title: Deep and superficial fibers of the lumbar multifidus muscle are differentially active during voluntary arm movements.
abstract: METHODS
  A cross-sectional study was conducted.
  
  
  OBJECTIVE
  To determine the activity of the deep and superficial fibers of the lumbar multifidus during voluntary movement of the arm.
  
  
  BACKGROUND
  The multifidus contributes to stability of the lumbar spine. Because the deep and superficial parts of the multifidus are near the center of lumbar joint rotation, the superficial fibers are well suited to control spine orientation, and the deep fibers to control intervertebral movement. However, there currently are limited in vivo data to support this distinction.
  
  
  METHODS
  Electromyographic activity was recorded in both the deep and superficial multifidus, transversus abdominis, erector spinae, and deltoid using selective intramuscular electrodes and surface electrodes during single and repetitive arm movements. The latency of electromyographic onset in each muscle during single movements and the pattern of electromyographic activity during repetitive movements were compared between muscles.
  
  
  RESULTS
  With single arm movements, the onset of electromyography in the erector spinae and superficial multifidus relative to the deltoid was dependent on the direction of movement, but the onset in the deep multifidus and transversus abdominis was not. With repetitive arm movements, peaks in superficial multifidus and erector spinae electromyography occurred only during flexion for most subjects, whereas peaks in deep multifidus electromyography occurred during movement in both directions.
  
  
  CONCLUSIONS
  The deep and superficial fibers of the multifidus are differentially active during single and repetitive movements of the arm. The data from this study support the hypothesis that the superficial multifidus contributes to the control of spine orientation, and that the deep multifidus has a role in controlling intersegmental motion.
authors.affiliation: Prince of Wales Medical Research Institute and the University of New South Wales, Sydney, Australia.
authors.forename: G Lorimer
authors.initials: GL
authors.lastname: Moseley
authors.forename: Paul W
authors.initials: PW
authors.lastname: Hodges
authors.forename: Simon C
authors.initials: SC
authors.lastname: Gandevia
mesh_terms: D000328:Adult; D001132:Arm / Q000502:physiology*; D003430:Cross-Sectional Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D008161:Lumbosacral Region; D008297:Male; D009068:Movement / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000502:physiology*