| 1. |
- Crommert, Martin Eriksson, 1974-
(författare)
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On the role of transversus abdominis in trunk motor control
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- All trunk muscles are important contributors to spine stability. However, the deepest abdominal muscle, transversus abdominis (TrA), with its characteristically horizontal fibre orientation seems to serve a unique function in trunk motor control. The main mechanical role of TrA is believed to be to contribute to vertebral alignment during imposed moments on the trunk, executed mainly via either regulating the pressure level within the abdominal cavity and/or transmit forces to the spine via the thoracolumbar fascia. However, the complete function of TrA and what factors affect its activation are still not fully understood. The purpose of the present thesis was to investigate the role of TrA in trunk motor control, specifically in relation to the presence or absence of postural demand on the trunk.The timing and magnitude of TrA activation were investigated, in relation to other trunk muscles, with intramuscular fine-wire electrodes in different loading situations and body positions with varying postural demand.In a side-lying position, with no postural demand of keeping the trunk upright, the activation of TrA was delayed relative the superficial abdominal muscles compared to previous experiments performed in a standing position. The timing and magnitude of activation of TrA did not depend upon the direction of perturbation. In the standing position, different static arm positions revealed that the activation of TrA co-varied with variations in the degree of postural demand on the trunk and also the imposed moments, regardless of moment direction. Finally, a study on rapid arm flexion movements confirmed that TrA is part of the pre-programmed anticipatory response in advance of known perturbations. The activation magnitude of TrA was the same regardless if the arm movement induced flexion or extension moments on the trunk.In conclusion, the activation of TrA is associated with the upright postural demand on the trunk and with balancing imposed moments acting on the spine, regardless their direction. The findings are in support of the beliefs that TrA act as a general, direction non specific, stabilizer of the lumbar spine.
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| 2. |
- Sandlund, Jonas
(författare)
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Position-matching and goal-directed reaching acuity of the upper limb in chronic neck pain : associations to self-rated characteristics
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Neck-shoulder pain is common in the general population and causes individual suffering as well as large costs for the society. Despite substantial efforts, there is still a shortage of methods for objective diagnosis and effective rehabilitation of such disorders. Thus, there is a great need to develop and evaluate new methods for these purposes. From clinical observations and recent research it has become evident that sensorimotor control can be impaired in people with neck-shoulder pain and may play a role in the pathogenesis of these disorders. In this thesis, precision of goal-directed arm movements, a previously unstudied class of movements in neck-shoulder pain, was studied. The main aim of the thesis was to investigate if people with chronic neck-shoulder pain have a reduced acuity of goal-directed movements of the upper extremity. A second aim was to study associations between reduced movement acuity and symptoms and self-rated characteristics. Upper limb repositioning acuity was assessed in blindfolded subjects performing tests of active, ipsilateral position-matching of two target positions (long and short) in movements constrained to horizontal-adduction of the shoulder. Reduced repositioning acuity, suggesting impaired shoulder proprioception, was found for both subjects with whiplash associated disorders (WAD) and non-specific neck-shoulder pain (NS). The degree of reduced acuity was shown to correlate with self-ratings of various health concepts, functioning and pain. A conspicuous finding was that there was lack of correlation between short and long target errors, along with the fact that associations between repositioning acuity and symptoms and self-rated characteristics was primarily found for the short target position. To further investigate the possible mechanisms underlying the disassociation between long and short target movement control, the association pattern between the outcome of several variants of ipsilateral position matching and velocity-discrimination tests, were studied. It was found that the perception of limb position in position-matching of short target locations appears to be predominantly based on movement velocity, whereas perception of limb position in movements to longer target locations may rely on a location-based perception mechanism. To extend the research on reduced upper extremity proprioception in neck-shoulder pain to a more natural movement situation, acuity of goal-directed pointing including full vision and 3D multi-joint movements was investigated in WAD, NS and healthy controls subjects. The results revealed a reduced acuity for both neck-pain groups. Moreover, distinct associations between end-point acuity and neck movement problems, limitations of some physical functions and, in WAD; some aspects of pain, were revealed. The findings demonstrate that the precision of upper limb movements can be reduced in chronic neck-shoulder pain. Substantial associations with symptoms and self-rated functioning suggest a clinical relevance of acuity measures of goal-directed arm movements. The findings indicate that tests of sensorimotor control can provide objective measures that may be useful in biopsychosocial profiling and characterization of subgroups of patients with chronic neck-shoulder pain, and that training target control of goal-directed movements should be considered in rehabilitation programs of people with these disorders.
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| 3. |
- Andersson, Eva A
(författare)
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EMG and strength in trunk and hip muscles
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall aim of this thesis was to study the myouelectric activity of all major muscles involved in the movements and stabilization of the trunk, pelvis and hips during training exercises, postures, motor tasks, maximal strength performance and locomotion. By use of ultra-sound, EMG electrodes could be guided safely and accurately into muscles situated even close to the spinal column, such as psoas, quadratus lumborum and deep parts of erector spinae. A task specific variation in activation levels were seen between muscle synergies, as well as between individual muscles within a synergy. Selective engagement of the abdominal muscles could be achieved in trunk flexion sit-ups, that is lifting only the upper trunk from the floor. An even higher activation of abdominal muscles was needed for static stabilization of the trunk and pelvis during hip flexion sit-ups, whereas single leg lifts were performed without involvement of the abdominal muscles. A selective activation of either the iliacus or psoas muscle was observed, for example in certain types of training exercises and in walking and running. Applying bending moments to the spine, resulted in a grading of the muscle activation response according to mechanical advantage, that is highest in the quadratus lumborum in lateral loading and in the superficial erector spinae in ventral loading. An exception was the most forward flexed position in standing where the superficial erector spinae "relaxed" but quadratus lumborum remained active. In general, the level of EMG in maximal efforts was maintained at the same high level irrespective of position in the range of motion, despite a marked variation in strength output. This position-dependency, as well as the strength values as such, varied in a specific way in groups of athletes, related to previous background. These data contribute to the understanding of muscle function and motor control of the trunk , pelvis and hips. They are also of relevance when evaluating and designing tests and training programs in rehabilitation and sport contexts as well as for improving biomechanical models of spinal loading.
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| 4. |
- Bjerkefors, Anna
(författare)
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Performance and trainability in paraplegics : motor function, shoulder muscle strength and sitting balance before and after kayak ergometer training
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Spinal cord injury (SCI) results in a complete or partial loss of motor and/or sensory function below the injury level. An SCI causes extensive functional impairment compelling many persons to wheelchair usage. Maintaining an adequate strength and control of trunk and shoulder muscles becomes essential, as the majority of every day tasks will be performed in a sitting position. Moreover, physical exercise is crucial to avoid risks connected with a sedentary life-style. Therefore, it becomes important to find suitable, effective, and attractive physical activities to retain and even improve motor functions achieved during rehabilitation. Ideally, such a training activity should be versatile and have the potential to improve several capacities beneficial to everyday life and thereby increase the independence of persons with SCI. Kayak paddling appears to fulfil several of the criteria for such an activity. Objectives: The overall aims were to see if, and to what extent, a period of training on a modified kayak ergometer could influence functional performance as well as specific qualities, such as, shoulder muscle strength and sitting balance control in a group of postrehabilitated persons with thoracic SCI. An additional aim was to understand more about the availability of the trunk muscles in a person with a clinically complete thoracic SCI and how the trunk muscles are used to maintain upright sitting in response to balance perturbations. Methods: Ten adult post-rehabilitated persons with thoracic SCI performed 30 sessions of kayak ergometer training for a 10-week period, with progressively increased intensity and balance demand in the medio-lateral direction. Pre- and post-training measurements included performance in functional wheelchair tests, maximal voluntary shoulder muscle strength, and trunk stability in response to support-surface translations. Electromyographic (EMG) recordings from deep and superficial trunk muscles were obtained in a sub-sample of two subjects, one with a high thoracic SCI and one able-bodied person. Results: There were significant improvements with training in functional performance, shoulder muscle strength, and the ability to maintain an upright sitting posture in response to balance perturbations in the group of persons with SCI. The EMG results revealed that the person with a high thoracic SCI, clinically classified as complete, was still able to activate trunk muscles below the injury, both in maximal voluntary efforts and in response to balance perturbations, but the response pattern differed from that of the ablebodied. Conclusions: The improvements in test-performance observed with the kayak ergometer training in the persons with SCI should enhance their capacity to master similar challenges in everyday life, which, in turn, might lead to a greater independence. The pilot data on muscle activation highlight the importance of including examination of trunk muscle function in persons with thoracic SCI in relation to injury classification, prognosis, and training prescription.
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| 5. |
- Kvist, Joanna, 1967-
(författare)
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Sagittal plane knee motion during activity in the anterior cruciate ligament deficient knee
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A complete rupture of the anterior cruciate ligament (ACL) results in static and often in functional instability. After an ACL-injury, most patients have to decrease their activity level, while some can cope with their injury and manage to keep a high activity level. A better tmderstanding of the influence of muscle activation and external load on the non-injured and injured knee, but also of the adaptive motion strategies employed by the patients with an unstable knee, is of importance for the construction of rehabilitation programs.The general purpose of this thesis was to study certain knee motions during activities focused on rehabilitation, in individuals with anterior cmciate ligament injury and uninjured controls. The sagittal tibial translation and knee flexion angle were registered during motion with the CA-4000 computerized electrogoniometer and EMG was used for analysis of muscle activity. The injured knee had increased static laxity compared to the contralateral non-injured knee and the non-impaired group.The amount of tibial translation increased with increased quadriceps torque during nonweight bearing activities (isokinetic and isotonic contractions). In the non-injured knees, the restraining mechanism was engaged above 50% of isokinetic concentric quadriceps torque and during the eccentric contractions already at low quadriceps torques (<10% of maximum). The motion pattern was similar in the injured knees and the amount of individual translation was larger during the eccentric contractions, compared to the non-injured knees.During weight bearing, tibia translated anteriorly and remained in that position. In the non-injured knee, different loads and performance of weight bearing activities produced different amount of translation. Level walking and squat with the center of gravity behind the feet produced somewhat smaller amount of translations, while other weight bearing activities produced similar amount of translation compared to the non-weight bearing isotonic knee extension. In the injured knee, all weight bearing activities produced similar amount of translation, smaller compared to the non-weight bearing isotonic knee extension.Quadriceps - hamstrings co-activation was not present during non-weight bearing quadriceps dominant activities and therefore, it was not shown to be a factor limiting anterior tibial translation. Also, during the weight bearing activities, hamstrings eo-contraction could not limit the anterior tibial translation. Quadriceps and gastrocnemius seems to work synergistically to stabilize the knee by maintaining an anterior position of tibia.In the injured knee, isokinetic concentric quadriceps contraction below 50% of maximum torque produced the smallest amount of tibial translation. Weight bearing exercises produced similar ammmt of translation despite of load and performance, indicating that when level walking is allowed after an injury, other weight bearing activities can be performed without increasing the amount of translation. Eccentric isokinetic quadriceps contractions above 50% of maximum torque and isotonic quadriceps exercise with and without weights at flexion angles less that 40°, should be avoided in order protect the knee joint.
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| 6. |
- Seger, Jan
(författare)
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Neuromuscular aspects of eccentric knee extensor actions : effects of electrical stimulation, age, gender and training
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall aim of this thesis was to study the effects of electrical stimulation, age, gender and training on the torque- and EMG-velocity relationships during eccentric knee extensor muscle actions in man. An isokinetic custom-built dynamometer was evaluated and used throughout the thesis. During maximal voluntary efforts eccentric torque output was similar to isometric and did not change with velocity. Superimposing electrical stimulation onto a maximal effort caused a specific increase in eccentric torque output. Submaximal electrical stimulation alone also produced a relatively higher eccentric than concentric torque. These results indicate the presence of a neural tension-regulating mechanism during maximal voluntary eccentric muscle actions in man. The hypothesis that such a mechanism would be more pronounced in children than adultswas not corroborated by the results from children, pre- and postpuberty. The adult pattern of interdependence between torque, EMG and muscle action type seemed to be established before puberty in both males and females. Comparisons between genders indicated a higher eccentric to concentric ratio of electromechanical eficiency at high velocity in postpuberty and adult females. Training with either pure eccentric or concentric maximal isokinetic muscle actions resulted in mode and velocity specific adaptations, particularly for eccentric training, in peak torque, muscle cross-sectional area, electromechanical efficiency and cross education, that is increase in strength of the contralateral leg. On the other hand, no or only minor training effects were seen on mean torque, muscle fibre morphology, eccentric to concentric EMG ratios and antagonist muscle activity. The expression of net eccentric torque output during maximal voluntary eccentric knee extensor actions have shown several distinct features separating it from concentric and isometric actions. Clarification of the underlying neuromuscular mechanisms remains a challenge for future research.
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