title: Sex differences in blood flow restricted isotonic knee extensions to fatigue.
abstract: OBJECTIVE
  It has been shown that females have greater muscular endurance than males and that this advantage is eliminated when blood flow is restricted. It is unknown if sex differences in dynamic endurance exist during low-load blood flow restricted (BFR) resistance exercise. The purpose of this study was to investigate sex differences in quadriceps femoris fatigability during isotonic knee extension exercise coupled with a blood flow restriction.
  
  
  METHODS
  Ten males and ten females completed three sets of low-load isotonic knee extension exercises (20% of peak torque) to volitional failure under two conditions: blood flow restricted (BFR) and non-restricted free flow (FF). The number of repetitions, exercise volume, post-exercise strength loss and surface electromyography (EMG) were measured.
  
  
  RESULTS
  Females performed more repetitions than males in the FF (252±37 vs. 112±17 repetitions; P<0.01) and BFR conditions (165±29 vs. 79±8 repetitions; P<0.01). Both sexes performed ~30% fewer repetitions during the BFR condition. MVC torque decreased approximately 37% following both conditions (P<0.01) and EMG activity increased (P<0.05) during the exercise bouts.
  
  
  CONCLUSIONS
  Similar fatigue characteristics were evident in FF and BFR conditions for both sexes, and females demonstrated greater endurance, as determined by the number of repetitions completed, in both conditions. It may be beneficial to increase the relative exercise load for females in order to decrease the time under BFR.
authors.affiliation: Department of Kinesiology, University of New Hampshire, Durham, NH, USA - summer.cook@unh.edu.
authors.forename: K E
authors.initials: KE
authors.lastname: Labarbera
authors.forename: B G
authors.initials: BG
authors.lastname: Murphy
authors.forename: D P
authors.initials: DP
authors.lastname: Laroche
authors.forename: S B
authors.initials: SB
authors.lastname: Cook
mesh_terms: D000293:Adolescent; D000328:Adult; D004576:Electromyography; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007551:Isotonic Contraction / Q000502:physiology*; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D052097:Quadriceps Muscle / Q000098:blood supply* / Q000502:physiology; D012039:Regional Blood Flow / Q000502:physiology*; D055070:Resistance Training / Q000379:methods*; D055815:Young Adult