title: Adiposity, physical activity, and muscle quality are independently related to physical function performance in middle-aged postmenopausal women.
abstract: OBJECTIVE
  Poor physical function performance is associated with risks for disability in late life; however, determinants of physical function are not well characterized in middle-aged women. The aim of this cross-sectional study was to examine the contributions of body composition, physical activity, muscle capacity, and muscle quality to physical function performance.
  
  
  METHODS
  Postmenopausal women (N = 64; mean [SD] age, 58.6 [3.6] y) were assessed for body composition via dual-energy x-ray absorptiometry, for physical activity via accelerometer (steps per day), and for physical function via Timed Up and Go, 30-second chair stand, and 6-minute walk. Leg strength was assessed using isokinetic dynamometry at 60° second. Leg power was assessed with the Nottingham Leg Extensor Power Rig. Muscle quality was calculated as (1) the ratio of leg strength at 60° second to upper leg lean mass and (2) the ratio of leg power to total lower body lean mass.
  
  
  RESULTS
  Regression analyses revealed the following: (1) age and muscle quality calculated with leg power are independently related to Timed Up and Go, explaining 12% and 11% of the variance, respectively (P < 0.05); (2) age and muscle quality calculated with leg strength are independently related to 30-second chair stand, explaining 12% and 10% of the variance, respectively (P < 0.05); and (3) number of medical conditions, muscle quality calculated with leg strength, steps per day, and adiposity are independent predictors of 6-minute walk, collectively explaining 51% of the variance.
  
  
  CONCLUSIONS
  In postmenopausal women, a more optimal body composition (including lower adiposity and higher lean mass) and higher levels of physical activity are associated with better physical function performance at midlife.
authors.affiliation: From the 1University of Georgia, Athens, GA; and 2University of Alabama at Birmingham, Birmingham, AL.
authors.forename: Christie L
authors.initials: CL
authors.lastname: Ward-Ritacco
authors.forename: Amanda L
authors.initials: AL
authors.lastname: Adrian
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Johnson
authors.forename: Laura Q
authors.initials: LQ
authors.lastname: Rogers
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Evans
mesh_terms: D015502:Absorptiometry, Photon; D061725:Accelerometry; D050154:Adiposity / Q000502:physiology; D000375:Aging / Q000502:physiology; D001823:Body Composition / Q000502:physiology*; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology*; D005260:Female; D006304:Health Status; D006801:Humans; D007866:Leg; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology*; D017698:Postmenopause / Q000502:physiology*; D016138:Walking