title: The effects of movement speed on kinematic variability and dynamic stability of the trunk in healthy individuals and low back pain patients.
abstract: BACKGROUND
  Comparison of the kinematic variability and dynamic stability of the trunk between healthy and low back pain patient groups can contribute to gaining valuable information about the movement patterns and neuromotor strategies involved in various movement tasks.
  
  
  METHODS
  Fourteen chronic low back pain patients with mild symptoms and twelve healthy male volunteers performed repeated trunk flexion-extension movements in the sagittal plane at three different speeds: 20 cycles/min, self-selected, and 40 cycles/min. Mean standard deviations, coefficient of variation and variance ratio as variability measures; maximum finite-time Lyapunov exponents and maximum Floquet multipliers as stability measures were computed from trunk kinematics.
  
  
  RESULTS
  Higher speed significantly reduced the kinematic variability, while it increased short-term Lyapunov exponents. Long-term Lyapunov exponents were higher at self-selected speed and lower in low back pain patients as compared to control volunteers. Floquet multipliers were larger at self-selected speed and during higher pace trunk movements.
  
  
  CONCLUSIONS
  Our findings suggest that slower pace flexion-extension trunk movements are associated with more motor variation as well as local and orbital stability, implying less potential risk of injury for the trunk. Individuals with and without low back pain consistently recruited a closed-loop control strategy towards achieving trunk stability. Chronic low back pain patients exhibited more stable trunk movements over long-term periods, indicating probable temporary pain relief functional adaption strategies. These results may be used towards the development of more effective personalized rehabilitation strategies and quantitative spinal analysis tools for low back pain detection, diagnosis and treatment, as well as improvement of workspace and occupational settings.
authors.affiliation: Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran. Electronic address: morteza_asgari@alum.sharif.edu.
authors.forename: Morteza
authors.initials: M
authors.lastname: Asgari
authors.affiliation: Biomechanics Lab, Rehabilitation Research Center, Faculty of Rehabilitation, Department of Rehabilitation Basic Sciences, Iran University of Medical Sciences, Tehran, Iran. Electronic address: sanjarima@alum.sharif.edu.
authors.forename: Mohammad Ali
authors.initials: MA
authors.lastname: Sanjari
authors.affiliation: Department of Ergonomics, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran. Electronic address: hrmokhtarinia@yahoo.com.
authors.forename: Hamid Reza
authors.initials: HR
authors.lastname: Mokhtarinia
authors.affiliation: Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran. Electronic address: s_moeini@mech.sharif.edu.
authors.forename: Samaneh
authors.initials: S
authors.lastname: Moeini Sedeh
authors.affiliation: Department of Biomedical Engineering, Khalifa University of Science Technology and Research, Abu Dhabi, United Arab Emirates. Electronic address: kinda.khalaf@kustar.ac.ae.
authors.forename: Kinda
authors.initials: K
authors.lastname: Khalaf
authors.affiliation: Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran. Electronic address: parnianpour@sharif.edu.
authors.forename: Mohamad
authors.initials: M
authors.lastname: Parnianpour
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001696:Biomechanical Phenomena / Q000502:physiology*; D016022:Case-Control Studies; D002908:Chronic Disease; D006801:Humans; D017116:Low Back Pain / Q000503:physiopathology*; D008297:Male; D009068:Movement / Q000502:physiology*; D060726:Torso / Q000502:physiology* / Q000503:physiopathology
keywords: Flexion–extension movements; Kinematic variability; Local stability; Low back pain; Orbital stability