| 1. |
- Rose, Linda M., et al.
(author)
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Fatigue and recovery during and after static loading
- 2014
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In: Ergonomics. - : Informa UK Limited. - 0014-0139 .- 1366-5847. ; 57:11, s. 1696-1710
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Journal article (peer-reviewed)abstract
- Subjectively assessed endurance time (ET), resumption time (RT) and perceived discomfort, pain or fatigue (PD), and objectively measured maximum force-exerting capacity were investigated for varying loads and durations of a pushing task with two repeated trials. Beyond the main results quantifying how the load scenario affected ET, RT and PD, three additional results are of note: (1) although the maximum pushing force did not change between trials, shorter ET, longer RT and higher PD indicated accumulation of fatigue in Trial 2; (2) the PD ratings showed a trend with a linear increase during loading and a curvilinear decrease during recovery; and (3) the RT and the load level for different relative loading times were found to have an unexpected U-shaped relationship, indicating lowest fatigue at the intermediate load level. These results can be used to model a more sustainable and productive work-recovery ratio.
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| 2. |
- Hägg, Göran M, et al.
(author)
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Knife force differences when cutting meat at different temperatures
- 2012
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In: NES2012. - Stockholm : KTH Royal Institute of Technology. - 9789163711497
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Conference paper (peer-reviewed)abstract
- IntroductionMeat cutters in abattoirs is a group with high risks for musculoskeletal disorders. A major reason for this is that they exert high hand forces over a great part of the day when cutting meat. Though meat is refrigerated due to hygienic demands, meat temperature can vary. Meat cutters have claimed that knife forces increase with lower temperatures. This study was performed to find out what effects the meat temperature has on cutting forces. In addition, the same issue was addressed for pure fat.MethodTo be able to do cuts in meat under controlled conditions while measuring cutting forces, a machine, Anago KST Sharpness Analyzer, was used. The machine normally runs a knife at constant speed through a standardized textile ribbon while the force exerted on the ribbon is recorded over time. For this investigation, the ribbon was replaced by a wooden fixture with a 10 mm wide slot where the knife could pass and where meat samples could be fixed.Meat obtained from hind loin and fat tissue of pork was cut into 5 cm long, 4 cm wide and 2 cm thick samples. The meat fibre orientation was aligned with the long axis of the sample. When fixated in the fixture and the machine was started, the knife made a 4 cm long cut through 2 cm thick meat or fat.One hundred and forty four samples of meat and as many of fat were collected and put overnight in one of three refrigerators with temperatures 2, 7 and 12 °C, 48 in each. Well sharpened standard knifes were used for the tests. The knife was changed after 24 cuts. During the procedure samples were taken directly from the refrigerator and put into the fixture and tested immediately. The sample order was generally 2, 7, 12 °C to avoid systematic effects of a gradually blunter knife.ResultsThere were no significant differences in knife forces at the three meat temperatures. The forces for fat were in average about three times higher than the meat forces. There was no significant difference between forces in fat at 7 and 12 °C. However there was a strongly significant difference between these two groups and the 2 °C fat group. The force was about 30% higher compared to the forces at 7 and 12 °C in fat.ConclusionIn the range 2-12 °C there are no differences in meat. For fat there are no differences in the range 7-12 °C while the force increases about 30% when going from 7 to 2 °C.
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| 3. |
- Hägg, Sara, et al.
(author)
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Carotid Plaque Age Is a Feature of Plaque Stability Inversely Related to Levels of Plasma Insulin
- 2011
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In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6:4, s. e18248-
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Journal article (peer-reviewed)abstract
- Background: The stability of atherosclerotic plaques determines the risk for rupture, which may lead to thrombus formation and potentially severe clinical complications such as myocardial infarction and stroke. Although the rate of plaque formation may be important for plaque stability, this process is not well understood. We took advantage of the atmospheric C-14-declination curve (a result of the atomic bomb tests in the 1950s and 1960s) to determine the average biological age of carotid plaques. Methodology/Principal Finding: The cores of carotid plaques were dissected from 29 well-characterized, symptomatic patients with carotid stenosis and analyzed for C-14 content by accelerator mass spectrometry. The average plaque age (i.e. formation time) was 9.6+/-3.3 years. All but two plaques had formed within 5-15 years before surgery. Plaque age was not associated with the chronological ages of the patients but was inversely related to plasma insulin levels (p=0.0014). Most plaques were echo-lucent rather than echo-rich (2.2460.97, range 1-5). However, plaques in the lowest tercile of plaque age (most recently formed) were characterized by further instability with a higher content of lipids and macrophages (67.8+/-12.4 vs. 50.4+/-6.2, p=0.00005; 57.6+/-26.1 vs. 39.8+/-25.7, p<0.0005, respectively), less collagen (45.3+/-6.1 vs. 51.1+/-9.8, p<0.05), and fewer smooth muscle cells (130+/-31 vs. 141+/-21, p<0.05) than plaques in the highest tercile. Microarray analysis of plaques in the lowest tercile also showed increased activity of genes involved in immune responses and oxidative phosphorylation. Conclusions/Significance: Our results show, for the first time, that plaque age, as judge by relative incorporation of C-14, can improve our understanding of carotid plaque stability and therefore risk for clinical complications. Our results also suggest that levels of plasma insulin might be involved in determining carotid plaque age.
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| 4. |
- Kihlstedt, Annika, et al.
(author)
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Checkout cashier work and counter design : Video movement analysis, musculoskeletal disorders and customer interaction
- 2011
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In: International Journal of Industrial Ergonomics. - : Elsevier BV. - 0169-8141 .- 1872-8219. ; 41:3, s. 201-207
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Journal article (peer-reviewed)abstract
- This study was conducted in order to analyse checkout cashiers' movements at a checkout counter during interaction with customers and the prevalence of work-related stress and musculoskeletal disorders in checkout cashiers. In one shop, six cashiers were videotaped during the workday, and 50 cashiers from seven shops from the same chain of stores responded a questionnaire. Cashier activities and movements, customer interaction and counter design issues were analysed from the video data. Prevalence of work-related stress and musculoskeletal disorders was obtained from the questionnaire. It was found that 76% of all items were manually turned or angled. With a better adjustment of the scanner and a standardised positioning of the EAN-code, many of these movements could be avoided. Furthermore the prevalence of musculoskeletal disorders was quite high (68% for the neck). The questionnaire results showed that many cashiers experienced stress, giving a high percentage of cashiers in the "dedication under pressure" group. The behaviour of the customers was the major cause of stress. Other sources of stress arose from bad design or function of the computer system or other technical equipment. Relevance to industry: In this study several problems regarding cashier work were identified and solutions, relevant to counter and package designers, shop managers and cashiers are suggested. Data obtained on cashier movements and prevalence of musculoskeletal disorders are given.
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| 5. |
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| 6. |
- Rezagholi, Mahmoud
(author)
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Cost-Efficient Designs for Assessing Work-Related Biomechanical Exposures
- 2012
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Doctoral thesis (other academic/artistic)abstract
- Work-related disorders due to biomechanical exposures have been subject to extensive research. Studies addressing these exposures have, however, paid limited attention to an efficient use of resources in exposure assessment. The present thesis investigates cost-efficient procedures for assessment of work-related biomechanical exposures, i.e. procedures aiming at a proper balance between statistical and economic performance.Paper I is a systematic review of tools used in literature providing cost-efficient data collection designs. Two main approaches were identified in nine publications, i.e. comparing cost efficiency among alternative data collection designs, and optimizing resource allocation between different stages of data collection, e.g. subjects and samples within subjects. The studies presented, in general, simplified analyses, in particular with respect to economics.Paper II compared the cost-efficiency of four video-based techniques for assessing upper arm postures. The comparison was based both on a comprehensive model of cost and error and additionally on two simplified models. Labour costs were a dominant factor in the cost efficiency comparison. Measurement bias and costs other than labour cost influenced the rank and economic evaluation of the assessment techniques.Paper III compared the cost efficiency of different combinations of direct and indirect methods for exposure assessments. Although a combination of methods could significantly reduce the total cost of obtaining a desired level of precision, the total cost was, in the investigated scenario, lowest when only direct measurements were performed. However, when the total number of measurements was fixed, a combination was the most cost efficient choice.In Paper IV, demand functions were derived for a four-stage measurement strategy with the focus of either minimizing the cost for a required precision, or maximizing the precision for a predetermined budget. The paper presents algorithms for identifying optimal values of measurement inputs at all four stages, adjusted to integers, as necessary for practical application.In summary, the thesis shows that it is important to address all sources of costs and errors associated with alternative measurement designs in any particular study, and that an optimal determination of samples at different stages can be identified in several cases not previously addressed in the literature.
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