Dans le domaine sidérurgique, l'ajustement des commandes de préréglage est un problème courant. L'objectif des systèmes de commande est d'obtenir des produits de qualité imposée. On observe cependant fréquemment des variations de comportement d'un lot à l'autre, ce qui nécessite de modifier les paramètres des modèles employés pour les préréglages suivants. Cela est particulièrement vrai pour le convertisseur à oxygène où les informations rassemblées pendant une coulée spécifique servent à ajuster les points de consigne de la coulée suivante.Dans cette thèse, nous présentons une méthode de validation de données s'appuyant sur un modèle incertain. Les incertitudes portant sur les mesures des variables et sur la connaissance des paramètres du modèle sont simultanément prises en compte pour fournir des estimées cohérentes qui pourront être mises à profit par le système de contrôle-commande du convertisseur à oxygène. L'estimation paramétrique étant sensible à la présence de mesures aberrantes , la méthode proposée a été rendue robuste à la présence de ces informations erronées par la prise en compte, dans la méthode d'estimation, de la notion de distribution statistique contaminée.Le modèle du convertisseur a été établi sur la base des principes de conservation de masse et d'énergie, mais aussi sur des relations d'équilibre chimique pour lesquelles certains paramètres sont assez mal connus ce qui justifie pleinement l'approche utilisée. Les estimations des variables et des paramètres fournissent une image plus juste de l'état réel du système ce qui en facilite la conduite. Appliquée au convertisseur à oxygène, cette méthode permet l'actualisation du modèle de calcul de charge utile au préréglage. De plus, le suivi de l'évolution de certains paramètres du modèle permet d'évaluer un niveau de dégradation du système (par exemple, l'endommagement du réfractaire de la poche / In the steel industry, tuning the control system set-points in order to reach given product specification is a common problem. The control system objective is to obtain products satisfying the given specifications. There are however frequent changes in the behavior from one batch to another, thus requiring the modification of model parameters used for the following presets. This is particularly true for the Basic Oxygen Furnace (BOF) where the information collected during a specific batch serves to adjust the set-points of the next batch.In this thesis, we proposed a method allowing simultaneously robust data reconciliation and model parameter estimation. This approach is original because the current data validation methods make the assumption that the system model is known perfectly. Here, the uncertainties on the measurements of variables and on the knowledge of the model parameters are simultaneously taken into account to provide consistent estimates that can be utilized by the control system of the BOF, especially for the determination of the set-points. Parameter estimation being sensitive to the presence of outliers, which is common in this type of process operating in highly disturbed environment, the proposed method has been made robust to the presence of these errors by including in the estimation method, the notion of contaminated statistical distribution.The model of the converter was based on the principles of mass and energy conservation, but also on chemical equilibrium relationships for which some parameters are not well known that fully justifies the proposed approach. The variable and parameter estimates provide a more accurate picture of the actual state of the system which facilitates its control. Applied to the BOF, this method allows the updating of the model used for the preset. In addition, monitoring the evolution of some model parameters can be used to evaluate the degradation level of the system (eg, damage to the refractory of the converter)

O objetivo deste estudo foi avaliar o efeito do treinamento de força muscular dos membros inferiores na estabilidade postural de mulheres idosas. As participantes (n =21) eram saudáveis, com idade entre 60 e 75 anos (M = 64,4 anos), e foram designadas a um grupo de treinamento (TF) ou a um grupo controle (CO). Esses grupos foram comparados em estabilidade postural e força antes e após um programa de treinamento de força para o grupo TF. A estabilidade postural foi avaliada em posturas eretas estáticas com apoio unipodal e bipodal, e em situações em que a estabilidade postural bipodal foi perturbada de forma previsível ou imprevisível. A perturbação previsível foi produzida por um movimento voluntário, por meio da elevação rápida com as mãos, de cargas conhecidas: 1 Kg, 3 Kg ou 5 Kg. A perturbação imprevisível foi produzida pela alteração inesperada da carga de 3 Kg para a carga de 1 Kg ou de 5 Kg antes de sua elevação. Os resultados indicaram aumento da força muscular após o treinamento de força. Quanto à estabilidade postural, nãob foram observadas diferenças significativas entre os grupos após o treinamento para as tarefas de apoio bipodal e apoio unipodal. A estabilidade postural foi afetada principalmente, quando uma carga mais leve foi elevada na situação imprevisível, gerando maior deslocamento anterior e posterior do CP. Entretanto, não houve efeito do treinamento de força no deslocamento do CP. Após o treinamento de força, o grupo TF apresentou uma redução do tempo de deslocamento posterior do CP e uma redução na variabilidade de amplitude do CP após ajustes compensatórios. Estes resultados sugerem que o treinamento de força não afeta o equilíbrio de idosos em situações estáticas ou componentes de ajustes iniciais com a perturbação da postura, mas houve um efeito positivo nos componentes tardios de ajustes após a perturbação / The goal of this study was to investigate the effect of strength training of the lower limbs on postural stability of older women. Participants (n =21) were healthy, with ages ranging between 60 and 75 years (M=64.4 years); they were assigned to two groups: strength training (ST) and control (CO). These groups were compared for postural stability and muscular strength before and after a strength training program for the ST group. Postural stability was evaluated in uni and bipodal static stance, and in situations of predictable and unpredictable perturbation of balance. The predictable disturbance was produced through the action of lifting a known load (1 kg, 3 kg or 5 kg) with the hands. The unpredictable disturbance was produced by an unexpected alteration of the load of 3 kg to 1 kg or 5 kg right before lifting the load up. The results indicated increased muscle strength after strength training. Regarding postural stability, no significant difference was detected between groups for uni/bipodal static postures. Postural stability was most affected when a lighter weight was lifted in the unpredictable situation, leading to greater anterior and posterior center of pressure (CP) displacement. Strength training, however, had no effect on the initial CP displacement. After training, the ST group showed shorter time of posterior CP displacement and lower variability of CP range after compensatory adjustments. These results suggest that strength training for elderly individuals does not affect stability in static postures or the early component of adjustments to balance perturbation, but it has a positive effect on the late component of adjustments to balance perturbation

A falha na estabilidade escapular e no ritmo escápulo-umeral são associadas ao risco de lesão no complexo do ombro. Apesar de se saber que a estabilização ativa dos músculos escapulares é fundamental para evitar disfunções ainda pouco se sabe sobre como o controle postural no complexo do ombro ocorre e como tais mecanismos poderiam auxiliar na estabilização da articulação perante uma tarefa. Será que há ajustes posturais antecipatórios (APA) e compensatórios (APC) nos músculos escapulares (serrátil anterior, trapézio inferior e trapézio superior) em tarefas motoras que envolvem o movimento dos membros superiores? Como as ações motoras modulam a resposta postural dos músculos escapulares e globais (músculos do tronco e membros inferiores) para estabilizar e orientar o corpo? O objetivo deste estudo foi analisar a existência dos ajustes posturais antecipatórios e compensatórios nos músculos escapulares e globais em sujeitos ativos saudáveis em tarefas de membros superiores. Para tal, participaram 70 indivíduos ativos saudáveis (18 mulheres e 52 homens, 28,0±7,2 anos, 70,5±13,4 kg e 1,72±0,07 m). Foi mensurada atividade eletromiográfica do músculo focal Deltóide Anterior, músculos escapulares (Serrátil Anterior, Trapézio Superior, Trapézio Inferior) e músculos globais (Reto Abdominal, Eretor Longuíssimo, Reto Femoral, Bíceps Femoral, Gastrocnêmio, Tibial Anterior) em 4 tarefas de membros superiores (abdução no plano escapular, adução, flexão e extensão) executadas com halteres de massa 1kg e 3kg. Os resultados mostraram a existência de ajustes posturais dos músculos escapulares (p<0,001); a tarefa e massa influenciaram nos ajustes posturais antecipatórios e compensatórios (p<0,001); as tarefas de adução versus extensão não apresentaram diferença entre si na atividade muscular dos músculos escapulares durante os ajustes posturais antecipatórios e compensatórios (p>0,05); as tarefas de abdução versus flexão são semelhantes com massa 1kg (p>0,05), mas se tornam diferentes com massa 3kg (p<0,001) com relação a atividade muscular dos músculos escapulares e globais; nas tarefas de flexão e abdução os maiores ajustes posturais foram dos músculos escapulares (Serrátil Anterior e Trapézio Inferior) (p<0,001); nas tarefas de adução e extensão os maiores são dos músculos globais (p<0,001); os ajustes posturais antecipatórios e compensatórios foram maiores nos músculos escapulares Serrátil Anterior e Trapézio Inferior do que no músculo focal Deltóide Anterior (p<0,001); existiu modulações nos tipos e níveis de APA e APC nas tarefas de membros superiores (p<0,001). Em conclusão, temos uma associação de ajustes posturais como mecanismos de estabilização e orientação do ombro em tarefas dos membros superiores. No entanto, a intensidade e modulação dos ajustes posturais são afetadas pela tarefa e massa. Acreditamos que a atividade muscular dos músculos escapulares esteja diretamente associada a necessidade de minimizar a perturbação para a manutenção da orientação e estabilidade segmento (ombro), assim como atividade dos músculos globais está associada a manutenção da estabilidade e orientação do corpo. Esses achados podem ser utilizados para futuros estudos comparando sujeitos com disfunção e saudáveis e assim entender se há atividade anormal dos músculos escapulares nos períodos de ajustes posturais antecipatórios e compensatórios e se esta atividade muscular contribui para disfunção do complexo do ombro / The failure of scapular stability and scapulohumeral rhythm is associated with the risk of injury to the shoulder complex. Although it is known that the active stabilization of the scapular muscles is fundamental to avoid dysfunctions, little is known about how postural control in the shoulder complex occurs and how such mechanisms could help stabilize the joint before a task. Are there anticipatory postural adjustments (APA) and compensatory (CPA) in the scapular muscles (serratus anterior, lower trapezius and upper trapezius) in motor tasks involving the movement of the upper limbs? How do motor actions modulate the postural response of the scapular and global muscles (trunk muscles and lower limbs) to stabilize and guide the body? The objective of this study was to analyze the existence of anticipatory and compensatory postural adjustments in the scapular and global muscles in healthy subjects in upper limb tasks. To do this, participated 70 healthy active individuals (18 women and 52 men, 28,0±7,2 years 70,5±13,4 kg and 1,72±0,07 m). It Was measured electromyographic activity of focal muscle (Deltoid Anterior), scapular muscles (Serratus Anterior, Upper Trapezius, Lower Trapezius) and global muscles (Rectus Abdominis, Longissimus, Rectus Femoris, Biceps Femoris, Gastrocnemius, Tibial Anterior) was measured in 4 upper limb tasks (abduction in the scapular plane, adduction, flexion and extension) performed with dumbbells of 1kg and 3kg mass. The results showed the existence of postural adjustments of the scapular muscles (p <0.001); the task and mass influenced the anticipatory and compensatory postural adjustments (p <0.001); the tasks of adduction versus extension did not difference among themselves in the muscular activity of the scapular muscles during the anticipatory and compensatory postural adjustments (p> 0.05); the abduction versus flexion tasks are similar with mass 1kg (p> 0.05), but become different with mass 3kg (p <0.001) in relation to muscular activity of the scapular and global muscles; during flexion and abduction tasks, the greatest postural adjustments were the scapular muscles (Serratus Anterior and Lower Trapezius) (p <0.001); during adduction and extension tasks, the largest of the global muscles (p <0.001); anticipatory and compensatory postural adjustments were higher in the serratus anterior and lower trapezius scapula muscles than in the anterior deltoid focal muscle (p <0.001); there were modulations in the types and levels of APA and CPA in upper limb tasks (p <0.001). In conclusion, we have an association of postural adjustments as mechanisms of stabilization and orientation of the shoulder in tasks of the upper limbs. However, the intensity and modulation of postural adjustments are affected by task and mass. We believe that the muscular activity of the scapular muscles is directly associated with the need to minimize the perturbation to the maintenance of the orietantion and stability segment (shoulder), as well as overall muscle activity is associated with maintaining stability and body orientation. These findings can be used for future studies comparing subjects with dysfunction and health and thus to understand if there is abnormal activity of the scapular muscles in the periods of anticipatory and compensatory postural adjustments and if this muscular activity contributes to dysfunction of the shoulder complex

Despite its prominent role in firms' external financing, debt is highly underrepresented in the academic literature, compared to equity financing (Cumming, 2016). This thesis investigates corporate debt under diverse bankruptcy regulation in Europe (Chapter 1), as well as benefits arising from debt renegotiation among US firms (Chapter 2 and 3). The first study examines whether corporate borrowing responds to the strength of creditor rights, which differ greatly across countries. We use a difference-in-differences (DiD) methodology around an EU-wide bankruptcy reform in 2002 as an exogenous shock that reshaped the institutional environment for corporate debtors and their creditors in Europe. Our findings suggest that subsidiaries in the EU decrease their leverage when they are exposed to less creditor-friendly regimes after 2002, while there is hardly any impact on leverage when shifting to an equally creditor-friendly regime, and even less so when shifting to a more creditor-friendly one. We conclude that the legal environment under which credit is granted matters for firms' access to finance. The following two studies take a closer look into the bank-firm relationship during which renegotiations of existing loans are frequently observed. While the area of private debt renegotiation (among healthy firms) is not very well researched so far, this is the first study to link between loan renegotiation and firms' credit rating (Chapter 2) and firms' adjustments toward capital structure targets (Chapter 3). Firms' credit rating is important as it determines the rate firms have to pay for private debt and it governs capital requirements of lenders (Basel II and III). The study shows a positive impact on a firm's credit ratings whenever there was a loan amendment in the month prior to the rating update. Amending loans after the initial loan contract therefore carries signalling power to the capital market (in line with existing literature) and implies benefits to both borrowers and lenders. The third study finds an additional beneficial effect of loan amendments for firms. We investigate whether loan amendments might serve as a channel available to firms to speed up their adjustments toward capital structure targets. Against a broad range of alternative leverage target definitions used in the capital structure literature recently, loan amendments tend to accelerate firms' speed of adjustments by up to 10.6 percent points within twelve months after the loan has been amended (in addition to firms' general speed of adjustment). Therefore, our studies provide evidence for additional, novel benefits of corporate debt renegotiation which encourages firms to update and optimise financial contract design even after origination.

Made available in DSpace on 2014-06-11T19:30:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-08-21Bitstream added on 2014-06-13T20:40:47Z : No. of bitstreams: 1 ferreira_dma_dr_rcla.pdf: 659123 bytes, checksum: baf4d8518bae6e1d0b27e68eae1725f9 (MD5) / O objetivo deste estudo foi avaliar as alterações estáticas e dinâmicas em pacientes com escoliose idiopática na posição ortostática, sem e com inclinação lateral com restrição associadas ou não as mudanças unilaterais de calços. O grupo experimental foi constituído por pacientes com escoliose idiopática com curva dupla (³ 10°) e o grupo controle por participantes sem escoliose na mesma faixa etária (13-24 anos). Foram utilizadas três câmeras de vídeo, 18 marcadores fixados em referências anatômicas dos participantes, dois calços, de 1 e de 3 cm de altura e uma escala para restrição e padronização da inclinação lateral. As tentativas foram realizadas aleatoriamente, nas condições sem calço ou com calço baixo ou alto sob o pé direito e esquerdo e nas tarefas, estática (15 segundos) ou dinâmica (5 movimentos de inclinação lateral para direita ou esquerda). Foram calculados os ângulos posturais: alfa 1 (torácico alto), alfa 2 (torácico médio), alfa 3 (tóraco-lombar) e alfa 4 (lombar) e os ângulos segmentares: beta 1 (ombros), beta 2 (escápulas), beta 3 (pelves) e beta 4 (joelhos). Na situação estática, os grupos e os calços tiveram uma maior influência nos ângulos posturais tóracolombar e lombar e nos ângulos segmentares da pelve e do joelho. Na situação dinâmica sem calço, nenhuma diferença foi observada entre grupos, porém o calço associado aos movimentos de inclinação lateral provocou ajustes posturais compensatórios nos ângulos posturais alfas e segmentares betas, sendo que as diferenças foram maiores com o calço alto nos pacientes com escoliose, indicando um possível mecanismo corretivo. Estas alterações posturais tanto estáticas como dinâmicas, indicam a busca de uma nova organização estrutural e equilíbrio do tronco, sendo que os segmentos superiores foram mais influenciados na condição dinâmica... / The purpose of this study was to evaluate static and dynamic changes in patients with idiopathic scoliosis in the orthostatic position, with and without restricted lateral inclination associated with or not unilateral changes of shoe lifting. The experimental group was constituted by patients with idiopathic scoliosis with double curve (³ 10°) and the control group by participants without scoliosis with the same age (13-24 years). Three video cameras were used, with 18 markers fixed on the participants' anatomical references, along with two shoe lifts, 1 and 3 cm of height, and a scale for restriction and standardization of the lateral inclination. The trails were accomplished randomly, in the conditions without or with shoe lift (low or high) under the right and left foot and in the tasks, static (15 seconds) or dynamic (5 movements of lateral inclination for right or left). Postural angles: alpha 1 (thoracic high), alpha 2 (thoracic medium), alpha 3 (thoracolumbar) and alpha 4 (lumbar); and segmental angles: beta 1 (shoulders), beta 2 (scapulas), beta 3 (pelvis) and beta 4 (knees) were calculated. In the static condition, group and shoe lift mostly influenced the postural angles, thoracic-lumbar and lumbar, and the segmental angles of the pelvis and knee. In the dynamic condition without shoe lift, no difference was observed between groups, however, with shoe lift.and lateral inclination compensatory postural adjustments were observed in the postural alpha angles and segmental beta angles, with the largest differences observed in the condition with the high shoe lifting in the patients with scoliosis, indicating a possible corrective mechanism. These, static and dynamics, postural changes suggest a new structural organization and equilibrium of the trunk, with the trunk upper segments being the ones more influenced by the dynamic condition with low and high shoe lifting whereas... (Complete abstract click electronic access below)

Os geradores distribuídos em sistemas de distribuição de energia elétrica devem ser desconectados em eventos de ilhamento, que ocorrem quando parte da rede elétrica torna-se eletricamente isolada da concessionária e o subsistema isolado continua a ser energizado pela geração distribuída. A proteção anti-ilhamento deve detectar tal condição operativa, porém pode não atuar em condições de pequenos desbalanços entre carga e geração, ou atuar incorretamente para eventos de outra natureza. Assim, um ajuste adequado dessa proteção deve desconectar o gerador rapidamente quando detecta o ilhamento e, simultaneamente, deve ser imune a eventos como curtos-circuitos e chaveamentos de carga, por exemplo. Esta pode ser uma tarefa muito difícil face às variações de carga e diferentes eventos de não ilhamento que podem ocorrer no sistema de distribuição. Portanto, nesta tese são propostas metodologias de ajuste das funções de proteção anti-ilhamento de sub/sobrefrequência, taxa de variação de frequência, salto de vetor e sub/sobretensão, que são técnicas convencionalmente utilizadas para a detecção de ilhamento de geração distribuída. O objetivo das metodologias é maximizar a detecção de ilhamento e minimizar a atuação incorreta, e são considerados cenários com múltiplos geradores distribuídos de diferentes tecnologias. Inicialmente, são explorados os principais fatores que afetam as proteções, tais como distribuição das cargas, fator de potência e desequilíbrio das cargas. Esta análise permite identificar os casos mais difíceis de detecção de ilhamento. Como segunda contribuição, foi proposta a metodologia de análise gráfica denominada Mapa de Ajustes, cuja eficácia foi comprovada por meio de casos de teste, mostrando ser capaz de melhorar a sensibilidade da proteção anti-ilhamento e minimizar atuação incorreta. Na sequência, é apresentado um método automático para ajuste e bloqueio de tensão e outro baseado em proteção adaptativa para ajuste das funções de proteção. Ambos são baseados na metodologia de mapa de ajustes. Os resultados indicam que é possível melhorar a detecção de ilhamento e diminuir a atuação incorreta quando utilizadas as metodologias propostas. / Distributed generators in power distribution systems must be disconnected after an islanding event, which occurs when part of the power grid becomes electrically isolated from the utility and the isolated subsystem continues to be energized by the distributed generation. The antiislanding protection has to detect such operating condition, which may fail for critical loading conditions, or operate incorrectly for events of other nature than islanding. Therefore, an appropriate protection setting should quickly disconnect the generator when an islanding event is detected, and simultaneously, must be immune to events such as short circuits and load switches. This can be a very difficult task due to load variations and different nonislanding events that may occur in the distribution system. Therefore, in this thesis is proposed methodologies to adjust the anti-islanding protection functions of under/overfrequency, rate of change of frequency, vector surge and under/overvoltage, which are techniques conventionally used for islanding detection of distributed generation. The methodologies goals are to maximize the performance of the anti-islanding protection and minimize the incorrect operation to events of other nature, and scenarios with multiple distributed generators of different technologies are considered. At first, the main factors that affect the frequency and voltage-based protection will be explored, such as load distribution, power factor and unbalanced loads. This analysis aims to identify the most critical cases of islanding detection. The second contribution of this thesis is the Setting Map methodology, which is a graphical analysis whose effectiveness has been proved by case studies, showing to be able to improve the sensitivity of anti-islanding protection, minimizing the chances of incorrect operation. In sequence, is presented an automatic method to adjust the protection functions and voltage blocking and other based on adaptive protection. Both methods are based on the Setting Map methodology. The results indicate that it is possible to improve the islanding detection and reduce the incorrect actuation when it is used the proposed methodologies.

A falha na estabilidade escapular e no ritmo escápulo-umeral são associadas ao risco de lesão no complexo do ombro. Apesar de se saber que a estabilização ativa dos músculos escapulares é fundamental para evitar disfunções ainda pouco se sabe sobre como o controle postural no complexo do ombro ocorre e como tais mecanismos poderiam auxiliar na estabilização da articulação perante uma tarefa. Será que há ajustes posturais antecipatórios (APA) e compensatórios (APC) nos músculos escapulares (serrátil anterior, trapézio inferior e trapézio superior) em tarefas motoras que envolvem o movimento dos membros superiores? Como as ações motoras modulam a resposta postural dos músculos escapulares e globais (músculos do tronco e membros inferiores) para estabilizar e orientar o corpo? O objetivo deste estudo foi analisar a existência dos ajustes posturais antecipatórios e compensatórios nos músculos escapulares e globais em sujeitos ativos saudáveis em tarefas de membros superiores. Para tal, participaram 70 indivíduos ativos saudáveis (18 mulheres e 52 homens, 28,0±7,2 anos, 70,5±13,4 kg e 1,72±0,07 m). Foi mensurada atividade eletromiográfica do músculo focal Deltóide Anterior, músculos escapulares (Serrátil Anterior, Trapézio Superior, Trapézio Inferior) e músculos globais (Reto Abdominal, Eretor Longuíssimo, Reto Femoral, Bíceps Femoral, Gastrocnêmio, Tibial Anterior) em 4 tarefas de membros superiores (abdução no plano escapular, adução, flexão e extensão) executadas com halteres de massa 1kg e 3kg. Os resultados mostraram a existência de ajustes posturais dos músculos escapulares (p<0,001); a tarefa e massa influenciaram nos ajustes posturais antecipatórios e compensatórios (p<0,001); as tarefas de adução versus extensão não apresentaram diferença entre si na atividade muscular dos músculos escapulares durante os ajustes posturais antecipatórios e compensatórios (p>0,05); as tarefas de abdução versus flexão são semelhantes com massa 1kg (p>0,05), mas se tornam diferentes com massa 3kg (p<0,001) com relação a atividade muscular dos músculos escapulares e globais; nas tarefas de flexão e abdução os maiores ajustes posturais foram dos músculos escapulares (Serrátil Anterior e Trapézio Inferior) (p<0,001); nas tarefas de adução e extensão os maiores são dos músculos globais (p<0,001); os ajustes posturais antecipatórios e compensatórios foram maiores nos músculos escapulares Serrátil Anterior e Trapézio Inferior do que no músculo focal Deltóide Anterior (p<0,001); existiu modulações nos tipos e níveis de APA e APC nas tarefas de membros superiores (p<0,001). Em conclusão, temos uma associação de ajustes posturais como mecanismos de estabilização e orientação do ombro em tarefas dos membros superiores. No entanto, a intensidade e modulação dos ajustes posturais são afetadas pela tarefa e massa. Acreditamos que a atividade muscular dos músculos escapulares esteja diretamente associada a necessidade de minimizar a perturbação para a manutenção da orientação e estabilidade segmento (ombro), assim como atividade dos músculos globais está associada a manutenção da estabilidade e orientação do corpo. Esses achados podem ser utilizados para futuros estudos comparando sujeitos com disfunção e saudáveis e assim entender se há atividade anormal dos músculos escapulares nos períodos de ajustes posturais antecipatórios e compensatórios e se esta atividade muscular contribui para disfunção do complexo do ombro / The failure of scapular stability and scapulohumeral rhythm is associated with the risk of injury to the shoulder complex. Although it is known that the active stabilization of the scapular muscles is fundamental to avoid dysfunctions, little is known about how postural control in the shoulder complex occurs and how such mechanisms could help stabilize the joint before a task. Are there anticipatory postural adjustments (APA) and compensatory (CPA) in the scapular muscles (serratus anterior, lower trapezius and upper trapezius) in motor tasks involving the movement of the upper limbs? How do motor actions modulate the postural response of the scapular and global muscles (trunk muscles and lower limbs) to stabilize and guide the body? The objective of this study was to analyze the existence of anticipatory and compensatory postural adjustments in the scapular and global muscles in healthy subjects in upper limb tasks. To do this, participated 70 healthy active individuals (18 women and 52 men, 28,0±7,2 years 70,5±13,4 kg and 1,72±0,07 m). It Was measured electromyographic activity of focal muscle (Deltoid Anterior), scapular muscles (Serratus Anterior, Upper Trapezius, Lower Trapezius) and global muscles (Rectus Abdominis, Longissimus, Rectus Femoris, Biceps Femoris, Gastrocnemius, Tibial Anterior) was measured in 4 upper limb tasks (abduction in the scapular plane, adduction, flexion and extension) performed with dumbbells of 1kg and 3kg mass. The results showed the existence of postural adjustments of the scapular muscles (p <0.001); the task and mass influenced the anticipatory and compensatory postural adjustments (p <0.001); the tasks of adduction versus extension did not difference among themselves in the muscular activity of the scapular muscles during the anticipatory and compensatory postural adjustments (p> 0.05); the abduction versus flexion tasks are similar with mass 1kg (p> 0.05), but become different with mass 3kg (p <0.001) in relation to muscular activity of the scapular and global muscles; during flexion and abduction tasks, the greatest postural adjustments were the scapular muscles (Serratus Anterior and Lower Trapezius) (p <0.001); during adduction and extension tasks, the largest of the global muscles (p <0.001); anticipatory and compensatory postural adjustments were higher in the serratus anterior and lower trapezius scapula muscles than in the anterior deltoid focal muscle (p <0.001); there were modulations in the types and levels of APA and CPA in upper limb tasks (p <0.001). In conclusion, we have an association of postural adjustments as mechanisms of stabilization and orientation of the shoulder in tasks of the upper limbs. However, the intensity and modulation of postural adjustments are affected by task and mass. We believe that the muscular activity of the scapular muscles is directly associated with the need to minimize the perturbation to the maintenance of the orietantion and stability segment (shoulder), as well as overall muscle activity is associated with maintaining stability and body orientation. These findings can be used for future studies comparing subjects with dysfunction and health and thus to understand if there is abnormal activity of the scapular muscles in the periods of anticipatory and compensatory postural adjustments and if this muscular activity contributes to dysfunction of the shoulder complex

O objetivo deste estudo foi avaliar o efeito do treinamento de força muscular dos membros inferiores na estabilidade postural de mulheres idosas. As participantes (n =21) eram saudáveis, com idade entre 60 e 75 anos (M = 64,4 anos), e foram designadas a um grupo de treinamento (TF) ou a um grupo controle (CO). Esses grupos foram comparados em estabilidade postural e força antes e após um programa de treinamento de força para o grupo TF. A estabilidade postural foi avaliada em posturas eretas estáticas com apoio unipodal e bipodal, e em situações em que a estabilidade postural bipodal foi perturbada de forma previsível ou imprevisível. A perturbação previsível foi produzida por um movimento voluntário, por meio da elevação rápida com as mãos, de cargas conhecidas: 1 Kg, 3 Kg ou 5 Kg. A perturbação imprevisível foi produzida pela alteração inesperada da carga de 3 Kg para a carga de 1 Kg ou de 5 Kg antes de sua elevação. Os resultados indicaram aumento da força muscular após o treinamento de força. Quanto à estabilidade postural, nãob foram observadas diferenças significativas entre os grupos após o treinamento para as tarefas de apoio bipodal e apoio unipodal. A estabilidade postural foi afetada principalmente, quando uma carga mais leve foi elevada na situação imprevisível, gerando maior deslocamento anterior e posterior do CP. Entretanto, não houve efeito do treinamento de força no deslocamento do CP. Após o treinamento de força, o grupo TF apresentou uma redução do tempo de deslocamento posterior do CP e uma redução na variabilidade de amplitude do CP após ajustes compensatórios. Estes resultados sugerem que o treinamento de força não afeta o equilíbrio de idosos em situações estáticas ou componentes de ajustes iniciais com a perturbação da postura, mas houve um efeito positivo nos componentes tardios de ajustes após a perturbação / The goal of this study was to investigate the effect of strength training of the lower limbs on postural stability of older women. Participants (n =21) were healthy, with ages ranging between 60 and 75 years (M=64.4 years); they were assigned to two groups: strength training (ST) and control (CO). These groups were compared for postural stability and muscular strength before and after a strength training program for the ST group. Postural stability was evaluated in uni and bipodal static stance, and in situations of predictable and unpredictable perturbation of balance. The predictable disturbance was produced through the action of lifting a known load (1 kg, 3 kg or 5 kg) with the hands. The unpredictable disturbance was produced by an unexpected alteration of the load of 3 kg to 1 kg or 5 kg right before lifting the load up. The results indicated increased muscle strength after strength training. Regarding postural stability, no significant difference was detected between groups for uni/bipodal static postures. Postural stability was most affected when a lighter weight was lifted in the unpredictable situation, leading to greater anterior and posterior center of pressure (CP) displacement. Strength training, however, had no effect on the initial CP displacement. After training, the ST group showed shorter time of posterior CP displacement and lower variability of CP range after compensatory adjustments. These results suggest that strength training for elderly individuals does not affect stability in static postures or the early component of adjustments to balance perturbation, but it has a positive effect on the late component of adjustments to balance perturbation

L’objectif de cette thèse était de mettre en évidence les différentes stratégies adaptatives posturales et motrices face à une contrainte temporelle chez le jeune adulte et la personne âgée lors de la production d’un mouvement complexe mobilisant l’ensemble du corps. Le modèle de mouvement choisi est composé d’une flexion rapide de la cuisse dominante associée à une extension simultanée de l’index ipsilatéral. Les résultats de la première étude ont montré que le mode de déclenchement de la commande motrice modifiait l’organisation posturale du mouvement. La durée des APA associés à la flexion de la cuisse était plus courte en condition de pression temporelle forte (condition temps de réaction, TR) qu’en condition de pression temporelle faible (condition auto-initiée, AI). Cette diminution de la durée des APA était compensée par une augmentation du pic de déplacement anticipateur du centre des pressions (CP) vers la jambe oscillante. De cette façon, la stabilité dynamique ainsi que la performance motrice restaient inchangées. Les résultats de la deuxième étude ont montré que les sujets âgés étaient également capables de réduire la durée des APA en condition TR. Cependant, au contraire des sujets jeunes, ils ne compensaient pas cette diminution par une augmentation du déplacement anticipé du CP. La stabilité dynamique au moment du décollement du pied était dégradée dans cette population. Par ailleurs, l’effet de la pression temporelle sur la synchronisation motrice ne changeait pas avec l’avancée en âge. Cependant, l’erreur de synchronisation était plus importante chez les âgés que chez les jeunes, en condition AI uniquement. Enfin, l’étude 3 a montré que la modification transitoire des propriétés mécaniques des membres inférieurs (par l’addition d’une charge de 5 kg aux chevilles) affectait l’ordre de synchronisation du mouvement, en condition TR uniquement. En présence d’une charge, les sujets semblent basculer d’un mode de synchronisation de type « réactif » vers un mode « prédictif », ce qui leur permettait de maintenir une précision de synchronisation optimale. En revanche, le mode de contrôle des APA ne changeait pas. Il semble donc que le mode de contrôle des APA et de la synchronisation des mouvements puissent être dissociés selon les contraintes biomécaniques imposées par l’expérimentation. L’ensemble de ces résultats met en évidence la capacité du SNC à moduler l’ordre temporel de la synchronisation du mouvement ainsi que les paramètres spatio-temporels des APA dans le but d’assurer une coordination temporelle et une stabilité dynamique optimales. / This work aimed to investigate the adaptive postural and motor strategies developed by young and elderly healthy subjects during a complex task involving the whole body when facing a temporal pressure constraint. The motor task chosen was a simultaneous rapid leg flexion paired with ipsilateral finger index extension. Results of the first study showed that the mode of triggering of movement modifies the postural organization of the leg flexion. The APA duration associated with leg flexion was shorter in the reaction-time (RT, high temporal pressure) condition as compared to the self-initiated (SI, low temporal pressure) condition. This APA shortening was compensated by an increase of APA amplitude so that the mediolateral (ML) stability and the motor performance were both unchanged. Results of the second study showed that elderly subjects were unable to compensate this APA shortening by an increase of anticipatory ML centre-of-pressure displacement. Dynamic stability at foot-off was degraded in this population, with a consequent increased risk of ML imbalance and falling. Besides, the effect of temporal pressure on motor synchronization was not affected by ageing. Of particular importance, the synchronization error was greater in elderly than in young subjects, but in the SI condition only. Finally, the third study showed that transitory changes in the mechanical properties of the lower limbs (by ankle loading) affect the order of movement synchronization, but in the RT condition only. With ankle loading, subjects thus switched from a “reactive” to a “predictive” mode of synchronization allowing then to maintain an optimal synchronization. In contrast, ankle loading did not modify the mode of control of the APA. Therefore, it seems that the mode of control of APA and of movement synchronization can be decorrelated according to the biomechanical constraints. These results provide novel insights into the capacity of the CNS to modulate motor synchronization and APA spatio-temporal features to ensure optimal motor coordination and dynamic stability across ages.

The purpose of this thesis was to determine whether practice-induced adjustments and retention of a goal directed isometric motor accuracy task were similar between ipsilateral upper and lower limb and whether there is an ipsilateral transfer between upper and lower limbs. In addition, this thesis project aimed to determine whether motor output variability and the activity of the involved agonist and antagonist muscles could predict any of the above stated changes. Sixteen young adults (8 men, 8 women; 22.1 or - 2.1 years) performed 80 trials of goal directed isometric contractions that involved accurately matching a target force of 25% MVC in 200 ms, either with the upper limb or the lower limb followed by the other limb. After an interval of 48 hours, 10 trials similar to the practice trials were performed to examine retention. Feedback of performance was provided in the form of a force-time trajectory along with numerical error values for force and time on each trial. End-point error was quantified as the absolute deviation from the targeted force and time. Motor output variability was quantified as the SD of force, SD of time to peak force and SD of force trajectory. The practice-induced adjustments for force and time endpoint accuracy were similar for the two limbs, however, two days later, retention of the force accuracy was better with the upper limb compared with the lower limb. Practice-induced reduction and practice-to-retention increase in force and time endpoint error were predicted by respective changes in peak force and time to peak force trial-to-trial variability for both limbs. In addition, the changes in accuracy were predicted by the changes in the activity of the involved agonist and antagonist muscles. Nonetheless, the changes in muscle activity differed between the two limbs. The adjustments in muscle activity were also different during the practice session despite the fact that the rate of improvement was similar for the two limbs. Finally, there was an asymmetric transfer of force accuracy from the lower limb to the ipsilateral upper limb, which was associated with the changes in motor output variability. The upper limb, which is inherently less variable as compared to the lower limb, may have retained the task better due to the formation of a stronger muscle synergy (or stronger internal model) to perform the contractions with accuracy. The lower limb, on the other hand may have formed a weaker internal model due to the greater interference from amplified signal-dependent noise (motor output variability) or an alternative motor plan, which may have been concerned primarily with the minimization of motor output variability instead of formation of a muscle synergy to perform the contractions accurately.