereinthepast.Analyzingrunningsymmetryinthis
waywillallowforintra-subjectcomparisonstobemadeestablishingbaselinesor“normal
gait”.Sincerunningsymmetryissovariedamongstindividualscomparingsymmetryto
one’sownselfprovidesmorepowerfulinsightthancomparingtoawholeteamaverageor
thateveryonehasperfectsymmetry.Assumingasubjecthassomenaturalasymmetryin
theirgaitusingacutevs.chronicallowsforustoseehowsimilarthatasymmetryoccurs
ideallyresultinginaratioof1[58].Ifsomeoneweretochronicallyover-trainorexperience
amusculoskeletalinjury,itwouldbeexpectedthatanunnaturalasymmetrywoulddevelop
comparedtoone’sownnaturalgait.Thiswouldresultinanincreasedacutevs.chronic
ratioandcouldbeusedasamarkerforinjury.Inarehabilitationsettingaphysiciancould
lookfortheacutevs.chronicratiotobelessthanoneduetothereductionofasymmetry
overtime.Thiswouldallowphysicianstobetterunderstandhowtherehabilitation
processisprogressingandhaspotentialasareturnto
ACLReconstructionClinicalCases:
ACLrupturesarethemostcommonsportsassociatedinjurythatrequiressurgeryto
repair[60].TheACLprotectstheproximaltibiafromanteriortranslocationfromthedistal
19
femurwhenthelegisinaflexedposition[Butler].Suchinjuryisassociatedwitha
disruptioningaitsymmetryduetoreducedrangeofmotion(ROM)andreducedstrength
specificallyinthequadriceps[61,62].Followingsurgeryphysician’smaingoalsrevolve
aroundpromotinglong-termjointfunctionalityandavoidre-injury,mostsusceptible7-8
monthspost-surgery.
InordertoaccomplishthisVirginiaTechsportsmedicineguidelinescallforthe
recoveryperiodisbrokenintofourstages(early,middle,late,post)eachfocusingon
restoringpainmanagement,ROM,strength,weightbearing/jointloading,and
neuromuscularcontrol.The“early”phasebeginsimmediatelyfollowingsurgeryand
generalextendstosix-weekpost-surgery.DuringthisperiodthefocusisrestoringROM,i.e
gainingfullextension,andneuromuscularfunction.Specialfocusisplacedonmuscle
activationandreestablishingnormalgaitpatterns.Thisincludesemphasisonavoiding
poorgaitmechanicslikestiff-kneegaitwhilepromotingnormaltoe-offtohelpestablish
normalgaitspeedandcadence.
Inordertoprogresstothe“middle”phasepatientsmustshowfullROMaswellas
accomplishbasicgaitgoalslikesteppingup/downandsymmetricalloadingduring
unassistedwalking.The“middle”phaseextendsfrom6-12weekspost-surgery.Duringthe
periodmoredynamicexercisesareemphasized.Joggingbeginsaswellasperturbed
balance;singlelegstanceonfoampad,duringthistimeasregainingendurancebecomesa
focusoftherehabilitationprescription.Asthisprescriptionprogresses,symmetrical
loadingisimportanttoensurenormalloadingoftherepairedjoint.Approximately12
weeks,3months,post-surgery,apatientwouldbeginthe“late”phase,whichonlylastsfor
fourweeks,16weekspost-surgery.Duringthisphasejoggingdurationandintensityis
20
increasedwithemphasisonminimizingeventslike“hardlandings”makingthepatient
focusonspecificmuscleactivationwithoutco-contraction,notcontractingquadricepswith
hamstringsIncreasingmulti-jointmaneuverslikesquats,speedladder,andplyo-jumpscan
beaddedaspermittedbypatient’spain.
Summary:
Areviewoftheliteratureisclearinestablishinggaitsymmetryasakeyvariable
thatcanbeusedtoidentifymusculoskeletalinjuryandpathology.Thismetricistypically
derivedusinglaboratorytechniquesandisgenerallydifficulttodetermineduringeveryday
activitiesperformedoutsideofaresearchorclinicalsetting.Recentlytrunk-mounted
accelerometersincorporatedaspartofaGPSbasedmonitoringdevicehaveshowed
promise.However,fewdataexisttovalidatethesedevicesagainstbi-lateralfootorankle
mountedaccelerometersandduringconditionswheresymmetricalandasymmetricalgait
exists.Thus,thereisaneedtovalidatetrunk-mountedagainstbi-lateraldevicesand
duringperiodofknownalteredgait.
21
Figure1.TheGPSportsSPIHPUunit.
22
Figure2.Synchronizationofleftandrightlowerextremitiesduringgaitcycle.Top:
Walkinggait,Bottom:Runninggait.Imageobtainedfrom:
http://clinicalgate.com/assessment-of-gait/
23
Figure3.Symmetryindexequation.XrandXlrepresentpeakverticalforcesduringright
andleftfootstrike,respectively(Z-axis)[19]
24
Figure4.SPIHPUwithvestfront(top)andback(bottom)showingunitinpocket
25
Figure5.RawSPIHPUaccelerationdata.ShownareZ-axis(yellow),X-axis(red)andYaxis(green).Theresultantisshowninblue.TheFigurewasobtainedfromGPSports
TeamAMSsoftwarepackage.
26
Figure6.Heartrateandvelocityvisualization.Theredlinerepresentsheartrateand
thebluelinerepresentsrunningvelocity.TheFigurewasobtainedfromGPSports
TeamAMSsoftwarepackage.
27
Chapter3
Methods
28
Subjects:
Thestudyusedhealthycollegiatesoccerplayerswithnocurrentlowerbodyinjury.
Currentlowerbodyinjurywillbedefinedasaninjurythathasoccurredwithinthepast
30days.Anadditionalsubjectrecoveringfromanteriorcruciateligament(ACL)
reconstructionsurgerywillalsobemonitored.Subject’sinformationcanbeseeninTable1.
AllprocedureswereapprovedbytheVirginiaTechInstitutionalReviewBoard(IRBand
16-387and16-619).Allprocedureswerefullyexplainedtoallsubjectsandinformed
consentwasobtainedpriortodatacollection.
Accelerometry:
Subjectswereaskedtowheretrunkmountedaccelerometers(SPIHPU,GPSsport)
(allstudies)aswellasbi-ankle-mountedaccelerometers(MSR145S,MSRElectronics
GmbH)(ValidationStudy).SPIHPUunitsweremountedinaccordancetomanufacture
recommendationbeingsecurednearvertebraeT-4andT-5withproprietaryvest.
CharacteristicsofthetwoaccelerometersareshowninTable2.Anklemountedunitswere
securedatthelateralmalleoluswithPowerFlextapeusingthelateralmalleolusandfibula
aslandmarksassupportedbyliterature[47].PowerFlexwaschosenasthebestmeansto
secureaccelerometerstotheankleduetoitsmaterialdesignswhichwouldminimally
perturbssubjectsnaturalgait.Onceunitsaremountedwarm-upactivitieswereperformed
tofamiliarizesubjectswithequipmentandprotocols.
Trunkmountedaccelerometersare100Hz,16gtri-axialaccelerometerequipped
witha50Hzmagnetometertodetermineaxialorientation.Theassociatedsoftware
producesasymmetryindexusingaproprietaryalgorithm(GPSports,TeamAMS).This
29
algorithmidentifiesandcomparespeakaccelerationvaluesofeachfootstrikeand
computessymmetryusingtheequationinFigure3.
Accelerometerdatafromthetwolowerleg-mountedaccelerometersweresampled
50Hzusingmanufacturerprovidedsoftware.TheywerethenanalyzedusingMATLAB.A
rollingaveragewasfirstusedtolow-passfilterthedatawhichallowedforidentificationof
peakacceleration(PA)alongtheverticalorZ-axisforeachfootstrike.Nextwewillneedto
compareeachunit’s(leftvsright)databyapplyingthepeakaccelerationalongtheZaxis
fromrightandleftstancephase(identifiedasXrandXlrespectively,inthesymmetry
equationusedinFigure3.
ValidationTrial:
Inordertoinducegaitasymmetry,subjectsweretestedunderthreetestconditions
intheorderofbi-lateralshod(wearingtwoshoes),uni-lateralshod(wearingleftshoe),
andunshod(noshoes)conditions.Subjectswereaskedtowearsoccercleatsoftheir
choice.Duringeachtrial,theyperformed15-50mrunsatapproximately70%intensity,
self-reported,withaminuterecoverybetweenefforts(5foreachcondition).Alltrialswere
administeredonthesamedayutilizingaflatartificialturffield(FieldTurf)tominimize
effectsfromvaryingsurfaces.
Symmetryscoresfromeachtrialwithinaconditionwereaveraged.Trunk-and
lowerleg-mountedsymmetryscoreswerecomparedusinga2-wayrepeatedmeasures
ANOVA(conditionXdevice)usingJMP.Runningvelocitieswerecomparedusinga1-way
ANOVA(condition).Significancewasestablishedatthep<.05level.Effectsizeswere
30
calculatedusingη2(η2=SSeffect/SStotal)with0.01consideredsmall,0.06considered
mediumand0.14consideredlarge.
ApplicationTrial:
Three,1600meffortstrialsofvaryingintensitieswereconductedonseparatedays.
Theseincludeda1600mrunperformedinapproximately16km/hr(6minutemile),16x
100msprintsperformedatnearmaximalvelocity,self-reported,anda1600mjogat
approximately8km/hr(12minutespermile).Trialswereconductedonseparatedays,to
betterisolatethefatiguingexerciseandwerecarriedoutaspartofroutine,off-season
training.Alleffortswereperformedona400moutdoorrunningtrackwithallsubjects
completingeachactivityatthesametime.Forthistrial,subjectswerefittedwiththe
trunk-mountedunitsalone.Runningsymmetryscoresweredeterminedforthefirstand
last100mofeach1600mtrialandforfirstandlastofthe100msprintsboutusingthe
SPIHPUandproprietarysoftware.
Differencesinrunningsymmetryandvelocityweredeterminedby2-wayrepeated
measuresANOVA(trialXtime)usingJMP.Significancewasestablishedatthep<.05level.
Effectsizeswerecalculatedusingη2asdescribedabove.
CaseStudies:
TwocasestudiesarepresentedasfurthervalidationoftheSPIHPUunitsabilityto
identifyrunningsymmetryandasymmetry.Inthefirstcasestudy,asinglemalesubject
whowasrecoveringfromACLreconstructionsurgerywasexamined.Datacollectionbegan
60dayspost-surgeryandcontinuedfor6weeks.Forthisindividual,recoverywas
31
monitoredsemi-weekly.Runningsymmetrywasdeterminedduringvaryinglengthsof
straight-lineconstantvelocityrunning.Asthesubjectwasclearedforgreatertraining
participation,runningspeed(intensity)wasallowedtoincrease.
Asecondsubjectsufferedablowtothelowerlegduringoff-seasontraining.He
continuedtotrainfortheremainderofthesession.Followingthesession,hewas
diagnosedwithananklesprainandenteredintoarehabilitationprogram.Running
symmetrywasassessedimmediatelybeforeandaftertheinjury.Itwasalsoassessedfor
10daysfollowinginjury(rehabilitationprogram)afterwhichthesubjectwasclearedfor
fullparticipationintrainingactivities.
Forbothsubjects,accelerometerdatawererecordedduringthedesignated
rehabilitationprotocolestablishedbyVirginiaTechSportsMedicinestaff.Runningspeeds
andexerciseintensitieswereadjustedbythestaffastoleratedbyeachsubject.Running
symmetryvaluesweredeterminedpriorto(acuteinjurystudy)andduringthe
rehabilitationperiodsasdescribedfortheValidationandApplicationstudies.
32
Variable
ValidationTrial(n=11)
ApplicationTrial
(n=16)
CaseStudies
(n=2)
Male:Female,
6:5
16:0
2:0
Age(years)
22.1(2.9)
21.2(1.4)
21(0)
Height(m)
1.76(0.09)
1.80(0.07)
1.85(0)
Bodymass(kg)
71.6(11.2)
74.9(6.7)
81.9(0)
BMI(m.kg-2)
22.9(1.9)
23.1(1.7)
23.9(0)
Table1.Subjectcharacteristicsforeachstudy.
Specification
SPIHPU
MSR145S
Size(mm)
74x42x16
18x14x62
Weight(gm)
66
18
Accelerometer
Tri-axial
Tri-axial
Magnetometer
Yes
No
Range(g)
±16
±10
Datacollection(Hz)
100
50
Table2.Accelerometerspecifications.
33
Chapter4
Results
34
ValidationTrial:
Rawaccelerationsforunilateral-shodrunningareshowninFigures7and8.Shown
areZ-axis(vertical)accelerationsdetectedwiththeSPIHPUunits(trunk-mounted)for
successivefootstrikesaswellasthebilateralanklemounteddevices.Ascanbeseen,peak
accelerationsarenoticeablydifferentbetweenrightandleftfootstrike
Themeansymmetry(Figure9)andmeanrunningvelocity(Figure10)were
comparedbetweeneachtrialforeachsubject(ANOVAtablesareshownintheAppendix).
Symmetryscoresweresignificantlygreaterfortheunilateralshodcondition(1S)
comparedtotheothertwoconditionsforbothtrunkandanklemountedaccelerometers.
Theeffectsizeforconditionwasconsideredlarge.Therewerenodifferencesinsymmetry
betweenthebilateral(2S)andun-shod(0S)conditions.Therewasasmalldifference
betweendatacollectedfromtrunk-andankle-mounteddeviceshowever,nodeviceby
conditioninteractionwasfound.Thisindicatesarunningasymmetrywhensubjects
experiencedanartificiallyinducedalterationingait.
Runningvelocityforthe2Sconditionwassignificantlylowerthanthe0Scondition.
Velocitiesduringthe1Sand0Sconditionwerenotdifferent.Thisamountedtoa4.7%
reductioninrunningvelocitycomparedtotheotherconditions(mediumtolargeeffect
size).
Theseresultssuggestthattrunk-mountedaccelerometrycandetectartificiallyinducedrunningasymmetry.Inaddition,themagnitudeofasymmetrydetectedbythe
trunk-mountedunitswassimilartothatdetectedbylowerlegmountedaccelerometers.
ApplicationTrial:
35
Themeanrunningsymmetryscores(Figure11)andrunningvelocities(Figure12)
showedthetypeofexerciseperformedaffectedrunningsymmetry.Theintensityof
activitydidnotsignificantlyaffectsymmetry.However,therewasahigherasymmetry
duringthefinal100mifthe1600mtrialThe1600mtrialwastheonlyactivitytoshowa
significantlyincreasedsymmetryscore.Theeffectsizesforactivity(trial),interval(first
andlast100m)andtheirinteractionwereallconsideredmedium.
The16x100mshowedasignificantdecreaseinvelocitybetweenfirstandlasttrial.
Asanticipated,runningvelocitieswerehighestduringthe16x100meffortsandlowest
duringthe1600mjog.Effectsizesforactivitywasconsideredlargeandconsideredsmall
fortheintervalandtheinteraction.
Theseresultssuggestthatrunningsymmetry,asdeterminedusingtrunk-mounted
accelerometry,isnotgreatlyaffectedbyrunningspeedbutisalteredbyfatiguingactivity.
CaseStudies:
Forthefirstcasestudy,asinglesubjectsufferedateartohisrightanteriorcruciate
ligament(ACL)andunderwentreconstructionsurgery.Fiveweeksfollowingsurgery,he
beganaprogramofslowjoggingalongwithtraditionalstrengtheningandrangeofmotion
exercises.Hisexerciseintensitywasgraduallyincreasedoverthenextthreemonths.
Figure13showssignificantasymmetryfollowingACLreconstruction.Inthiscase,
symmetryscoresarepositivereflectinganinjurytotherightleg.Aninitialincreased
runningasymmetryappearstoariseastherehabilitationprogrambegins.Thislikely
reflectsthegradualincreaseinrunningvelocityduringtherehabilitationprogram.After
36
twomonthsofrehabilitation,runningasymmetrywasstillevidentbothvisuallyandfrom
SPIHPUdata.
Forthesecondcasestudy,anindividualsufferedanankleinjurytohisleftleg
resultingfrombeingkickedonduringatrainingsession.Aftersustainingtheinjury,the
subjectcontinuedtotrainforseveralminutesafterwhichthesessionended(Figure14).
Hewaslaterdiagnosedwithananklesprainandhistrainingwaslimitedforseveraldays.
Ashebecamesymptomfree,hisactivitieswereincreasedandresumedfulltrainingwithin
twoweeks.Figure14showsacutechangesinrunningsymmetryfromtheperiodbefore
theinjuryandafter.Priortotheinjury,therearelargevariationsinrunningsymmetry.
Thislikelyreflectsthenatureoftheactivitybeingperformed.Soccertrainingrequires
playerstoexecuteanumberofdirectionalchangesatbothlowandhighrunningvelocities.
Theincreasedimpactforceduringachangeofdirectionmovementwouldlikelyaffectthe
symmetrycalculation.Followingtheinjury,thissubjectshowsamarkedincreasein
symmetryreflectinganasymmetricalgaitpattern.Alsonotethelargechangeinsymmetry
occurringimmediateaftertheinjurycomparedtothevalidationandapplicationtrials.
InFigure15theplayer’ssymmetryscoresoverthedaysbeforeandfollowingthe
injury.Thisshowsalargenegativeasymmetryscoresinthedaysfollowingtheinjury.
Thesearefollowedbydecreasingasymmetrythroughtherecoveryandrehabilitation
period.
Bothcasestudiesindicatethatrunningsymmetrydeterminedbytrunk-mounted
accelerometryisalteredimmediatelyafteraninjuryandremainssoduringrehabilitation.
37
Figure7.RawaccelerometrydataobtainedfromtheHPISPUunit.RandLdenoteright
andleftfootstrikes,respectively.
38
Figure8.Rawaccelerometrydatafromthebi-lateralaccelerometers.RandLdenote
rightandleftfootstrikes,respectively.
39
Figure9.Runningsymmetryvaluesduringbi-lateralshod(2s),uni-lateralshod(1s)and
unshod(0s)runningtrials.*p<.05vs0sand2sconditions.
40
Figure10.Runningvelocityduringbi-lateralshod(2s),uni-lateralshod(1s)andunshod
(0s)runningtrials.*p<.05versus0sand2s.
41
Figure11.Runningsymmetryvaluesduringthethree1600mtrials.*p<.05versusthe
first100mofthetrail.
42
Figure12.Runningvelocityvaluesduringthethree1600mtrials.*p<.05versus100s
andjog,†p<.05versus100sand1600m.‡ p<.05versus100sfirst100mandlast100m
43
Figure13.MeanrunningsymmetryscoresduringanACLreconstructionrehabilitation
program.
44
Figure14.Runningimbalancescoredduringatrainingsessioninasingleplayerbefore
andaftersustainingafootinjury.Thesessionconsistedofawarm-up,fitnesstraining
andmatchplay.Approximately140afterthestartofthesession,theplayersustaineda
footinjury.Trainingendedapproximately15minuteslater.
45
Figure15.Runningimbalancescoresbeforeandaftersufferinganankleinjury.The
injuryoccurredonday0.Thesubjectwasrestrictedfromfulltrainingbetweendays1
and9.Afterday9,thesubjectresumedfullparticipation.
46
Chapter5
Discussion
47
TheresultsofthisstudyshowthattheSPIHPUaccelerometercanbeusedtodetect
asymmetricalgaitpatterns.Fourpiecesofevidencesupportthisconclusion:1)An
artificiallyinducedgaitabnormalityinducedarunningasymmetry2)Changesinrunning
symmetrywerequalitativelyandquantitativelysimilar(visualandSPIHPUdata),3)
Runningsymmetryisaffectedbyexercisetofatigueand4)twocasestudiesofinjured
subjectsrevealedalterationsinrunningsymmetry.Basedontheseresults,itisevident
thattheSPIHPUunitscandetectbothnormalandabnormalgaitpatterns.
ValidationTrial:
Thistrialdemonstratedanovelapproachtoinducingarunningasymmetryin
normallyhealthysubjects.Byhavingsubjectsremovetheirrightshoe,aleglength
discrepancywascreated.Thisdiscrepancyledtoanincreasedpositive(favoringtheright
leg),runningsymmetryproducedbytheGPSportsproprietarysoftwareandankleunits.
Thedatashowedastatisticallysignificantdifferencewhencomparingsymmetryscoresof
thebilateral-,unilateral-andun-shodconditions.Whencalculatingthesymmetryscorea
trenddevelopedinwhichtheproprietarysymmetryalgorithmbegandetectingarunning
symmetryduringtheearlypartofsteadystate,constantvelocity,runningandcontinued
untilthesubjectsspeedfellbelowthethresholdof8km/h.Itwashypothesizedthatthis
delayindetectionofrunningsymmetrywasduetothe10stepminimumneededforthe
proprietaryalgorithmtocalculateasymmetryscore.Unfortunately,withoutknowingtheir
exactalgorithmitishardtomakedefinitiveconclusionsastothesourceofthisabnormal
distributionoffoot-strikestakenintoconsiderationtodevelopthesymmetryscore.By
validatingthescoreagainstankleaccelerometersweshowedsimilartrendsindatawhere
48
theankleunitsreportedincreasedscores.Thiswasexpectedasdatawasbeingcollected
closertothepointofcontact.
Aninterestingfindingofthisstudyexperimentwasthestatisticallysignificance
betweenunshodandshodvelocitieswheretheunshodconditionshowedanincreased
velocity.Thefirstthoughtwasthatthismayhavebeenaresultoffatiguebutallsubjects
wentthroughtheexperimentalprotocolprogressingfromshodtouni-shodtounshod
wherefatiguewouldmostaffecttheunshodtrials.Duetotherestandorderofexerciseswe
donotfeelasthoughfatiguehadanyeffectonourexperimentratheritmaybethe
biomechanicsresponseofthefoot.Kellyetal.conductedanexperimentthatcomparedfoot
biomechanicsduringshodandunshodrunning.Themainfindingswerethatwhenvelocity
wascontrolled,14km/h,shodrunningledtoanincreasedstridedurationandground
contacttimewhiledecreasingpeakloadingrateandpeakpropulsiveforcewhencompared
tounshodconditions.Thisbeginstomakemoresenseifthelongitudinalarch(LA)ofthe
footismodeledasaspring.DuringtheloadingphasetheLAiscompressedconverting
kineticenergytopotentialenergystoredinthetendonsandligaments.Asthegaitcycle
entersterminalstancetheLAextendsthispotentialenergyisreturnedtothegroundand
propulsionoccurs.
ApplicationTrial:
Toourknowledgethisstudywasthefirsttolookathowfatiguingactivities
contributetorunningsymmetry.Duringthe16x100sand1600mtrialssubjectswere
exertingmaximaleffortduetotheintervalsofeachtrial.Consideringthe16x100sand
1600mwerestatisticallysignificantforvelocityandsymmetryrespectivelywewereable
49
toinfluencedirectlyandindirectlyalterrunningsymmetry.Duringthe1600mbout,
velocitywasconsistentbetweenfirstandlast100mportionwhilesymmetryscore
doubled,2.106%.The16x100sshowedasignificantreductioninvelocity,~2.56km/h,
andanincreaseinsymmetryscore,0.731%,whichhadarelativelylowpvalueof0.062.
Althoughthechangeinsymmetryscoreswerenotstatisticallysignificantthelowp-value
supportsfurtherstudieswherevelocitycouldbebettercontrolled.Thedevelopmentof
increasedrunningasymmetryandchangeinvelocitiesisthoughttobetheresultof
musculaturebecomingfatiguedandlargermusclegroupsbeingrecruitedasthesmaller
musclegroupsfatigue.Thesesmallermusclegroupswouldbemusclesassociatedwithfine
motorcontrolcontributingtorunningtechnique.Alossoftechniquecanleadtoalterations
inrunningmechanicsultimatelyresultinginadifferencebetweenhowthebodywasbeing
loadedfromthebeginningofeachtrialtotheend.
Duringthejogtherewasasmallreductioninrunningsymmetry,0.156%,maygive
supportforawarm-upactivity.Thejogwasperformedataself-selectedspeedbelow40%
ofmaximaleffort.Ifawarm-upistopreparethebodythroughactivestretchingandmuscle
warming,thismayalsoreduceasubjectsrunningsymmetryscoreoffthesubject.Alimitto
thisexperimentwasthatsubjectperformedeachtrialonseparatedaysduetotheintensity
ofthe100sand1600m.
Althoughsomephysiologicalorpsychologicaldifferencesmayhavebeenpresentin
subjectsbetweendaysthetrialswereconductedinthesameweekminimizingthese
effects.FuturestudiescouldutilizeRPEscorestobetterunderstandthesepotentialsources
oferror.Studyinghowdifferentathleteswouldrespondtothesameexperimentcouldalso
changethefindings.Asprintermaymaintainmoreconsistentvelocitieswhileatrack
50
athletespecializinginthe1600mmaynotshowassevereofanasymmetrydevelopment
duetothespecificityoftrainingscheme.Findingsofthisnaturecangivecoachesdata
whichcanbeusedtoidentifypointsofraceswhereathletescanfocusonbeingmore
efficient.
CaseStudies:
Wewereabletodetectsignificantrunningsymmetryscoresdirectlyfollowingthe
subjectsleftfootbeingstruckbyanotherplayer.Thiscouldbeusedtodetect
musculoskeletalinjuryasshowninFigure14,whichwarrantsfurtherresearchpotentially
inathletesimmediatelyfollowingaconcussivegradeimpact.Wealsoshowedhow
symmetryscoresreducedthroughouttherehabilitationperiodandwerenearnormalas
theplayerwasclearedtoreturntoplay.ThisspeakshighlyofVirginiaTechsports
medicineteambutalsoshowsauseinunderstaffedclinics.Severalsubjectscanbe
monitoredsimultaneouslyandbecomparedacrosssuccessivedays.
WhenlookingatthesubjectrecoveringfromACLreconstructiondatainitiallylooks
irregular.Whendataiscomparedtotherehabilitationprescriptionthescoresbeginto
makemoresense.EarlyphasesofrehabfocusonregainingstrengthandgainingROM,
consideringthesubjectsdonotbegintoperformunassistedwalkinguntilthemiddle
phase,6weeks,intotheprescription.Thisperiodisrecordedassymmetryscoresfavoring
therightsideofmoderatemagnitude.Asthesubjectenterslatephase,morechallenging
intensitiesareencouragedleadingtohighersymmetryscores.Wewereabletocontinue
monitoringthesubjectpasttheinitialphysicaltherapyprescription.Thisisimportant
consideringpatientsaremostsusceptibletore-injuryuptoeightmonths
51
post-surgery[60].Sincemostinsurancecompanieswillnotapprovepatientstoattend
sessionspastacertaindateorallotmentsofsessionsthisgivespromisetowearables.If
thesepatientscoulddoactivitieswearinganaccelerometerthatuploadeddatatoa
databaseandinterpretedforthem,thentheycouldcontinuereceivingfeedbackastohow
they’rerehabilitationisprogressing.
DuringtheACLdatacollectionthereweretwo10-dayperiods,53-62and65-75,
whereoursystemwasdown.Thiswouldhavebeenkeydataforinterpretationstobemade
andutilizeacutevs.chronicratios.Furtherresearchshouldbedoneonsubjectsrecovering
frominjuriestoidentifypotentialriskfactorstore-injurysuchasexcessiveasymmetry.
Conclusions:
Consideringthefewstudiesutilizingtrunk-mountedaccelerometersourpurpose
wasfirsttovalidatetrunk-unitsagainstankle-unitsthenshowhowrunningsymmetry
varieswithfatigueandlastlyshowsomerealworldutilizationofsuchvariables.Similar
trendsbetweensymmetryscoresgeneratedfromtrunk-mountedandankle-mounted
accelerometerssupportedtheuseoftheSPIHPUunitforcollectingaccelerationdata.
Detectingachangeinrunningsymmetryduringvaryingfatigableactivitieshighlightsa
potentiallynewmetrictomeasureanathlete’shealth.Potentialusesinsettingslike
physicaltherapyclinicsarenumerousinprovidingfeedbackonhowrecoveryis
progressing.Trunk-mountedunitsallowforcollectionofdataacrossalargegroupof
athletesprovidinginformationtopersonnelonadaytodaybasis.
Futurestudiescouldidentifyhowrunningsymmetryvariesbetweentimesof
acceleration,steadystate,anddecelerationrunning.Theseperiodsofmovementmaygive
52
informationhelpfultogroupslikesprinterswhoarelookingtomaximizeefficiency.
Anotherareaofpotentialuseistheuseoftrunk-mountedaccelerometersforbalancetest
suchastheY-test.Thereisaneedformorequantitativewaystoassesssubjectsafter
concussiveblowsincontactsports.Teamsalreadyutilizingsuchproductsshowsa
potentialinevaluatingtheircapacitytomeasureposturalswayallowingforquickand
effectiveevaluationofplayers.
53
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Appendix
61
AnalysisofvariancetablesfortheValidationStudy
Variable–RunningSymmetry
Source
df
SS
MS
Subject
Condition
ConditionxSubject
Device
DevicexSubject
ConditionxDevice
Residual
Total
p
ES(η2)
106.5
241.5
7.1
56.6
81.0
5.0
3.7
34.0
0.7
1.3
<.001
0.292
0.240
0.028
0.005
SS
MS
F
p
ES(η2)
29.7
4.6
7.2
41.5
3.0
2.3
0.4
6.3
0.007
0.111
7 745.8
2 483.0
14
99.6
1
56.6
7 567.0
2
10.0
14
52.3
47 2014.1
Variable–RunningVelocity
Source
df
BetweenSubjects
Withinsubjects
Residual
Total
F
10
2
20
32
0.043
62
AnalysisofvariancetablesfortheApplicationStudy
Variable–RunningSymmetry
Source
df
SS
MS
Subject
Activity
ActivityxSubject
Interval
IntervalxSubject
ActivityxInterval
Residual
Total
15
2
30
1
15
2
30
95
42.0
44.6
182.6
25.1
36.0
20.6
86.7
437.6
Variable–RunningVelocity
Source
df
SS
Subject
Activity
ActivityxSubject
Interval
IntervalxSubject
ActivityxInterval
Residual
Total
15
39.1
2 5283.8
30
13.6
1
28.2
15
20.9
2
28.7
30
40.0
95 5574.2
F
p
ES(η2)
3.7
10.5
3.6
0.038
0.102
0.006
0.057
0.041
0.047
F
p
ES
2.6
2641.9 593.2
0.5
28.2 20.2
1.4
14.4 10.8
1.3
0.038
0.948
0.006
0.005
0.041
0.005
2.8
22.3
6.1
25.1
2.4
10.3
2.9
MS
63
InformedConsentDocuments
64
65
66
67
68
69
VITA
DavidJosephSaba
DavidwasborninNewportNewsVa.onMay111993toDaveandLisaandolder
brothertoAshley.AftermovingtoPittsburghPa.DavidattendedSetonLaSallehighschool
inMt.LebanonPa.whereheenjoyedparticipatingincrewandswimming.Followinghigh
schoolDavidattendedVirginiaPolytechnicInstituteandStateUniversitywherehemajored
inHumanNutrition,Foods,andExercise.Afteridentifyinganinterestinexercise
physiologyDaviddecidedtocontinuewithapost-bachelorprogramfocusingonsports
analyticsandhumanbiomechanics.David’smasterresearchlookedatidentifyingthe
capacityofapopulartrunk-mountedmonitoringsystemaswellashowrunningintensity
influencedgaitsymmetry.AftercompletinghismastersDavidwillattendtheSouthwest
CollegeofNaturopathicMedicinewherehehopestofocusonpainmanagementandsports
medicine.
70