title: Strength and muscle quality in a well-functioning cohort of older adults: the Health, Aging and Body Composition Study.
abstract: OBJECTIVE
  To determine whether lower lean mass and higher fat mass have independent effects on the loss of strength and muscle quality in older adults and might explain part of the effect of age.
  
  
  METHODS
  Single-episode, cross-sectional analyses of a cohort of subjects in the Health, Aging and Body Composition (Health ABC) Study.
  
  
  METHODS
  Ambulatory clinic and research laboratory.
  
  
  METHODS
  Two thousand six hundred twenty-three men and women aged 70 to 79 from the Health ABC Study.
  
  
  METHODS
  Upper and lower extremity strength was measured using isokinetic (knee extension) and isometric (grip strength) dynamometers. Body composition (lean mass and fat mass) was determined by measuring lean mass of upper and lower extremities and the total body by dual-energy x-ray absorptiometry. Muscle quality was ascertained by taking the ratio of strength to muscle mass for both upper and lower extremities.
  
  
  RESULTS
  Upper and lower extremity strength and muscle quality decreased as age increased. Most of the explained variance in strength was due to differences in muscle mass, but, in those at the extremes of body fat and lower leg muscle quality, the association with body fat was independent of the effect of age. Although blacks had greater muscle strength and mass than whites, leg muscle quality tended to be lower in blacks than in whites. Upper extremity strength adjusted for lean mass and muscle quality were also associated inversely and independently with age, body fat, and black race.
  
  
  CONCLUSIONS
  In this older cohort, lower strength with older age was predominantly due to a lower muscle mass. Age and body fat also had significant inverse associations with strength and muscle quality. Both preservation of lean mass and prevention of gain in fat may be important in maintaining strength and muscle quality in old age.
authors.affiliation: Department of Medicine, Division of Geriatric Medicine, University of Pittsburgh School of Medicine, 3520 5th Avenue, Suite 300, Pittsburgh, PA 15213, USA. anewman@pitt.edu
authors.forename: Anne B
authors.initials: AB
authors.lastname: Newman
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Haggerty
authors.forename: Bret
authors.initials: B
authors.lastname: Goodpaster
authors.forename: Tamara
authors.initials: T
authors.lastname: Harris
authors.forename: Steve
authors.initials: S
authors.lastname: Kritchevsky
authors.forename: Michael
authors.initials: M
authors.lastname: Nevitt
authors.forename: Toni P
authors.initials: TP
authors.lastname: Miles
authors.forename: Marjolein
authors.initials: M
authors.lastname: Visser
mesh_terms: D000367:Age Factors; D000368:Aged; D000375:Aging; D001823:Body Composition; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D012044:Regression Analysis