DTIC ADA541324: The Role of Lower Extremity Joint Powers in Successful Stair Ambulation

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Gait & Posture
journal homepage: www.elsevier.com/locate/gaitpost
Short Communication
The role of lower extremity joint powers in successful stair ambulation
Jason M. Wilken*, Emily H. Sinitski, Elizabeth A. Bagg
MilitaryPerformanceLaboratory,DepartmentofOrthopedicsandRehabilitation,CenterfortheIntrepid,BrookeArmyMedicalCenter,FortSamHouston,TX,USA
AR TI CLE I NFO ABS TRA CT
Articlehistory: Ascendingstairsisanimportantfunctionalactivitythatisaffectedbylowerextremitypathology
Received30June2010 includingamputation.Althoughseveralstudieshavedemonstratedstairascentismorechallengingthan
Receivedinrevisedform9March2011 levelgroundwalking,ourunderstandingofthemechanicsremainslimited.Thepurposeofthisstudy
Accepted11March2011
wastodeterminetheassociationbetweenlowerextremityjointpowergenerationandverticalCOM
acceleration(COM )duringstairascent.Twenty-twohealthyindividualsunderwentabiomechanical
A
Keywords: gaitassessmentwhilewalkingupa16-stepinstrumentedstaircase.Theassociationbetweenthepeak
Stairs
jointpowersandpeakCOM duringstancewereassessedwithrespecttotimingandmagnitude.With
Plantarflexors A
respecttotiming,peakanklejointpowerwashighlycorrelatedwithpeakCOM (R2=0.93),whilepeak
Anklepower A
knee and hip joint powers demonstrated limited association with COM (R2=0.41 and 0.08,
Centerofmass A
respectively).OnlythemagnitudeofpeakanklepowerwasassociatedwithpeakCOM (R2=0.3).
A
SignificanttemporalandmagnitudeassociationsbetweenpeakanklejointpowerandpeakCOM
A
suggest ankle power is a key contributor to COM . Although peak knee joint power and COM are
A A
temporallyassociated,theassociationisweakerandtheoccurrenceofpeakjointkneepowerisnearly
10%afterpeakCOM ,suggestingkneejointpowerplaysalesserroleinCOM .Thesecombinedfindings
A A
indicatetheroleoftraillimbankleplantarflexorsshouldberecognizedinthestairascentcycledefinition
anddemonstratethepotentialimportanceofapowergeneratedbytheankleplantarflexorstonormalize
stairascentperformancefollowinglowerextremityamputation.
PublishedbyElsevierB.V.
1. Introduction contributionsoflowerextremityjointpowers,toincluderelative
timingandmagnitudehavenotbeenpreviouslyexplored.
Ascendingstairsisacommonandimportantfunctionalactivity The aim of this study was to investigate the role of lower
thatisaffectedbyarangeofconditionsincludinglowerextremity extremitymusculatureonelevationofthebody,byassessingthe
amputation [1]. Although several studies have demonstrated temporal and magnitude relationships between vertical COM
ascending stairs is more challenging than level ground walking, acceleration (COM ) and lower extremity joint powers. We
A
and performance is limited by pathology, our understanding of hypothesizedthetraillimbankleplantarflexorsplayanimportant
stairascentmechanicsremainslimited[1–4]. rolegiventheirrecognizedimportanceintheperformanceofother
As with early definitions of the gait cycle for level ground ambulatoryactivities[7].
walking,thestairascent(SA)gaitcycleissubdividedintophases
based on the current understanding of the role of the limb in
successful activity performance. The stair ascent cycle definition 2. Methods
firstproposedbyMcFadyenetal.[5]includestheactionsofweight
acceptance,pull-up,forwardcontinuance,footclearance,andfoot Twenty-twohealthyindividuals(13male,9female)between
placement and emphasized the role of the leading limb knee theages18and45withnocurrentpainorhistoryofmajorlower
extensorsinpullingtheindividualupthestep[5].Thisframework extremityinjuryvolunteeredtoparticipateinthisstudy.Subjects
was modified by Zachazewski et al. [6] by replacing the pull-up wereonaverage21(cid:2)4yearsoldwithameanbodymassandheight
phasewiththetermverticalthrust.Althoughtheroleofthelead of 74(cid:2)15kg and 1.71(cid:2)0.08m, respectively. Following written
limbinsuccessfulstairascenthasbeenemphasized,therelative informed consent, all subjects participated in a biomechanical gait
assessmentduringstairascentwalking.Atotalof55markerswere
usedtotrackwholebodymotionwhilesubjectswalkedupa16-step
instrumentedstaircase(AMTI,Inc.,Watertown,MA)atacontrolled
cadenceof80stepsperminute(Fig.1).Kinematicdatawerecollected
* Correspondingauthor.Tel.:[phone];fax:[phone].
at120Hzusinga26cameraoptoelectronicmotioncapturesystem
E-mailaddresses:[email protected],[email protected]
(J.M.Wilken). (MotionAnalysisCorp.,SantaRosa,CA).
0966-6362/$–seefrontmatter.PublishedbyElsevierB.V.
doi:10.1016/j.gaitpost.2011.03.015
Pleasecitethisarticleinpressas:WilkenJM,etal.Theroleoflowerextremityjointpowersinsuccessfulstairambulation.GaitPosture
(2011),doi:10.1016/j.gaitpost.2011.03.015
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4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER
The Role Of Lower Extremity Joint Powers In Successful Stair Ambulation
5b. GRANT NUMBER
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7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING
Brooke Army Medical Center,Military ORGANIZATION REPORT
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PerformanceLaboratory,DepartmentofOrthopedicsandRehabilitation,,Fort Sam
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Article in Press,11 March 2011
14. ABSTRACT

15. SUBJECT TERMS
16. SECURITY CLASSIFICATION OF: 17. 18. 19a. NAME OF
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2 J.M.Wilkenetal./Gait&Posturexxx(2011)xxx–xxx
3
Ankle Power
g) Knee Power
W/k 2 Hip Power
er ( 1
w
o
P
0
6
Vertical COM
2s) 4 Acceleration
m/
n ( 2
o
ati 0
cerl −2
c
A
−4

0 10 20 30 40 50 60 70 80 90 100
% Gait Cycle
Weight Acceptance Forward Continuance Foot Clearance Foot Placement
Pull−up Push−up
Fig.1.Photographofinstrumentedstaircase.
Fig.2.Meanjointpowersandverticalcenterofmassaccelerationforallsubjects.
Textatthebottomofthefigureillustratesstairascentgaitcyclephasesincluding
Segmentalmarkersand20anatomicallandmarkswereusedto theproposedpush-upphaseduringlatestance.Theverticalgreybandsrepresent
createa13segmentmodelconsistingoftwofeet,twoshanks,two thedoublelimbsupportphaseofthegaitcycle.Thecontributionofpeakkneeand
hippowersduringearlystancewereassessedinrelationtothefirstpeakinvertical
thighs,twoarms,twoforearms,pelvis,trunk,andheadbasedon
centerofmassacceleration,whilethepeakanklepowerattheendofstancewas
International Society of Biomechanics standards. Segmental assessedrelativetothesecondpeakinverticalcenterofmassacceleration.
masseswereassignedbasedontotalbodyweightandDempster’s
anthropometric data [8]. Kinetic data were collected at 1200Hz
usinganinterlacedstaircasedesignontwoforceplates(AMTI,Inc., 3. Results
Watertown, MA) similar to that described by Della Croce and
Bonato[9].Kineticsfromstepsfiveandsevenwererecordedusing Fig. 2 displays the mean lower extremity joint powers and
thefirstforceplateandstepssixandeightwererecordedusingthe COM during stair ascent for all subjects. The center of mass
A
secondforceplate.Fivetrialswithunobstructedmarkerdataand acceleratesverticallytwiceduringtheSAgaitcyclewithpeaksat
clean foot contact were recorded for each subject. Marker and 6(cid:2)1%and56(cid:2)1%oftheSAgaitcycle.Duringearlystance,theleg
analogdatacollectedusingEVaRTsoftware(MotionAnalysisCorp., acts as the lead limb and generates positive power at the knee
Santa Rosa, CA) were exported and analyzed using Visual3D (C- (15(cid:2)2%cycle)andhip(8(cid:2)4%cycle),whichcontributestothefirst
Motion Inc., Germantown, MD) and Matlab (The Mathworks, peak COM . During late stance, the leg acts as the trail limb and
A
Natick,MA)software.Wholebodycenterofmasswascalculatedas generatespowerattheankle(57(cid:2)1%cycle),whichcontributesto
theweightedaverageofeachsegment.Centerofmassacceleration thesecondpeakCOM .
A
was calculated as the second derivative of the center of mass ThetimingofpeakanklejointpowerandpeakCOM (Fig.3A)
A
position using a 3-point difference formula. Calculated joint duringlatestancearesignificantlycorrelated(R2=0.93,p<0.01).
powersandverticalCOMacceleration(COM )werenormalizedto The timing of peak knee joint power and peak COM (Fig. 3B)
A A
100%ofSAgaitcycle. duringearlystancedemonstratedaR2valuelowerthanobserved
APearsonproductmomentcorrelationcoefficientwasusedto for ankle joint power (R2=0.41, p<0.01). The relationship
determinetheassociationbetweenthetimingofpeakjointpowers betweenhipjointpowertimingandpeakCOM (Fig.3C)timing
A
andpeakCOM ,andbetweenthemagnitudevaluesforpeakjoint during early stance was not significantly correlated (R2=0.08,
A
powersandpeakCOM . p=0.21).
A
Timing Relationship Between Peak
Vertical COM Acceleration and Peak Joint Powers
A Ankle B Knee C Hip
60 10 10
ation yR 2= =0 .08.99x3 + 4.87 9 yR 2= =0 .04.54x1 − 1.23 9 yR 2= =0 .00.90x8 + 4.85
elere) 58 8 8
ccycl 7 7
M Aait c 56 6 6
Og
k C(% 54 5 5
ea 4 4
P
52 3 3
52 54 56 58 60 12 14 16 18 0 5 10 15
Peak Joint Power (% gait cycle)
Fig.3.Therelationshipbetweenthetimingofpeakanklejointpowerandverticalcenterofmassacceleration(A),therelationshipbetweenthetimingofpeakkneejoint
powerandverticalcenterofmassacceleration(B),andtherelationshipbetweenthetimingofpeakhipjointpowerandverticalcenterofmassacceleration(C).
Pleasecitethisarticleinpressas:WilkenJM,etal.Theroleoflowerextremityjointpowersinsuccessfulstairambulation.GaitPosture
(2011),doi:10.1016/j.gaitpost.2011.03.015
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J.M.Wilkenetal./Gait&Posturexxx(2011)xxx–xxx 3
ThemagnitudeofpeakanklejointpowerandpeakCOM were current study suggest the importance of ankle plantarflexors in
A
significantlyassociatedwithanR2valueof0.3(p<0.01).Thepeak successful stair ascent and warrant further investigation. An
kneeandhipjointpowermagnitudewerenotassociatedwithpeak improved understanding of the mechanics of stair ascent has
verticalCOM magnitude(R2<0.13,p<0.16). potentialimplicationsforthedevelopmentandtestingofpowered
A
prostheticandorthoticdevicesdesignedtofacilitatethenormali-
4. Discussion zationofstairperformancethroughtherestorationofanklepower.
Thecurrentinvestigationwasconductedtobetterunderstand Acknowledgement
theroleoflowerextremityjointpowersinsuccessfulstairascent.
The results of this study suggest the ankle plantarflexors Supportprovided by theMilitaryAmputeeResearch Program
contributesubstantiallytoverticalaccelerationofthebodyduring (toJMW).
stair ascent. Peak ankle power is similar in timing and relative
magnitude to peak COM . Although peak ankle and knee joint
A Conflictofintereststatement
powerarebothtemporallyassociatedwithCOM ,peakanklejoint
A
power and peak COM events occur within 1% of SA gait cycle
A Theauthorshavenoconflictsofinteresttoreport.
whereas peak knee power occurs 9% of SA gait cycle after peak
COM .Duringthefirsthalfofstancethereissignificantpositive
A References
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A
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Pleasecitethisarticleinpressas:WilkenJM,etal.Theroleoflowerextremityjointpowersinsuccessfulstairambulation.GaitPosture
(2011),doi:10.1016/j.gaitpost.2011.03.015