title: Sex-specific relationships of physical activity, body composition, and muscle quality with lower-extremity physical function in older men and women.
abstract: OBJECTIVE
  This study aims to determine the sex-specific relationships of physical activity, body composition, and muscle quality with lower-extremity physical function in older men and women.
  
  
  METHODS
  Seventy-nine community-dwelling men (n = 39; mean [SD] age, 76.1 [6.2] y; mean [SD] body mass index, 27.3 [3.8] kg/m(2)) and women (n = 40; mean [SD] age, 75.8 [5.5] y; mean [SD] body mass index, 27.0 [3.8] kg/m(2)) were assessed for physical activity via questionnaire, body composition via dual-energy x-ray absorptiometry scanning, leg extension power using the Nottingham power rig, and muscle quality (W/kg; the ratio of leg extension power [W] to lower-body mineral-free lean mass [kg]). A composite measure of physical function was obtained by summing Z scores from the 6-minute walk, 8-ft up-and-go test, and 30-second chair-stand test.
  
  
  RESULTS
  As expected, men had significantly greater levels of physical activity, lower adiposity, greater lean mass, higher leg extension power, and greater muscle quality compared with women (all P < 0.05). In linear regression analyses, muscle quality and physical activity were the strongest predictors of lower-extremity physical function in men and independently explained 42% and 29% of the variance, respectively. In women, muscle quality (16%) and percent body fat (12%) were independent predictors after adjustment for covariates.
  
  
  CONCLUSIONS
  Muscle quality is the strongest predictor of lower-extremity physical function in men and women, but sex impacts the importance of physical activity and adiposity. These findings suggest that older men and women may benefit from different intervention strategies for preventing physical disability and also highlight the importance of weight management for older women to preserve physical function.
authors.affiliation: From the 1Department of Kinesiology, University of Georgia, Athens, GA; and 2Department of Kinesiology, University of North Carolina at Greensboro, Greensboro, NC.
authors.forename: Chad R
authors.initials: CR
authors.lastname: Straight
authors.forename: Anne O
authors.initials: AO
authors.lastname: Brady
authors.forename: Ellen
authors.initials: E
authors.lastname: Evans
mesh_terms: D015502:Absorptiometry, Photon; D050154:Adiposity / Q000502:physiology; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D001823:Body Composition / Q000502:physiology*; D015992:Body Mass Index; D005260:Female; D006801:Humans; D007866:Leg; D016014:Linear Models; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D012737:Sex Factors; D011795:Surveys and Questionnaires; D016138:Walking