title: Fitness and bone density in women: the role of age, weight, calcium, vitamin D, and menopause.
abstract: BACKGROUND
  The purpose of the present study was to evaluate the relationship between manifold measures of fitness and bone mineral density (BMD) of the hip and spine in 233 middle-aged women. An additional objective was to determine the effect of several potential confounding variables, including age, body weight, calcium consumption, vitamin D intake, and menopause status on the relationships between fitness and BMD.
  
  
  METHODS
  A cross-sectional design was used. Fitness was indexed using multiple variables: bench press, sit-ups, best jump, VO2max, and total fitness. Total fitness was indexed using the mean Z-score of the other fitness tests. Hip and spine BMD were assessed using dual energy X-ray absorptiometry.
  
  
  RESULTS
  The associations between hip BMD and bench press (F=5.3, P=0.0219), sit-up (F=7.5, P=0.0065), best jump (F=11.6, P=0.0008), VO2max (F=9.3, P=0.0025), and Total Fitness (F=16.1, P≤0.0001) were statistically significant. Relationships between spine BMD and four of the dimensions of fitness were significant: bench press (F=9.4, P=0.0025), sit-up (F=11.7, P=0.0007), best jump (F=6.9, P=0.0093), and the composite fitness score (F=13.4, P=0.0003). VO2max was not predictive of spine BMD (F=2.0, P=0.1610). Age had the strongest confounding effect on the hip BMD associations, whereas menopause status had the strongest influence on the spine BMD relationships.
  
  
  CONCLUSIONS
  In conclusion, findings suggest that objectively measured fitness is a strong predictor of differences in BMD of the hip and spine in middle-aged women, before and after adjusting for differences in several potential confounding variables.
authors.affiliation: Department of Medical Laboratory Sciences, Weber State University, Ogden, UT, USA - tucker@byu.edu.
authors.forename: Brady M
authors.initials: BM
authors.lastname: Hansen
authors.forename: Larry A
authors.initials: LA
authors.lastname: Tucker
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000367:Age Factors; D001835:Body Weight; D015519:Bone Density / Q000502:physiology*; D002136:Calcium, Dietary / Q000008:administration & dosage*; D003430:Cross-Sectional Studies; D005080:Exercise Test / Q000379:methods; D005260:Female; D006801:Humans; D008593:Menopause; D008875:Middle Aged; D010809:Physical Fitness / Q000502:physiology*; D014807:Vitamin D / Q000008:administration & dosage*
chemical_list: D002136:Calcium, Dietary; D014807:Vitamin D