Magister Public Health - MPH / Background: Protecting and promoting health in the workplace is imperative, both for individual employee health and workplace productivity. High rates of workplace injuries, particularly in environments where high levels of physical activity are required, point to the need for effective occupational interventions, minimization of workplace inhibitors that increase the risk of developing musculoskeletal disorders (MSDs), and occupational management checks to reduce the onset of MSDs in the workplace. However, for these measures to be successful, it would be important to identify individual and workplace-related factors associated with the development and duration of MSDs. Aim: To determine potential risk and protective factors associated with MSDs among employees in a workplace where heavy lifting is a key job function.

A elevação de uma carga leva ao surgimento de uma força de contato a região lombar (L5-S1) que pode atingir algumas vezes o valor do próprio peso do indivíduo, valor este que depende da carga elevada. A análise das forças (musculares, peso, carga), considerando a coluna como uma haste rígida, cuja extensão é feita unicamente pelo eretor espinhal, representa uma aproximação muito pobre para o sistema, uma vez que as diversas forças musculares envolvidas não são adequadamente analisadas e o movimento de retificação da coluna vertebral é desprezado. O objetivo do presente trabalho foi o desenvolvimento de um modelo biomecânico simplificado em 2 dimesões, para a avaliação das forças atuantes durante atividades de levantamento impróprio de carga e o movimento de flexão/extensão a coluna lombar. A coluna vertebral foi modelada como um conjunto de três segmentos retilíneos rígidos articulados e entre si. Utiliza do o método da dinâmica inversa, aplicado a um modelo de segmentos articulados simplificado, foram estimadas as forças musculares médias e a força de contato articular na articulação vertebral L5-S1 como função dos â ângulos de inserção da musculatura extensora da coluna. Para a construção do modelo foram identificados: musculatura principal, dados antropométricos, ângulos de inserção musculares, modelo antropométrico e registro da imagem do levantamento de peso. O modelo matemático forneceu um sistema de equações que avaliam as forças que atuam na coluna vertebral durante o movimento de extensão, em função de dados a atômicos. / Load lifting yields a contact force in the lumbar region (L5-S1) that can sometimes reach the value of the body weight, depending upon the elevated load. Force analyses (muscular, weight, load), the spine being consided as a rigid shank, with extension beimg done only by the erector spine musculature, represent a poor approximation, since the several muscular forces involved are not adequately analysed and the rectification movement of the spine is not taken into account. The purpose of this study was to develop a simplified two dimensional biomechanical model in order to evaluate the forces during activities of improper load bearing and the movement of flexion/extension in the lumbar spine. The spine was assumed as a linear rigid array of articulate segments. Using inverse dynamics applied to a simplified link segment model,the average muscular forces and bone-to-bone contact force in the L5-S1 vertebral joint were evaluated as a function of the back extension muscles insertion angles. For the model construction the main musculature, the anthropometric data, and model the muscle insertion angles, and the image acquisition register of the weight loading movement were identified. The mathematical model yielded a system of equations that evaluates the acting forces on the spine during the extension movement, as a function of the a atomical data.

Although much effort has been placed into the reduction of risks associated with manual materials handling, risk of musculoskeletal disorder development remains high. This may be due to the additional muscle activity necessary for the maintenance of postural equilibrium during work tasks. This research proposes that postural control and subsequent additional muscle activity is influenced by the magnitude of the external load and the degree of body movement. The objective of this research was to identify whether performing tasks with increased external load and with a greater degree of trunk motion places additional strain on the musculoskeletal system in excess of that imposed by task demands. Twenty-four male and twenty-four female subjects performed four load manipulation tasks under three loading conditions (0.8kg, 1.6kg, and 4kg). Each task comprised of a static and dynamic condition. For the static condition, subjects maintained a stipulated posture for ten seconds. The dynamic condition required subjects to move and replace a box once every three seconds, such that a complete lift and lower cycle was performed in six seconds. Throughout task completion, muscle activity of six pairs of trunk muscles were analysed using surface electromyography. This was accompanied by data regarding ground reaction forces obtained through the use of a force platform. After the completion of each condition subjects were required to identify and rate body discomfort. Differential analysis was used to isolate the muscle activity and ground reaction forces attributed to increased external load and increased trunk movement. It was found that the heaviest loading conditions (4kg) resulted in significantly greater (p<0.05) muscle activation in the majority of muscles during all tasks investigated. The trend of muscle activity attributed to load was similar in all significantly altered muscles and activation was greatest in the heaviest loading condition. A degree of movement efficiency occurred in some muscles when manipulating loads of 0.8kg and 1.6kg. At greater loads, this did not occur suggesting that heavier loading conditions result in additional strain on the body in excess of that imposed by task demands. In manipulated data, trend of vertical ground reaction forces increased with increased load in all tasks. Sagittal movement of the centre of pressure attributed to load was significantly affected in manipulated data in the second movement phase of the “hip shoulder” task and the second movement phase of the “hip twist” task. The “hip reach” task was most affected by increased load magnitude as muscle activity attributed to load was significantly different (p<0.05) under increased loading conditions in both movement phases in all muscles. Further, a significant interactional effect (p<0.05) between condition and data point was found in all muscles with the exception of the right and left lumbar erector spinae during the second movement phase of the “hip reach” task. Muscle activity associated with increased trunk motion resulted in additional strain on the trunk muscles in the “hip shoulder” and “hip reach” tasks as muscle activity associated with the static component of each of the above tasks was greater than that of the dynamic tasks. Trend of ground reaction forces attributed to increased trunk motion generally increased under increased loading conditions. Additionally, a significant interactional effect (p<0.05) between load and muscle activity pattern was found in all muscles during all tasks, with the exception of the right rectus abdominis in the first movement phase of the “hip shoulder’ task, the left rectus abdominis in the second movement phase of the “hip knee” task and the right latissimus dorsi during the first movement phase of the “hip twist” task. This was accompanied by a significant interactional effect (p<0.05) between load and sagittal centre of pressure movement attributed to load, in both movement phases of all tasks investigated. From this research it can be proposed that guidelines may underestimate risk and subsequently under predict the strain in tasks performed with greater external loads as well as tasks which require a greater degree of trunk motion. Therefore, this study illustrates the importance of the consideration of the muscle activity necessary to maintain postural equilibrium in overall load analyses.

The current manuscript has been adapted from the official position statement of the UK Strength and Conditioning Association on youth resistance training. It has subsequently been reviewed and endorsed by leading professional organisations within the fields of sports medicine, exercise science and paediatrics. The authorship team for this article was selected from the fields of paediatric exercise science, paediatric medicine, physical education, strength and conditioning and sports medicine.

A fundamental aerodynamic analysis technique for a single straight fixed wing has been expounded upon and turned into a modern technique that can analyze multiple wings of more realistic shapes common on aircraft. This modern technique is extended further to apply towards propellers. A method to overcome propeller analysis problems at low airspeeds is presented. This method is compared to more traditional propeller analysis techniques.

Résumé / Abstract

The lifting associated with childcare has been linked to musculoskeletal disorders (MSDs) in mothers (Griffin & Price, 2000; Sanders & Morse, 2005). The purpose of the current study was to investigate, for the first time through observation, the lifting of young children by mothers in the home environment to identify risk factors which might give rise to MSDs. Twenty five mothers with one or two children weighing between 9 and 15kg (n = 30) completed a self-report survey modified for the New Zealand context (The Ergonomics of Caring for Children (Sanders & Morse, 2005)). They also took part in a structured observation of lifting in the home using a checklist based on the New Zealand Manual Handling Hazard Control Record NZMHHCR (OSH & ACC, 2001). Modifications were derived from careful consultation of current literature to enable contributory factors related to the load, the mother, the environment and the task to be assessed and a rating of low, medium, or high risk to be assigned to each factor. A protocol to guide risk assessment was developed to accompany the tool. The modified observational checklist was named the OMLITH (Observing Mothers Lifting In The Home). Survey data identified the mothers as aged between 28 and 40 years, predominantly NZ European, and of average height (χ = 1.69cm) and weight (Body Mass Index = 24). The children in the sample weighed between 9 and 14.5kg and had an average age of 17months. All the mothers were either married (n=20) or living with a significant other (n=5) and their partners frequently (n=13) or always (n=12) helped with childcare. The mean time mothers spent per week on the following activities were: sleep, 6.8hrs (n=25), housework, 14.9hrs (n=25), exercise, 2.9hrs (n=22), watching television or using the home computer, 4.3hrs (n=22), hobbies, 2.2hrs (n=19), gardening or home maintenance, 2.9hrs (n=18). Thirteen of the mothers worked (3 full-time, 10 part-time) and 20 mothers used childcare services. Ratings of the physical stress associated with 50 childcare tasks showed that mothers differentiated between tasks in terms of physical stress to a significant degree (p.000), typically rating ‘Bending while carrying a child’ as almost twice as stressful as the average rating. Other categories rated significantly above the average stress rating were: ‘Use of a backpack to carry infant/child’, ‘Use of baby jogger’, ‘Carrying child on your shoulders’, ‘Standing bent over to wash child in bath or sink’, ‘Lifting child into or out of cot’, ‘Prolonged squatting or stooping while playing with child’, and ‘Placing child in car seat or removing child from car seat’. Mothers reported experiencing MSDs most commonly in the low back (n=16), and the neck, shoulder and upper back (n=8 each). Data from the 87 observations using the OMLITH showed that children were a challenging load due to their moving centre of gravity, and were often unpredictable or awkward to handle. The grip required to lift a child more often than not fell outside the National Institute for Occupational Safety and Health (NIOSH) recommendation. In 72.9% of tasks the child’s weight created a high risk level. The lifting tasks involved horizontal and vertical lift distances that presented a moderate to high risk level in 82.8% of situations. Lifting while twisting and side-bending was assigned a moderate to high risk level in 72.4% of tasks. Risk associated with working at an externally controlled pace; and handling children while seated or kneeling/crouching was also observed. The home environment presented risk associated with obstacles, a variety of floor surfaces and stairs or slopes. Mothers were also observed lifting in confined spaces. Individual factors identified as important considerations were: a mismatch between mothers’ strength and fitness and the lifting requirements, pain or injury, pregnancy, and fatigue. The structured checklist proved to be an appropriate tool to identify the contributory risk factors present when mothers lift in the home and to make an assessment of the level of risk. Results suggest a notable number of risk factors which might give rise to MSDs are present when mothers lift their children at home. The author concludes that further research is warranted to quantify risks, to identify prevention strategies for MSDs in this population, and to guide health providers with regard to treatment and rehabilitation of mothers with MSDs.

Military load carrying has occupied the attention of military developers, researchers and commanders over centuries. The Army backpack remains the means of carriage for ammunition and rations for the soldier in the field. The traditional rationale for its use has been that the infantry soldier must be able to sustain himself in combat and live independently for days at a time without resupply. At the Royal Military College, Duntroon (RMC), the mission is to produce men and women who are capable and effective officers and soldiers. The weight of the pack with the items required at RMC is often in excess of 40 kg. In evaluating the effectiveness of current practice, this thesis takes an anthropometric perspective in exploring the historical, physiological and social context of current loads carried by Australian soldiers, It does not, however, evaluate the content of the load itself. Research methods include: a/. Systematic examination of past research findings on the social and physiological aspects of military load carrying since the Roman Centurions. b/. Biophysical tesing of nine soldiers, using a battery of physiological tests to determine heart rates and energy expenditure at various loads. c/. A survey of 100 soldiers from the Royal Military College, Duntroon and in-depth interviews with a sample of four experienced soldiers to obtain the views of the load carriers. The research concludes that the optimum approach to load carrying, and so to the design of the Army backpack, is that it be task-and soldier-specific. This runs directly counter to the longstanding Army traditions of preparing all soldiers for every possible contingency in battle and regarding all soldiers as equivalent units. The study findings offer some specific directions in which the design of the army backpack can be improved. / Master of Science (Hons)

<p>Outokumpu Stainless tillverkar rostfri styckeplåt. ABB Industriunderhåll AB har sedan</p><p>11 år tillbaks i tiden ansvarat för underhållet på anläggningen i Degerfors åt avdelningen</p><p>Hot Rolled Plate. Hjälpmedel för att transportera och förflytta plåtar är vakuumlyftok och</p><p>en undersökning har gjorts om det finns möjlighet att modifiera vakuumlyftoken så att</p><p>bättre underhållsmässighet uppnås.</p><p>Två stycken äldre vakuumlyftok har modifierats med förslag på nya komponenter valda</p><p>för att få en standard både för nya och äldre vakuumlyftok.</p><p>Vakuumlyftok 173 (fr.1978): Ny vakuumvakt (PN7009), vakuummeter (AM80-N) och</p><p>filter (PIAB G3/8”).</p><p>Total kostnad för modifiering: 122 695 kr</p><p>Underhållskostnad (år 2007): 538 127 kr</p><p>Nytt vakuumlyftok (inköpspris): 700 000 – 1 200 000 kr</p><p>Nytt vakuumlyftok med antisvajsystem rekommenderas för att få ner</p><p>underhållskostnader som till stor del består av trasiga sugkoppar.</p><p>Vakummlyftok 332 (fr.1992): Ny vakuumvakt (PN7009).</p><p>Total kostnad för modifiering: 38 505 kr</p><p>Underhållskostnad (år 2007): 69 230 kr</p><p>Vakuumvakten är utgående och behöver ersättas med en ny.</p><p>Plåtar som anses vara problem att lyfta med vakuumlyftok är de med en tjocklek på</p><p>20 mm då det händer att dessa tappas. FEM-analyser på tre valda vakummlyftok har</p><p>gjorts i PRO/E Mechanica och Ansys som resulterat i följande:</p><p>Vakuumlyftok 173: Maximal plåtlängd ca 12 170 mm och maximalt utstick ca 2000 mm</p><p>Vakuumlyftok 332: Maximal plåtlängd +14 000 mm och maximalt utstick +1900 mm</p><p>Vakuumlyftok 457: Maximal plåtlängd ca 11 300 mm och maximalt utstick ca 1900 mm</p> / <p>Outokumpu Stainless manufactures stainless steel plates. ABB Industriunderhåll AB has</p><p>since 11 years been responsible for the maintenance of Hot Rolled Plate at Outokumpu,</p><p>Degerfors. Transportation of plates is made with the help of vacuum lifting beams.</p><p>Investigation has been made whether it is possible or not to modify vacuum lifting beams</p><p>to achieve better maintainability.</p><p>Two elderly vacuum lifting beams have been modified with proposals for new</p><p>components selected to achieve a standard for both new and older vacuum lifting beams</p><p>Vacuum lifting beam 173 (fr.1978): New underpressure switch (PN7009), vacuum gauge</p><p>(AM80-N) and vacuum filters (PIAB G3/8") .</p><p>Total cost of the modification: 122 695 SEK</p><p>Cost of maintenance (year 2007): 538 127 SEK</p><p>New vacuum lifting beam (purchase): 700 000 - 1 200 000 SEK</p><p>A new vacuum lifting beam with a swing compensating system recommends to</p><p>reduce maintenance costs of broken suction plates.</p><p>Vacuum lifting beam 332 (fr.1992): New underpressure switch (PN7009).</p><p>Total cost for modification: 38 505 SEK</p><p>Cost of maintenance (year 2007): 69 230 SEK</p><p>The underpressure switch is outgoing and needs to be replaced with a new one.</p><p>Plates that considered causing problems for vacuum lifting beams are the long plates with</p><p>a thickness of 20mm. Sometimes steel plates come loose which violates the safety. Three</p><p>selected vacuum lifting beams have been FEM-analyzed in Pro/E Mechanica and Ansys,</p><p>which resulted in the following.</p><p>Vacuum lifting beam 173: Max. plate length 12 170 mm and a maximum projecting</p><p>2000 mm</p><p>Vacuum lifting beam 332: Max. plate length +14 000 mm and a maximum projecting</p><p>+1900 mm</p><p>Vacuum lifting beam 457: Max. plate length 11 300 mm and a maximum projecting</p><p>1900 mm</p>

In this thesis we consider four topics all related to using problem reformulations in order to solve integer programs, i.e. optimization problems in which the decision variables must be integer. We first consider the polyhedral approach. We start by addressing the question of lifting valid inequalities, i.e. finding a valid inequality for a set Y from the knowledge of a valid inequality for a lower-dimensional restriction X of Y. We simplify and clarify the presentation of the procedure. This allows us to derive conditions under which the computation of the lifting is tractable. The second topic is the study of valid inequalities for the single node flow set. The single node flow set is the problem obtained by considering one node of a fixed charge network flow problem. We derive valid inequalities for this set and various generalizations. Our approach is a systematic procedure using only basic tools of integer programming: fixing and complementing variables, mixed-integer rounding and lifting. The method allows us to explain and generate a large range of inequalities describing the convex hull of such sets. The last two topics are based on non-standard approaches for integer programming. We first show how the group relaxation approach can be used to provide reformulations for the integral basis method. This is based on a study of extended formulations for the group problem. We present four extended formulations and show that the projections of three of these formulations provide the convex hull of the original group problem. Initial computational tests of the approach are also reported. Finally we consider a problem that is difficult for the standard branch-and-bound approach even for small instances. A reformulation based on lattice basis reduction is known to be more effective. However the step to compute the reduced basis is O(n^4) and becomes a bottleneck for small to medium instances. By using the structure of the problem, we show that we can decompose the problem and obtain the basis by taking the kronecker product of two smaller bases easier to compute. Furthermore, if the two small bases are reduced, the kronecker product is also reduced up to a reordering of the vectors. Computational results show the gain from such an approach.