The musculoskeletal structure of the human and animal body provides multiple solutions for performing any single motor behavior. The long-term goal of the work presented here is to determine the neuromechanical strategies used by the nervous system to appropriately coordinate muscles in order to achieve the performance of daily motor tasks. The overall hypothesis is that the nervous system simplifies muscle coordination by the flexible activation of muscle synergies, defined as a group of muscles activated as a unit, that perform task-level biomechanical functions. To test this hypothesis we investigated whether muscle synergies can be robustly used as building blocks for constructing the spatiotemporal muscle coordination patterns in human and feline postural control under a variety of biomechanical contexts. We demonstrated the generality and robustness of muscle synergies as a simplification strategy for both human and animal postural control. A few robust muscle synergies were able to reproduce the spatial and temporal variability in human and cat postural responses, regardless of stance configuration and perturbation type. In addition inter-trial variability in human postural responses was also accounted for by these muscle synergies. Finally, the activation of each muscle synergy in cat produced a specific stabilizing force vector, suggesting that muscle synergies control task-level variables. The identified muscle synergies may represent general modules of motor output underlying muscle coordination in posture that can be activated in different sensory contexts to achieve different postural goals. Therefore muscle synergies represents a simplifying mechanism for muscle coordination in natural behaviors not only because it is a strategy for reducing the number of variables to be controlled, but because it represents a mechanism for simply controlling multi-segmental task-level variables.

The investigation of the influence of emotions on human cognition and behavior challenges scientist since a long time. So far the most popular approach to investigate this phenomenon was to observe brain processes and behavior. In the recent decade the field of computational neuroscience proposed a new methodology: the construction of embodied models of emotions and their verification in real world environments. In this thesis we present different studies that use computational models of emotions to control the behavior and the expressions of situated agents. Using different methodologies we evaluate both, the performance of the models and the behavioral responses of humans interacting with them. Our results add to a deeper understanding of the multidimensional phenomena of emotions on three levels: Perception, interaction and how the processing of emotional cues influences learning and behavior / La investigació/recerca sobre la influència de les emocions en la cognició i el comportament humà constitueix un repte científic des de fa molt temps. Fins ara el mètode més popular per a investigar aquest fenòmen ha estat el d'observar els processos cerebrals i el comportament. En l'última dècada el camp de la neurociència computacional ha proposat una nova metodologia: la construcció dels models incorporats d’emocions i la seva verificació en entorns del món real. En aquesta tesi presentem diferents estudis que han utilitzat models computacionals de les emocions per controlar el comportament i les expressions d’agents localitzats. Utilitzant diferents metodologies, hem avaluat tant el rendiment d’aquests models així com les respostes conductuals dels éssers humans que han interactuen amb ells.Els nostres resultats se sumen a una comprensió més profunda dels fenòmens multidimensionals de les emocions en tres nivells: la percepció, la interacció i com el processament dels senyals emocionals influeixen en l'aprenentatge i el comportament

This project presented a biomechanical model of the lumbosacral spine and pelvis, including novel methodologies associated with the measurement of human mechanics. This research has, for the first time, produced accurate three-dimensional geometric models of the human skeleton from living subjects using magnetic resonance imaging technology, enabling the prediction of physiological muscle action within individuals. The model was used to examine changes in the mechanics of the lumbopelvic musculoskeletal system between the standing and seated postures due to the increasing prevalence of the seated posture in the work and home environment. The outcomes of this research included a novel bone wrapping algorithm used to describe the effect of muscle-bone interactions. a novel method for creating three-dimensional in vivo spinal reconstructions using MRI, three dimensional in vivo helical axis measurements and subject specific normalised moment data.

The aim of this thesis is to develop a quantitative measure of postural defects known as lordosis and kyphosis. The measurement of these is an important part of their identification and treatment.

Background: Clinical ergonomic advice for sitting posture has been inferred from anthropometry theory and physiology studies. Qualitative observation of posture has been used to argue that postures are too flexed, too extended, too static, too mobile, require insufficient muscle activity or require too much. In other fields of healthcare, evidence is progressed from basic science to clinical trials before an intervention is prescribed, but postural advice has been prescribed from basic science without quantitative studies of postural behaviour. Spinal neuromuscular control can predict development of low back pain, it is affected by spinal pain, and can be trained, but studies examining these variables rarely measure the spinal position of their test subjects. There is a need for more detail of how spinal positions affect regional muscle activity. Study Objectives: The overall aims of this thesis were to quantify sagittal spinal postures in sitting for comparison within and between subjects and tasks, and to detail paraspinal and abdominal muscle activity associated with sitting postures. The studies quantified regional spinal curves in - Study I: typical posture behaviour during a computer task in comparison with standing, - Study II: postures that are achievable in sitting, - Study III: the regional muscle activity associated with sitting postures that have been clinically advocated as ‘ideal’, - Study IV: cohorts with and without a history of low back pain for comparison of regional muscle activity. Results and Conclusions: For clinical trials quantifying postural behaviour, the postural variation within subjects and task conditions in Study I demonstrated the importance of measurement over a prolonged period and subjects performing relevant tasks (as opposed to brief measures such as radiography that have been the standard for posture assessment). The use of surface tracking to quantify regional spinal curves and sagittal balance establish a foundation to investigate the effect of interventions on posture behaviour (eg. chair geometry, posture training, task variables and subject cohorts). Study I also showed that typical sitting posture for a computer task was more flexed at the thoracolumbar spinal region than when subjects deliberately ‘corrected’ their sitting posture, and both sitting postures were flexed at the lumbar region relative to standing. Study II showed that most subjects were unable to sit with spinal curves like those adopted in standing unless facilitation and feedback were provided, although these curves have been clinically advocated as ‘ideal’ posture. If clinical theories about ‘ideal’ sitting posture are correct, then teaching individuals the awareness of spinal position or skill to adopt these postures could be as important for workplace health and safety as other variables such as design and adjustment of office furniture. Study III showed three upright sitting postures that have been clinically advocated as ‘ideal’ were distinguished by incremental changes in activity of the lumbar multifidus muscles. In Study IV, individuals with a history of low back pain showed more incremental activity at the longissimus thoracis muscle to achieve the same sitting postures. If particular postures are shown to be ‘ideal’ in clinical trials, then training for these postures may need to focus on muscular strategies as well as spinal position. The distinct differences in regional muscle activity observed with spinal curves and subject cohorts (Studies III and IV) imply that studies of spinal neuromuscular control should measure or control spinal curves during testing. If spinal posture were controlled, the flat posture (flat surface from ~T5 to sacrum) would have the advantages of being achievable, commonly used in sitting and easily assessed. The flat posture also demonstrated the lowest muscle activity of the upright sitting postures examined, which may improve accuracy of determining muscle activity onset/offset used as an outcome measure for interventions, distinguishing cohorts or as a predictor for low back pain occurrence.

Axial rotation is regarded as an essential movement of the trunk that allows many individuals to participate in vocations, sports and activities of daily living. Unfortunately when the destabilising nature of rotation is combined with that of spinal flexion, the risk of injuring the spine can increase significantly. Few studies have investigated the potential benefits that maximizing trunk rotation has in certain vocation and sport-related arenas and none have looked at whether adopting certain spinal postures in the sagittal plane can maximise trunk rotation more than others. The aim of the study was to determine the effects of alterations of trunk inclination, spinal posture, pelvic fixation and turning direction on the active range of motion (ROM) of trunk rotation. Twenty healthy individuals participated in the main study. Retro-reflective markers were placed on key anatomical locations and used to track the movement of the thorax and pelvis during a series of repeated maximal trunk rotations in ten different spinal positions within the sagittal plane. Trunk kinematics and kinetics were recorded simultaneously using an optoelectronic motion analysis and force platform measuring system. A repeated-measures multiple analysis of variance (MANOVA) was used to test for the main effects of trunk inclination, spinal posture, fixation of pelvis and direction of turn on maximum active ROM of trunk rotation, maximum pelvic rotation and the anterior-posterior and lateral displacement of the centre of pressure (COP). To investigate test-retest reliability, ten participants were tested on two separate days. Repeatability for each outcome measure was investigated using interclass correlation coefficients (ICC) and Bland Altman graphs. The majority of subjects showed reasonable test-retest reliability for trunk rotation measures in each of the test positions, with ICC’s ranging between 0.562 – 0.731. Overall, trunk inclination (0°, 22.5°, 45°) forward in the sagittal plane had a significant effect on trunk and pelvic rotation (p<0.001) and lateral displacement of the COP (p<0.005) during trunk rotation. As trunk inclination increased from 0° to 45° there was an average increase in trunk rotation ROM of approximately 10 % (approximately 3.4°). Furthermore, increasing trunk inclination led to an increase in lateral displacement of the COP and a decrease in pelvic rotation. Spinal posture (neutral, flexed, extended) at a forward inclination of 45° had a significant effect on trunk rotation (p<0.01) and pelvic rotation (p<0.05), with a neutral spine averaging approximately 3 % (approximately 1.1°) more trunk rotation than a flexed or extended posture. The position and posture of the spine in the sagittal plane appears to have a significant influence on ranges of trunk rotation. The study suggests that rotating the trunk when adopting a neutral spine inclined to 45° will maximise range of trunk rotation and encourage a natural stabilisation of the lower body. This posture meets the unique set of biomechanical requirements for the sport of golf and may help to reduce the risk of injury in manual material handling tasks. Conversely, rotating the trunk whilst the thoracolumbar spine is flexed leads to a reduction in trunk rotation ROM, encourages greater pelvic and lower body rotation, reduces torque production of the trunk and may increase the risk of lower back injury. These findings have important implications in relation to the teaching of spinal position during vocations, sports and activities of daily living that seek to maximise trunk rotation.

Thesis (D. Music)--Northwestern University, 2006. / Includes bibliographical references (leaves 132-136).

Diss. (sammanfattning) Linköping : Univ., 2002. / Härtill 4 uppsatser.

Dissertation (Ph.D.)--University of South Florida, 2007. / Title from PDF of title page. Document formatted into pages; contains 115 pages. Includes vita. Includes bibliographical references.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2006. / Härtill 5 uppsatser.