• Journal of the Korean Society of Safety
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• v.31 no.4
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• pp.111-119
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• 2016

This study aimed to analyze postures that were frequently conducted in manufacturing industry. To find grip strength and muscle activities of each posture, Maximum Voluntary Contraction (MVC) and ElectroMyoGraphy (EMG) were measured. Based on the results of this study, the most appropriate posture could be suggested and used as a basic information for preventing musculoskeletal disorders. Most work-related musculoskeletal disorders have been occurred in the fields of manufacturing industry. According to previous studies, it was reported that the rate of musculoskeletal diseases of upper extremity was higher than that of other body parts. Accordingly, there were many studies about discomfort and grip strength of upper extremity. However, these studies dealt with single selection of wrist, elbow and shoulder. So, it was insufficient for comprehensive studies about upper extremity. And in order to improve the work posture, the physiological changes being generated by the combination of wrist, elbow and shoulder postures should be observed and analyzed. In order to conduct this study, thirty university students who had no records of MSDs involved were recruited. Independent variables were postures of wrist(pronation, neutral, supination), postures of elbow(flexion $45^{\circ}$, $90^{\circ}$) and postures of shoulder(flexion $0^{\circ}$, $90^{\circ}$). And dependent variables were MVC values and EMG values. Jamar dynamometer and TeleMyo 2400T G2 was used to measure MVC and EMG. MVC and EMG for 12 postures were measured for three second and for three times. Experiment was performed randomly. A 10 minutes rest period was provided after each t. To measure muscle load, the EMG signals of eight muscles (Biceps, Medial triceps, Lateral triceps, Brachioradialis, Extensor carpi ulnaris, Extensor carpi radialis, Flexor carpi ulnaris and Flexor carpi radialis) were evaluated. MVC values and EMG values were analyzed using Minitab ver. 14. The results showed that MVC value was the highest at shoulder $0^{\circ}$, elbow $45^{\circ}$ and wrist supination. In case of wrist postures, MVC of supination is the highest. In case of elbow and shoulder postures, MVC of flexion $45^{\circ}$ and $0^{\circ}$ was the highest. It was found that there were interaction between wrist and elbow posture under shoulder flexion and between shoulder and wrist under elbow flexion $45^{\circ}$. In case of the angle of shoulder $0^{\circ}$, elbow $45^{\circ}$ and wrist supination, the EMG values of four muscles(Medial Triceps, Extensor carpi ulnaris, Extensor carpi radialis, Flexor carpi ulnaris) were the highest. Based on this study, it is worth to note that the combination postures of upper extremity have a large impact on the MVC and EMG. The optimal condition upper extremity was shoulder flexion $0^{\circ}$, elbow flexion $45^{\circ}$ and wrist supination for preventing work-related musculoskeletal disease.

• Safety and Health at Work
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• v.1 no.2
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• pp.124-133
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• 2010

Objectives: This study was conducted to develop a model describing the interaction between lifestyle, job, and postural factors and parts of the upper extremities in shipyard workers. Methods: A questionnaire survey was given to 2,140 workers at a shipyard in Ulsan City. The questionnaire consisted of questions regarding the subjects' general characteristics, lifestyle, tenure, physical burden, job control, posture and musculoskeletal symptoms. The overall relationship between variables was analyzed by a structural equation model (SEM). Results: The positive rate of upper extremity musculoskeletal symptoms increased in employees who worked longer hours, had severe physical burden, and did not have any control over their job. Work with a more frequent unstable posture and for longer hours was also associated with an increased positive rate of musculoskeletal symptoms. Multiple logistic regression analysis showed that unstable posture and physical burden were closely related to the positive rate of musculoskeletal symptoms after controlling for age, smoking, drinking, exercise, tenure, and job control. In SEM analysis, work-related musculoskeletal disease was influenced directly and indirectly by physical and job stress factors, lifestyle, age, and tenure (p < 0.05). The strongest correlations were found between physical factors and work-related musculoskeletal disease. Conclusion: The model in this study provides a better approximation of the complexity of the actual relationship between risk factors and work-related musculoskeletal disorders. Among the variables evaluated in this study, physical factors (work posture) had the strongest association with musculoskeletal disorders.

• Journal of the Korean Society of Safety
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• v.26 no.6
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• pp.97-103
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• 2011

This study compared the effects of different frequencies of self-monitoring on safe sitting postures. Participants were four office workers. The dependent variable was the safety percentage for four body positions. The independent variable was self-monitoring frequency: high and low self-monitoring frequencies. Results showed that the safety percentage increased when self-monitoring was introduced. However, the effects of the two different self-monitoring frequencies on safe performance were not statistically different.

• Journal of the Ergonomics Society of Korea
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• v.32 no.5
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• pp.475-480
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• 2013

Objective: In this study, virtual reality was adopted to consider ergonomic factors in yacht design. Virtual human which is the same actual human was created in virtual environment using Digital Human Modeling which has been used in the manufacturing communities to design better workplaces and maximize the safety of workers. Background: During the past 40 years yachting has expanded from being, generally speaking, a minority sport - too expensive for the large majority of people - into a major recreational activity practiced by millions all over the world. Many new yacht designs have appeared and number of professional, as well as amateur designers has increased steadily. But they had not considered ergonomic factors in yacht design. Method: Worker's posture, traffic line and workload had been analyzed in sailing yacht. After the caution level was evaluated, we pointed out clues which had high workload and interference. To reduce workload, we applied ergonomic principles for improving working conditions and environments in Digital Human Model. Results: We found the space problems and workload of postures. Conclusion: (1) Unnatural posture of crews was sustained. (2) Workload that occurs in the human body was overloaded. (3) Crew's work space was very narrow. Application: This study will be applied the new ergonomic design of yacht.

• Journal of Auto-vehicle Safety Association
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• v.15 no.3
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• pp.59-65
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• 2023

As advanced driving assistance system (ADAS) and autonomous driving performance continue to improve, existing crash accidents and crash types are changing. Accordingly, the collision angle and the seating posture of the occupant are changed. It is necessary to study how the occupant injury mechanism changes according to these different crash types. In this regard, a representative crash test mode was derived when the automatic emergency braking system (AEB), one of the autonomous driving performance, was applied to the representative car-to-car crash scenario in Korea. The derived crash test mode was used to analyse the mechanisms of collision injuries according to both impact angle and the occupant seating posture (reclined seat-back angle). The results obtained through this study can be utilized as reference data for the development of new crash evaluation methods and improvements in crash restraint systems for enhancing crash safety.

• Journal of the Korean Society of Safety
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• v.28 no.2
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• pp.73-77
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• 2013

Leisure activities alter overland tourism into marine tourism according to a rise in national income. It is expected that the leisure boat with period of introduction in marine tourism will be developed rapidly. It needs to unite with marine technology, optimized layout design, interior design and so on in order to build a yacht of high quality. Because optimized layout design and interior design technique increase the added value of the yacht, it needs to be convergence technology between Ergonomics, Sensibility Ergonomics, and design technique. In this study, we analyzed traffic line of crews in a sailing yacht and assessed working posture using OWAS, RULA and REBA tools. Also we suggested tips of Ergonomic design in the sailing yacht.

• International Journal of Safety
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• v.7 no.1
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• pp.35-38
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• 2008

The purpose of this study is to extract typical body shape of Korean VDT workers based on the three-dimensional Korean shape data and recommendation supported by Korea Occupational Safety & Health Agency during VDT task. Desirable desk heights and chair heights for the selection of the VDT working posture is proposed by analyzing moment, compression and joint shear for lumbar and spine of Korean adult(male and female). The desirable heights for desk and chair can be selected by the least load method during VDT tasks. In the current work the figures of Korean 50th percentile offered by CATIA-HUMAN are used as the average body type of the grown-ups and this research is accomplished with the recommended size of all working attitude such as the height of a monitor except for the height of desk and chair and the degree of watching the monitor.

• Journal of the Korean Society of Safety
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• v.21 no.3 s.75
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• pp.122-126
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• 2006

This study investigated effect of arm posture, wrist motion repetition and external load on perceived discomfort through an experiment. Eleven female college students participated in the experiment, where shoulder, elbow and wrist motion, wrist motion repetition, and external load were used as independent variables. The results showed that only external load had a significant effect on perceived discomfort. The perceived discomfort linearly increased with external load. Based on the results of this and the previous study for males, it was concluded that effect of external load on perceived discomfort was larger than that of other posture and motion repetition related variables. This implies that effect of external load is the most important factor considered in the first place when assessing postural load.

• Journal of the Korean Society of Safety
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• v.17 no.4
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• pp.178-183
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• 2002

The purpose of this study was to quantitatively investigate the effects of external load upper extremity posture on perceived discomfort. An experiment was conducted for measuring discomfort scores depending upon external loads and upper extremity postures, in which the free modules and numeric estimate method of the magnitude estimation was adopted as a tool for obtaining discomfort ratings. The upper extremity postures were controlled by wrist flexion/extension, elbow foexion, shoulder flexion, and shoulder adduction/abduction. The results showed that all experimental variables except shoulder adduction/abduction were significant at ${\alpha}$=0.01 or 0.05. The effect of external load was very much larger than that of upper extremity postures. Therefore, it is recommended that a new posture classification scheme taking effect of external load to into consideration be developed for quantifying postural load.

• Journal of the Korean Society of Safety
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• v.19 no.4 s.68
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• pp.123-128
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• 2004

This study investigated effect of arm posture, repetition of wrist motion and external load on perceived discomfort. The arm postures were controlled by shoulder flexion, elbow flexion, and ist motions such as flexion, extension, radial deviation and ulnar deviation. An experiment was conducted to measure discomfort scores for experimental treatments using the magnitude estimation, in which the L16 orthogonal array was adopted for reducing the size of experiment. The results showed that while the effect of the shoulder flexion, repetition of wrist motion and external load was statistically significant at $\alpha=0.05$or 0.10, that of the elbow and wrist motions was not. Discomfor ratings increased linearly as levels of wrist repetition and external load increased. This implies that the existing posture classification schemes such as OWAS, RULA, which do not properly consider effect of motion repetition and external load, may underestimate postural load. Based on the regression equation for wrist repetition and external load, isocomfort region indicating the region within which discomfort scores were expected to be the same was proposed. It is recommended that when assessing risk of postures or developing new posture classification schemes, motion repetition and external load as well as posture itself be fully taken into consideration for precisely evaluating postural stress.