title: A preliminary multifactorial approach describing the relationships among lower extremity alignment, hip muscle activation, and lower extremity joint excursion.
abstract: BACKGROUND
  Multiple factors have been suggested to increase the risk of faulty dynamic alignments that predict noncontact anterior cruciate ligament injury. Few researchers have examined this relationship using an integrated, multifactorial approach.
  
  
  OBJECTIVE
  To describe the relationship among static lower extremity alignment (LEA), hip muscle activation, and hip and knee motion during a single-leg squat.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Research laboratory.
  
  
  METHODS
  Thirty men (age= 23.9± 3.6 years, height =178.5± 9.9 cm, mass= 82.0± 14.1 kg) and 30 women (age= 22.2± 2.6 years, height= 162.4± 6.3 cm, mass= 60.3± 8.1 kg).
  
  
  METHODS
  Pelvic angle, femoral anteversion, quadriceps angle, tibiofemoral angle, and genu recurvatum were measured to the nearest degree; navicular drop was measured to the nearest millimeter. The average root mean square amplitude of the gluteus medius and maximus muscles was assessed during the single-leg squat and normalized to the peak root mean square value during maximal contractions for each muscle. Kinematic data of hip and knee were also assessed during the single-leg squat. Structural equation modeling was used to describe the relationships among static LEA, hip muscle activation, and joint kinematics, while also accounting for an individual's sex and hip strength.
  
  
  RESULTS
  Smaller pelvic angle and greater femoral anteversion, tibiofemoral angle, and navicular drop predicted greater hip internal-rotation excursion and knee external-rotation excursion. Decreased gluteus maximus activation predicted greater hip internal-rotation excursion but decreased knee valgus excursion. No LEA characteristic predicted gluteus medius or gluteus maximus muscle activation during the single-leg squat.
  
  
  CONCLUSIONS
  Static LEA, characterized by a more internally rotated hip and valgus knee alignment and less gluteus maximus activation, was related to commonly observed components of functional valgus collapse during the single-leg squat. This exploratory analysis suggests that LEA does not influence hip muscle activation in controlling joint motion during a single-leg squat.
authors.affiliation: Department of Health and Human Performance, College of Charleston, SC 29424, USA. NguyenY@cofc.edu
authors.forename: Anh-Dung
authors.initials: AD
authors.lastname: Nguyen
authors.forename: Sandra J
authors.initials: SJ
authors.lastname: Shultz
authors.forename: Randy J
authors.initials: RJ
authors.lastname: Schmitz
authors.forename: Richard M
authors.initials: RM
authors.lastname: Luecht
authors.forename: David H
authors.initials: DH
authors.lastname: Perrin
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000502:physiology / Q000503:physiopathology; D000070598:Anterior Cruciate Ligament Injuries; D017760:Bone Malalignment / Q000503:physiopathology*; D004576:Electromyography; D005260:Female; D033023:Foot Joints / Q000502:physiology* / Q000503:physiopathology; D006621:Hip Joint / Q000502:physiology / Q000503:physiopathology; D006801:Humans; D007717:Knee / Q000503:physiopathology; D007718:Knee Injuries / Q000503:physiopathology; D035002:Lower Extremity / Q000502:physiology* / Q000503:physiopathology*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology* / Q000503:physiopathology; D011187:Posture / Q000502:physiology; D052097:Quadriceps Muscle / Q000503:physiopathology; D012737:Sex Factors