Sharif Digital Repository

This paper presents recent developments on effects of rest and fatigue loading on properties of healthy vertebra discs. A comparison of different approaches used in literature to study the properties of intervertebral disc is presented. The major achievements in this area so far are discussed in the context of their advantages and disadvantages. The past approaches are based on bio-mechanical models which mostly used statistical techniques for the analysis and estimation of fatigue loaded Intervertebral Disc (IVD). However, those modeling techniques were not flexible enough for analysis of customized tests. In this paper, we applied System Identification (SI) based NLARX modeling technique... 

Study Design. A cross-sectional study to quantify trunk motor control during multidirectional isometric tracking tasks.Objective. To investigate the effect of chronic low back pain (LBP) on trunk neuromuscular performance while participants performed isometric exertions of trunk muscles to track targets in different angles with various magnitudes.Summary of Background Data. Tracking tasks especially in multidirectional activities are among the common research methods to quantify human motor control in different conditions. However, little information is available on trunk motor control during these tasks. There is no study investigating trunk accuracy during multidirectional isometric... 

Background: Poor balance performance and impaired postural control have been frequently reported in patients with low back pain.However, postural control is rarely monitored during the course of treatment even though poor postural control may contribute tochronicity and recurrence of symptoms. Therefore, the present study aimed at investigating the effect of a nonextensible lumbosacralorthosis (LSO) versus routine physical therapy on postural stability of patients with nonspecific chronic low back pain.Methods: This was a randomized controlled trial conducted between November 2015 and May 2016 at the outpatient physical therapyclinic of the School of Rehabilitation Sciences. Patients with... 

Purpose: The aims of the present study were to examine electromyographic (EMG) activity of six bilateral trunk muscles during maximal contraction in three cardinal planes and to determine the direction of contraction that gives maximal activation for each muscle, both for healthy subjects and back-pain patients. Methods: Twenty-eight healthy subjects and 15 back-pain patients performed maximum voluntary contractions in three cardinal planes. Surface EMG signals were recorded from rectus abdominis, external oblique, internal oblique, latissimus dorsi, iliocostalis lumborum, and multifidus bilaterally. Root mean square values of the EMG data were calculated to quantify the amplitude of EMG... 

Reliability is a population-specific property, but to the authors' knowledge there has been no study to determine the test-retest reliability of the postural stability measures such as center of pressure (COP) measures in the population of patients with musculoskeletal disorders (MSDs), while their clinical applications have been presented in literature. So, 33 patients with low back pain (LBP), anterior cruciate ligament (ACL) injury and functional ankle instability (FAI) randomly completed postural measurements with three levels of difficulty (rigid surface-eyes open, rigid surface-eyes closed, and foam surface-eyes closed) in two sessions. COP data were used to calculate standard... 

This paper focuses on characterization of intervertebral disc behavior upon fatigue stress. It consists in in-vitro experiments to measure intervertebral disc deformation with regard to forces applied to produce fatigues test. In this paper, a system modeling based non-invasive method to assess back pain is proposed which may be used for designing of prediction model to predict the failure of intervertebral disc (IVD) experiencing fatigue loading. An artificial compression fracture was simulated in the lower level of vertebra followed by a poly(methyl methacrylate) (PMMA) bone cement injection. Fatigue loading was applied on the specimens and the load was incrementally increased form 650 N... 

Sit-to-stand (STS) is an important functional task affected by low back pain (LBP). It requires fundamental coordination among all segments of the body to control important performance variables such as body's center of mass (CM) and head positions. This study was conducted to determine whether LBPs could coordinate their multiple joints to achieve the task stability to the same extent as healthy controls. About 11 non-specific chronic LBP and 12 healthy control subjects performed STS task at three postural difficulty levels: rigid surface - open eyes (RO), rigid surface - closed eyes (RC) and narrow surface - closed eyes (NC). Motion variability of seven body segments, CM and head positions... 

Background: Lumbosacral orthosis (LSO) is commonly used for the treatment of back pain. The clinical and mechanical effectiveness of this device has been repeatedly investigated in several studies; however, its sensorimotor effectiveness has been rarely considered. Regarding this, the aim of the current study was to investigate the effect of a non-extensible LSO on postural stability (as a construct of sensorimotor function) in patients with nonspecific chronic low back pain (LBP). Methods: This preliminary study was conducted on 17 patients with nonspecific chronic LBP using a single-group quasi-experimental design. Postural stability was measured while the participants were placed in a... 

Sit to stand (STS) task requires variability of all body segments to achieve the stability of the important control variables (i.e., center of mass (CM) and head positions). In this study, the possible differences in the variability patterns of various body segments were investigated between 11 chronic low back pain (LBP) and 12 control subjects during STS task through two types of variability analyses; first by calculating the variability of seven limb angles, CM and head positions across 15 trials and second by principal component analysis (PCA) of seven limb angles. Participants performed the task at 3 postural difficulty levels: rigid surface, open eyes (RO), rigid surface, close eyes... 

Sit to stand (STS) is one of the most important activities of daily living that is shown to be affected in low back pain (LBP) patients. It requires a fundamental coordination action among all segments (DOFs) of the body in order to control important performance variables such as body's center of mass (CM) within base of support (BOS). In this study, possible differences in joint coordination and variability patterns between chronic LBP and healthy control subjects were investigated during STS task. Eleven adults with nonspecific chronic LBP and 12 healthy controls were recruited in the study. The participants performed the task in 3 exerimental conditions including: rigid surface, open eyes... 

Recurrence quantification analysis (RQA), a nonlinear method of postural analysis, was used to explore the effects of dual-tasking on postural performance in people with nonspecific low back pain (LBP) compared with healthy participants. Postural performance was quantified by RQA % recurrence, % determinism, entropy and trend. People with nonspecific LBP (n = 22) and unimpaired individuals (n = 22) randomly performed quiet standing tasks with three levels of difficulty (rigid-surface eyes open, rigid-surface eyes closed and foam-surface eyes closed). These tasks were performed in isolation or concurrently with an easy or difficult cognitive task. Increasing postural difficulty was associated... 

Multiple joint interactions are critical to produce stable coordinated movements and can be influenced by low back pain and task conditions. Inter-segmental coordination pattern and variability were assessed in subjects with and without chronic nonspecific low back pain (CNSLBP). Kinematic data were collected from 22 CNSLBP and 22 healthy volunteers during repeated trunk flexion-extension in various conditions of symmetry, velocity, and loading; each at two levels. Sagittal plane angular data were time normalized and used to calculate continuous relative phase for each data point. Mean absolute relative phase (MARP) and deviation phase (DP) were derived to quantify lumbar-pelvis and... 

STUDY DESIGN. Three factors mixed-design with 1 between-subject and 2 within-subject factors. OBJECTIVE. To compare the main effects and interactions of postural and cognitive difficulty on quiet stance between subjects with and without nonspecific low back pain (LBP). SUMMARY OF BACKGROUND DATA. The interference between postural control and cognitive tasks depends on factors such as sensorimotor/cognitive integrity. Changes in peripheral sensory and muscular systems as well as cognitive processes have been observed in LBP patients. It was hypothesized that the effect of cognitive task on postural performance might be different in subjects with nonspecific LBP as compared with healthy...