INTRODUCTION: Coupling in the distal foot may be due, at least in part, to the foot's windlass mechanism. This mechanism has been demonstrated passively, but its role in dynamic movement is still unclear. A systematic manipulation of metatarsophalangeal (MTP) mechanics may help determine to what extent distal foot coupling during dynamic and active movement is due to the windlass mechanism versus active muscle contractions or springlike ligaments. Furthermore, exploring the windlass mechanism in feet with varying foot structure may aid our understanding of the relationship between foot structure and foot function. PURPOSE: The overall purpose of this study is to investigate the kinematic and kinetic coupling between the MTP and midtarsal joints through a systematic manipulation of the windlass mechanism (achieved through methodical changes to MTP motion). Additionally, we aimed to explore the relationship between foot structure and the efficacy of the windlass mechanism during passive, active, and dynamic movement. METHODS: First, arch height and flexibility were measured using the Arch Height Index Measurement System. Next, participants performed four order-randomized conditions where MTP extension was isolated: 1) Seated Passive MTP Extension, 2) Seated Active MTP Extension, 3) Standing Passive MTP Extension, and 4) Standing Active MTP Extension. Lastly, participants performed three heel raise conditions that manipulated the starting position of the MTP joint: 1) Neutral: normal heel raise, 2) ToeExt: heel raise with the toes placed on an inclined surface of 30 degrees to put the MTP joint into extension, and 3) ToeFlex: heel raise with the toes placed on a declined surface of 30 degrees to put the MTP joint into flexion. All conditions were performed to a metronome of 40 beats per minute to control angular velocity. A kinetic multisegment foot model was created in Visual 3D software and used to calculate ankle, midtarsal, and MTP joint angles, moments, powers, and work. RESULTS: Kinematic coupling was approximately six times greater in the heel raise conditions compared to the isolated MTP extension conditions and suggests that the windlass mechanism only plays a small role in dynamic tasks. This is likely due to the greater involvement of active muscle contractions during heel raises. As the starting position of the MTP joint became increasingly extended, the amount of negative work at the MTP joint increased concomitantly with increased positive work done at the midtarsal joint, while net distal-to-hindfoot work remained unchanged. Our combined results suggest that there is substantial coupling within the distal foot, but this coupling is likely attributed to more than simple passive energy transfer from the windlass mechanism. Future investigations into the intrinsic foot muscle activation and biarticular muscle effects are likely needed to determine the source of this coupling. Lastly, the relationship between foot structure and function is still unclear and our results suggest that arch height or arch flexibility alone may not be adequate predictors of dynamic foot function.

This study was conducted to investigate whether hamstring muscle activation rate could potentially serve as an indicator for slip-induced falls, particularly for older adults. Kinematics (heel contact velocity, walking velocity, slip distance, and step length), kinetics (friction demand), and electromyography (EMG) while walking over a slippery surface were collected and examined in the study. Normalized EMG data were examined in term of activation rate and compared to heel contact velocity. Twenty-eight subjects from two age groups (14 young and 14 elderly) walked across a track with embedded force platforms while wearing a fall arresting harness attached to an arresting rig for safety. In order to obtain realistic unexpected slip-induced fall data, the slippery surface was hidden from the subjects and unexpectedly introduced. The primary objective of the study was to evaluate if hamstring activation rate could be a valid indicator for the initiation of slip-induced falls. The results suggested that hamstring activation rate in younger adults was higher than older adults, whereas, younger adults’ heel contact velocity was not different from older adults. These results suggested that heel contact velocity in younger adults was sufficiently reduced before the heel contact phase of the gait cycle. This could be due to the outcome of higher hamstring activation rate in younger adults in comparison to older adults. However, an equal number of falls in two age groups, in spite of older adults’ slower walking velocity, lower RCOF, shorter slip distance, and slower peak sliding heel velocity, suggested that the recovery phase of the slip-induced fall accidents should be studied further. / Master of Science

Research has shown that older adults who have experienced a previous fall are 60-70% more likely to suffer future falls. A study was conducted to investigate if stress and anxiety associated with a fear of falling contributes to the increased incidents of falls among older adults. The investigation compared physiological parameters, with biomechanical parameters of walking for twenty-eight participants in two age groups: (18-35) and (65 or older). Both age groups were evaluated while walking over dry and slippery floor surfaces. Biomechanical parameters included: step length, required coefficient of friction (RCOF), slip distance, and heel contact velocity. Physiological parameters included: stress and anxiety. Overall, the results indicated that there were differences between older and younger adult's biomechanical parameters of walking, and their physiological stress and anxiety associated with an inadvertent slip. Younger adult's normal RCOF was higher and their normal step length was longer compared to older adults. Older adult's stress level after a slip was significantly higher than younger adults. However, younger and older adult's anxiety scores were not significantly different. Furthermore, younger and older adults modified their step length differently to avoid slipping, when walking over the slippery floor surface. It was concluded that some anxiety and stress may be beneficial in reducing the occurrence of inadvertent slips and falls due to an increased awareness of one's external environment. / Master of Science

Title The effect of wearing high heel shoes on pelvis motion Aim of the thesis The main aim of this thesis is the verification of the influence of wearing high heel shoes on pelvis motion in the sagittal plane, while walking on high heel shoes and walking on heel less shoes. After then, we want to monitori the impact of walking in these shoes on the trajectory of pelvis motion. Methods Objectification method was 3D record of human gait (= kinematic analysis), which was performed using the Qualisys Track Manager. In our thesis we used the method of comparison. The aim of the study is the comparison of parameters measured in different types of shoes (high heeled shoes, high heeled less shoes with barefoot gait) and the influence on pelvis motion in the sagittal plane. Measurements were carried out in the gym at the Faculty of Physical Education and Sport at ten probands. Results Pelvis tilt to retroversion was more significant when walking on heel less shoes compared with high heel shoes and barefooted walking, also an angle of the trunk and pelvis were most significantly diminished when walking on heel less shoes compared to barefooted walking and high heel shoes. Objectively, a larger deflection of pelvis trajectory while walking on high heel shoes was not confirmed compared to walking on heel less...

A camada semi-redutora (CSR), definida como a espessura de um material absorvedor que colocado sob um feixe de raios-X reduz sua intensidade à metade, é um parâmetro que deve ser avaliado periodicamente nos programas de garantia de qualidade em radiologia médica, pois fornece informações a respeito do desempenho do feixe radiográfico produzido pelo aparelho. Todavia, sua medida é normalmente feita na região central do campo de exposição e não considera a variação da qualidade relativa do feixe ao longo de toda a sua extensão, causada essencialmente pelo efeito heel. Em vista disso, o presente trabalho propõe um algoritmo de simulação computacional para determinar a CSR de aparelhos radiográficos em qualquer posição no campo através de uma única medida na região central, para permitir uma avaliação mais completa da variação da qualidade do feixe em função do posicionamento do objeto no plano imagem. Além disso, a partir dos resultados obtidos, também é proposto um procedimento computacional capaz de determinar filtros de características específicas para compensar essas variações na qualidade da imagem causadas pelo efeito heel e também por variações na espessura do objeto radiografado. Os resultados obtidos com os programas de simulação desenvolvidos mostraram-se coerentes com os obtidos em testes práticos realizados com aparelhos radiográficos hospitalares, comprovando a validade dos algoritmos propostos. / The half-value layer (HVL) is defined as the thickness of an absorbing material which placed under an X-Ray beam reduces its intensity to half. It is a parameter that should be periodically evaluated in medical radiology quality control programs because it gives information related to the radiographic system beam performance. However, its measurement is done normally at the center of the radiation field, not taking into account the beam relative quality variation along the field, caused essentially by the heel effect. Bearing that in mind, the present work proposes a computer simulation algorithm to determine the radiographic systems HVL at any location on the field based on a single measurement at the central area, to allow a more complete evaluation of the beam quality variation due to the object location on the image plane. Furthermore, from these results, another computer simulation procedure is proposed to determine particular filter characteristics to compensate these image quality variations caused by the heel effect and also by the X-rayed object thickness variation. The results obtained from the simulation programs are consistent with the experimental results performed in medical radiographic systems, confirming therefore the validity of the proposed algorithms.

A camada semi-redutora (CSR), definida como a espessura de um material absorvedor que colocado sob um feixe de raios-X reduz sua intensidade à metade, é um parâmetro que deve ser avaliado periodicamente nos programas de garantia de qualidade em radiologia médica, pois fornece informações a respeito do desempenho do feixe radiográfico produzido pelo aparelho. Todavia, sua medida é normalmente feita na região central do campo de exposição e não considera a variação da qualidade relativa do feixe ao longo de toda a sua extensão, causada essencialmente pelo efeito heel. Em vista disso, o presente trabalho propõe um algoritmo de simulação computacional para determinar a CSR de aparelhos radiográficos em qualquer posição no campo através de uma única medida na região central, para permitir uma avaliação mais completa da variação da qualidade do feixe em função do posicionamento do objeto no plano imagem. Além disso, a partir dos resultados obtidos, também é proposto um procedimento computacional capaz de determinar filtros de características específicas para compensar essas variações na qualidade da imagem causadas pelo efeito heel e também por variações na espessura do objeto radiografado. Os resultados obtidos com os programas de simulação desenvolvidos mostraram-se coerentes com os obtidos em testes práticos realizados com aparelhos radiográficos hospitalares, comprovando a validade dos algoritmos propostos. / The half-value layer (HVL) is defined as the thickness of an absorbing material which placed under an X-Ray beam reduces its intensity to half. It is a parameter that should be periodically evaluated in medical radiology quality control programs because it gives information related to the radiographic system beam performance. However, its measurement is done normally at the center of the radiation field, not taking into account the beam relative quality variation along the field, caused essentially by the heel effect. Bearing that in mind, the present work proposes a computer simulation algorithm to determine the radiographic systems HVL at any location on the field based on a single measurement at the central area, to allow a more complete evaluation of the beam quality variation due to the object location on the image plane. Furthermore, from these results, another computer simulation procedure is proposed to determine particular filter characteristics to compensate these image quality variations caused by the heel effect and also by the X-rayed object thickness variation. The results obtained from the simulation programs are consistent with the experimental results performed in medical radiographic systems, confirming therefore the validity of the proposed algorithms.

Este trabalho apresenta uma metodologia semi-automática e simplificada para estimação da idade óssea baseada no método de Eklof & Ringertz. Fundamenta-se no processamento e extração de informações de imagens radiográficas da mão, mostrando a real influência do efeito Heel nesse tipo de imagem. Apresenta resultados obtidos com a aplicação de algoritmos de thresholding, com e sem a correção do efeito Heel,e propõe uma metodologia para isolar os ossos do tecido da mão para obtenção de dimensões dos mesmos. Essas dimensões foram usadas como informações para a estimação da idade óssea de seres humanos em fase de crescimento, buscando uma simplificação do método de Eklof & Ringertz. / This research presents a semi-automatic and simplified methodology to estimate skeletal age by using the Eklof & Ringertz method. The method is based on processing and extraction of hand radiographic images information, showing the Heel effect real influence in this type of image. The results obtained with application of thresholding algorithms, with and without Heel effect correction are presented and a methodology to isolate bone from hands tissue for dimension measurements is proposed. These dimensions were used as the information for skeletal age estimation of humans in the growth phase, on order to simplify the Eklof & Ringertz method.

O diagnóstico radiográfico é baseado na análise das diferenças das densidades ópticas (DO) do filme, que deveriam ser provocadas apenas pelas estruturas anatômicas do paciente. Entretanto, a intensidade do feixe de raios X não é uniforme devido a um efeito intrínseco do equipamento de aquisição de imagem, conhecido como efeito \"heel\". Estas variações prejudicam tanto a análise visual quanto o processamento computacional (CAD) das pequenas estruturas anatômicas. O presente trabalho apresenta um método computacional que corrige as diferenças de densidades ópticas produzidas na radiografia pelo efeito \"heel\". Esse método foi implementado utilizando ambiente de programação Delphi, rotinas em C e Matlab. O método simula a distribuição da intensidade ao longo do campo de radiação, determinando o caminho de absorção que os fótons sofrem dentro do alvo utilizando os modelos de Kramers e Fritz Livingston. Calcula a correlação espacial entre a radiografia e a imagem simulada, localizando o eixo anodo/catodo e o centro do campo nas duas imagens, empregando a função de correlação estatística de Pratt e a função de mapeamento de Zitová e Flusser. Calcula tanto os percentuais de radiação recebidos para cada ponto simulado em relação à radiação ao centro do campo, quanto os percentuais dos níveis de cinza de cada pixel da radiografia e corrige esse valor em função do correspondente na simulação. O algoritmo desenvolvido permitiu determinar a posição do centro do campo de radiação com precisão em torno de 1% e eliminou aproximadamente 90% do efeito \"heel\" na radiografia permitindo que os objetos apresentassem densidades ópticas coerentes com suas absorções específicas. Um estudo preliminar mostrou que esse método poderá ser utilizado como pré-processamento dos sistemas CAD. / The radiographic diagnosis is based on the analysis of the film optical density differences that should be created only by the patient anatomical structures. However, the intensity of the x-ray beam is not uniform due to an intrinsic effect to the image acquisition equipment, known as heel effect. These variations damage the visual analysis as well the (CAD) computer processing of the small anatomical structures. The current work presents a computer method that corrects the optical densities differences generated in the radiography by heel effect. This method was implemented using Delphi Programming Environment, routines in C and Matlab. The method simulates the intensity distribution along the radiation field, determining the absorption path that photons suffer inside the target using the models of Kramers and Fritz and Livingston. It calculates the space correlation between the radiography and the simulated image, determining the anode/cathode axis and the field center in the two images, using the statistics function of Pratt and the mapping function of Zitová and Flusser. It calculates as much the received radiation, percentage for each simulated point in relation the field center radiation, as the gray scales percentage of each radiography pixel and corrects their values as function of the correspondent in the simulation. The developed algorithm has allowed to determine the center position of the radiation field with about 1% precision and approximately eliminated 90%of the heel effect in the radiography, allowing the objects to present optical densities coherent with their specific absorptions. A preliminary study has showen that this method can be used as preprocessing of CAD systems.

Este trabalho apresenta uma metodologia semi-automática e simplificada para estimação da idade óssea baseada no método de Eklof & Ringertz. Fundamenta-se no processamento e extração de informações de imagens radiográficas da mão, mostrando a real influência do efeito Heel nesse tipo de imagem. Apresenta resultados obtidos com a aplicação de algoritmos de thresholding, com e sem a correção do efeito Heel,e propõe uma metodologia para isolar os ossos do tecido da mão para obtenção de dimensões dos mesmos. Essas dimensões foram usadas como informações para a estimação da idade óssea de seres humanos em fase de crescimento, buscando uma simplificação do método de Eklof & Ringertz. / This research presents a semi-automatic and simplified methodology to estimate skeletal age by using the Eklof & Ringertz method. The method is based on processing and extraction of hand radiographic images information, showing the Heel effect real influence in this type of image. The results obtained with application of thresholding algorithms, with and without Heel effect correction are presented and a methodology to isolate bone from hands tissue for dimension measurements is proposed. These dimensions were used as the information for skeletal age estimation of humans in the growth phase, on order to simplify the Eklof & Ringertz method.

O diagnóstico radiográfico é baseado na análise das diferenças das densidades ópticas (DO) do filme, que deveriam ser provocadas apenas pelas estruturas anatômicas do paciente. Entretanto, a intensidade do feixe de raios X não é uniforme devido a um efeito intrínseco do equipamento de aquisição de imagem, conhecido como efeito \"heel\". Estas variações prejudicam tanto a análise visual quanto o processamento computacional (CAD) das pequenas estruturas anatômicas. O presente trabalho apresenta um método computacional que corrige as diferenças de densidades ópticas produzidas na radiografia pelo efeito \"heel\". Esse método foi implementado utilizando ambiente de programação Delphi, rotinas em C e Matlab. O método simula a distribuição da intensidade ao longo do campo de radiação, determinando o caminho de absorção que os fótons sofrem dentro do alvo utilizando os modelos de Kramers e Fritz Livingston. Calcula a correlação espacial entre a radiografia e a imagem simulada, localizando o eixo anodo/catodo e o centro do campo nas duas imagens, empregando a função de correlação estatística de Pratt e a função de mapeamento de Zitová e Flusser. Calcula tanto os percentuais de radiação recebidos para cada ponto simulado em relação à radiação ao centro do campo, quanto os percentuais dos níveis de cinza de cada pixel da radiografia e corrige esse valor em função do correspondente na simulação. O algoritmo desenvolvido permitiu determinar a posição do centro do campo de radiação com precisão em torno de 1% e eliminou aproximadamente 90% do efeito \"heel\" na radiografia permitindo que os objetos apresentassem densidades ópticas coerentes com suas absorções específicas. Um estudo preliminar mostrou que esse método poderá ser utilizado como pré-processamento dos sistemas CAD. / The radiographic diagnosis is based on the analysis of the film optical density differences that should be created only by the patient anatomical structures. However, the intensity of the x-ray beam is not uniform due to an intrinsic effect to the image acquisition equipment, known as heel effect. These variations damage the visual analysis as well the (CAD) computer processing of the small anatomical structures. The current work presents a computer method that corrects the optical densities differences generated in the radiography by heel effect. This method was implemented using Delphi Programming Environment, routines in C and Matlab. The method simulates the intensity distribution along the radiation field, determining the absorption path that photons suffer inside the target using the models of Kramers and Fritz and Livingston. It calculates the space correlation between the radiography and the simulated image, determining the anode/cathode axis and the field center in the two images, using the statistics function of Pratt and the mapping function of Zitová and Flusser. It calculates as much the received radiation, percentage for each simulated point in relation the field center radiation, as the gray scales percentage of each radiography pixel and corrects their values as function of the correspondent in the simulation. The developed algorithm has allowed to determine the center position of the radiation field with about 1% precision and approximately eliminated 90%of the heel effect in the radiography, allowing the objects to present optical densities coherent with their specific absorptions. A preliminary study has showen that this method can be used as preprocessing of CAD systems.