title: The effects of a three-week use of lumbosacral orthoses on trunk muscle activity and on the muscular response to trunk perturbations.
abstract: BACKGROUND
  The effects of lumbosacral orthoses (LSOs) on neuromuscular control of the trunk are not known. There is a concern that wearing LSOs for a long period may adversely alter muscle control, making individuals more susceptible to injury if they discontinue wearing the LSOs. The purpose of this study was to document neuromuscular changes in healthy subjects during a 3-week period while they regularly wore a LSO.
  
  
  METHODS
  Fourteen subjects wore LSOs 3 hrs a day for 3 weeks. Trunk muscle activity prior to and following a quick force release (trunk perturbation) was measured with EMG in 3 sessions on days 0, 7, and 21. A longitudinal, repeated-measures, factorial design was used. Muscle reflex response to trunk perturbations, spine compression force, as well as effective trunk stiffness and damping were dependent variables. The LSO, direction of perturbation, and testing session were the independent variables.
  
  
  RESULTS
  The LSO significantly (P < 0.001) increased the effective trunk stiffness by 160 Nm/rad (27%) across all directions and testing sessions. The number of antagonist muscles that responded with an onset activity was significantly reduced after 7 days of wearing the LSO, but this difference disappeared on day 21 and is likely not clinically relevant. The average number of agonist muscles switching off following the quick force release was significantly greater with the LSO, compared to without the LSO (P = 0.003).
  
  
  CONCLUSIONS
  The LSO increased trunk stiffness and resulted in a greater number of agonist muscles shutting-off in response to a quick force release. However, these effects did not result in detrimental changes to the neuromuscular function of trunk muscles after 3 weeks of wearing a LSO 3 hours a day by healthy subjects.
authors.affiliation: Department of Surgical Specialties, College of Osteopathic Medicine, Michigan State University, East Lansing, MI, USA. cholewic@msu.edu
authors.forename: Jacek
authors.initials: J
authors.lastname: Cholewicki
authors.forename: Kevin C
authors.initials: KC
authors.lastname: McGill
authors.forename: Krupal R
authors.initials: KR
authors.lastname: Shah
authors.forename: Angela S
authors.initials: AS
authors.lastname: Lee
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology; D004185:Disability Evaluation; D004576:Electromyography; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy; D008159:Lumbar Vertebrae / Q000033:anatomy & histology / Q000503:physiopathology; D008161:Lumbosacral Region / Q000033:anatomy & histology / Q000503:physiopathology*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000503:physiopathology*; D009989:Orthotic Devices / Q000009:adverse effects*; D016059:Range of Motion, Articular / Q000502:physiology; D018570:Risk Assessment; D013997:Time Factors; D016474:Weight-Bearing / Q000502:physiology