Spinal stability describes the ability of the neuromuscular system to maintain equilibrium in the presence of kinematic and control variability, and may play an important role in the etiology of low-back disorders (LBDs). The primary mechanism for the neuromuscular control of spinal stability is the recruitment and control of active paraspinal muscle stiffness (i.e., trunk stiffness). The two major components of active muscle stiffness include the immediate stiffness contribution provided by the intrinsic stiffness of actively contracted muscles, and the delayed stiffness contribution provided by the reflex response. The combined behavior of these two components of active muscle stiffness is often referred to as "effective stiffness". In order to understand the neuromuscular control of spinal stability, stochastic system identification methods were utilized and nonparametric impulse response functions (IRFs) calculated in three separate studies in an effort to: 1) Quantify the effective dynamics (stiffness, damping, mass) of the trunk Nonparametric IRFs were implemented to estimate the dynamics of the trunk during active voluntary trunk extension exertions. IRFs were determined from the movement following pseudo-random stochastic force disturbances applied to the trunk. Results demonstrated a significant increase in effective stiffness and damping with voluntary exertion forces. 2) Quantify the reflex dynamics of the trunk Nonparametric IRFs were computed from the muscle electromyographic (EMG) reflex response following a similar pseudo-random force disturbance protocol. Reflexes were observed with a mean response delay of 67 msec. Reflex gain was estimated from the peak of the IRF and increased significantly with exertion effort. 3) Separate the intrinsic and reflexive components of the effective dynamics and determine the relative role of each in the control of spinal stability. Both intrinsic muscle and reflexive components of activation contribute to the effective trunk stiffness. To evaluate the relative role of these components, a nonlinear parallel-cascade system identification procedure was used to separate the intrinsic and reflexive dynamics. Results revealed that the intrinsic dynamics of the trunk alone can be insufficient to counteract the destabilizing effects of gravity. This illustrates the extreme importance of reflexive feedback in the maintenance of spinal stability and warrants the inclusion of reflexes in any comprehensive trunk model. / Ph. D.

The neuromuscular response to prolonged lumbar flexion has recently been extensively studied in felines but has not been examined in humans. Animal studies suggest that prolonged lumbar flexion disturbs neuromuscular control of paraspinal muscles. This disturbance was linked to creep deformation of passive spinal tissues. Past research indicates that disturbance of paraspinal reflexes may limit spinal stability. The current study aimed to examine this behavior in humans. We hypothesized that prolonged lumbar flexion will disturb paraspinal reflex behavior in human subjects. Reflex behavior was quantified following a fifteen minute period of static flexion. There was a trend suggesting an increase in reflex magnitude after flexion (p = 0.055). This trend was only significant in female subjects (p < 0.003). Increased reflex following flexion was associated with a transient period of EMG hyperexcitability similar to felines. A second study was performed to quantify reflex behavior and creep deformation during flexion and recovery. Results indicated that creep occurred during prolonged flexion (p < 0.001). Reflexes were inhibited following flexion (p < 0.03). Both creep deformation and paraspinal reflex (p > 0.05) failed to exhibit significant recovery during the length of the test. Inhibited paraspinal reflexes may contribute to spinal instability and risk of low back pain for workers using flexed postures, due to the inability of the neuromuscular system to coordinate an appropriate muscle response following an unexpected loading event. Future studies must examine appropriate work/rest intervals for workers using flexed postures to limit reflex disturbance from prolonged ligament strain. / Master of Science

Low back pain (LBP) is associated with altered neuromuscular control of the trunk, as well as impaired performance during functional tasks highly dependent upon trunk neuromuscular control. Comparing measurements between individuals with and without LBP does not distinguish whether the LBP individual exhibits altered neuromuscular control only while experiencing LBP versus at all times. Additional insight was gained on the relationship between trunk neuromuscular control and LBP by investigating individuals who experience recurrent exercise-induced LBP (eiLBP). To differentiate the effects of LBP from individual differences, comparisons were made between episodes of pain and no pain within eiLBP individuals, and between eiLBP individuals while pain free and a group of healthy controls. Three studies were completed based on repeated measurements from both eiLBP and healthy individuals. Study 1 investigated effects of eiLBP on fundamental measures of neuromuscular control, including intrinsic trunk stiffness and the paraspinal reflex delay using a series of pseudo-random position perturbations. eiLBP individuals exhibited increased stiffness compared to healthy controls unaffected by the presence of pain, and increased reflex delays concurrent only with pain. Study 2 investigated effects of eiLBP on seated sway during a functional task involving maintaining balance. Seat and trunk kinematics were obtained while participants balanced on a wobble chair at two difficulty levels. eiLBP individuals exhibited impaired seat measures at all times, with altered trunk measures only while in pain and when the task was not challenging. Study 3 investigated effects of eiLBP on the underlying control of seated sway using a model of wobble chair balance. Quantified neuromuscular control indicated increases in proportional and noise gains for a challenging level compared to an easy level, more so for eiLBP individuals compared to controls and while experiencing pain compared to pain free. Overall, fundamental measures, seated sway measures, and identified control parameters using a model of wobble chair balance were all affected by the presence of pain within the eiLBP individuals and/or the eiLBP individuals compared to healthy controls. Therefore, this study shows that some characteristics appear to be inherent to the LBP individual, while others are only concurrent with pain. / Ph. D.

Yip Yin Bing. / "July 1999." / Thesis (Ph.D.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (p. 163-177). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese. / Yip Yin Bing.

There is a practice gap in the self-management education of patients with chronic low back pain. Insufficient self-management leads to increased frequency of flare-ups of low back pain, disability, loss of productivity, and increased cost of health care. The guiding practice-focused question was focused on the unmet self-management support needs of the chronic low back pain patients in a Midwestern state local pain clinic. The purpose of this descriptive cross-sectional study was to ascertain the unmet needs of patients' self-management support by analyzing the results of a patient study performed by this clinic. The theoretical principles of the model for evidence-based practice change, the chronic care model, and the middle-range theory of self-care of chronic illness were used. The evidence included the analysis of the Patient Assessment of Chronic Illness Care Survey (PACIC) data from 100 patients treated in this pain clinic. The clinic used the PACIC questionnaire to collect data from its 100 chronic low back pain patients, selected by simple random sampling method. The average weighted scores of these patients' responses were below the norm on all PACIC subscales and summary scores. According to study results, this pain clinic did not meet the self-management support needs of its chronic low back pain patients. Evidence-based recommendations were made for the improvement in the medical model of patient care by including nurse-led patient education and support. The positive social change is the improvement in the health status of this growing health population by meeting their identified education and support needs. Positive results from this nurse-led intervention could lead to the dissemination and widespread implementation of these recommendations in other pain clinics.

A descriptive quantitative cross-sectional survey using convenience sampling was used to gather data with a self-administered questionnaire on a sample of 226 nurses. The study population included all registered nurses of Kabgayi District Hospital and Nyanza District Hospitals and their respective health centers. To be included, the nurses had to have suffered from WRLBP during the previous 6 months before data collection. The Nordic Back Pain Questionnaire, the Oswestry Disability Index and an open-ended questionnaire regarding perceived risk factors have been used. Descriptive statistics to summarize data and inferential statistics such as chi- square test to test the relationship between different variables of the study have been studied at 5% levels. Correlation coefficients in terms of cross-tabulation were also studied at 1% level of significance.

Low back disorders (LBDs) are the most common musculoskeletal problem among farmers, with higher prevalence rates than in other occupations. Operators of tractors and other farm machinery such as combines and all terrain vehicles (ATV) can have considerable accumulation of exposure to whole body vibration (WBV). The causal relationship between LBDs and WBV is not fully clear; however, it may be different among farmers as their work context and exposure is unique. Objectives: The objectives of the two studies which form two manuscripts or chapters in this thesis were to: 1) investigate the associations between WBV and LBDs among farmers using a) systematic review (manuscript 1) and cohort studies (manuscript 2). Methods: Objective 1: Nine databases were searched using groups of terms for two concepts: ‘farming’ and ‘low back disorder’. Screening, data extraction and quality assessment was performed by two reviewers independently. The population was adult farmers or agricultural workers globally irrespective of sex. The intervention was considered to be WBV exposure, such tractor, combine and ATV use. The control was no exposure or low exposure to WBV and the outcome was low back disorders. No limits in date of publication and type of study design were applied in the literature search, and only full text, English language studies were considered. Objective 2: The data source was the Saskatchewan Farm Injury Cohort Study. In 2007, baseline data were collected on accumulated yearly tractor, combine, ATV operation, as well as several biopsychosocial covariates thought to be associated with LBDs. Follow-up data on LBDs and related symptoms were collected during 2013 (6 year follow-up) and 2014 (1-year). This resulted in two datasets for each of two cohorts: 1) the first cohort with 1,149 farm people who had been followed for six years, and 2) the second with 605 participants who had been followed for one year. Generalized estimating equation-modified Poisson regressions were performed with low back and hip symptoms as the outcome. Results: Objective 1: After 276 full texts screened, we found 12 articles which analyzed WBV as a risk factor for LBD. Three were case-control, 6 cross-sectional and 3 retrospective cohorts. Four studies showed no association between WBV and LBDs, 4 studies showed a positive association and for the remaining 4 studies, results were mixed depending on the exposure or the outcome measure. Objective 2: The adjusted model in cohort 1 found LBDs to be associated to tractor operation for 1-150 hrs/year (RR=1.23, 95%CI 1.05-1.44), 151-400 hrs/year (RR=1.32, 95%CI 1.14-1.54) and 401+ hrs/year (RR=1.34, 95%CI 1.15-1.56). In addition, tractor operation for 151-400 hrs/year (RR=1.95, 95%CI 1.45-2.62) and 401+ hrs/year (RR=1.79, 95%CI 1.32-2.45) was also found to be related to hip symptoms. Although combine operation ≥ 61 hrs/year and ATV operation 81+ days/year was related to LBD in the bivariate analysis in cohort 1, this association did not persist after adjustment for confounders. Due to limited power, no significant bivariate association was found between WBV and either LBDs and hip symptoms in cohort 2. Conclusions: Objective 1: A firm conclusion is difficult due to heterogeneity in statistical strategy, LBDs definition, type of farm commodity, and study design. Direct comparisons and synthesis were not possible. Although retrospective cohort studies tended to show a relationship, future studies with a prospective cohort design can help clarify this association further. Objective 2: Although duration of tractor operation and older age showed with both LBDs and hip symptoms in farmers in cohort 1, the true prospective cohort 2 found no significant association between WBV and LBDs.

A descriptive quantitative cross-sectional survey using convenience sampling was used to gather data with a self-administered questionnaire on a sample of 226 nurses. The study population included all registered nurses of Kabgayi District Hospital and Nyanza District Hospitals and their respective health centers. To be included, the nurses had to have suffered from WRLBP during the previous 6 months before data collection. The Nordic Back Pain Questionnaire, the Oswestry Disability Index and an open-ended questionnaire regarding perceived risk factors have been used. Descriptive statistics to summarize data and inferential statistics such as chi- square test to test the relationship between different variables of the study have been studied at 5% levels. Correlation coefficients in terms of cross-tabulation were also studied at 1% level of significance.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.