title: Effect of exercise intensity on bone density, strength, and calcium turnover in older women.
abstract: OBJECTIVE
  This study examined the effects of 24 wk of high intensity strength training or low intensity walking on lumbar bone mineral density (BMD), muscular strength, and calcium turnover in Australian women either taking hormone replacement therapy (HRT) or not taking HRT.
  
  
  METHODS
  A subject pool of 64 women between 45-65 yr and randomly allocated into weights (N = 21), walking (N = 20), weightsHRT (N = 14), and walkingHRT (N = 9) groups completed this study. All subjects trained twice weekly in either a 50-min walking or weight-training program (60-90% IRM). Measurements included maximal isometric knee strength, IRM bench press, IRM squat, isokinetic back strength, lumbar (L2-L4) BMD, serum osteocalcin, and urinary deoxypyridinoline crosslinks (Dpd).
  
  
  RESULTS
  No significant group differences in BMD were evident at the completion of training. However, a significant (P < 0.05) within group change was apparent for the walking group since BMD decreased 1.3% below baseline testing. Osteocalcin levels increased significantly (P < 0.05) in the walking (22%) group. Maximal bench press and squat strength improved significantly (P < 0.05) in the weights (25.8% and 37.7%) and weightsHRT (25.4% and 35.7%) groups. The weights group also increased significantly (P < 0.05) in isokinetic back strength (22.2%).
  
  
  CONCLUSIONS
  It was concluded that short-term high intensity resistance training provides an effective means for increasing muscular strength in women between 45 and 65 yr. The training effects on lumbar BMD were not apparent in the present study.
authors.affiliation: The School of Health and Human Performance, Central Queensland University, Rockhampton, Australia. b.humphries@cqu.edu.au
authors.forename: B
authors.initials: B
authors.lastname: Humphries
authors.forename: R U
authors.initials: RU
authors.lastname: Newton
authors.forename: R
authors.initials: R
authors.lastname: Bronks
authors.forename: S
authors.initials: S
authors.lastname: Marshall
authors.forename: J
authors.initials: J
authors.lastname: McBride
authors.forename: T
authors.initials: T
authors.lastname: Triplett-McBride
authors.forename: K
authors.initials: K
authors.lastname: Häkkinen
authors.forename: W J
authors.initials: WJ
authors.lastname: Kraemer
authors.forename: N
authors.initials: N
authors.lastname: Humphries
mesh_terms: D000368:Aged; D015519:Bone Density; D002118:Calcium / Q000378:metabolism*; D015444:Exercise; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology; D010809:Physical Fitness; D016474:Weight-Bearing
chemical_list: D002118:Calcium