简介:Background:Thesteady-stateincreaseinmuscleforcegeneratingpotentialfollowingalengtheningcontractioniscalledresidualforceenhancement(RFE).Inthisstudy,weaimedtotestfordifferencesintorque,electromyographicactivity(EMG),andtheassociatedneuromuscularefficiency(NME)betweenisometricvoluntarycontractionsofelbowflexorsprecededandnotprecededbyalengtheningcontraction.Thedependenceofsuchdifferenceson(i)stretchamplitude,(ii)theregionoftheforce-length(FxL)relationshipwherecontractionoccurs,and(iii)theindividual'sabilitytoproduce(negative)workduringthestretchwasinvestigated.Methods:Sixteenhealthyadultsparticipatedinthestudy.Elbowflexortorque,angle,andbicepsbrachiiEMGforpurelyisometriccontractions(referencecontractions)andforisometriccontractionsprecededbyactivestretchesof20°and40°weremeasuredattheascending,plateau,anddescendingregionsofsubject-specificFxLcurves.Allcontractionswereperformedinanisokineticdynamometer.Two-factor(stretch×FxLregion)repeatedmeasuresanalysisofvarianceANOVAswasusedtoanalyzetheeffectofactivestretchonEMG,torque,andNMEacrossconditions.Therelationshipsbetweenmechanicalworkduringstretch-calculatedasthetorque-angulardisplacementintegral-andthechangesinEMG,torque,andNMEwereanalyzedusingPearsoncorrelation.Results:Ingeneral,torque,EMG,andNMEfollowingactivestretchesdifferedfromthevaluesobservedforthepurelyisometricreferencecontractions.WhilealthoughthedetailedeffectsofactivestretchontorqueandEMGdifferedbetweenregionsoftheFxLrelationship,NMEincreasedbyabout19%forallmusclelengths.Upto30%oftheinterindividualvariabilityintorquegeneratingpotentialchangeinresponsetoactivestretchingwasaccountedforbydifferencesin(negative)workcapacitybetweensubjects.Conclusion:Ourresultssuggestthat(i)RFEcontributesto"flatten"theelbowflexortorque-anglerela
简介:Thereisadearthofinformationaboutthedistributionoftraceelementsinkerogenfromshalerocksdespiteseveralreportsontraceelementcompositioninmanyshalesamples.Inthisstudy,traceelementsinshalerocksandtheirresidualkerogensweredeterminedbyinductivelycoupledplasma–massspectrometry.Theresultsfromthisstudyshowredox-sensitiveelementsrelativelyconcentratedinthekerogensascomparedtotheshales.Thismaybeprimarilyduetotheadsorptionandcomplexationabilityofkerogen,whichenablesenrichmentinNi,Co,Cu,andZn.Fortherareearthelements(REEs),distinctdistributioncharacteristicswereobservedforshalesdominatedbyterrigenousmineralsandtheirkerogencounterparts.However,shaleswithlessinputofterrigenousmineralsshowedsimilarREEdistributionpatternstotheirresidualkerogen.ItisspeculatedthatthedistributionpatternsoftheREEsinshalesandkerogensmaybesourcerelated.