title: Electrically induced muscle contractions influence bone density decline after spinal cord injury.
abstract: METHODS
  Longitudinal repeated-measures; within-subject control.
  
  
  OBJECTIVE
  We examined the extent to which an isometric plantar flexion training protocol attenuates bone loss longitudinally after SCI.
  
  
  BACKGROUND
  After spinal cord injury (SCI), bone mineral density (BMD) of paralyzed extremities rapidly declines, likely because of loss of mechanical loading of bone via muscle contractions.
  
  
  METHODS
  Six individuals with complete paralysis began a 3-year unilateral plantar flexor muscle activation program within 4.5 months after SCI. The opposite limb served as a control. Compliance with recommended dose was > 80%. Tibia compressive force was > 140% of body weight.
  
  
  RESULTS
  Bilateral hip and untrained tibia BMD declined significantly over the course of the training. Lumbar spine BMD showed minimal change. Percent decline in BMD (from the baseline condition) for the trained tibia (approximately 10%) was significantly less than the untrained tibia (approximately 25%) (P < 0.05). Trained limb percent decline in BMD remained steady over the first 1.5 years of the study (P < 0.05).
  
  
  CONCLUSIONS
  Compressive loads of approximately 1 to 2 times body weight, induced by muscle contractions, partially prevent the loss of BMD after SCI. Future studies should establish dose-response curves for attenuation of bone loss after SCI.
authors.affiliation: Graduate Program in Physical Therapy and Rehabilitation Science, University of Iowa, Iowa City, IA 52242-1190, USA. richard-shields@uiowa.edu
authors.forename: Richard K
authors.initials: RK
authors.lastname: Shields
authors.forename: Shauna
authors.initials: S
authors.lastname: Dudley-Javoroski
authors.forename: Laura A Frey
authors.initials: LA
authors.lastname: Law
mesh_terms: D000328:Adult; D015519:Bone Density; D001842:Bone and Bones / Q000378:metabolism*; D019245:Compressive Strength / Q000502:physiology; D004599:Electric Stimulation Therapy / Q000379:methods*; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008137:Longitudinal Studies; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D013119:Spinal Cord Injuries / Q000378:metabolism* / Q000503:physiopathology; D013977:Tibia / Q000378:metabolism; D016474:Weight-Bearing / Q000502:physiology