• Journal of the Korea Safety Management & Science
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• v.15 no.4
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• pp.123-129
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• 2013

Among various manual materials handling tasks, pushing/pulling was known to be one of the risk factors for the low back and shoulder musculoskeletal disorders (MSDs). This study was conducted to find out an optimal solution set of the handle height and distance for 4-wheel cart with two vertical handles. Ten male college students participated in the pushing force measurement experiment. The face-centered cube design, one of the central composite designs, was applied for the experiment, and the isometric voluntary pushing force was measured in 9 treatment conditions. The second order response surface model was predicted by using the pushing strength as a response variable, and the handle height and distance as independent factors. According to the 2nd order response model, the handle height and distance showed nonlinear relationship with the isometric pushing strength. To maximize the 2nd order response model (pushing force), the handle height and distance were optimized. The optimal handle height was 'xyphoid process height - stature', and the optimal handle distance was '$1.25{\times}shoulder$ width'. When calculated using the anthropometric data of the subjects of this study, the optimal handle height was $115.4{\pm}3.4$ cm, slightly higher than the elbow height, and the handle distance was $52.9{\pm}2.3$ cm.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.21 no.4
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• pp.209-214
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• 2011

Objectives: To assess the risk of pushing or pulling the yarn-carrying cart, the survey was performed in some fiber manufacturing factories. Methods: We selected 6 fiber-twisting factories which agreed to in-site survey of their workplace. To measure both initial and sustained forces of the push-pull tasks, Chatillon CSD500 dynamometer(2004, Ametek, USA) was used. The mean of 3 tests for the same cart was adopted as the measured forces. Height and width of cart, weight of spooled yarns, and distance of movement were also measured. Inspection of cart wheel, moving path, and the actual hand position while moving was done. Results: More than one pushing or pulling task exceeded the push-pull force limits of design goal in 5 factories. Though the cart was not loaded the heaviest weight in the factory, the measured push or pull force exceeded the limits several times. A few cart wheels were worn out and tangled with pieces of yarn. It was also observed some holes in the moving path. Conclusions: While the push-pull task is not included in the 11 scopes of over-burdened work notified by Korean government, it should be recognized as risk factor of work-related musculoskeletal disorders. The maintenance work such as regular change and frequent cleaning of cart wheel, the use of fitting wheel, and flattening of bumpy floor through the moving path should be advised importantly in the worksite management of work-related musculoskeletal disorders.

• Journal of Biosystems Engineering
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• v.34 no.4
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• pp.286-294
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• 2009

A high prevalence of protected horticulture farmer's work-related musculo-skeletal disorders (MSDs) have been reported in precedent studies. One of the tasks required ergonomic intervention to reduce the musculo-skeletal risks is the task of product transporting. The purpose of this study is to evaluate quantitatively the spinal load of operator using manual vehicles to predict and prevent musculo-skeletal risks. Spinal load in operators using 4 kinds of manual vehicle were analyzed. Before evaluating spinal load on operator using the manual vehicles by bio-mechanical approach, it is needed to validate human model. In this study, ADAMS LifeMOD human model shows satisfactory results, comparing with already validated model's results or measured results. While Operators pushed the manual vehicles(wheelbarrow, Trolley, 2 wheel cart, and 4 wheel cart) contained loads that were 0 N and 800 N, their spinal loads(compression force, shear force) were evaluated. The compression force demonstrated under the NIOSH action limits - 3410N - for all 4 manual vehicle's operators(McGill 1997; Marras 2000). However, the lateral shear force demonstrated over the University of Waterloo - 500N - for all 3 manual vehicle's operators except 4Wheel cart (Yingline and McGill, 1999). Therefore, operators have risks in prevalence of the musculo-skeletal disorders due to shear force. The findings of this study suggest that it need to be determine the spinal load, especially lateral shear force in designing the manual vehicles in the future.

• Journal of the Ergonomics Society of Korea
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• v.30 no.4
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• pp.541-550
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• 2011

Objective: The objective of this study is to present varying cases of ergonomic improvements in equipments for agricultural work. Background: In Korean agricultural sector, many older people and females, who may be more vulnerable to musculoskeletal diseases than young males, are doing high stressful tasks such as manual materials tasks, harvesting, etc. For reducing the work stress of the farmers, the Korean government has been performing support projects to provide the farmers with agricultural implements specified for their crops. In the projects, ergonomics experts have participated and helped modify the equipments. Method: Fifty cases of equipment improvements, which were carried out in 33 farming organizations cultivating 13 different crops, were reviewed and presented by equipments and their parts. Results: In total, 283 cases of improvements for 12 equipments including 4-wheel, 1-wheel, and 3-wheel powered carts, grass cutter, conveyer, pest control machine, and so on, were presented. The improvements were also classified according to the ergonomic principles like compatibility, ease of use, safety and fitting to the anthropometry, etc. Frequencies of improvements by equipment and its part were the highest in carts and controls, respectively. Principles of safety and ease of use were adopted more frequently in improving equipments than others. Conclusion: The tables of examples of improvements of agricultural implements are main results of this study and the systematical summaries are expected to be widely used in the development of more improved agricultural implements. Application: The results could be used as practical guidelines in ergonomically developing and modifying agricultural implements by both the experts and non-experts in ergonomics. The improvements would contribute to reduction of stress in farm work, which result in increasing the level of safety and health of Korean agricultural society.