Com o propósito de contribuir com os estudos do comportamento do tecido ósseo e auxiliá-los em uma situação próxima da real, que é a de comportamento dinâmico, foi construí da uma maquina de ensaio de fadiga (MEF) para corpos de prova de ossos. Utilizaram-se corpos de prova de mesma dimensão retirados de um mesmo animal (boi), no qual os corpos de prova da tíbia esquerda foram submetidos a 42.000 ciclos na máquina de ensaio de fadiga e, posteriormente, submetidos à flexão na máquina universal de ensaio e os corpos de prova da tíbia direita foram levados aos ensaios de flexão sem terem passados por fadiga. Os resultados obtidos para os CDPs, com e sem fadiga, demonstraram que as propriedades mecânicas dos CDPs tiveram sensível índice de variança, caracterizando assim a eficiência da MEF. Além disso, a MEF é capaz de executar ensaios com valores de amplitude de 0,5 mm e de 1,0 mm, bastando para isso a troca do excêntrico por um destes que já foram confeccionados. / A fatigue\'s testing machine (MEF) was built to be used in bone samples, with the purpose of giving aid and contribution to the study of bone tissue\'s behavior in a situation close to a real one, that is the dynamic behavior. Samples all with the same dimension taken from only one animal (an ox) were used. From those samples some were from the left shaft (diaphysis) and were submitted to 42.000 cycles in the fatigue\'s testing machine and after that submitted to bending test in the universal machine. Meanwhile, the right shinbone samples were submitted to bending tests without going through previous fatigue. Results were obtained from bone samples (also called CDPs) which went through fatigue and from those that didn\'t. The results showed that mechanical properties from the CDPs had a sensible variant rate, which then characterized how efficient the fatigue testing machine is. Besides, the MEF is capable of making tests with the values of amplitude of 0,5 mm and 1,0 mm, just by switching the eccentric by one of those which were already pre-fabricated.

This thesis presents a biomechanical characterisation of eccentric (EL) and concentric loading (CL) of the triceps surae. EL is commonly adopted as an effective treatment for Achilles tendinopathy, with notably better treatment success compared with CL. However, there is a lack of consensus about the most appropriate protocols for completing triceps surae exercises. Exercise parameters such as speed and load are important and may affect the stimuli sensed by the muscle-tendon unit and thus influence repair. This thesis aims to biomechanically characterise and compare EL and CL as a basis for trying to understand treatment effects. A measuring system comprising motion tracking, 2D ultrasound, force plates and EMG was adopted and a semi-automatic tracking algorithm developed to track the muscle-tendon junction throughout the loading cycle (Chapter 3). Having validated the accuracy of measurements (Chapter 4), the effect of variables such as speed of exercise (chapter 5) and addition of load (Chapter 6) were assessed on Achilles tendon force, stiffness, stress, strain and force perturbations as well as muscle activation and contraction frequency (Chapter 7), in healthy subjects. It was found that EL and CL do not differ in terms of tendon force, stiffness or strain. However, EL is characterised by lower muscle activation and by 10 Hz perturbations present within the tendon. These perturbations were found to be significantly dependent on movement speed and load applied during EL movements only. However, no effect of speed was found on tendon force, stiffness and strain during either exercise movement. Finally, temporo-spatial analysis of the calf revealed region specific variations in muscle activation during both EL and CL, with 10 Hz perturbations coming predominantly from medial soleus and medial gastrocnemius muscle activity. These studies provide new information about the biomechanics of EL or CL, which should enhance understanding, and development, of conservative Achilles tendinopathy management.

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Various types of mammalian cells exhibit the remarkable ability to adapt to external applied mechanical stresses and strains. This ability allows cells to maintain a stable endogenous mechanical tension at a preferred (homeostatic) level, which is of great importance for normal physiological function of cells and tissues, and for a protection from various diseases, including atherosclerosis and cancer. Previous studies have shown that the cell ability to maintain tensional homeostasis is cell type-dependent. For example, isolated endothelial cell cannot maintain tensional homeostasis, whereas clusters of endothelial cells can, more so the greater the size of the cluster is. On the other hand, cell clustering does not affect tensional homeostasis of fibroblasts and vascular smooth muscle cells. Underlying mechanisms for these behaviors of different cell types are largely unknown. In this study, we combined theoretical analysis and mathematical modeling to investigate several biophysical factors, including cluster shape and size, magnitude and dynamics of cellular traction forces, and applied shear forces that may influence tensional homeostasis in cells and clusters. We developed two-dimensional models of cells clusters of different shapes and sizes. To simulate temporal fluctuations of cell-extracellular matrix traction forces, we used a Monte Carlo approach. We also applied physical forces obtained from previous experimental measurements to the models. Results of the analysis and modeling revealed that cluster size, magnitude and dynamics of focal adhesion traction forces have a major influence on traction field variability, whereas the influence of cluster shape appears to be minor. The dynamics of traction forces seems to be related to cell types and it can explain why in certain cell types, such as endothelial cells, cell clustering promotes tensional homeostasis, whereas in other cell types, such as fibroblasts, clustering has virtually no effect on homeostasis. To further investigate mechanisms that may affect tensional homeostasis, we investigated the effect of applied steady shear stress on the traction field dynamics of endothelial cells and clusters. We applied steady shear stress to our two-dimensional model of cell clusters and then computed ensuing changes in the traction force variability. These simulations mimicked the effect of flow-induced shear stress on tensional homeostasis of endothelial cells and clusters. We found that under steady shear stress, temporal fluctuations of the traction field of endothelial cells became attenuated. This result agrees with the viewpoint that steady shear flow promotes tensional homeostasis in the endothelium. Together, results of this study advance our understanding of biophysical mechanisms that contribute to the cell ability to maintain tensional homeostasis. Furthermore, these results will help us to modify our current experimental procedures, as well as to design new experiments for our investigation of tensional homeostasis. / 2020-10-22T00:00:00Z

Orientador: José Elias Tomazini / Coorientador: Renato José Soares / Banca: Luiz Fernando Costa Nascimento / Banca: Eugênia Casella Tavares de Mattos / Resumo: A entorse do tornozelo em inversão e flexão plantar é uma das lesões mais comuns que ocorrem nas atividades de vida diária e no esporte. Embora os sintomas agudos possam se resolver rapidamente, muitos indivíduos relatam persistência de dor e instabilidade. Este tipo de lesão frequentemente acontece na fase final de um treino ou competição, e mesmo sabendo que a entorse é multifatorial, tal particularidade propicia estabelecer uma relação entre o evento da entorse e a fadiga. Diante disto, o presente estudo propõe analisar a latência e a intensidade de ativação dos músculos fibulares curto e longo em condições de fadiga, e ainda comparar indivíduos com estabilidade e instabilidade do tornozelo. Para esse fim, inicialmente foi desenvolvida uma plataforma simuladora da entorse em inversão e flexão plantar, na qual ambos os pés das voluntárias foram fixados e abaixo de onde se apoiava os pés foram acoplados transdutores de força, um de cada lado. Participaram do estudo 23 voluntárias do sexo feminino, fisicamente ativas, separadas em dois grupos: 11 fizeram parte do grupo estabilidade, não apresentavam histórico de lesão no complexo articular do tornozelo nos últimos 12 meses e outras 12 no grupo instabilidade funcional, classificadas pelo Questionário Cumberland Ankle Instability Tool. Para indução da fadiga, inicialmente foi registrada a Contração Isométrica Voluntária Máxima (CIVM) em eversão e flexão plantar. Durante a indução as voluntárias foram orientadas a manter 70% da CIVM. No momento em que a força aplicada fosse menor que 60% da CIVM o protocolo era interrompido e as voluntárias posicionadas em ortostatismo sobre a plataforma simuladora. Antes e após a fadiga foram realizadas dez simulações da entorse bilateralmente de forma randomizada e simultaneamente com o registro do sinal ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The inversion and plantar flexion ankle sprain is one of the most common injuries that occur in daily life activities and sports. Although acute symptoms can be resolved quickly, many people report persistent pain and instability. This type of injury often occurs in the final phase of a training or competition, and even though the sprain is multifactorial, such particularity provides the establishment of a relationship between the event sprain and fatigue. In this view, the present study aims to analyze the latency and activation intensity of the brevis and longus peroneus muscles in conditions of fatigue and also compare individuals with stability and instability of the ankle. For this purpose it was initially developed a simulated platform sprains in inversion and plantar flexion, in which both feet of the volunteers were fixed and below where rested his feet were coupled force transducers, one on each side. The study included 23 female volunteers, physically active, separated into two groups: 11 were part of the group stability, had no injury history in the joint complex of the ankle in the last 12 months and another 12 in functional instability group, classified by Cumberland Questionnaire Ankle Instability Tool. To induce fatigue, it was initially recorded a Contraction Isometric Maximal Voluntary (MVIC) in eversion and plantar flexion. During the induction, the participants were instructed to maintain 70% of the MVIC. At the time the force applied was below 60% of the MVIC the protocol was interrupted and the volunteers placed in standing position on the simulator platform. Before and after fatigue were held ten simulations sprain bilaterally randomly and simultaneously to record the electromyographic signal. Thus, it was observed that after the fatigue did not change the latency, but there was a reduction of muscle contraction level, ... (Complete abstract click electronic access below) / Mestre

Orientador: Luiz Fernando Costa Nascimento / Banca: José Geraldo Trani Brandão / Banca: Luis Carlos Ribeiro Lara / Resumo: O objetivo deste trabalho foi estudar o movimento de levantar de uma cadeira com três alturas pré-estabelecidas tendo como parâmetro de altura do assento os ângulos de 75, 90 e 105 graus nas articulações dos joelhos. Participaram 23 voluntários, (10 mulheres e 13 homens): idade média de 24,91 anos, estatura média de 1,70 m e peso corporal médio de 64,55 kgf. Duas plataformas de força mediram as forças de reação na posição sentada e durante o movimento de levantar, uma no assento da cadeira e outra no solo. Estabeleceram-se várias correlações entre as variáveis (peso corporal, altura, idade, e índice de massa corporal), entre as forças medidas e entre os tempos dos eventos. Foi evidenciado em toda a amostra que na medida em que se diminuía a altura do assento, maior foi a força aplicada ao solo para realizar o movimento de levantar. Diferenças na distribuição de peso entre assento e solo na posição sentada estática foram encontradas entre o assento que colocava os joelhos em 75° com a altura que os colocava nos outros dois ângulos. Não houve diferenças estatísticas significativas das médias dos valores de força e tempos no levantar comparados entre os sexos. Também não houve diferenças significativas entre as variáveis e os dados adquiridos nas plataformas. / Abstract: The aim of this work was to study the raising movement of a chair with three preestablished heights having as parameter of height of the seat the angles of 75, 90 and 105 degrees in the knee joints. Twenty three volunteers had participated, (10 women and 13 men): mean age of 24,91 years old, mean height of 1,70 m and mean body weight of 64,55 kgf. Two force plates had measured the reaction forces in the seated position and during the raising movement, one in the chair's seat and the other in the floor. It was established several correlations between some variables (body weight, height, age, and body mass index), between measured forces and between the events times. It was evidenced in all the sample that as soon as the seat's height decreased, greater was the force imposed to the floor to make real the raising movement. Differences in the weight distribution between seat and floor in the static seated position has been found between the seat that placed the knees in 75° with the height that placed it in the others two angles. There were not significant differences in the statistics of the load average values and times in the raising compared between the genders. Also they had not had significant differences between the variables and the data acquired in force plates. / Mestre

Orientador: José Elias Tomazini / Banca: Marcelo Sampaio Martins / Banca: Elaine Cristina Martinez Teodoro / Resumo : O presente trabalho teve como objetivo desenvolver um dispositivo capaz de mensurar a força de preensão palmar de forma dinâmica e, a verificação do funcionamento e adaptabilidade desse dispositivo, através de um estudo comparativo da força e a atividade muscular por meio da Eletromiografia do Flexor Superficial dos Dedos em sujeitos saudáveis em uma atividade laborativa de grampeação em uma empresa do ramo automotivo. Para isso o estudo idealizou um Dispositivo de Mensuração da Força de Preensão Palmar contendo extensômetros para avaliar a força muscular de preensão palmar a partir da reprodução de movimentos de grampeação. Participaram do estudo 7 sujeitos do sexo masculino, com idade entre 20 a 30 anos, massa corpórea entre 55 e 80 kg (77,39 ± 13,46 kg) e com estatura entre 1,65 e 1,75 m (1,71 ± 0,03 m), saudáveis e sem história clínica de patologia ortopédica ou qualquer tipo de lesão no sistema musculoesquelético. Foram realizadas 3 coletas simulando o movimento de grampeação. Através da análise comparativa dos dados, não foi observada diferença estatística intrasujeitos entre as forças de preensão e o RMS em cada coleta. Conclui-se que o dispositivo construído e testado apresenta possibilidades de mensuração de parâmetros quantitativos e que possa ser direcionado a novos estudos ergonômicos e biomecânicos / Abstract: This study aimed to develop a device capable of measuring handgrip strength dynamically and verification of operation and adaptability of this device, through a comparative study of strength and muscle activity through electromyography Flexor Superficial fingers in healthy subjects in a work activity of bolting in a automotive company. For this study devised a Device for Measuring Force Gripping Palmar containing gages to evaluate muscle grip strength from playing movements stapling. The study included seven male subjects, aged 20 to 30 years, body mass index between 55 and 80 kg (77.39 ± 13.46 kg) and height between 1.65 and 1.75 m (1.71 ± 0.03 m), healthy with no history of orthopedic disease or any type of injury in the musculoskeletal system. Three collections were performed simulating the motion stitching. Through comparative analysis of the data, no statistical difference between intrasubjectives forces hold and RMS in each collection was observed. It is concluded that the device has built and tested possibilities of quantitative measurement of parameters and the new ergonomic and biomechanical studies can be directed / Mestre

Orientador: Tamotsu Hirata / Coorientador: Marcelo Sampaio Martins / Banca: José Elias Tomazini / Banca: Glauce Gonzaga Silva / Resumo: As dores lombares acometem 80% da população em geral. Os levantamentos manuais ocupacionais e a rotação axial do tronco estão amplamente relacionados às dores e lesões lombares. A Rotação Axial sozinha é a causa de 33% de todas as lesões na coluna vertebral, mas pouco é sabido sobre ela e o carregamento manual. O objetivo do presente estudo foi analisar a atividade de músculos específicos do tronco e a relação entre a rotação do ombro e do quadril durante a rotação axial. Nove voluntários do sexo masculino (idade: 22,4 ±1,06 anos; IMC: 20,79 ± 2,23 kg/m²; % gordura: 9 ± 3,84 %), sem prévia de dor lombar, participaram da pesquisa, realizando o movimento de Rotação axial com o carregamento de uma caixa. Utilizou-se a eletromiografia de superfície (EMG) para a captação dos sinais dos músculos oblíquo interno ipsilateral, oblíquo externo contralateral e dos eretores lombares direito e esquerdo, todos agonistas do movimento de rotação, e cinemetria 2D para a análise do comportamento do tronco ao longo da tarefa. Para o tratamento estatístico dos dados obtidos, o teste de variância simples, one-way ANOVA foi selecionado para as comparações (p<0,05). Os resultados da eletromiografia apresentaram um padrão muscular diferente apenas para o ângulo de 90° de Rotação axial, principalmente em relação à ativação muscular médio-lateral esquerda (p=0.001), co-ativação médio-lateral direita (p=0.004), atividade muscular individual do músculo eretor contralateral (p=0.001) e músculo oblíquo externo contralateral (p=0.01). Os achados da cinemetria sugerem que 90° de rotação é a posição de maior potencial lesivo, uma vez que foi encontrada uma maior diferença entre a rotação do quadril e do ombro para esse ponto de referência (p=0.001). Como conclusão, recomenda-se que sejam evitadas as angulações de 90° de Rotação Axial em tarefas de carregamento de carga / Abstract: Back pain affect 80% of the general population. The manual occupational lifting are widely related to lumbar disorders as well as axial rotation of the trunk. The axial rotation of the trunk alone is the cause of 33% of all spinal injuries, a fact that needs to be better understood, especially when it is performed together with the manual loading. The aim of this study was to analyze the activity of the erector and abdominal muscles, the load-carrying task agonists with asymmetry, and the relationship between the rotation of the shoulder and hip during axial rotation. Nine male volunteers (age: 22.4 ± 1.06 years; BMI: 20.79 ± 2.23 kg / m²;% fat: 9 ± 3.84%), without low back pain participated in the survey performing the motion of the axial rotation of the trunk with loading a box in four different conditions by varying the loaded weight and speed of execution during the task. We used surface electromyography (EMG) to capture the signs of the ipsilateral internal oblique muscle, contralateral external oblique and lumbar erector spine right and left and 2D kinematics for the analysis of trunk behavior along the axial rotation of the trunk with manual loading. The statistical treatment of the data obtained, the simple variance test, one-way ANOVA was selected for the comparisons (p <0.05). The results of the electromyography showed a different muscle pattern only for the angle of 90 ° axial rotation, especially in relation to medium-lateral muscle activation (p = 0.001), co-activation middle-right side (p = 0.004), activity individual muscle of the contralateral erector muscle (p = 0.001) and contralateral external oblique muscle (p = 0.01). The findings of the kinematics suggest that 90 ° of rotation is the most injury potential position since we found a larger difference between the hip and shoulder rotation to this reference point (p = 0.001) ... (Complete abstract click electronic access below) / Mestre

The characterization of the mechanical behavior of cells has always captured the interest of scientists and, in the last decades, has been facilitated by the development of techniques capable of measuring a cell’s deformability. However, if on one hand, cells are active, living materials that regulate their physiology by generating and transmitting forces throughout their volume, common mechanical characterizations of cells involve material science approaches, which mostly address them as inert materials. As a consequence, although mechanical characterizations of cells have so far provided a wealth of correlations between stiffness and physio-pathological states, they have rarely provided insights into biological function and regulation. In this thesis, a cell nanomechanical platform is presented, whose resolution allows the isolation of the mechanical contribution of load-bearing cellular components. We first demonstrated that tensional forces - rather than the passive viscoelastic properties of the cytoplasm - govern the stiffness of cells at the nanoscale. We then quantitatively characterized the relationship between intracellular forces and the µm-scale patterns of stiffness across the cell surface. This analysis allowed us to calculate multiple physiologically-relevant quantities, such as membrane tension, cortex tension, actin bundle tension, tension-free elastic modulus, and mechanical coupling distances, all from single high-resolution cell stiffness images, providing an unprecedented connection between distinct mechanobiology fields.

Focal adhesions are dynamic multiprotein structures connecting cells to their surrounding microenvironment. Cells receive critical mechanical signals from adhesions that control many cellular processes including wound healing, differentiation, development, and cancer. Proteins that form adhesions are called adhesion proteins and some of these proteins can be mechanosensitive, meaning that they respond to mechanical stimuli. During spreading and migration, cells mechanically test extracellular matrix rigidity by contracting matrix to a constant displacement. Transmission and processing of such mechanical signals rely upon the dynamic regulation of the adhesions, which is tightly coordinated with activation of intracellular signaling cascades involving various adhesion molecules. However, the molecular mechanisms of mechanical signals that are transmitted through the adhesions to control cell behavior are poorly understood. In this thesis, we discovered novel phenomenon and mechanisms to elucidate roles of mechanical signals for multiple key aspects of basic cell behavior, especially cell growth. We performed live cell imaging of cells spreading on fibronectin coated micropillars to understand adhesion formation, adhesion regulation, and their impact on cell behavior. One of the earliest molecules to arrive at an adhesion formation site is a mechanosensitive protein called talin which binds to several other entities to form the backbone of focal adhesions. We found a novel role of talin cleavage, which previously was thought to play a role only in focal adhesion turnover. We found that talin cleavage is a force dependent process that regulates proper adhesion formation, thereby governing several critical cellular processes. In the absence of this talin cleavage, cells formed abnormal adhesions and showed inhibited growth. Further, we found that upon inhibition of talin cleavage, one of the key cellular behaviors of increased cellular motility upon stimulation by epidermal growth factor seemed to disappear. Epidermal growth factor receptor is a transmembrane protein and has previously been shown to play important role in various cancers where cells exhibit altered rigidity sensing. Surprisingly, we found that epidermal growth factor receptor was required for cellular rigidity sensing only on rigid substrates, highlighting the importance of the interplay between mechanical and biochemical signals in determining cell behavior.