title: Low-level, high-frequency mechanical signals enhance musculoskeletal development of young women with low BMD.
abstract: The potential for brief periods of low-magnitude, high-frequency mechanical signals to enhance the musculoskeletal system was evaluated in young women with low BMD. Twelve months of this noninvasive signal, induced as whole body vibration for at least 2 minutes each day, increased bone and muscle mass in the axial skeleton and lower extremities compared with controls.
  
  
  BACKGROUND
  The incidence of osteoporosis, a disease that manifests in the elderly, may be reduced by increasing peak bone mass in the young. Preliminary data indicate that extremely low-level mechanical signals are anabolic to bone tissue, and their ability to enhance bone and muscle mass in young women was investigated in this study.
  
  
  METHODS
  A 12-month trial was conducted in 48 young women (15-20 years) with low BMD and a history of at least one skeletal fracture. One half of the subjects underwent brief (10 minutes requested), daily, low-level whole body vibration (30 Hz, 0.3g); the remaining women served as controls. Quantitative CT performed at baseline and at the end of study was used to establish changes in muscle and bone mass in the weight-bearing skeleton.
  
  
  RESULTS
  Using an intention-to-treat (ITT) analysis, cancellous bone in the lumbar vertebrae and cortical bone in the femoral midshaft of the experimental group increased by 2.1% (p = 0.025) and 3.4% (p < 0.001), respectively, compared with 0.1% (p = 0.74) and 1.1% (p = 0.14), in controls. Increases in cancellous and cortical bone were 2.0% (p = 0.06) and 2.3% (p = 0.04) greater, respectively, in the experimental group compared with controls. Cross-sectional area of paraspinous musculature was 4.9% greater (p = 0.002) in the experimental group versus controls. When a per protocol analysis was considered, gains in both muscle and bone were strongly correlated to a threshold in compliance, where the benefit of the mechanical intervention compared with controls was realized once subjects used the device for at least 2 minute/day (n = 18), as reflected by a 3.9% increase in cancellous bone of the spine (p = 0.007), 2.9% increase in cortical bone of the femur (p = 0.009), and 7.2% increase in musculature of the spine (p = 0.001) compared with controls and low compliers (n = 30).
  
  
  CONCLUSIONS
  Short bouts of extremely low-level mechanical signals, several orders of magnitude below that associated with vigorous exercise, increased bone and muscle mass in the weight-bearing skeleton of young adult females with low BMD. Should these musculoskeletal enhancements be preserved through adulthood, this intervention may prove to be a deterrent to osteoporosis in the elderly.
authors.affiliation: Department of Radiology, Childrens Hospital of Los Angeles, University of Southern California, Keck School of Medicine, Los Angeles, California 90027, USA. vgilsanz@chla.usc.edu
authors.forename: Vicente
authors.initials: V
authors.lastname: Gilsanz
authors.forename: Tishya A L
authors.initials: TA
authors.lastname: Wren
authors.forename: Monique
authors.initials: M
authors.lastname: Sanchez
authors.forename: Frederick
authors.initials: F
authors.lastname: Dorey
authors.forename: Stefan
authors.initials: S
authors.lastname: Judex
authors.forename: Clinton
authors.initials: C
authors.lastname: Rubin
mesh_terms: D000293:Adolescent; D000328:Adult; D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight; D015519:Bone Density; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging; D006801:Humans; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging; D041641:Musculoskeletal Development / Q000502:physiology*; D010024:Osteoporosis / Q000000981:diagnostic imaging / Q000628:therapy*; D010349:Patient Compliance; D013131:Spine / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed; D014732:Vibration / Q000627:therapeutic use*; D051598:Whole Body Imaging