title: Interaction of gender and body composition on rectus femoris morphology as measured with musculoskeletal ultrasound imaging.
abstract: BACKGROUND
  Quadriceps function is an important measure in patients recovering postoperatively. Traditionally, strength measures that require high levels of resistance are contraindicated during the early postoperative phase. Thus it may be helpful to evaluate the utilization of other tools, such as ultrasound imaging, that allow for assessment during a position of low resistance.
  
  
  OBJECTIVE
  The rectus femoris cross-sectional area (CSA) is affected by sex and body composition in healthy subjects.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  Level 4.
  
  
  METHODS
  Thirty-two healthy subjects (16 women, 16 men), selected from a previously larger study, were chosen for analysis. All subjects underwent a maximal volitional isometric contraction protocol from 0° to 90° of knee motion controlled by an isokinetic dynamometer. In the contracted and resting positions, the rectus femoris CSA was measured at each angle using ultrasound imaging. The contractile index (contracted - resting CSA) was calculated at each position. Subjects were separated into 1 of 4 groups based on sex and fat percentage (low or high). These data were analyzed using mixed-factor analysis of variance (group × angle) for each variable, with a critical α level of 0.05.
  
  
  RESULTS
  A significant interaction was noted for the CSA of the rectus femoris at rest (P < 0.03) and during contraction (P < 0.02). For both variables, all groups performed similarly, with the exception of women with high body fat percentage. No statistically significant interaction existed for the contractile index; however, a main effect for angle (P < 0.01) was observed.
  
  
  CONCLUSIONS
  Rectus femoris CSA appears to depend on sex as well as the body composition of individuals.
  
  
  CONCLUSIONS
  Traditional subjective assessment measures of quadriceps strength and function have low reliability and functional validity. With the improved feasibility of ultrasound imaging in the clinical setting, quadriceps size may be more accurately measured during the early postoperative stages.
authors.affiliation: Department of Physical and Occupational Therapy, Sports Medicine Division, Duke University Health System, Durham, North Carolina.
authors.forename: Corina
authors.initials: C
authors.lastname: Martinez
authors.affiliation: Department of Physical and Occupational Therapy, Sports Medicine Division, Duke University Health System, Durham, North Carolina.
authors.forename: Ashley
authors.initials: A
authors.lastname: Davis
authors.affiliation: Department of Physical and Occupational Therapy, Sports Medicine Division, Duke University Health System, Durham, North Carolina.
authors.forename: Heather
authors.initials: H
authors.lastname: Myers
authors.affiliation: Department of Physical and Occupational Therapy, Sports Medicine Division, Duke University Health System, Durham, North Carolina ; Division of Physical Therapy, Department of Community Health and Family Medicine, Duke University, Durham, North Carolina.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Butler
keywords: body composition; cross-sectional area; gender; muscle activation; ultrasound imaging