Eccentric overload in training settings utilizes loads higher than concentric one repetition maximum (1RM). There is no clear definition of eccentric “failure” or 1RM using conventional weights, so eccentric 1RM is estimated to be between 145-190% concentric 1RM. Historically, the highest intensity used for eccentric overload is typically 120% of concentric 1RM despite little research using conventional weights with higher eccentric intensities. The purpose of this study was to conduct an exploratory neuro-mechanical analysis of different intensities of elbow flexors eccentric overload using free weights by examining angular kinematics during contraction. Twenty male participants with weight training experience had unilateral concentration curl isometric peak torque assessed on a Humac Norm Dynamometer and concentric 1RM assessed with dumbbells while biceps brachii electromyography (EMG) and elbow joint angle were recorded. Angles were recorded using a custom made electrogoniometer and elbow joint torque was estimated using inverse dynamics. Participants were randomly assigned in counter balanced order to perform eccentric actions at 120%, 140%, 150%, 160% and 170% concentric 1RM with 4 minutes rest between. Variables included peak torque, angular velocity at peak torque, impulse, power, mean EMG, and EMG normalized to peak. Data were analyzed using repeated measures ANOVA or a Friedman test. Angular velocity at peak torque was significantly lower for 120% (65.3 ± 40.8°/s) compared to all other conditions (range: 65.3 ± 40.8 to 162.1 ± 75.2°/s; p<0.01). Peak torque for all conditions (range: 98.2 ± 16.2 to 108.2 ± 21.6 Nm) was significantly higher than isometric peak torque (77.4 ± 16.8Nm; p<0.05). Peak torque at 160% (108.2 ± 21.6Nm) was significantly higher than at 120% (98.2 ± 16.2Nm; p<0.05). Power for 140-170% (range: 166.2 ± 85.7W to 265.8 ± 111.3W) was significantly higher than power at 120% (79.9 ± 66.8W; p<0.05). Impulse was highest at 120% (56.1 ± 54.6Nms) compared to all other conditions (range: 56.2 ± 54.6 to 9.6 ± 3.8Nms; p≤0.05). Impulse at 140% (20.6 ± 11.8Nms) was significantly higher than 170% (9.6 ± 3.8Nms; p<0.05). Isometric mean EMG (0.792 ± 0.285 mV) was significantly higher than all eccentric conditions (range: 0.654 ± 0.313 to 0.533 ± 0.259mV; p<0.05) with no difference between eccentric conditions for mean EMG or EMG normalized to peak. It was concluded that compared to 120%, eccentric overload with intensity ranging from 140-170% concentric 1RM involves minimal increases in peak torque and no change in EMG activation. Intensities above 120% enhance power and decrease impulse. This research has implications on future training prescription of eccentric exercise.

Made available in DSpace on 2016-06-02T19:50:01Z (GMT). No. of bitstreams: 1 TeseLCP.pdf: 9583238 bytes, checksum: c2137a635f05713171b01b2d0f229f21 (MD5) Previous issue date: 2003-01-01 / The usability is one of the main aspects of the performance and quality of the interface hand/instruments whose applicability is based on methodologies of ergonomic design. In spite of the technological evolution, some hand instruments still do not attend the criteria of usability and may generate ergonomic problems in users. An example of it is the transductor employed in breast ultrasonography (US) occupational activities, which requires large biomechanical efforts. This study aimed at proposing a method of assessment and analysis based on subjective and physiological records during the application of criteria of usability in the ergonomic redesign of the transductor for US breast examinations. In order to conductthe physiological records, a Biometrics electrogoniometer was used for the analysis of wrist movements, and FSRs sensors were used for the analysis of palmar pressure. As for the subjective assesments, graphic scales of perception were applied. The collection of data occurred in experimental phases: First Experimentation assessment of wrist postures during the simulation of activity with two commercial types of transductors (n= 18); Ergonomic design application of the criteria of usability in the redesign and prepraration of the mock-up; Second Experimentation assessment of the postures and points of palmar pressure during the simulation of activity with the new mock-up and the commercial transductors (n = 10); Ergonomic design/project revision revision of the criteria of usability and development of two new mock-ups; Third experimentation assessment of the postures and points of palmar pressure during the simulation of activity with the new mock-ups and the commercial transductors (n = 10); Fourth experimentation subjective assessment of all the transductors (n = 11). The results of the first experimentation indicated high median and maximal amplitudes. The ergonomic design turned up into mock-up 01. The results of the second experimentation indicated that mock-up 01 did not present improvements in terms of wrist posture, but rather a better distribution of pressure in the palmar region. The ergonomic design/project revision turned up into two new mock-ups, 02 and 03, which presented (in the results of the third experimentation) a lower amplitude for movements and a better distribution of the percentage of time in the different pre-established ranges of amplitude, as well as in the pressure of the palmar region, mainly when mock-up 02 is concerned. Statistically meaningful differences (p < 0,05) were found only in the third experimentation, indicating that mock-ups 02 and 03 presented better performance. The results of the fourth experimentation indicated similar results from the physiological assessment, corroborating its results. Such procedures characterized a consistent alternative to the traditional methods for assessing and analyzing hand instruments in ergonomic design. / A usabilidade é um dos principais aspectos do desempenho e qualidade da interface mão/instrumentos, cuja aplicação baseia-se em metodologias de design ergonômico. Apesar da evolução tecnológica, alguns instrumentos manuais ainda não atendem aos critérios da usabilidade e podem gerar problemas ergonômicos em seus usuários. Um exemplo disso é o transdutor utilizado nas atividades ocupacionais da ultra-sonografia (US) de mama, o qual exige grandes esforços biomecânicos. Este estudo teve como objetivo propor um método de avaliação e análise, com base em registros fisiológicos e subjetivos, durante a aplicação de critérios de usabilidade no redesenho ergonômico do transdutor de US de mama. Para a realização dos registros fisiológicos, foi utilizado um eletrogoniômetro Biometrics, para análise dos movimentos do punho, e sensores FSRs para análise de pressão palmar. Para as avaliações subjetivas, foram aplicadas escalas gráficas de percepção. A coleta dos dados ocorreu em fases experimentais: Primeira experimentação - avaliação das posturas de punho durante simulação da atividade com dois modelos comerciais de transdutores (n = 18); Design ergonômico - aplicação dos critérios de usabilidade no redesenho e confecção de mock-up; Segunda experimentação - avaliação das posturas e pontos de pressão palmar, durante simulação da atividade com o novo mock-up e os transdutores comerciais (n = 10); Design ergonômico/Revisão projetual - revisão dos critérios de usabilidade e desenvolvimento de dois novos mockups; Terceira experimentação - avaliação de posturas e pontos de pressão palmar, durante simulação da atividade com os novos mock-ups e os transdutores comerciais (n= 10); Quarta experimentação - avaliação subjetiva de todos os transdutores (n = 11). Os resultados da Primeira experimentação demonstraram elevadas amplitudes médias e máximas. O Design ergonômico resultou no Mock-up 01. Os resultados da Segunda experimentação demonstraram que o Mock-up 01 não apresentou melhorias quanto a posturas de punho, mas uma melhor distribuição de pressão na região palmar. O Design ergonômico/Revisão projetual resultou em dois novos Mock-ups, 02 e 03, os quais apresentaram (nos resultados da terceira experimentação) uma menor amplitude de movimentos e uma melhor distribuição da porcentagem de tempo nas diferentes faixas de amplitude preestabelecidas, bem como da pressão na região palmar, principalmente quanto ao Mock-up 02. Diferenças estatisticamente significativas (p _ 0,05) foram encontradas somente na terceira experimentação, indicando em quais situações os Mock-up 02 e 03 apresentaram melhor desempenho. Os resultados da Quarta experimentação demonstraram o mesmo indicativo da avaliação fisiológica, corroborando seus resultados. Esses procedimentos caracterizaram um método de avaliação e análise de instrumentos manuais, expressivo e complementar para as metodologias de design ergonômico.

Appropriate sampling strategies for estimation of exposure to physical risk factors require knowledge of exposure variability over time. Limited information is available about the variability of exposure to physical risk factors for upper extremity musculoskeletal disorders, especially during non-cyclic work activities. We investigated the magnitude and relative contributions of several sources of variance to the total exposure variance among office, custodial, or maintenance workers (N = 5 per group). In addition, we examined the homogeneity of exposure within each group of workers and exposure contrast between groups of workers. Activation of the flexor carpi radialis and upper trapezius muscle groups was assessed with surface electromyography (EMG) and wrist motion was assessed with electrogoniometry. Exposure information was collected continuously over a complete work shift on two occasions. We observed a substantial contribution of the within-day-within-subject variance component to the total exposure variance for all EMG and electrogoniometer summary measures. We also observed limited exposure contrast between the occupational groups in summary measures of upper trapezius EMG and most electrogoniometry summary measures. The large within-day-within-subject variance suggests the need for prolonged measurement durations (e.g., more than 1 hr) in future epidemiologic investigations of associations between exposure to physical risk factors and upper extremity musculoskeletal disorders.

The process of capturing solid geometry as 3 dimensional data requires the use of laser based reverse engineering hardware, known as a digitizer. Many digitizers exist as articulated coordinate measuring machines augmented with a laser, which forces the operator into many postures that are not ergonomically sound, particularly in the operator's upper body. This study analyzes the traditional method of laser digitizing using modern methods and technologies. An alternative user interface using a head-mounted monocular display is hypothesized and evaluated.

Made available in DSpace on 2016-06-02T20:19:04Z (GMT). No. of bitstreams: 1 DissRLC.pdf: 4124701 bytes, checksum: 7ad00279ff99c72a1e55ee44b80f553a (MD5) Previous issue date: 2007-02-02 / Financiadora de Estudos e Projetos / Despite recent technological advances, occupational activities of manual nature are still essential in many sectors and industries. Such activities impose risky conditions, which are inherent to its nature and can be responsible for musculoskeletal injuries. In addiction, the complexity and the interaction of risk factors, many still not comprehended, that act together during the performance of manual material handlings confer challenges and stimulations to the preventive approach. In this way, two main studies (Studies I and II) and two unfolding studies had been carried through. The main studies contextualized the hamstrings flexibility and its influence on the performance of occupational tasks. The objectives of Study I had been to compare the results of two clinical tests used to evaluate hamstrings flexibility and to evaluate the reliability of the photogrammetric procedure adopted for the analysis. The fingertip-to-floor test and straight leg raise test were applied in 35 healthy male subjects. Based on tests results, subjects were divided into two groups: normal and reduced flexibility. Superficial anatomical landmarks were fixed on bony references by means of manual palpation in order to permit the tracing of the hip, thoracic-lumbar, leg, knee and tibio-tarsal angles. The student t test was applied to evaluate the differences between the two groups, for each variable. Findings showed that hip angle was significant lower at the reduced flexibility group and that the straight leg raise test was more sensible for detecting subjects with reduced flexibility. The aim of Study II was to evaluate the influence of hamstrings flexibility on the movement strategy of the trunk and pelvis adopted by healthy subjects during the performance of the manual handling. Subjects were divided into two groups, based on the straight leg raise test. A JVC digital camera with a sampling of 50 frames/second and positioned perpendicularly to the sagittal plane of the subjects was used to register the activity. The cross-correlation coefficient was used to quantify movement patterns relationship between groups, and the student t test applied to the movement variables in order to determine differences between groups. The results had demonstrated that subjects with reduced flexibility used a lesser pelvic amplitude and bigger amplitudes of the trunk during handling. Still, subjects with reduced flexibility adopted a retroverted movement of the pelvis, without great alterations during the activity. The unfolding studies contextualized the comparison of the strategies adopted by subjects with experience in load handling activities and inexperienced individuals. The Study III had as objective to evaluate the manual handling performed by 16 experienced subjects and 15 inexperienced ones. It was used a flexible electrogoniometer to measure trunk movements and the University of Michigan 3D software to estimate the intradiscal compression in L5/S1 during the handling. The normalized movement patterns were evaluated and the coefficient of variation was applied to quantify the variability of this movement. The student t test determined the differences between variables. Results pointed out to great variability of adopted postures. Smaller amplitudes of flexion had been found, but bigger amplitudes of trunk extension when the loads were deposited, respectively, in low and high surfaces for experienced individuals. Experienced subjects presented lower intradiscal compression during box deposition and the lowering task was characterized by the highest intradiscal compression. Study IV aimed to compare manual handling strategies adopted by experienced and inexperienced subjects with relation to the positioning of the feet and trunk during lowering and inclination of the box during lowering and lifting activities. Ten experienced workers and 10 subjects without professional experience with the handling activity had been selected. The manual handling carried out between different heights was filmed. By means of one edition software, the images referring to the instant of 50% of the task had been selected and used to classify the postures and to measure the inclination of the box. An ANOVA with 3 factors was used to evaluate the inclination of the box with relation to the experience, handled load and type of handling (lifting and lowering). The results had indicated that subjects with professional experience adopted strategies characterized by biggest inclination of the box and adoption of balanced postures of the trunk, with widening of the support base. Professional experience determined the adoption of different movement strategies, when compared to inexperienced ones, in response to task conditions. However, other studies are suggested in order to determine if such strategies were protective or risky ones. The results presented in this dissertation raise the hypothesis that hamstrings flexibility is a risk factor for the increase of trunk overload, during the performance of manual material handling. / Apesar dos recentes avanços tecnológicos, as atividades ocupacionais de natureza manual ainda são imprescindíveis e amplamente utilizadas em muitos setores e indústrias. Tais atividades impõem condições de risco, que são inerentes à sua natureza e podem ser responsáveis por lesões músculo-esqueléticas. Em adição, a complexidade e a interação de fatores de risco, muitos ainda não totalmente compreendidos, que atuam em conjunto durante a realização do manuseio de materiais conferem desafios e estímulos à abordagem preventiva. Deste modo, foram realizados dois estudos principais e dois estudos decorrentes das pesquisas direcionadas ao estudo do manuseio de carga. Os estudos principais (Estudos I e II) contextualizam a flexibilidade dos músculos isquiotibiais e sua influência na performance de tarefas ocupacionais. Os objetivos do Estudo I foram comparar os resultados de dois testes clínicos utilizados para avaliar a flexibilidade dos músculos isquiotibiais e avaliar a confiabilidade do procedimento fotogramétrico utilizado. Os testes de Dedos ao Chão e Elevação dos Membros Inferiores (MMII) em Extensão foram aplicados em 35 sujeitos sadios do gênero masculino. Com base nos resultados dos testes, os sujeitos foram divididos em dois grupos: flexibilidade normal e reduzida. Marcadores superficiais refletivos foram fixados em referências ósseas por meio da palpação para permitir o traçado dos ângulos do quadril, tóraco-lombar, perna, joelho e tíbio-tarsico. Aplicou-se o teste t de student para avaliar as diferenças de cada variável entre os dois grupos. Os achados demonstraram que o ângulo do quadril foi significativamente menor no grupo com flexibilidade reduzida e o teste de Elevação dos MMII foi mais sensível para detectar sujeitos com redução de flexibilidade. O objetivo do Estudo II foi avaliar a influência da flexibilidade dos músculos isquiotibiais na estratégia de movimento do tronco e pelve adotada por sujeitos sadios durante a realização do manuseio de carga. Os sujeitos foram divididos em dois grupos, com base na aplicação do teste de Elevação dos MMII. Uma câmera digital JVC com amostragem de 50 quadros/segundo e posicionada perpendicularmente ao plano sagital dos sujeitos foi utilizada para registrar a atividade. O coeficiente de correlação cruzada foi utilizado para quantificar a relação dos padrões de movimento entre os grupos, e o teste t de student aplicado nas variáveis de movimento para determinar as diferenças entre grupos. Os resultados indicaram que sujeitos com flexibilidade reduzida utilizaram uma menor amplitude pélvica e uma maior amplitude do tronco durante o manuseio. Ainda, sujeitos com flexibilidade reduzida adotam movimento em retroversão da pelve, sem grandes alterações ao longo da atividade. Os desdobramentos (Estudos III e IV) contextualizaram a comparação das estratégias adotadas por sujeitos com experiência no manuseio de cargas e por indivíduos inexperientes em tais atividades. O Estudo III teve como objetivo avaliar o manuseio realizado por 16 sujeitos experientes e 15 inexperientes. Utilizou-se um eletrogoniômetro flexível para mensurar o movimento da coluna e o programa 3D da Universidade de Michigan para estimar a compressão intradiscal em L5/S1 durante o manuseio. Foram avaliados os padrões de movimento normalizados e o coeficiente de variação foi aplicado para quantificar a variabilidade deste movimento. O teste t de student foi aplicado na determinação das diferenças para as variáveis em estudo. Os resultados apontam para uma grande variabilidade de posturas adotadas. Foram encontradas menores amplitudes de flexão, mas maiores amplitudes de extensão da coluna quando as cargas eram depositadas, respectivamente, em superfícies baixas e altas para indivíduos experientes. Sujeitos experientes apresentaram menores valores de compressão intradiscal durante a deposição da caixa e a atividade de abaixamento com 15kg foi caracterizada por maior sobrecarga intradiscal. O Estudo IV teve como objetivos comparar as estratégias de manuseio realizadas por sujeitos experientes e inexperientes com relação ao posicionamento dos pés e tronco durante atividade de abaixamento e de inclinação da carga no levantamento e abaixamento. Foram selecionados 10 trabalhadores experientes e 10 sujeitos sem experiência profissional com o manuseio de cargas. O manuseio realizado entre diferentes alturas foi filmado. Por meio de um programa de edição, as imagens referentes ao instante de 50% da tarefa foram selecionadas e utilizadas para classificar as posturas e mensurar a inclinação da caixa. Utilizou-se uma ANOVA com 3 fatores para avaliar a inclinação da carga com relação à experiência, carga manuseada e tipo de manuseio (levantamento e abaixamento). Os resultados indicaram que sujeitos com experiência profissional do manuseio adotaram estratégias caracterizadas pela maior inclinação da caixa e adoção de posturas mais equilibradas do tronco, com afastamento dos pés. A experiência profissional parece determinar a adoção de estratégias de movimento diferentes do grupo inexperiente, em resposta às condições da atividade. Entretanto, novos estudos são sugeridos com o intuito de determinar se tais estratégias foram protetoras ou de risco. Ainda, o conjunto de resultados apresentados na dissertação levanta a hipótese de que a flexibilidade dos isquiotibiais seja um fator de risco para o aumento de sobrecarga na coluna, durante a realização do manuseio de materiais.