title: Females recruit quadriceps faster than males at multiple knee flexion angles following a weight-bearing rotary perturbation.
abstract: OBJECTIVE
  To compare the effect of knee angle on muscle response times and neuromuscular recruitment patterns between sexes following a perturbation in single leg stance at 10 degrees, 20 degrees, and 30 degrees. We hypothesized that response times would be faster at lesser knee flexion angles and that females would recruit their quadriceps faster than males at all angles.
  
  
  METHODS
  A repeated-measures design.
  
  
  METHODS
  Motion analysis laboratory.
  
  
  METHODS
  Twenty (10 female; 10 male) healthy, recreationally active volunteers.
  
  
  METHODS
  A rotary perturbation in single leg stance.
  
  
  METHODS
  Response times of the medial and lateral quadriceps, hamstrings, and gastrocnemius.
  
  
  RESULTS
  There was a trend toward faster response times for all muscles closer toward extension. A consistent neuromuscular recruitment pattern for both males and females was evident for each knee angle tested. Females, however, contracted their quadriceps faster than males at all knee flexion angles.
  
  
  CONCLUSIONS
  Small changes in knee angle near extension do not alter muscle response times and hence neuromuscular recruitment patterns in males and females. Regardless of knee flexion angle, following a perturbation in single leg stance, females contract their quadriceps faster than males.
  
  
  CONCLUSIONS
  Earlier contraction of the quadriceps in females may increase anterior tibial translation and hence anterior cruciate ligament strain, thereby heightening injury risk.
authors.affiliation: Department of Physical Therapy, Rangos School of Health Sciences, Duquesne University, Pittsburgh, PA 15282, USA. carcia@duq.edu
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Carcia
authors.forename: Sandra J
authors.initials: SJ
authors.lastname: Shultz
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Granata
authors.forename: David H
authors.initials: DH
authors.lastname: Perrin
authors.forename: Robroy L
authors.initials: RL
authors.lastname: Martin
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D007719:Knee Joint; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D011336:Probability; D011446:Prospective Studies; D016059:Range of Motion, Articular / Q000502:physiology*; D012016:Reference Values; D012680:Sensitivity and Specificity; D012737:Sex Factors; D013314:Stress, Mechanical; D013996:Time and Motion Studies; D016474:Weight-Bearing