title: Differences in lumbopelvic rhythm between trunk flexion and extension.
abstract: BACKGROUND
  Trunk flexion and extension have already been found to have different characteristics, such as those in lumbopelvic rhythm. Although a more advanced method of quantifying such rhythm, lumbopelvic continuous relative phase and phase variability have not been used to explore the differences between trunk flexion and extension motions. This information is important since abnormal lumbopelvic coordination patterns increase the risk of low back pain. The current study investigated the differences in lumbopelvic rhythm between trunk flexion and extension, and how the rhythm changed within each of the two motions.
  
  
  METHODS
  Thirteen subjects performed pace-controlled trunk flexion/extension motions in the sagittal plane while lumbar and pelvis kinematics data were recorded, such that the lumbopelvic continuous relative phase and phase variability could be calculated to quantify lumbopelvic rhythm.
  
  
  RESULTS
  Trunk extension motion had significantly smaller lumbopelvic continuous relative phase and phase variability than flexion motion, which indicated a more in-phase and stable rhythm. Additionally, the lumbopelvic rhythm within trunk extension motion changed from a more in-phase and stable pattern to a more out-of-phase and unstable pattern; by contrast, the opposite change (from out-of-phase and unstable to in-phase and stable) was observed in trunk flexion.
  
  
  CONCLUSIONS
  Findings of the current study provided important information about the differences in lumbopelvic rhythm between trunk flexion and extension motions. Quantifying these patterns provides the means for identifying abnormal patterns in a clinical setting, and could serve as normative benchmarks during low back pain rehabilitation plans.
authors.affiliation: Department of Biological and Agricultural Engineering, University of California at Davis, Davis, CA 95616, USA. Electronic address: jiezhou@ucdavis.edu.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Department of Industrial and Management Systems Engineering, West Virginia University, Morgantown, WV 26506, USA. Electronic address: xiaopeng.ning@mail.wvu.edu.
authors.forename: Xiaopeng
authors.initials: X
authors.lastname: Ning
authors.affiliation: Department of Biological and Agricultural Engineering, University of California at Davis, Davis, CA 95616, USA. Electronic address: fathallah@ucdavis.edu.
authors.forename: Fadi
authors.initials: F
authors.lastname: Fathallah
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D006801:Humans; D021621:Imaging, Three-Dimensional; D017116:Low Back Pain / Q000503:physiopathology; D008161:Lumbosacral Region / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology*; D010388:Pelvis / Q000502:physiology*; D011187:Posture / Q000502:physiology; D016059:Range of Motion, Articular; D060726:Torso / Q000502:physiology*; D055815:Young Adult
keywords: Continuous relative phase; Low back pain; Lumbopelvic rhythm; Spinal loading; Trunk flexion/extension