title: Goal equivalent manifold analysis of task performance in non-specific LBP and healthy subjects during repetitive trunk movement: Effect of load, velocity, symmetry.
abstract: Motor abundance allows reliability of motor performance despite its variability. The nature of this variability provides important information on the flexibility of control strategies. This feature of control may be affected by low back pain (LPB) and trunk flexion/extension conditions. Goal equivalent manifold (GEM) analysis was used to quantify the ability to exploit motor abundance during repeated trunk flexion/extension in healthy individuals and people with chronic non-specific LBP (CNSLBP). Kinematic data were collected from 22 healthy volunteers and 22 CNSLBP patients during metronomically timed, repeated trunk flexion/extension in three conditions of symmetry, velocity, and loading; each at two levels. A goal function for the task was defined as maintaining a constant movement time at each cycle. Given the GEM, flexibility index and performance index were calculated respectively as amounts of goal-equivalent variability and the ratio of goal-equivalent to non-goal-equivalent variability. CNSLBP group was as similar as healthy individuals in both flexibility index (p=0.41) and performance index (p=0.24). Performance index was higher in asymmetric (p<0.001), high velocity (p<0.001), and loaded (p=0.006) conditions. Performance and flexibility in using motor abundance were influenced by repeated trunk flexion/extension conditions. However, these measures were not significantly affected by CNSLBP.
authors.affiliation: Department of Physical Therapy, Faculty of Rehabilitation, Tehran University of Medical Sciences, Tehran, Iran. Electronic address: m.chehrehrazi@gmail.com.
authors.forename: Mahshid
authors.initials: M
authors.lastname: Chehrehrazi
authors.affiliation: Biomechanics Lab, Rehabilitation Research Center, and 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 Physical Therapy, Faculty of Rehabilitation, Iran University of Medical Sciences, Tehran, Iran. Electronic address: Aliajamshidi@yahoo.com.
authors.forename: Ali Ashraf
authors.initials: AA
authors.lastname: Jamshidi
authors.affiliation: Department of Physical Therapy, Faculty of Rehabilitation, Iran University of Medical Sciences, Tehran, Iran. Electronic address: Naderpt46@yahoo.com.
authors.forename: Nader
authors.initials: N
authors.lastname: Maroufi
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; D001696:Biomechanical Phenomena / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D017116:Low Back Pain / Q000503:physiopathology*; D008159:Lumbar Vertebrae / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D060726:Torso / Q000503:physiopathology*; D016474:Weight-Bearing / Q000502:physiology*; D055815:Young Adult
keywords: Goal equivalent manifold; Low back pain; Motor abundance; Performance; Variability