简介：Thehumanfootisaverycomplexstructurecomprisingnumerousbones,muscles,ligamentsandsynovialjoints.Astheonlycomponentincontactwiththeground,thefootcomplexdeliversavarietyofbiomechanicalfunctionsduringhumanlocomotion,e.g.bodysupportandpropulsion,stabilitymaintenanceandimpactabsorption.Theseneedthehumanfoottoberigidanddampedtotransmitgroundreactionforcestotheupperbodyandmaintainbodystability,andalsotobecompliantandresilienttomoderateriskyimpactsandsaveenergy.Howdoesthehumanfootachievetheseapparentconflictingfunctions?Inthisstudy,weproposeaphase-dependenthypothesisfortheoveralllocomotorfunctionsofthehumanfootcomplexbasedonin-vivomeasurementsofhumannaturalgaitandsimulationresultsofamathematicalfootmodel.Wepropsethatfootfunctionsarehighlydependentongaitphase,whichisamajorcharacteristicsofhumanlocomotion.Inearlystancejustafterheelstrike,thefootmainlyworksasashockabsorberbymoderatinghighimpactsusingtheviscouselasticheelpadinbothverticalandhorizontaldirections.Inmid-stancephase(~80%ofstancephase),thefootcomplexcanbeconsideredasaspringyrocker,reservingexternalmechanicalworkusingthefootarchwhilstmovinggroundcontactpointforwardalongacurvedpathtomaintainbodystability.Inlatestanceafterheeloff,thefootcomplexmainlyservesasaforcemodulatorlikeagearbox,modulatingeffectivemechanicaladvantagesofankleplantiflexormusclesusingmetatarsal-phalangealjoints.Asoundunderstandingofhowdiversefunctionsareimplementedinasimplefootsegmentduringhumanlocomotionmightbeusefultogaininsightintotheoverallfootlocomotorfunctionsandhencetofacilitateclinicaldiagnosis,rehabilitationproductdesignandhumanoidrobotdevelopment.

简介：Theobjectiveofthisstudyistoinvestigatethebiomechanicalfunctionsofthehumanankle-tootcomplexduringthestancephaseofwalking.Thethree-dimensional(3D)gaitmeasurementwasconductedbyusinga3Dinfraredmulti-camerasystemandaforceplatearraytorecordtheGroundReactionForces(GRF)andsegmentalmotionssimultaneously.Theankle-footcomplexwasmodelledasafour-segmentsystem,connectedbythreejoints:talocruraljoint,sub-talarjointandmetatarsophalangealjoint.Thesubject-specificjointorientationsandlocationsweredeterminedusingafunctionaljointmethodbasedontheparticleswarmoptimisationalgorithm.TheGRFmomentarmsandjointmomentsactingaroundthetalocruralandsub-talarjointswerecalculatedovertheentirestancephase.Theestimatedtalocruralandsub-talarjointlocationsshownoticeableobliquity.Thekinematicandkineticresultsstronglysuggestthatthehumanankle-footcomplexworksasamechanicalmechanismwithtwodifferentconfigurationsinstancephaseofwalking.TheseleadtoasignificantdecreaseintheGRFmomentarmstherebyincreasingtheeffectivemechanicaladvantagesoftheankleplantarflexormuscles.Thisreconfigurablemechanismenhancesmuscleeffectivenessduringlocomotionbymodulatingthegearratiooftheankleplantarflexormusclesinstance.Thisstudyalsorevealsmanyfactorsmaycontributetothelocomotorfunctionofthehumanankle-footcomplex,whichincludenotonlyitsre-configurablestructure,butalsoitsobliquelyarrangedjoints,thecharacteristicheel-to-toeCentreofPressure(COP)motionandalsothemediallyactingGRFpattern.Althoughthehumanankle-footstructureisimmenselycomplex,itseemsthatitsconfigurationandeachconstitutivecomponentarewelltunedtomaximiselocomotorefficiencyandalsotominimiseriskofinjury.Thisresultwouldadvanceourunderstandingofthelocomotorfunctionoftheankle-footcomplex,andalsotheintrinsicdesignoftheankle-footmusculoskeletalstructure.Moreover,this