title: Effect of different upright sitting postures on spinal-pelvic curvature and trunk muscle activation in a pain-free population.
abstract: METHODS
  A normative within-subjects single-group study.
  
  
  OBJECTIVE
  To compare spinal-pelvic curvature and trunk muscle activation in 2 upright sitting postures ("thoracic" and "lumbo-pelvic") and slump sitting in a pain-free population.
  
  
  BACKGROUND
  Clinical observations suggest that both upright and slump sitting postures can exacerbate low back pain. Little research has investigated the effects of different upright sitting postures on trunk muscle activation.
  
  
  METHODS
  Spinal-pelvic curvature and surface electromyography of 6 trunk muscles were measured bilaterally in 2 upright (thoracic and lumbo-pelvic) sitting postures and slump sitting in 22 subjects.
  
  
  RESULTS
  Thoracic, compared to lumbo-pelvic, upright sitting showed significantly greater thoracic extension (P < 0.001), with significantly less lumbar extension (P < 0.001) and anterior pelvic tilt (P = 0.03). Furthermore, there was significantly less superficial lumbar multifidus (P < 0.001) and internal oblique (P = 0.03) activity, with significantly higher thoracic erector spinae (P < 0.001) and external oblique (P = 0.04) activity in thoracic upright sitting. There was no significant difference in superficial lumbar multifidus activity between thoracic upright and slump sitting.
  
  
  CONCLUSIONS
  Different upright sitting postures resulted in altered trunk muscle activation. Thoracic when compared to lumbo-pelvic upright sitting involved less coactivation of the local spinal muscles, with greater coactivation of the global muscles. These results highlight the importance of postural training specificity when the aim is to activate the lumbo-pelvic stabilizing muscles in subjects with back pain.
authors.affiliation: School of Physiotherapy, Curtin University of Technology, Perth, Western Australia. P.OSullivan@curtin.edu.au
authors.forename: Peter B
authors.initials: PB
authors.lastname: O'Sullivan
authors.forename: Wim
authors.initials: W
authors.lastname: Dankaerts
authors.forename: Angus F
authors.initials: AF
authors.lastname: Burnett
authors.forename: Garreth T
authors.initials: GT
authors.lastname: Farrell
authors.forename: Evonne
authors.initials: E
authors.lastname: Jefford
authors.forename: Clare S
authors.initials: CS
authors.lastname: Naylor
authors.forename: Kieran J
authors.initials: KJ
authors.lastname: O'Sullivan
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004576:Electromyography; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology*; D010388:Pelvis; D011187:Posture / Q000502:physiology*; D013121:Spinal Curvatures / Q000503:physiopathology*; D013904:Thoracic Vertebrae