Background: Low back pain (LBP) is the leading cause of disability and is often accompanied with a back-related leg pain (around 60%), where those with radiating pain show worse overall clinical outcomes. Previous studies comparing these two groups have involved individuals with chronic LBP. It is not known if subjects who currently have LBP differ in pain sensitivity from those who have currently LBP accompanied with pain radiation to lower limbs. Aim: The aim of this study was to investigate whether there are differences in self-reported health and pain sensitivity between individuals currently having LBP with and without pain radiation to lower limbs. Method: Individuals with LBP (n=100) aged 40 to 70 years participated in this study. According the first question of STarT Back Pain Screening Tool about the pain radiation to leg(s), individuals were divided into two groups: radiation group (RG, n=36) and no radiation group (noRG, n=64). To gain the information about self-reported health, following questionnaires were used: Roland-Morris Disability Questionnaire, Fear-Avoidance Beliefs Questionnaire and Hospital Anxiety and Depression Scale. Pressure pain thresholds (PPTs) were measured with algometer (6 sites and 4 points of ’lower body’: gluteal and knee points). Mann-Whitney U-test was used to calculate differences on group and gender level. A logistic regression analyses was calculated (crude model), where belong to RG or not was the dependent variable and all self-reported data and PPTs were independent variables, all data were controlled for gender and age. Results: The RG reported worse disability (p=0.017), higher fear-avoidance beliefs (FAB) about physical activity (p=0.003), worse score in anxiety (p=0.002) and depression (p=0.001), and increased pain sensitivity (p=0.043) in 6 sites PPTs compared to the noRG. Higher score of disability, FAB (physical activity and work), anxiety and depression were associated with an increased risk of belonging to the RG (OR 1.05-1.50, 95% CI 1.01-1.94), controlled for gender and age. Conclusion: Individuals with LBP and pain radiation to lower limbs showed worse self-reported disability and fear-avoidance beliefs about physical activity than those with LBP only. Further, those with pain radiation were more sensitive to pain in general. Worse scores of all studied self-reported data were associated with an increased risk of belonging to the groups with pain radiation. To study gender differences larger sample sizes are needed. Individuals with LBP and pain radiation to lower limbs showed worse outcomes and therefore should receive a different treatment approach than those who have only LBP.

Stress and monotonous work contribute substantially to the development of chronic musculoskeletal disorders. Yet, the pathophysiological mechanisms underlying the process, particularly the involvement of autonomic regulation, remain unclear. It has been suggested that altered motor control resulting from distorted sensory information from fatigued muscles may be an important component in the development of musculoskeletal disorders. Animal studies have shown that sympathetic nervous system activation exerts actions in skeletal muscles, such as vasoconstriction and modulation of afferent information from muscle spindles. However, few attempts have been made to address this issue in humans. Therefore, the first aim of the thesis was to investigate the impact of repetitive computer work with and without additional stressors on muscle oxygenation and position sense in the upper extremity. Assuming an important role of stress in the development of chronic musculoskeletal symptoms, one may expect open or latent manifestations of such symptoms in patients with non-specific stress-related illnesses. It is possible that sympathetic activation may influence pain perception, and that treatments aimed at reducing stress may also affect the pain experience. Thus, the second aim of the thesis was to evaluate the effects of a cognitive-behavioral training program and a physical activity program for patients with stress-related illnesses on autonomic reactivity, pain, and perceived health. First, a laboratory model of computer mouse use was characterized in terms of biomechanical exposure of the wrist, and wrist position sense was determined before and after 45 minutes of continuous mouse use. Then, the effects of performing the computer mouse work under time pressure and precision demands were determined. Autonomic activity and muscle oxygenation in the upper extremity were measured during the work, and wrist position sense was assessed before and after the work. When patients with stress-related illnesses were compared to healthy individuals in autonomic reactivity to functional tests, pressure-pain thresholds, and ratings of health, indications of a relation between autonomic reactivity and symptoms of pain was found. Hence, in a subsequent evaluation of a cognitive-behavioral training program and a physical activity program for patients with stress-related illnesses, post intervention effects on autonomic reactivity to functional tests, pressure-pain thresholds, ratings of health and return-to-work were studied during a period of 12 months after the intervention. The main findings were the following. 1) Wrist kinetics data obtained during the computer mouse work showed similarities to previously presented data for mouse-operated design tasks. 2) When time pressure and precision demands were added to the computer work, increased autonomic activity paralleled with decreased muscle oxygenation in the upper extremity was found. Wrist position sense accuracy, however, did not decrease after the work as it did when the work was performed without the additional demands. The result is intriguing, as it does not appear to be in concordance with previous animal studies. 3) Patients with stress-related illnesses showed higher autonomic reactivity to cognitive and physical laboratory tests than healthy control subjects. They also had substantially lower pressure-pain thresholds in the back, and rated poorer health and health-related behavior than the control subjects. 4) We found little difference in effect of cognitive-behavioral training and physical activity, compared to usual care, for patients with stress-related illnesses. Patients in the control group showed an improvement of about the same magnitude as in the treatment groups over the 12-month follow-up period. The present findings indicate a non-additive relation between autonomic activity during repetitive work and position sense inaccuracy. Furthermore, patients with stress-related illnesses often reported pain in the neck, shoulders, and lower back. This was associated with lower pressure-pain thresholds in the back and a modest increase in sympathetic reactivity to physical and mental tests, which might suggest a potential use of these methods in the clinical examination and rehabilitation of patients with stress-related illnesses.