简介：Muscleactionsaretypicallydividedinto3categories：concentric,isometric,andeccentric.Anactivemusclethatisshorteningandproducespositivemechanicalworkissaidtoworkconcentrically;anactivemusclethatisnotchangingitslength,andthusdoesnotproducenetwork,issaidtoworkisometrically;andanactivemusclethatiselongatedbyexternalforces,andthusabsorbswork,orproducesnegativework,issaidtoworkeccentrically．1

简介：Eccentricphoto-refractionusuallyisusedasearlyeyesightdiagnostictestofinfantsandsmallchildren.Unlikecurrentlyapprovedgeometricalopticalmodelofeccentricphotorefractometer,thecrescentformationandthelight-intensitydistributioninthepupilimageofamyopiceyeareanalyzedbyFourieropticswiththeassumptionofanisotropicscatteringretina.Inthecaseoflittlecircularlightsourceandrectangularslit,thesimulationresultsofdifferentmyopicdioptersareobtainedbygeometricalopticaltheoryandFourieropticsrespectively.ItisfoundthatthesimulationresultsbyFourieropticsaresimilarasthoseobtainedbygeometricaloptics,andallsimulationsarealmostcorrespondingtotheexperimentalresult.Theresultdemonstratesthatthenewmethodpresentedhereisfeasible.

简介：Theforcedlengtheningofanactivatedskeletalmusclehasbeentermedaneccentriccontraction（EC）.ThisreviewhighlightsthemechanicallyuniquenatureoftheECandfocusesonthespecificdisruptionofproteinswithinthecellknownascytoskeletalproteins.Themajorintermediatefilamentcytoskeletalprotein,desmin,hasbeenthefocusofworkinthisareabecausechangestodesminoccurwithinminutesofECsandbecausedesminhasbeenshowntoplaybothamechanicalandbiologicroleinamuscle＇sresponsetoEC.Itishopedthatthesetypesofstudieswillassistindecreasingtheincidenceofmuscleinjuryinathletesandfacilitatingthedevelopmentofnewtherapiestotreatmuscleinjuries.

简介：IntheirrecentpapersintheJournalofSportandHealthScienceonhamstringinjuriesinsprinting,~(1,2)andtheircorrespondingcommentariesoneachother'sresearch,3,4Yuetal.andLiuetal.proposeddifferentviewsofthemechanismsofmuscleinjuriesingeneral,andhamstringinjuriesinsprintingspecifically.WhileYuetal.~(1,3)arguedthatmuscleinjuriesareprimarily,ifnotexclusively,causedbymusclestrainmagnitudeineccentriccontractions,andthushamstringinjuriesoccurprimarilyat

简介：Duringeccentriccontractions,muscularforceproductioncapacityisenhancedcomparedtoisometriccontractions.Althoughthisiswellacceptedintermsofmusclemechanics,maximalvoluntaryeccentriccontractionsareassociatedwithneuralinhibitionthatpreventsincreasedforceproductionofinvivohumanmuscles.However,becauseitwasshownthatmaximalvoluntaryeccentricforcescanexceedmaximumisometricforcesbyafactorof1.2-1.4,thisreviewfocusesonthequestionofwhethertheabsenteccentricforceenhancement,asobservedinmanystudies,canunambiguouslybeattributedtoaninherentneuralinhibition.First,wedemonstratethatparticipantfamiliarization,preload,andfasciclebehaviorarecrucialfactorsinfluencingmaximalvoluntaryeccentricforceproduction.Second,weshowthatmusclemechanicssuchasmusclelength,lengtheningvelocity,andstretchamplitudeinteractwhenitcomestomaximalvoluntaryeccentricforceproduction.Finally,wediscussthedivergingfindingsonneuralinhibitionduringmaximalvoluntaryeccentriccontractions.Becausetherewasnoinhibitionofthemajormotorpathwaysinthepresenceofenhancedmaximalvoluntaryeccentricforces,furtherresearchisneededtotesttheconceptofneuralinhibitionandtounderstandwhymaximalvoluntaryforceproductionisreducedcomparedtotheforcecapacityofisolatedmusclepreparations.

简介：Thepeculiarattributesofmusclesthatarestretchedwhenactivehavebeennotedfornearlyacentury.Understandably,thefocusofmusclephysiologyhasbeenprimarilyonshorteningandisometriccontractions,aseloquentlyrevealedbyA.V.Hillandsubsequentlybyhisstudents.WhentheslidingfilamenttheorywasintroducedbyA.F.HuxleyandH.E.Huxley,itwasarelativelysimpletasktolinkHill＇smechanicalobservationstotheactionsofthecrossbridgesduringtheseshorteningandisometriccontractions.Incontrast,lengtheningoreccentriccontractionshaveremainedsomewhatenigmatic.Dismissedasnecessarilycausingmuscledamage,eccentriccontractionshavebeenmuchmoredifficulttofitintothecross-bridgetheory.Therelativelyrecentdiscoveryofthegiantelasticsarcomericfilamenttitinhasthrustapreviouslymissingelementintoanydiscussionofmusclefunction,inparticularduringactivestretch.Indeed,theunexpectedcontributionofgiantelasticproteinstomusclecontractilefunctionishighlightedbyrecentdiscoveriesthattwitchin-actininteractionsareresponsibleforthe＂catch＂propertyofinvertebratemuscle.Inthisreview,weexamineseveralcurrenttheoriesthathavebeenproposedtoaccountforthepropertiesofmuscleduringeccentriccontraction.Weaskhowwelleachoftheseexplainsexistingdataandhowanelasticfilamentcanbeincorporatedintotheslidingfilamentmodel.Finally,wereviewtheincreasingbodyofevidenceforthebenefitsofincludingeccentriccontractionsintoaprogramofmusclerehabilitationandstrengthening.

简介：Itiswellacknowledgedthatmusclesthatareelongatedwhileactivated（i.e.,eccentricmuscleaction）arestrongerandrequirelessenergy（perunitofforce）thanmusclesthatareshortening（i.e.,concentriccontraction）orthatremainataconstantlength（i.e.,isometriccontraction）.Althoughthecross-bridgetheoryofmusclecontractionprovidesagoodexplanationfortheincreaseinforceinactivemusclelengthening,itdoesnotexplaintheresidualincreaseinforcefollowingactivelengthening（residualforceenhancement）,orexceptwithadditionalassumptions,thereducedmetabolicrequirementofmuscleduringandfollowingactivestretch.Asidefromthecross-bridgetheory,2otherprimaryexplanationsforthemechanicalpropertiesofactivelystretchedmuscleshaveemerged：（1）theso-calledsarcomerelengthnonuniformitytheoryand（2）theengagementofapassivestructuralelementtheory.Inthisarticle,thesetheoriesarediscussed,anditisshownthatthelastofthese—theengagementofapassivestructuralelementineccentricmuscleaction—offersasimpleandcompleteexplanationformanyhithertounexplainedobservationsinactivelylengtheningmuscle.Althoughbynomeansfullyproven,thetheoryhasgreatappealforitssimplicityandbeauty,andevenifovertimeitisshowntobewrong,itneverthelessformsausefulframeworkfordirecthypothesistesting.

简介：AnanalyticalsolutionofvelocityprofilesforNon-Newtonianfluidsdescribedbythepower-lawequationinaxiallaminarflowthrougheccentricannuliispresented.Theexpressionsoflimitvelocitiesandcontoursofequalvelocityareobtained.Themainapproaches,claimedinthispaper,arethatthetermTrz/rinthedifferentialequationofflowandthenon-symmetricalvelocitydistributionaboutthegeometriccenteroftheradialclearanceareconsidered.

简介：Fibre-reinforcedpolymer(FRP)compositeswerewidelyutilizedincivilengineeringstructuresastheretrofitofreinforcedconcrete(RC)columns.TodesignFRPjacketssafelyandeconomically,thebehaviourofsuchcolumnsshouldbepredictedfirst.ThispaperisconcernedwiththeanalysisandbehaviourofFRP-confinedRCcircularandrectangularshortcol-umnssubjectedtoeccentricloading.Asimpledesign-orientedstress-strainmodelforFRP-confinedconcreteinasectionanalysiswasfirstproposed.Theaccuracywasthenprovedbytwotestdata.Followingthat,aparametricstudyincludingamountofFRPconfinement,FRPstraincapacity,unconfinedconcretestrengthandshapeofcolumnsectionisprovided.Someconclusionswereobtainedattheendofthepaper.TheworkherewillprovideacomprehensiveunderstandingofthebehaviourofFRP-confinedconcretecolumns.Thesimplicityofthemodelalsoenablesasimpleequivalentstressblocktobedevelopedfordirectuseinpracticaldesign.

简介：Background：Theisometricsteady-statefollowingactivelengtheningisassociatedwithgreatertorqueproductionandloweractivation,asmeasuredbyelectromyographicactivity（EMG）,incomparisonwithapurelyisometriccontraction（ISO）atthesamejointangle.Thisphenomenonistermedresidualforceenhancement（RFE）.WhiletherehasbeenagreatdealofresearchinvestigatingthebasicmechanismsofRFE,littleworkhasbeenperformedtounderstandtheeverydayrelevanceofRFE.ThepurposeofthisstudywastoinvestigatewhetherneuromuscularcontrolstrategiesdifferbetweenISOandRFEbymeasuringtorquesteadinessofthehumanankleplantarflexors.Methods：FollowingISOmaximalvoluntarycontractionsin12males（25±4years）,anactivelengtheningcontractionwasperformedat15°/sovera30°ankleexcursion,endingatthesamejointangleasISO（5°dorsiflexion;RFE）.SurfaceEMGofthetibialisanteriorandsoleusmuscleswasrecordedduringalltasks.Torquesteadinesswasdeterminedasthestandarddeviation（SD）andcoefficientofvariation（CV）ofthetorquetraceintheISOandRFEconditionduringactivation-matching（20%and60%integratedEMG）andtorque-matching（20%and60%maximalvoluntarycontraction）experiments.Two-tailed,pairedttestswereused,withinsubjects,todeterminethepresenceofRFE/activationreduction（AR）andwhethertherewasadifferenceintorquesteadinessbetweenISOandRFEconditions.Results：Duringthemaximalandsubmaximalconditions,therewas5%-9%RFEwitha9%-11%AR（p〈0.05）,respectively,withnodifferenceinantagonistcoactivationbetweenRFEandISO（p〉0.05）.TherewerenodifferencesinSDandCVofthetorquetraceforthe20%and60%activation-matchingorthe60%andmaximaltorque-matchingtrialsineithertheRFEorISOcondition（p〉0.05）.Duringthe20%torquematchingtrial,therewere～37%highervaluesforSDandCVintheRFEascomparedwiththeISOcondition（p〈0.05）.Asignificantmoderate-to-strongnegativerelatio

简介：Neuromuscularactivityissuppressedduringmaximaleccentric（ECC）musclecontractioninuntrainedsubjectsowingtoattenuatedlevelsofcentralactivationandreducedspinalmotorneuron（MN）excitabilityindicatedbyreducedelectromyographysignalamplitude,diminishedevokedH-reflexresponses,increasedautogenicMNinhibition,anddecreasedexcitabilityindescendingcorticospinalmotorpathways.MaximumECCmuscleforcerecordedduringmaximalvoluntarycontractioncanbeincreasedbysuperimposedelectricalmusclestimulationonlyinuntrainedindividualsandnotintrainedstrengthathletes,indicatingthatthesuppressioninMNactivationismodifiablebyresistancetraining.Insupportofthisnotion,maximumECCmusclestrengthcanbeincreasedbyuseofheavy-loadresistancetrainingowingtoaremovedordiminishedsuppressioninneuromuscularactivity.Prolonged（weekstomonths）ofheavy-loadresistancetrainingresultsinincreasedH-reflexandV-waveresponsesduringmaximalECCmuscleactionsalongwithmarkedgainsinmaximalECCmusclestrength,indicatingincreasedexcitabilityofspinalMNs,decreasedpresynapticand/orpostsynapticMNinhibition,andelevateddescendingmotordrive.Notably,theuseofsupramaximalECCresistancetrainingcanleadtoselectivelyelevatedV-waveresponsesduringmaximalECCcontraction,demonstratingthatadaptivechangesinspinalcircuitryfunctionand/orgainsindescendingmotordrivecanbeachievedduringmaximalECCcontractioninresponsetoheavy-loadresistancetraining.

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