title: Evaluation of the lumbar kinematic measures that most consistently characterize lumbar muscle activation patterns during trunk flexion: a cross-sectional study.
abstract: OBJECTIVE
  The purpose of this study was to determine which kinematic measure most consistently determined onset and cessation of the flexion-relaxation response.
  
  
  METHODS
  The study was a cross-sectional design in a laboratory setting in which 20 asymptomatic university-aged (19.8-33.3 years old) participants were tested. Muscle activation was measured for the lumbar erector spinae, and 3-dimensional motion was recorded. Flexion-relaxation onset and cessation occurrences were determined for 10 standing maximum voluntary flexion trials. The lumbar and trunk angles at both events were expressed as unnormalized (°) and normalized (%Max: percentage of maximum voluntary flexion) measures. Intraclass correlation coefficients and coefficients of variation were calculated to determine within- and between-participant reliability, respectively.
  
  
  RESULTS
  Mean (SD) unnormalized flexion-relaxation angles ranged from 46.28° (11.63) (lumbar onset) to 108.10° (12.26) (trunk cessation), whereas normalized angles ranged from 71.31%Max (16.44) (trunk onset) to 94.83%Max (lumbar cessation). Intraclass correlation coefficients ranged from 0.905 (normalized lumbar, left side, onset) to 0.995 (unnormalized lumbar, both sides, cessation). Coefficients of variation ranged from 3.56% (normalized lumbar, right side, cessation) to 26.02% (unnormalized trunk, left side, onset).
  
  
  CONCLUSIONS
  The data suggest that, for asymptomatic individuals, unnormalized and normalized lumbar kinematics most consistently characterized flexion-relaxation angles within and between participants, respectively. Lumbar measures may be preferential when the flexion-relaxation response is investigated in future clinical and biomechanical studies.
authors.affiliation: MSc Student in Physiotherapy, Queen's University; CSCS, School of Kinesiology & Health Science, York University.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Lühring
authors.affiliation: PhD Candidate, York University, School of Kinesiology & Health Science, York University.
authors.forename: Alison
authors.initials: A
authors.lastname: Schinkel-Ivy
authors.affiliation: Assistant Professor, York University, School of Kinesiology & Health Science, York University. Electronic address: jdrake@yorku.ca.
authors.forename: Janessa Dm
authors.initials: JD
authors.lastname: Drake
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology; D003430:Cross-Sectional Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D008161:Lumbosacral Region / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology*; D009126:Muscle Relaxation / Q000502:physiology; D064170:Paraspinal Muscles / Q000502:physiology*; D060726:Torso; D055815:Young Adult
keywords: Biomechanics; Electromyography; Kinematics; Low Back Pain; Spine