title: Relationships among body weight, joint moments generated during functional activities, and hip bone mass in older adults.
abstract: OBJECTIVE
  To investigate the relationships among hip joint moments produced during functional activities and hip bone mass in sedentary older adults.
  
  
  METHODS
  Eight male and eight female older adults (70-85 yr) performed functional activities including walking, chair sit-stand-sit, and stair stepping at a self-selected pace while instrumented for biomechanical analysis. Bone mass at proximal femur, femoral neck, and greater trochanter were measured by dual-energy X-ray absorptiometry. Three-dimensional hip moments were obtained using a six-camera motion analysis system, force platforms, and inverse dynamics techniques. Pearson's correlation coefficients were employed to assess the relationships among hip bone mass, height, weight, age, and joint moments. Stepwise regression analyses were performed to determine the factors that significantly predicted bone mass using all significant variables identified in the correlation analysis.
  
  
  RESULTS
  Hip bone mass was not significantly correlated with moments during activities in men. Conversely, in women bone mass at all sites were significantly correlated with weight, moments generated with stepping, and moments generated with walking (p<0.05 to p<0.001). Regression analysis results further indicated that the overall moments during stepping independently predicted up to 93% of the variability in bone mass at femoral neck and proximal femur; whereas weight independently predicted up to 92% of the variability in bone mass at greater trochanter.
  
  
  CONCLUSIONS
  Submaximal loading events produced during functional activities were highly correlated with hip bone mass in sedentary older women, but not men. The findings may ultimately be used to modify exercise prescription for the preservation of bone mass.
authors.affiliation: Department of Kinesiology, California State University, Northridge, CA, USA. emilywang@alumni.usc.edu
authors.forename: Man-Ying
authors.initials: MY
authors.lastname: Wang
authors.forename: Sean P
authors.initials: SP
authors.lastname: Flanagan
authors.forename: Joo-Eun
authors.initials: JE
authors.lastname: Song
authors.forename: Gail A
authors.initials: GA
authors.lastname: Greendale
authors.forename: George J
authors.initials: GJ
authors.lastname: Salem
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001835:Body Weight / Q000502:physiology*; D015519:Bone Density / Q000502:physiology; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000502:physiology*; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D009929:Organ Size / Q000502:physiology; D011859:Radiography; D013223:Statistics as Topic; D013314:Stress, Mechanical; D019415:Torque; D016474:Weight-Bearing / Q000502:physiology