title: The interrelationship of the thorax and pelvis under varying task constraints.
abstract: The purpose of this study was to investigate the interrelationship between the thorax and pelvis during coupled movement patterns. Fifty-seven participants were assessed using an infrared motion analysis system to track trunk movement during maximal pelvis and thorax rotations over four trunk inclinations and two pelvic constraint conditions. A repeated-measures multivariate analysis of variance investigated the effects of forward trunk inclination and pelvic constraint on thorax and pelvic rotation. Forward trunk inclination from neutral to 45° resulted in a 46% (p < 0.001) decrease in axial pelvic rotation and a 15% (p < 0.001) decrease in axial thorax rotation with an unconstrained pelvis. A constrained pelvis resulted in a 15% (p < 0.001) decrease in axial thorax rotation. An externally constrained pelvis allowed the thorax to achieve an average of 18° (SD = 2°) greater rotational range of motion across all angles. This study reinforced the importance of allowing the pelvis to rotate during whole body axial rotation tasks.
  Results indicated that maximum axial trunk rotation is best achieved in a neutral posture, when the pelvis is allowed to contribute and flexion at the hips should be minimised. For example, if a recumbent task requires rotation of the torso, then the chair seat should be allowed to swivel.
authors.affiliation: School of Health and Sport Sciences, University of the Sunshine Coast, Maroochydore, DC, Australia. edelphin@usc.edu.au
authors.forename: Elias M
authors.initials: EM
authors.lastname: Delphinus
authors.forename: Mark Gregory Leigh
authors.initials: MG
authors.lastname: Sayers
mesh_terms: D000328:Adult; D053587:Arthrometry, Articular / Q000379:methods; D001696:Biomechanical Phenomena / Q000502:physiology; D006804:Ergonomics; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement; D015999:Multivariate Analysis; D010388:Pelvis / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D016059:Range of Motion, Articular; D012399:Rotation; D013131:Spine / Q000502:physiology; D013909:Thorax / Q000502:physiology*