Lateral rotation of the left and right hip, knee, ankle and intertarsal joints during three trials of turnout from the straight leg and demi-plie positions was quantified with the use of a specially designed friction-free weightbearing goniometer, projecting fin-like body markers, and overhead photography. The female subjects were dancers (10 beginners, 11 advanced) recruited from University of Arizona ballet classes. MANOVAS revealed that turnout as measured from the feet was (1) significantly greater in the advanced group in both positions, (2) significantly greater in the demi-plie position than in the straight leg, (3) a cumulative joint rotation effect with the hip contributing the greatest absolute and relative amounts. Positive significant correlations occurred between: (1) pedal turnout and lateral hip rotation for the advanced group in both positions and for the beginning group in demi-plie, and (2) pedal turnout and lateral ankle rotation for the advanced dancers in the straight leg position. Alignment of the lower extremity segments during turnout from both positions did not exist for either group.

Postural set and body image are described as two interactive components of a dancer's expressive skills as a performing artist. The ways in which these components interact are influenced by numerous factors, including the dancer's physique, the environment in which movement is learned and practiced, the aesthetic requirements of particular dance techniques, and the kinds of body images the dancer has created or is in the process of creating. Postural set refers to a habitual, bipedal position of the body that is recognized by the central nervous system as an established motor response. Body image is defined as the summary notion, at any given moment, of one's body proportions and properties. Postural set and body image are functionally interrelated on psychological and physical levels, and both contribute to the experience of the body as a sensing, moving, and emotional entity.

This thesis examined Autonomic Nervous System activity evoked by postural instability. Autonomic reactions were assessed using measures of electrodermal activity at the surface of the skin. Perturbation-evoked electrodermal responses (EDRs) were consistently observed in conjunction with both upper and lower limb postural reactions. These autonomic responses were sensitive to perturbation amplitude, as well as experimental manipulations which did not influence the perturbation itself but which affected response execution. In particular, stimulus predictability and movement challenge modulated EDRs, although purely cognitive manipulations did not significantly affect autonomic responses. Probes examining the potential role of such autonomic potentials in compensatory balance control revealed that EDRs evoked during compensatory postural reactions were larger and more consistent than potentials evoked by purely motor or sensory stimuli, suggesting that evoked autonomic activity plays a role in compensatory behavior. While the specific role of autonomic contributions in compensatory balance control require further study, speculative models for autonomic contributions propose either feedback-based pathways for detection of instability to initiate the postural reaction, and/ or an adaptive role to higher centers important for establishing sensorimotor gain in future conditions. This thesis presents new evidence regarding basic neural mechanisms engaged in the recognition and response to postural instability, and future work may extend these findings in clinical populations with high fall incidence and offer clues as to alternative causes for falls and fall prevention.

It is well establish that posture deformities are a common problem among children that is often ignored by parent and teachers. Posture deformities in children could be related to their socio-economic status, lifestyle, culture, tradition, environmental factors, as well as activity levels and are associated with numerous adverse health effects, which include lung and heart defects, indigestion and back pain. Children who experience back pain are at increased risk of having back pain as adults. The economic impact of back pain affects the industry, were back problems are the most expensive type of injury claim. The increase in spinal problems, such as lower back pain in children and adolescents, points to the need for continued screening. It is suggested that early detection of postural deviation could provide an improve chance for corrective remedies and posture development. On investigating the relevant literature it becomes clear that attempts to define the prevalence of posture deformities among children have focused on reporting selected deformities only. Consequently the literature contains insufficient information on posture deformities involving the entire musculoskeletal system, as well as the prevalence of posture deformities among black African people. The purpose of this study was firstly to determine the incidence of posture deviations among black African children in the North West Province and secondly to determine the difference in the prevalence of posture deformities between boys and girls. In a longitudinal study posture deformities including the entire musculoskeletal system were assessed in 251 schoolchildren (136 girls and 115 boys). Posture screening was done according to the New York Posture test and a posture grid. Subjects were evaluated in a standing position from the rear and lateral side. Foot deformities (flat foot) were also measured with the use of white chalk and a black board. Thereafter the "Adam's test" (forward bending test) were used for further scoliosis evaluation. The prevalence of posture deformities was reported to be high among black African schoolchildren. The incidence of lordosis (84%) and protruding abdomen (67%) was the highest, while twisted head (8%) was reported as the lowest. Gender difference in the prevalence of posture deformities was also found, with a higher incidence of posture deformities reported in girls (54%) as in boys (46%). / Thesis (M.Sc. (Human Movement Science))--North-West University, Potchefstroom Campus, 2007.

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Bien que l’exposition professionnelle et chronique aux solvants organiques constitue un problème de santé publique, les effets neurotoxiques engendrés, notamment sur la fonction d’équilibration, sont encore mal connus. Cette thèse a pour objectif d’identifier les signes précoces d’une atteinte neurotoxique provoqués par une exposition chronique et subchronique à des solvants organiques à des concentrations inférieures aux valeurs limites d’exposition professionnelle. Ainsi, l’organisation sensorielle, la régulation posturale et la stabilisation du regard, ont été évaluées par différents examens posturographiques et vidéonystagmographiques, chez des salariés régulièrement exposés à des solvants. Une première étude exposés – non-exposés, menée au CHU de Nancy, a montré qu’une exposition chronique, en particulier au toluène et à l’éthanol, altérait la qualité du contrôle postural, notamment en situations de conflits sensoriels nécessitant le traitement des informations vestibulaires. Le temps de réaction oculomotrice était également plus long chez les exposés à des solvants, suggérant ainsi une atteinte des structures corticales et sous-corticales régulant la stabilisation du regard. Une seconde étude exposés – non-exposés, menée à Sfax (Tunisie), a montré qu’une exposition chronique et subchronique, en particulier au n-hexane et au toluène, générait des effets neurotoxiques précoces, qui ont été confirmés par évaluation du contrôle postural sur une plateforme ambulatoire de posturographie. Ainsi, une dégradation de la qualité du contrôle postural, notamment lors d’une situation de conflit sensoriel nécessitant des informations vestibulaires, a été observée, suggérant ainsi des atteintes des structures corticales, sous-corticales et des voies vestibulaires régulant l’équilibre. La qualité du contrôle postural lors de situations de conflits sensoriels peut constituer un indicateur prédictif de mise en évidence d’atteintes précoces, non seulement par les solvants, mais aussi par d’autres agents neurotoxiques, par l’utilisation de la posturographie, outil d’investigation performant et non invasif. / Occupational and chronic exposure to organic solvents is a public health problem. However, there is limited knowledge of effects on equilibrium function after this exposure. The aim of this study was to identify predictive signs of neurotoxic alterations due to a chronic and subchronic exposure to certain organic solvents below the threshold limit value. Thus, the sensorial organisation and the postural and gaze control have been evaluated by posturography and videonystagmography in chronically exposed workers. A first study exposed – non-exposed, was carried out in the university hospital of Nancy, has shown that chronic exposure, mainly to toluene and ethanol, altered on the one hand, quality of balance control specifically during sensorial conflict situations managed by vestibular information, and, on the other hand, saccadic reaction time. These results suggest an alteration of the cortical and subcortical structures involved in postural and gaze control. A second study exposed – non-exposed, was carried out in Sfax (Tunisia), has shown that chronic and subchronic exposure, mainly to n-hexane and toluene, generated neurotoxic predictive effects on balance control, which was evaluated on a posturography ambulatory platform. Thus, balance control was lower in chronically exposed workers, and got worse after subchronic exposure, particularly during conflict situations where vestibular information was important. These results suggest an alteration of the cortical and subcortical structures and vestibular pathway involved in balance control. Balance control performance during sensorial conflict situations could be considerate as a predictive indicator of neurotoxicity induced by an exposure to solvents and to other chemical substances, evaluated by posturography which is a discriminating and not-invasive method.

Objetivos: analisar a postura corporal em pacientes disfônicos e correlacioná-los com indivíduos sem alteração de voz, a fim de estabelecer novos recursos terapêutico para reabilitar o portador de disfonia. Método: estudo prospectivo. Foram avaliados 43 indivíduos (23 disfônicos e 20 sem alteração de voz) do sexo feminino,com idade entre 18 e 40 anos ,sem alterações neurológicas ,respiratórias e reumáticas. Todos os pacientes foram encaminhado pelo serviço de Otorrinolaringologia da Escola Paulista de Medicina ( UNIFESP- EPM),após anamnese, exame do otorrinolaringologista e laringoscopia ,tendo como diagnostico de disfonia funcional ou organofuncional. Nessa população foi avaliado: 1- Postura corporal in loco, 2 – Documentação fotográfica, 3 – Exame Eletromiografia, 4 – Questionário das algias. Resultados: não houve diferença estatisticamente significante em relação à queixa,porem foi encontrado um numero maior de tensão muscular e dor na região cervical, onde se encontra situado a laringe, nos portadores de disfonia. Na avaliação postural, os indivíduos disfônicos apresentarão assimetria de ombros, alteração no posicionamento da escapula, retificação com anteriorização da região cervical em relação ao grupo controle. Nos resultados da eletromiografia houve aumento das atividades nos músculos supra-hióideo em emissão prolongada, controlada e deglutição. Nos músculos infra-hióideo houve alteração no traçado eletromiógrafico na emissão prolongada. Conclusão: pode- se concluir que o estudo mostra a existência da correlação positiva entre indivíduos portadores de disfonia e alteração na postura, baseado nas diferenças dos achados clínicos e medidas eletromiográficas. / Objectives: This study analyzed the body posture of dysphonic patients and correlated them with individuals without voice alterations, in order to establish new therapeutic resources to rehabilitate the patients with dysphonia. Method: prospective study. A total of 43 individuals were analyzed (23 with dysphonia and 20 without voice alterations), of female gender, aged 18 to 40 years, without neurological, respiratory and rheumatic alterations. All patients were referred by the ENT Sector of Paulista Medical School (UNIFESP- EPM) after anamnesis, ENT examination and laryngoscopy, with diagnosis of functional or organofunctional dysphonia. The following parameters were investigated in this population: 1- Body posture in loco, 2- Photographic records, 3- Electromyographic examination, 4- Questionnaire on pain. Results: The results indicated no statistically significant difference with regard to the complaint, yet a larger number of individuals with dysphonia reported muscle tension and pain at the cervical region, where the larynx is located. Posture evaluation revealed that dysphonic individuals presented shoulder asymmetry, alterations in scapular positioning and rectification with forward displacement of the cervical region compared to the control group. The results of electromyographic analysis demonstrated increased activity of the suprahyoid muscle in prolonged emission, controlled emission and swallowing. The infrahyoid muscles exhibited altered electromyographic tracing during prolonged emission. Conclusion: It was concluded that there is correlation between individuals with dysphonia and posture alterations, based on the differences in clinical findings and electromyographic measurements.

Durante a postura ereta quieta (PEQ) há oscilações aleatórias do centro de pressão, que podem ser medidas por uma plataforma de força. Esse movimento aleatório, que ocorre mesmo durante uma posição ortostática, é devido a fontes de variabilidade que vão desde a periferia do sistema sensorial até o sistema muscular na geração de torques, passando pelo sistema nervoso central. Uma vez gerados os comandos motores descendentes pelo encéfalo, fontes de variabilidade geradas na medula espinhal e nas unidades motoras contribuem para variabilidade na força desenvolvida e que não estão contidas nos comandos descendentes. O foco desta tese foi dirigido ao estudo da contribuição de fontes associadas à medula espinhal e às unidades motoras na geração de variabilidades do torque na articulação do tornozelo associadas ao controle do grupo muscular tríceps sural, que é de grande importância no controle da postura ortostática. A metodologia desenvolvida constou no estudo da variabilidade do torque de flexão plantar gerado em diferentes condições juntamente com a análise dos eletromiogramas dos músculos que compõem o tríceps sural. Foram realizados três conjuntos de experimentos: 1) sujeito sentado, com joelho estendido (JE) e joelho flexionado (JF) em tarefa de contração isométrica (tarefa de força - TF); 2) sujeito sentado, com joelho estendido, comparando TF com tarefa de controle de posição (TP); 3) sujeito em posição ortostática livre e apoiada, comparada com TF e TP executadas na posição sentada com o joelho estendido, na manutenção do mesmo torque de flexão plantar mensurado na posição ortostática. Essas últimas condições foram também testadas por meio do reflexo H do músculo SO. Para os experimentos 1 e 2 a amostra constou de 13 sujeitos e para o experimento 3 de 9 sujeitos, todos saudáveis. Os quantificadores utilizados para caracterizar os sinais captados foram o valor médio (), o desvio padrão () e o coeficiente de variação (CV), para os sinais de torque e da envoltória do eletromiograma (EMG) dos músculos sóleo (SO), gastronêmio lateral (GL) e gastronêmio medial (GM) nas condições acima. Os resultados do Experimento 1 são sintetizados a seguir. O torque em contração voluntária máxima (CVM) foi 58% maior na posição JE quando comparado com o valor em JF, mas a variabilidade ( e CV) foi maior em JF do que em JE. Para contrações de 10 a 80% da CVM, a variabilidade do torque ( e CV) também foi maior na posição JF do que na JE. Foi observada relação linear entre e do torque gerado pelo tríceps sural em JE e JF ( e normalizados em relação aos respectivos torques em CVM), aumentando a variabilidade da força gerada ao aumentar o valor médio da força. Os níveis de ativação muscular ( da envoltória) foram maiores em JE do que em JF, principalmente devido à maior ativação de GM e GL. O músculo SO apresentou intensidade de ativação normalizada maior do que a do GM e GL, tanto em JE quanto em JF. Tanto a intensidade do EMG quanto o da envoltória do EMG aumentaram com o valor do torque de flexão plantar exercido, para os três músculos que compõe o tríceps sural. No Experimento 2 foram obtidos os resultados descritos a seguir. A variabilidade do torque ( e CV) foi menor em TP do que em TF. Houve uma relação crescente entre o e o do torque gerado pelo tríceps sural, e entre o e o das envoltórias dos EMG dos três músculos em função do do torque 8 gerado pelo tríceps sural, em ambas as tarefas TF e TP. O da envoltória do EMG mostrou correlação positiva em relação ao do torque de flexão plantar, ambos normalizados em relação aos respectivos valores em CVM. Os resultados do Experimento 3 são sintetizados a seguir. A variabilidade do torque ( e CV) de flexão plantar durante a PEQ foi maior do que nas demais condições, havendo na amostra de sujeitos uma correlação positiva entre os valores de em PEQ e em TF ou TP. Por outro lado, em postura ereta apoiada (PEA), o do torque apresentou correlação nula com o do torque em TF ou TP. Os níveis de ativação muscular no tríceps sural foram maiores em TF do que nas demais condições, em grande parte devido ao nível de ativação do músculo SO em TF ter sido maior do que nas demais condições. O da envoltória do EMG dos músculos SO e GM variaram com as condições analisadas e o CV da envoltória do GM foi maior em PEQ do que nas demais condições. Não houve diferenças significativas no e no CV das amplitudes do reflexo H nas diferentes condições. Os resultados no geral podem sugerir que: i há uma otimização do controle neuromuscular na posição JE quanto comparado com JF no sentido de haver menor variabilidade do torque de flexão plantar em JE do que em JF para uma larga gama de forças; ii o grau de recrutamento relativo dos três músculos do tríceps sural é sensível ao ângulo articular no joelho (pelo menos entre 90º e 180º); iii o músculo SO é o mais ativado no tríceps sural, tanto em JE quanto em JF, para todos os níveis de torque analisados; iv na TP há menor variabilidade no torque de flexão plantar do que na TF, possivelmente devido à ação de diferentes proprioceptores, não se espelhando, entretanto, em diferenças nos graus de ativação ou de variabilidade das envoltórias dos EMGs dos três músculos do tríceps sural; v a variabilidade de torque em PEQ é maior do que nas demais condições, em PEA e TF são equivalentes, mas maiores do que em TP; vi um sujeito com maior variabilidade em TF ou TP apresentaria maior variabilidade em PEQ (como apresentado na análise de correlação), sugerindo que uma fração da variabilidade em PEQ é devida a fatores medulares e neuromusculares; vii em TF houve maior ativação do SO do que nas demais condições (PEQ, PEA e TP), que deve ser uma estratégia do sistema nervoso em face dos diferentes desafios postos pelas diferentes tarefas; viii de forma geral, a amplitude do reflexo H por si, não parece ser um indicador sensível dos diferentes eventos neurais ocorrendo na medula espinhal durante as várias condições experimentais PEQ, PEA, TF e TP / Random oscillations of the center of pressure are an inevitable feature associated with quiet standing (PEQ). This random movement may be attributed to different sources of variability including the sensory inputs at the periphery, the central nervous system and the neuromuscular system that generates the torques. Once the descending commands are generated by the brain, there are sources at the spinal cord and at the motor units that contribute with an added variability to the force generated by synergist muscles acting around a joint. These sources of force variability (generated at the spinal cord and at the motor units) were the focus of the present research, with a specific emphasis on the ankle joint and the triceps surae muscle group, which are directly involved in postural control during PEQ. The methodology consisted in studying the plantarflexion torque variability generated in different conditions together with the analyses of the electromyograms (EMGs) of the three triceps surae muscles. Three sets of experiments were used in the research: 1) subject seated, with either extended knee (JE) or flexed knee (JF), executing isometric contractions; 2) subject seated, with extended knee, comparing force task (isometric contraction, with force control TF) with position task (non-isometric force generation with position control TP); 3) subject standing, either naturally (PEQ) or attached to a fixed structure (PEA), compared with TF and TP exerted while seated, with JE, and with same torque as during PEQ. These conditions were also tested with the soleus H reflex. For experiments 1 and 2 the number of subjects was 13, while for experiment 3 it was 9, all healthy. The quantifiers that were used to characterize the signals were the mean value (), the standard deviation () and the coefficient of variation (CV). These were applied to the torque signal and for the EMG envelope of the muscles soleus (SO), lateral gastrocnemius (GL) and medial gastrocnemius (GM). The results of Experiment 1 are synthesized in what follows. The torque during maximal contraction (CVM) was 58% higher in JE as compared with JF, but the variability ( and CV) was higher in JF than in JE. The variability was also higher in JF for torque levels in the range 10 to 80% CVM. There was a linearly increasing relation between and of the torque generated by the triceps surae in JE and JF ( and normalized with respect to the respective CVMs). The levels of muscle activation (envelope ) were higher in JE than in JF, mainly due to the higher activation of GM and GL in JE when compared with JF. The SO muscle was more activated than GM and GL, both in JE and JF. Both the EMG level and envelope increased as a function of the plantarflexion torque, for SO, GL and GM. The results for Experiment 2 are described in what follows. Torque variability ( e CV) was lower in TP than in TF. There was an increasing relation between and of the torque generated by the triceps surae, and between and of the EMG envelopes of the three muscles as a function of the plantarflexion torque , during TF and TP. The EMG envelope was positively correlated with the plantarflexion torque , both normalized with respect to the respective values at CVM. The results of Experiment 3 are summarized in what follows. Plantarflexion torque variability ( e CV) during PEQ was higher than in the other conditions, the subject sample showing a positive correlation between torque in PEQ and in TF or TP. On the other hand, during 10 PEA, torque was uncorrelated with torque measured in TF and TP. The muscle activation levels in triceps surae were higher in TF than in the other conditions, mainly due to the higher SO activation in TF as compared with the other conditions. The EMG envelope of SO and GM varied with the conditions analyzed, and the GM envelope CV was higher in PEQ than in the other conditions. There were no statistical differences in the values of and CV of the H reflex amplitudes in the different conditions. The results in general may suggest the following: i there is an optimization of the neuromuscular control in position JE with respect to that in JF from the point of view that a lower variability of plantarflexion torque occurs in JE than in JF for a wide force range; ii the relative level of recruitment among the three muscles is sensitive to the knee angle (at least at 90º and 0o); iii the SO muscle is the most activated in the triceps surae, both in JE and JF, for all torque levels analyzed; iv there is less variability in plantarflexion torque in TP than in TF, perhaps due to the action of different proprioceptors, but without significant difference in muscle activation or EMG envelope variability between the two conditions; v plantarflexion torque variability in PEQ is higher than in the other conditions, being similar in PEA and TF and in TP being the smallest of all; vi a subject with a higher torque variability in TF or TP will present a higher variability in PEQ (as suggested by correlation analysis), suggesting that a fraction of the variability in PEQ originates in the spinal cord and neuromuscular system; vii the SO was more activated in TF than in the other conditions (PEQ, PEA and TP), which could be a strategy of the central nervous system to cope with the different tasks; viii in a general sense, the H reflex amplitude does not seem to be a sensitive indicator of the different neural events occurring in the spinal cord during the different experimental conditions (PEQ, PEA, TF and TP)

Luk Tze Chung. / "August 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (p. 79-105). / Available also through the Internet via Dissertations & theses @ Chinese University of Hong Kong. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / Luk Tze Chung.