| 1. |
- Aasa, Ulrika
(författare)
-
Ambulance Work : Relationships between occupational demands, individual characteristics and health-related outcomes
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Although musculoskeletal disorders (MSDs) and other health complaints are an occupational problem for ambulance personnel, there is a lack of knowledge regarding work-related factors associated with MSDs and other health complaints. The overall aim of this thesis was to investigate the relationships between occupational demands, individual characteristics and health-related outcomes among ambulance personnel. A random sample of 234 female and 953 male ambulance personnel participated in a national questionnaire survey on work-related factors, and musculoskeletal and other health complaints. Physical demands was associated with activity limitation due to neck-shoulder and low-back complaints among the female personnel. Among the male personnel, physical demands was associated with low-back complaints and activity limitation due to low-back complaints. Psychological demands was significantly associated with neck-shoulder complaints, sleeping problems, headache and stomach symptoms among both female and male ambulance personnel. Worry about work conditions was associated with musculoskeletal disorders and sleeping problems, headache and stomach symptoms. A local sample of 26 ambulance personnel was followed during a 24-hour work shift and for the next two work-free days. Subjective stress- and energy levels, and cortisol levels were measured at regular intervals, and heart rate was registered continuously by electrocardiogram (ECG). Autonomic reactivity to standardized tests before (pre-work) and at the end of the work shift (post-work) was also investigated. For the whole group, baseline values of heart rate were higher pre-work than post-work, but autonomic reactivity did not differ. Increased reactivity to the mental test, modest deviation in heart rate variability (HRV) pattern during the late night hours at work and higher morning cortisol values during work than during leisure time were observed in personnel with many health complaints, but not among their co-workers without or with few complaints. Ambulance personnel with many health complaints also reported higher psychological demands and tended to be more worried about work conditions. Heart rate (HR), lactate level (LL) and perceived exertion (RPE) were investigated in 17 female and 48 male ambulance personnel during a simulated standardized work task “carry a loaded stretcher”. The ambulance personnel had to carry the loaded stretcher (920 N) up and down three flights of stairs twice. The high physiological strain (HR, LL, RPE) for the male, and near or at maximal strain for the female ambulance personnel, implied the importance to identify what kind of physical capacity is most important for ambulance personnel. Therefore, the explained variance of developed fatigue by tests of cardiorespiratory capacity, muscular strength and endurance, and coordination was investigated. The results showed that VO2max and isometric back endurance were important predictors for development of fatigue when carrying a loaded stretcher. The influence of body size on the relationships between maximal strength and functional performance was investigated in a methodological study. The results confirm that the assessment of physical performance could be confounded by the body weight. Therefore, the models for explaining development of fatigue when carrying the loaded stretcher were adjusted for height and weight. Including height in the models significantly increased the explained variance of accumulated lactate among female, but not among male personnel. Lactate levels were higher among short compared to tall female personnel. Weight had no effect on any of the models. In conclusion, the national survey showed that self-reported physical demands was a risk factor of having MSDs, and that self-reported psychological demands and worry about work were important risk factors of having MSDs and other health complaints. Stress monitoring of ambulance personnel during work and leisure time showed that physiological and subjective stress markers did not show any differences between the 24-hour ambulance work shift and leisure time afterwards. However, ambulance personnel with many health complaints had certain physiological changes during the work shift in comparison with the next two work-free days. The physiological and subjective responses during carrying a loaded stretcher, especially among the female ambulance personnel, showed that female and male ambulance personnel could be exposed to internal exposures at different levels when performing the same work task. A better understanding of the relationships between occupational demands and health-related outcomes require further studies on age- and gender matched groups in long-term perspective studies.
|
|
| 2. |
- Björklund, Martin, 1961-
(författare)
-
Effects of repetitive work on proprioception and of stretching on sensory mechanisms : implications for work-related neuromuscular disorders
- 2004
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aims of the thesis were (i) to investigate the impact of repetitive low-intensity work exposure on proprioception and (ii) to examine effects of muscle stretching (especially sensory effects and effects on muscle nociception) and to relate its application to the prevention, alleviation and/or treatment of work-related neuromuscular disorders. The effects of low-intensity repetitive work on the shoulder proprioception were tested in healthy subjects. The effect of working time on the retention of subjective fatigue and their relation to changes in proprioception, and the immediate effect of stretching on shoulder proprioception were investigated. A new method to test the stretchability of the rectus femoris muscle was investigated for reliability and validity and used to assess the effects of a two-week stretching regimen on range of motion and on subjective stretch sensation. Finally, the interactions between innocuous muscle stretch and nociceptive chemical stimulation on discharge behavior of nociceptive dorsal horn neurons in the feline spinal cord were explored. The main findings were as follows: 1) The repetitive low-intensity work to fatigue diminished the shoulder proprioception; the working time as well as the retention of subjective fatigue were partly related to the extent of changed proprioception. 2) There was no effect of acute muscle stretching on the proprioception. 3) The new method for testing muscle stretchability proved valid and reliable. A two-week stretching regimen increased the tolerance to stretch torque, but the range of motion remained unchanged. 4) Half of the nociceptive dorsal horn neurons that responded to close arterial injections of bradykinin were modulated by muscle stretching applied directly after the injections. Altogether, the results give credence to the hypothesis of an involvement of sensory information distortion due to repetitive low-intensity work exposure in the development of work-related neuromuscular disorders. Increased tolerance to stretch torque may be an important mechanism in explaining improvements following stretch treatment. The spinal interactions between innocuous stretch and nociceptive muscle afferent inputs indicate a possible mechanism involved in stretching-induced pain alleviation.
|
|
| 3. |
- Blomqvist, Sven
(författare)
-
Postural balance, physical activity and capacity among young people with intellectual disability
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall aim of this thesis was to investigate postural balance, physical activity, physical capacity and their associations in young people (16-20 years) with intellectual disability (ID), mild to moderate. The aim was also to study the reliability and concurrent validity of postural balance tests.To evaluate postural balance, one assessor used five common postural balance tests and one new test. The tests were performed twice for 89 young people with ID (one to twelve days apart). Intraclass correlation coefficients greater than 0.80 were achieved for four of the common balance tests: Extended Timed Up and Go Test (ETUGT), Modified Forward Reach Test (MFRT), One-Leg Stance Test (OLS), and a Force Platform Test (FPT). The smallest real difference ranged from 12% to 40%; less than 20% is considered to be low. For the six balance tests, the concurrent validity varied between none to low.Falls are more common for young people with ID compared to young people without ID. One reason could be impaired postural balance. The postural balance for young people with ID has not been thoroughly investigated. Therefore, five balance tests and three muscle strength tests were used to compare young people with ID with an age-matched control group without ID (n=255). The young people with ID had significantly lower scores on most of the postural balance tests and muscle strength tests of the trunk and lower limbs. Muscle strength, height, and body mass index had no strong association with postural balance. The results also illustrated that young people with ID did not rely more on vision for their balance ability compared to peers without ID.It seems that postural balance is impaired for young people with ID when evaluated with common tests. An everyday situation is to react to unexpected balance disturbances to avoid falls by using different postural responses. Since young people with ID seem to fall more often than peers without ID, it is valuable to investigate if those postural responses are different between the groups. Therefore, young people with and without ID (n=99) were exposed to six backward surface translations and several postural muscle responses were evaluated: muscle synergies and strategies, muscle onset latency, time-to-peak amplitude, and adaptation. The responses of the investigated muscles – the gastrocnemius, the biceps femoris, and the erector spinae L4 level – were measured using electromyography. The results showed that there were no differences between the two groups with respect to synergies or strategies, muscle onset latency, and time-to-peak amplitude. An overall pattern was seen, that young people with ID adapted their muscle response slower in all three muscles than peers without ID, but this pattern was not statistically significant.Studies have shown that people with ID have impaired postural balance, a lower level of physical activity, and lower aerobic capacity compared to people without ID. The association is however not investigated. Therefore, postural balance (postural sway indirectly measured with the subjects standing on a force platform), physical activity (measured with a pedometer), and aerobic capacity (measured with a sub-maximal ergometer cycle test) were used to assess young people with and without ID (n=106). To investigate the subjects’ view of their own health, the subjects completed an adapted questionnaire that addressed their perceived health. The analysis showed no significant associations between postural balance, level of physical activity, and aerobic capacity. The subjects in the ID group, both men and women, had significantly lower aerobic capacity compared to subjects without ID. The answers from the health questionnaire did not correspond to the measured outcomes from the physical tests for young people with ID.In conclusion, ETUGT and MFRT can be used to evaluate change in postural balance over time in young people with mild to moderate ID. The low concurrent validity suggests that the postural balance tests probably challenge various subsystems. Young people with ID have impaired postural balance and perform lower on muscle strength tests than age-matched controls. Postural muscle responses after external perturbations seem to be similar for young people with and without ID, but the ability to adapt muscle responses after repeated perturbations appears to be slower for young people with ID. The studies in the thesis also indicate that young people with ID have reduced level of physical activity and lower aerobic capacity. The lack of association between the different physical functions indicates that they should be evaluated and exercised separately. Young persons with ID might have more difficulty realising the health advantage of being physically active, as they do not seem to make this connection. Because of this, it is important that parents/guardians, school staff, physiotherapists, and others encourage them to participate in physical activity.
|
|
| 4. |
- Domkin, Dmitry
(författare)
-
Perception and control of upper limb movement: Insights gained by analysis of sensory and motor variability
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Chronic neck-shoulder pain is associated with impairments of proprioception and motor control. Thus, assessment of proprioceptive and motor function may be powerful tools both for research and clinical practice. However, insufficient knowledge of certain features of human sensorimotor control hampers both development and interpretation of results of clinically relevant tests. For example, evidence is lacking which proprioception submodalities are reflected in common tests of proprioception. For testing motor function, a better understanding of the control of goal directed arm movements is needed. The purpose of the thesis was to gain further insights into the sensorimotor control of the upper limb in healthy subjects, with implications for clinical testing. The main aims were: (1) to study relationships of outcomes of different tests of shoulder proprioception and (2) to study control strategies in bimanual pointing tasks by analysis of the structure of joint angle variability with the Uncontrolled Manifold (UCM) method. Correlations between proprioceptive acuity in different variants of ipsilateral position-matching and velocity-discrimination were studied. The main finding was that two uncorrelated mechanisms based either on perception of position or movement might underlie perception of limb location in ipsilateral position-matching. The results provided important information for interpretation of common and development of novel tests of shoulder proprioception. The structure of joint angle variance was computed with respect to several task variables during bimanual pointing. Joint angle variability was decomposed in variance affecting and not affecting a task variable. The results showed that the variance in joint space was structured according to the predictions of the UCM hypothesis. It was also shown that the arms were united into one synergy to significantly larger degree than joints within each arm were united into single-arm synergies. It was concluded that the UCM approach might quantify components of motor variability during repetitive motor tasks.
|
|
| 5. |
- Elcadi, Guilherme H.
(författare)
-
Near infrared spectroscopy for assessing oxygenation and hemodynamics in the upper extremities of healthy subjects and patients with work-related muscle pain
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The prevalence of work-related muscle pain (WRMP) is large in the general population in the industrialized world. Despite significant advances over recent years in some research areas, the mechanisms of why WRMP occurs and the pathophysiological mechanisms behind the disorders are still unclear. One suggested explanation is that WRMP is caused initially by a limitation of the local muscle circulation and oxidative metabolism. There is a lack of objective methods to gauge the development and diagnosis of WRMP. Near infrared spectroscopy (NIRS) is a non-invasive technique that allows for determinations of oxygenation and blood flow. The purpose of this thesis was to evaluate NIRS (1) as a method for measuring muscle oxygenation and hemodynamics for the extensor carpi radialis (ECR) and trapezius descendens muscles (TD), and (2) to investigate whether variables measured by NIRS differed between patients diagnosed with WRMP and healthy subjects. Several variables of NIRS were produced and investigated. These included muscle oxygenation (StO2%), changes during contractions (∆StO2%) and StO2% recovery (Rslope), total hemoglobin (HbT) as an indication of blood volume and its changes during contractions (∆HbT). In addition, for the ECR, by applying an upper arm venous occlusion (VO) HbTslope increase as a surrogate of blood flow, and for both VO and arterial occlusion (AO) HHbslope increase (i.e. deoxyhemoglobin slope) as a surrogate of oxygen consumption were variables of interest. A first objective was to determine how StO2% and HbT responded to various contraction forces and how it related to muscle activation measured by electromyography (EMG). For both muscles isometric contractions of 10, 30, 50 and 70% of maximal voluntary contraction (MVC) were maintained for 20 s each by healthy males and females; additionally a 10% MVC contraction was sustained for 5 min. For the different contraction levels, predictable relationships were seen between ∆StO2% and force, and between ∆StO2% and EMG RMS amplitude. The general trend was a decrease in ∆StO2% with increasing force and increasing EMG. Females showed a tendency for a higher oxygen use (i.e., drop in StO2%) for the ECR over force levels than males and a higher RMS% MVC for the TD. For the 10% MVC contraction sustained for 5 min gender specific changes over time for HbT and RMS for the ECR, and for StO2% for the TD muscle were seen. A second objective was to determine the day-to-day reliability of NIRS variables for the ECR and TD muscles at group level (Pooled data) and at gender level (males and females). Measurements were performed on two occasions separated by 4-6 days and intraclass correlation coefficients (ICC) and limits of agreement (LOA) were determined as reliability and reproducibility indicators, respectively. Variables tested were ∆StO2% during submaximal isometric contractions of 10, 30, 50 and 70% MVC and StO2% recovery (Rslope) after contractions and after AO. For the ECR, HbTslope as an indication of blood flow (using VO) and HHbslope as a surrogate of oxygen consumption for both VO and AO were computed. For ∆StO2% for the ECR the highest ICC was at 30% MVC for both the pooled data and at gender level. For the TD ICCs were comparably high for 30, 50, 70 % MVC (for both muscles the ∆StO2% at 10% MVC showed the lowest ICC). Further, females showed a higher ICC than males for contraction levels of 50 and 70% MVC. For both muscles, LOA for ∆StO2% was lowest at 10% and highest at 50 and 70% MVC. For the ECR Rslope ICCs were high for all contraction levels, but was lower for AO; LOA was lowest at 70% MVC. For the TD, Rslope ICCs were also high for all contraction levels and LOA was lowest at 30 % MVC. ICC for HbTslope was the lowest of all variables tested. For HHbslope ICC was higher for AO than for VO, and LOA was lower for AO. A third objective was to determine if there were differences between healthy subjects and patients diagnosed with WRMP in ∆StO2% and ∆HbT responses during varying submaximal contractions (10, 30, 50 and 70% MVC), and StO2% recovery (Rslope) immediately after contractions and AO. Additional variables tested in the ECR at rest were HHbslope to indicate oxygen consumption (using AO) and HbTslope as an indication of blood flow. There were no differences between groups in ∆StO2% and ∆HbT variables during the contractions or Rslope in the recovery after contractions or AO. Furthermore, HbTslope was not different between groups However, oxygen consumption for the ECR and StO2% for the TD at rest were significantly greater for healthy subjects compared to patients. A fourth objective was to determine if there were differences in StO2% and HbT between healthy subjects and WRMP patients during a 12 min sustained contraction of 15 % MVC. In addition, the protocol included a recovery period of 30 min. Prior to contraction, as well as during the recovery period, HbTslope as a surrogate of blood flow was determined for the ECR. Neither the ECR nor the TD exhibited significant differences between groups for StO2% and HbT during the contraction. For the TD patients showed a lower StO2% value at rest and throughout the contraction than healthy subjects. For the ECR HbT during the sustained contraction the general trend was an initial decrease with gradual increase throughout the contraction for both groups. For HbTslope no differences were seen between patients and healthy subjects before the sustained contraction and during the recovery period for both muscles.NIRS is deemed a suitable technique for assessing physiological measurements of the upper extremity, including for day-to-day testing.NIRS was not able to distinguish between the patients with WRMP and controls. A concern in the thesis is the characteristics of the patient group in being equally active in recreational sports, actively working, and similar in muscle strength as controls. Thus, applying NIRS for studying a more severe patient group could yield different results.
|
|
| 6. |
- Flodgren, Gerd, 1961-
(författare)
-
Effects of low-load repetitive work and mental load on sensitising substances and metabolism in the trapezius muscle
- 2007
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Low-load repetitive work (LLRW) and mental load are important risk factors for the development of workrelated muscle pain. The link between these risk factors and the development of pain is still not understood, but stimulation of chemo-sensitive receptors in the muscle probably plays an important role. It has been suggested that sensitising substances may accumulate in the muscle during LLRW, especially when combined with mental load. The overall purpose of this thesis was to try to shed some light on the effects of LLRW on the concentration of sensitising substances (glutamate, prostaglandin E2 (PGE2), norepinephrine (NE)) and on metabolism (lactate, pyruvate and oxygenation) in the trapezius muscle of healthy controls (CON) and subjects with trapezius myalgia (TM). A first step was to investigate whether females with TM exhibit higher absolute concentrations of glutamate and PGE2 in the affected muscle during rest. Using Microdialysis (MD) females with TM and asymptomatic controls were studied during four hours of rest. [Glutamate] and [PGE2] during rest did not differ between groups. A second step was to investigate, in a simulated occupational setting, the effects of LLRW on the concentration of sensitising substances and metabolism in the trapezius muscle of TM and CON, and whether increased work duration resulted in a progressive effect. Asymptomatic females were studied during baseline rest, 30 versus 60 min work and recovery, using MD and near infrared spectroscopy (NIRS). Subjects with TM were studied during baseline rest, 30 min work and recovery. [Glutamate] and [lactate] increased in response to work, but not progressively with increased work duration. [Glutamate] was at all time points significantly lower in TM. [PGE2]and oxygenation remained unchanged during work for CON, while for TM oxygenation decreased significantly during work. In TM [pyruvate] increased during both work and recovery, and a significant interaction between groups was found for [pyruvate] during recovery; while moderately increased in CON it increased progressively in TM. The effects of LLRW with and without superimposed mental load on intramuscular [NE], muscle activity and oxygen saturation in the trapezius were also investigated and compared. Using MD, electromyography and NIRS, healthy females were studied on two occasions; during 30 min LLRW and during 30 min LLRW with superimposed mental load. During work [NE], and muscle activity, were increased, while oxygenation decreased, but no differences between occasions. However, recovery of [NE] to baseline was slower after LLRW with superimposed mental load. The findings of the present thesis suggest: (i) no inflammation, or increased interstitial [glutamate] in TM; (ii) LLRW causes an increased anaerobic metabolism in both TM and CON; (iii) no effect of work duration was found; (iv) a significant difference in the effects of LLRW on the interstitial milieu of the trapezius muscle in TM as compared to CON; (v) LLRW causes a significant increase in [NE], but superimposed mental load does not cause a further increase; (vi) LLRW with a superimposed mental load may result in a slower recovery to baseline [NE] as compared with LLRW alone.
|
|
| 7. |
- Hadrévi, Jenny, 1977-
(författare)
-
Applying proteomics and metabolomics for studying human skeletal muscle with a focus on chronic trapezius myalgia
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Work related musculoskeletal disorders are the dominating causes of reported ill-health in industrialized countries. These chronic pain conditions are one of the most costly public health problems in Europe and North America. When work related musculoskeletal disorders are considered to be of muscular origin and the trapezius muscle is affected, the common appellation is trapezius myalgia. Since little is known about the genesis or how it is maintained, it is of great importance to better understand the pathophysiology of trapezius myalgia; doing so will better enable recommendations for prevention, treatment and rehabilitation. Several hypotheses have been presented based on biochemical alterations in the muscle, suggesting increased signaling of inflammatory substances and altered metabolism. Previous research has not been able to present the comprehensive picture of the muscle in pain. Thus there is a demand for more comprehensive research regarding the biochemical milleu of the chronic trapezius muscle.Proteomic and metabolomic methods allow non-targeted simultaneous analyses of a large number of proteins and metabolites. The main emphasis in this thesis is on a proteomic method, two-dimensional differential gel electrophoresis (2D-DIGE). The method is validated to human skeletal muscle biopsy research with laboratory specific settings. In the baseline study, there were 14 metabolic, contractile, structural and regulatory proteins that differed significantly in abundance when trapezius and vastus lateralis muscles were compared. Using the validated 2D-DIGE method and the baseline study, a comparison between healthy and myalgic muscles was made. Biopsies from female cleaners with and without myalgia were compared to obtain results from women with the same type of work exposure. In the multivariate model, 28 identified unique proteins separated healthy and myalgic muscle and were grouped according to function: metabolic (n=10), contractile (n=9), regulatory (n=3), structural (n=4), and other (n=2). Finally, a second screening method, metabolomics, was introduced to analyze differences in metabolite content as a complement to and verification of the proteomic results. Gas chromatography-mass spectrometry (GC-MS) was performed on muscle interstitial fluid samples obtained with microdialysis, and differences in the abundance of extracellular metabolites were revealed. The 2D-DIGE method is a reliable method to analyze human skeletal muscle. The outcomes of the proteomic analyses were dependant on the statistical approach. Systematic differences in protein and metabolite content were detected using a multivariate approach. Univariate analyses were used to analyze individual proteins for their significance. The significant proteins in the baseline study were predominately related to muscle fiber type which correlated with the differences in fiber type content between trapezius and vastus lateralis. The proteomic and metabolomics studies where myalgic and healthy muscles were compared provide us with new clues and new aspects regarding the pathophysiology of the myalgic muscle.Technically advanced methods employed in the thesis enabled an explorative screening of proteins of relevance for the pathophysiology of the myalgic muscle. The results of these analyses may contribute to the formulation of future hypothesis that need to be further evaluated.
|
|
| 8. |
- Heiden, Marina
(författare)
-
Psychophysiological reactions to experimental stress : relations to pain sensitivity, position sense and stress perception
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
|
|
| 9. |
- Kalezic, Ivana
(författare)
-
Experimental studies of spinal mechanisms associated with muscle fatigue
- 2004
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Muscle fatigue is ubiquitous in every day life.Muscle fatigue might be considered as an altered state of motor behaviour, which impairs motor performance. By contrast, muscle fatigue could also be considered a positive phenomenon, which protects muscle tissue from damage that might be incurred to it by overuse. The principal aim of the thesis was to explore some of the mechanisms of muscle fatigue at the spinal level in animal models.The activation of multiple motor units of a single calf muscle may influence contractile properties of its neighbouring, otherwise inactive units, providing evidence for spatial spreading of fatigue between different muscle parts. The release of metabolites, their action on inactive muscle units and the effects of local hypoxia are the most likely causes. Fatigue-induced metabolite shift in the interstitium provokes excitation and/or sensitisation of high-threshold afferent fibers, with complex effects on the spinal premotoneuronal network involved in the modulation of motoneuronal output. This was examined by studing the intrasegmental lamellar distribution of the lumbar spinal interneurons following fatiguing contractions of the triceps surae muscle. Furthermore, fatigue of calf muscles enhanced the activity of fusimotor neurons to these muscles irrespective of the regime of muscle activity (isometric vs. lengthening) in conditions that simulate locomotion. Altered fusimotor activity, through increased or maintained muscle spindle afferent responsiveness may be advantageous, providing support to the skeletomotor activity and enhanced information about muscle periphery to higher nervous centres. The particular effects of interneuronal network at motor input (presynaptic inhibition system) and output (recurrent inhibition system) stages were then addressed. Fatigue of triceps surae muscle induced a suppression of the monosynaptic reflex. The intensity of presynaptic inhibition increased, while the intensity of recurrent inhibition decreased. Post fatigue-evoked changes in monosynaptic reflexes and presynaptic inhibition indicate the possibility that high-threshold afferents inhibit group Ia terminals pre-synaptically, which would allow fatigue-induced signals from the muscle to reduce the relevance of proprioceptive feedback. Besides intrasegmental, intersegmental spreading of nociceptive signals was explored. Activation of sensory afferents from dorsal neck muscles by capsaicin induces powerful activation of interneurons located in the cervical spinal cord, as well as a widespread activation of cells in lumbar spinal cord segments. The results confirm the pivotal role of small diameter muscle afferents in the orchestration of segmental responses to fatigue and show complex interactions that may lead to limited accuracy of motor output. They also depict processes that may be related to, and even become precursors of chronic muscle pain.
|
|
| 10. |
- Kalezic, Nebojsa
(författare)
-
Autonomic reactivity in muscle pain : clinical and experimental assessment
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There are numerous indications of possible involvement of the autonomic nervous system in the genesis of chronic pain. The possibility exists that sympathetic activation is related to motor dysfunction and changes in sensory processing, which have otherwise been implicated in musculoskeletal disorders.The primary aim of the thesis has been to investigate autonomic regulation at rest and in response to laboratory tests of autonomic function in subjects suffering from chronic pain in different localisations (lower back, neck-shoulder and neck-jaw), as well as to study the relations between autonomic regulation, proprioceptive acuity and clinical data. Secondary aim has been to assess autonomic regulation in fit, pain-free subjects in response to experimentally induced pain and in occupationally relevant settings.A total of 194 subjects suffering from chronic pain participated [low back pain (LBP) n=93; non-traumatic neck pain (NT) n=40, Whiplash associated disorder (WAD) n=40, Whiplash with temporomandibular dysfunction (WADj) n=21]. Each chronic pain group was subjected to a battery of autonomic function tests combining cognitive (Stroop Colour-Word conflict tests), physical (handgrip), sensory (unpleasant sound) and motor tasks (chewing tests) as well as the activation of reflex pathways (paced breathing and the orthostatic test) and compared to an age- and gender balanced control group. Autonomic regulation was also assessed in exposure to experimentally induced muscle pain in healthy subjects (n=24) in order to describe acute pain reaction. Further assessment was carried out during monotonous repetitive work and dynamic work in healthy subjects (n=10) and in a three-day monitoring of ambulance personnel (n=26) in occupational settings.Autonomic regulation was evaluated using cardiovascular (heart rate and heart rate variability, local blood flow and blood pressure), respiratory (breathing rate) electrodermal (skin conductance), muscular (trapezius and masseter EMG) and biochemical (insulin, cortisol, catecholamines) variables. Proprioceptive acuity was assessed using active-active repositioning tests. Pain levels were assessed using Visual-analogue or Numerical Rating scales. General health was evaluated through the Short-Form SF-36 Health Related Quality of Life questionnaire and Self-Efficacy Score questionnaires, whereas dysfunction was evaluated using the Oswestry Low Back Pain questionnaire, Pain Disability and Neck Disability Index questionnaires, the McKenzie evaluation and primary healthcare diagnoses. Self-reports of pain, stress and exertion were acquired prior to, during and post-testing.Chronic pain subjects were characterised by increased sympathetic and decreased parasympathetic activity as reflected in heart rate (LBP, WAD, WADj), heart rate variability (LBP, WAD, WADj), blood pressure (WADj) and electrodermal activity (LBP). In general, WAD showed more pain and dysfunction than NT, with lower self-efficacy and health-related quality of life. Differential reactivity was observed only in WAD, with increased responsiveness to sensory stimuli (heart rate variability, electrodermal activity), and motor tasks (heart rate) and a decreased response to cognitive challenge (heart rate variability, electrodermal activity). A significant part of WADj subjects showed sensorimotor impairment and low endurance in chewing tests, concomitant with a cardiovascular response that correlated with pain levels. Proprioceptive acuity was not found to be impaired among subjects suffering from chronic pain, and there were no indications of significant individual response specificity. Response to experimentally induced muscle pain in healthy subjects was also characterised by a prominent cardiovascular component. In simulated occupational settings autonomic activation and transient insulin resistance were detected in healthy subjects following monotonous repetitive work, with no similar effects following dynamic exercise. Modest deviations in circadian heart rate variability patterns during workdays were detected in ambulance personnel reporting more pronounced musculoskeletal symptoms, with no such effects on work-free days.Autonomic balance observed in chronic pain subjects was characterised by a trend towards increased sympathetic activity in comparison with pain-free controls. Moderate signs of affected reactivity to autonomic function tests were observed in patients with WAD, however no specific reaction patterns have been observed in any chronic pain group. Correspondence between the intensity of pain and autonomic activity was observed in acute pain and in chronic pain groups characterised by higher pain levels. As indicated by autonomic and neurohormonal changes in the recovery from real and simulated work, further studies with physiological monitoring of the effects of work-related stress are warranted for better understanding of the mechanism of musculoskeletal disorders.
|
|
