Background：Thesteady-stateincreaseinmuscleforcegeneratingpotentialfollowingalengtheningcontractioniscalledresidualforceenhancement（RFE）.Inthisstudy,weaimedtotestfordifferencesintorque,electromyographicactivity（EMG）,andtheassociatedneuromuscularefficiency（NME）betweenisometricvoluntarycontractionsofelbowflexorsprecededandnotprecededbyalengtheningcontraction.Thedependenceofsuchdifferenceson（i）stretchamplitude,（ii）theregionoftheforce-length（FxL）relationshipwherecontractionoccurs,and（iii）theinpidual＇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%oftheinterinpidualvariabilityintorquegeneratingpotentialchangeinresponsetoactivestretchingwasaccountedforbydifferencesin（negative）workcapacitybetweensubjects.Conclusion：Ourresultssuggestthat（i）RFEcontributesto＂flatten＂theelbowflexortorque-anglerela
