Thesis (Ph.D.)--University of Delaware, 2009. / Principal faculty advisors: Charles B. Swanik and Kathleen A. Swanik, Dept. of Health, Nutrition, & Exercise Sciences Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains viii, 135 p. Includes abstract. Includes bibliographical references.

Thesis (M.Tech.:Chiropractic)-Dept. of Chiropractic, Durban Institute of Technology, 2005 xii, [137] leaves / Musculoskeletal injuries in computer users are an increasing concern. The computer has become an essential working tool that is used throughout all levels of companies and organisations. Management and professional personnel are required to use computers, often without training in typing skills, this combined with higher stress and responsibility levels and lengthy work hours. Potentially this makes them a high-risk group for work related injury. Previous research has focused mainly on data entry and secretarial workers, who are often competent in typing and keyboard skills. There is an increasing body of literature that implicates a wide variety of factors responsible for computer and office related musculoskeletal injury, however there is still much conflict as to what factors play the most influential role in development of these disorders. Conflict largely remains over the role of individual and constitutional factors versus workplace factors such as ergonomic design and patterns of computer use. The aim of this study was therefore to determine the prevalence of and related risk factors associated with work related musculoskeletal injuries of the neck and shoulder in non-secretarial computer users within the South African context.

Introduction: Breast cancer is the most frequently diagnosed cancer and leading cause of cancer death among women and represents a considerable public health burden in South Africa and other low-middle income countries. Breast cancer management comprises single or combination treatment including surgery, radiotherapy and chemotherapy. Short and long-term complications of these treatments include shoulder morbidities such as pain, decreased range of motion, tightness, weakness, pain, numbness and lymphoedema, and may be present for up to 6 years post-surgery. An understanding of baseline demographic and clinical risk factors can guide rehabilitation and management strategies for high risk patients. Materials and Methods: This study was a cross-sectional analysis of the prevalence of shoulder pain and dysfunction in women attending their post-treatment annual follow up visit for unilateral breast carcinoma. The aim of this study was to quantify the burden of shoulder pain and disability in a tertiary academic hospital in Cape Town, South Africa, and identify potential risk factors for the development of shoulder morbidity. The primary objective of this study was to determine the prevalence of shoulder morbidity and the secondary objective was to evaluate associations between shoulder morbidity and risk factors such as treatment protocol or baseline demographics. Results: The majority of patients were of mixed ancestry, had their left side affected, received ALND and had undergone Modified Radical Mastectomy. The mean age was 60 years with a mean follow-up since surgery of 6 years. Three-quarters of patients reported a presence of pain or disability; 9% experienced severe pain and disability. Multivariable ordinal logistic regression analysis identified race, side, axillary surgery, chemotherapy and age as significant predictors of pain, and chemotherapy a significant predictor of disability. Discussion: The substantial burden of shoulder morbidity in this population represents a significant public health burden. The use of identified clinical and demographic characteristics may guide in the development of survivorship programmes incorporating surveillance and management of these high risk patients.

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Repetitive work is common in the workplace and can lead to the development of muscle fatigue. The purpose of this thesis was to improve our understanding of muscular and kinematic adaptation strategies of the shoulder complex throughout the process of fatigue and recovery. To achieve this I completed 6 studies, three studies investigating various aspects of repetitive work and fatigue and three methodological studies that were needed to interpret results. The muscular and kinematic effects of repetitive work were first investigated by incorporating a fatigue protocol between pre- and post-fatigue, simulated, repetitive work (Chapter 2). Fatigue is a complex process and how fatigue develops has been shown to influence its effects. To address this, Chapter 6 and 7 respectively, investigated the response to dynamic and static, fatiguing, repetitive work performed until participants reached termination criteria. Electromyography (EMG) was used throughout this thesis to assess muscle activity, which presented challenges because of its time consuming MVE protocols, the effects of myoelectric fatigue on its interpretation and between participants, fatigue developed in different muscles and at different rates, making comparisons between individuals challenging. For more efficient data collection, a method was developed to reduce the number of maximum voluntary exertions (MVE) required to elicit repeatable, maximum shoulder muscle activity, without eliciting muscle fatigue (Chapter 3). Methods were developed (Chapters 4 and 5) to mitigate the effects of myoelectric fatigue on EMG data and to calculate a multi-muscle fatigue score. This improved interpretation of how prolonged repetitive work impacted load sharing in the shoulder muscles and allowed the calculation of a multi-muscle fatigue score. Overall, this thesis found that the response to repetitive work is complex, multi-faceted and varies between individuals. Repetitive work impacts kinematics, muscle activity, muscle fatigue, strength, affective valence and perceived mental and physical fatigue in both static and dynamic work tasks (Chapters 2, 6, 7). Participants utilized the degrees of freedom in the shoulder complex and use coordinated compensation strategies to maintain their task performance, both following muscle fatigue (Chapter 2) and while developing muscle fatigue (Chapter 6, 7). These responses changed over time, as different muscles fatigued and recovered and were variable between individuals (Chapters 2, 6, 7). Removing fatigue artifacts from the EMG showed that muscle activity changes observed are due to load sharing between the musculature of the shoulder complex (Chapter 6, 7). Participants can adapt to the challenge of fatiguing, repetitive work and individuals will use different, coordinated strategies to maintain task performance. / Thesis / Doctor of Philosophy (PhD)

This study was conducted to measure the reliability of fatigue measures in an intermittent overhead work task. Fatigue measures included several EMG based parameters and subjective discomfort ratings through use of the Borg CR-10 scale. This study was part of a larger existing study that simulates overhead work in an automobile manufacturing plant. Ten participants used a drill tool to perform an overhead tapping task for one hour at a height relative to individual anthropometry. Reliability indexes, including Intraclass Correlation Coefficients, Standard Errors of Measurement, and Coefficients of Variation were determined for each fatigue measure for each of three shoulder muscles (anterior deltoid, middle deltoid, and trapezius). High reliability implies repeatable results, and precise and credible methods. Conversely, measurement error and subject variability can lead to low reliability of measures. The results indicated that ratings of perceived discomfort (RPD) parameters (slope and final rating) showed relatively high reliability. Intercepts for mean power frequency (MnPF), median power frequency (MdPF), and root means square (RMS) also showed very high reliability. Actual slopes for MnPF, MdPF, and RMS showed low reliability overall, and normalizing slopes did not necessarily improve reliability. Taking the absolute value of slopes led to a noticeable increase in reliability. RPD slope did not correlate with any of the EMG slopes. The high reliability of RPD parameters allows for its inexpensive application to the industrial setting for similar overhead tasks. The reliability of EMG intercepts implies consistent methods; however the reliability of overall EMG trends is suspect if the slope is not reliable. Some EMG slope parameters show promise; however, more research is needed to determine if these parameters are reliable for complex tasks. / Master of Science

The purpose of this study was to further investigate the relationship between patterns of shoulder movement and muscular response. Thirteen females were tested against maximal manual resistance in twelve different patterns, eight straight plane, and four diagonal. Five of the six subjects who met established kinematic criteria were used for electromyographic (EMG) analysis of the anterior deltoid (AD), the middle deltoid, the posteroir deltoid (PD), and the pectoralis major. No significant differences were found between number of muscles solicited or duration of muscular effort during the different movements. Maximal EMG was significantly higher for the AD in abduction and in flexion than in the other patterns, and for the PD in diagonal flexion with abduction and in transverse abduction.

Diss. (sammanfattning) Linköping : Univ., 2004. / Härtill 4 uppsatser.

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