title: Effect of exercise on bone mineral density and lean mass in postmenopausal women.
abstract: OBJECTIVE
  To evaluate the effects of physical activity on bone mineral density, bone mineral content, and lean mass in postmenopausal, overweight/obese women.
  
  
  METHODS
  We conducted a 12-month randomized controlled aerobic exercise intervention versus control in 173 sedentary, overweight/obese, postmenopausal women, aged 50-75 yr. The exercise prescription consisted of >or=45 min of moderate-intensity aerobic exercise (60-75% of maximal heart rate), 5 d.wk for 12 months. Control participants attended 45-min stretching sessions once a week. Ninety-eight percent (N=170) completed the trial. Exercisers averaged 172 min.wk (SD=89) of exercise and expended 3828 kJ.wk (SD=2053). We assessed body fat, total lean mass, and total body bone mineral density and content using dual-energy x-ray absortiometry (DXA). We compared baseline with 12-month changes in exercisers versus controls.
  
  
  RESULTS
  Exercisers lost significantly more weight than stretchers (1.3-kg loss vs 0.1-kg gain, P=0.01). However, no differences between exercisers and controls in the change from baseline to 12 months were detected: exercisers' average bone mineral density increased by 0.005 g.cm and controls' by 0.003 g.cm (P=0.61). Similarly, no significant differences were detected for bone mineral content. Lean mass increased by 0.2 kg in both groups (P=0.84).
  
  
  CONCLUSIONS
  Overall, the results from this randomized controlled study suggest that a yearlong moderate-intensity aerobic exercise intervention does not affect total body bone mineral density, bone mineral content, or lean mass in overweight/obese postmenopausal women.
authors.affiliation: Fred Hutchinson Cancer Research Center, Cancer Prevention Research Program, and University of Washington, School of Public Health and Community Medicine, Department of Epidemiology, Seattle, WA 98109-1024, USA.
authors.forename: Jessica
authors.initials: J
authors.lastname: Chubak
authors.forename: Cornelia M
authors.initials: CM
authors.lastname: Ulrich
authors.forename: Shelley S
authors.initials: SS
authors.lastname: Tworoger
authors.forename: Bess
authors.initials: B
authors.lastname: Sorensen
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Yasui
authors.forename: Melinda L
authors.initials: ML
authors.lastname: Irwin
authors.forename: Frank Z
authors.initials: FZ
authors.lastname: Stanczyk
authors.forename: John D
authors.initials: JD
authors.lastname: Potter
authors.forename: Anne
authors.initials: A
authors.lastname: McTiernan
mesh_terms: D000368:Aged; D015519:Bone Density / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D050177:Overweight; D017698:Postmenopause; D013851:Thinness; D014861:Washington