• 한국안전학회지
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• 제26권3호
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• pp.69-74
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• 2011

Despite most of tasks in manufacturing, construction and agriculture, etc., were currently mechanized and automated, manual materials handling still existed in atypical working condition. In case of manual materials handling, repetitive work, inappropriate working posture, excessive force, contact stress might cause overload, which could lead to work-related musculoskeletal disorders and low back pains. On this basis, the goal of this study is to reveal the effects of various lifting postures of trunk angles and lower extremity postures on maximum holding time(MHT). Twenty two subjects were recruited from a university population. The experiment was designed by a combination of three trunk angle ($0^{\circ}$, $20^{\circ}$, $60^{\circ}$) and three lower extremity postures(straight, bent, kneeling). Before experimental trials, subjects performed MVC(maximum voluntary contraction) exertions in three trunk angles ($0^{\circ}$, $20^{\circ}$, $60^{\circ}$) to calculate 30%MVC at designated postures. In each trial, they were required to hold the handheld load(30%MVC) for a designated posture as long as they could. The results of MVC by trunk angles were measured in $0^{\circ}$ > $20^{\circ}$ > $60^{\circ}$ orders, but those of MHT measured in $20^{\circ}$ > $0^{\circ}$ > $60^{\circ}$ orders. These results showed that straight posture is the ideal working posture in work exerted a strong force for a short time, but the ability to work might be improved in the trunk angle $20^{\circ}$ in work required 30%MVC for a long time. Also, results of MVC and MHT by lower extremity postures measured in straight > bent > kneeling orders.

• 한국산업보건학회지
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• 제19권2호
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• pp.88-95
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• 2009

There are many assessment techniques used for occupational risk factors of MSDs in the workplaces. However, because all ergonomic assesment techniques or tools are based on theoretical background derived from workphysiology, biomechanics, psychophysics, industrial hygiene, work system, and etc, it is impossible to compare the assessment techniques. This study was conducted to compare the excess rates of risk factors among ergonomic assessment techniques and to make alternative methods. Site-visits to 6 automobile products and parts company provided data for process repeated work where the produced data was examined for evaluating the relationship between workplace lay-out and work posture by using ergonomic assessment techniques. We evaluated 157 jobs for simple repeated work and 37 jobs for manual materials handling (MMH). In simple repeated work, the exceeded rates of AC were 36.3% in OWAS method and 93.0% in RULA method. The exceeded rate for RULA method was significantly higher than those for OWAS method (p<0.05). In MMH, the exceeded rates of AC were 80.0% in NLE method and 76.5% in WAC method. Statistically significant differences were not identified in the exceeded rates for NLE and MAC methods (p<0.05). The analyzed results among ergonomic assessment techniques (OWAS, RULA, NLE/WAC) were applied to the same work places performing simple repeated work and manual materials handling simultaneously. The applied results showed statistically significant differences (p<0.05) among ergonomic assessment techniques (OWAS, RULA, NLE/WAC). Exceeded rates of four ergonomic assessment techniques in decreasing order was "RULA>NLE>WAC>OWAS". The RULA method was the strongest assessment technique for automobile products and parts company. We discovered that the results could easily be overestimated or underestimated when the ergonomic assessment techniques were not applied correctly during the evaluation process. Therefore, we recommend using at least 2 methods when evaluating and analysing the results.

• 대한인간공학회지
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• 제28권3호
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• pp.17-25
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• 2009

This study was aimed to analyze of characteristics of Musculoskeletal disorders (MSDs) based on the industrial accident statistics which were extracted from the Ministry of Labor. In this study all MSDs cases in 2007, 7,723 cases, were investigated. First of all, for the analysis of a wide view point concerning the characteristics of MSDs, We have inspected characteristics of the user population (i.e. age, gender, employed periods, etc.). Secondly, work-related risk factors such as repetitive motions, awkward postures, manual material handling were analyzed in terms of disease code, injured part of body, types of business, etc. Next, characteristics of handling of heavy materials were analyzed according to weight, types of handling, agency of cause, etc. Finally, we have compared and analyzed the features between the period of hospitalization and other variables. In addition to that we also conducted statistics analysis. The study results showed that there were significant characteristics of MSDs that could be used as basis data for the MSDs prevention policy.

• 기술사
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• 제30권5호
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• pp.96-104
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• 1997

This study analyze industrial safety and health planning report for manufacture. The purpose of accident analysis is to obtain accurate and objective information about the causes of accidents in order to prevent accidents from reoccurring. This study investigated the causes and conditions of occupational accidents in Korean industry. As the most accidents are occurred in lifting material, the questionnaire analyses about injuries are operated for occur to deal with the Manual Materials Handing. The results show that there are some characteristics in the accidents of Korean industry since 1986: (1) accidents rates tend to have lower since 1983(1994-1.18%, 1995-0.99%, 1996-0.88%), (2) larger companies tend to have lower accident rates than the smaller ones, (3) inexperience is related to high accident rates(1995-51.26%, 1996-48.82%1, because of the careless education for freshman such as OJT which in order to prevent accident, and (4) the body sites most vulnerable to injury are the hands and fingers and increased the back(caused of Back pain). The results of questionnaire analysis show that operator(n= 104) interested in reinforce the back & belly(42.86%). These finding identified in this study can be used to prevent the industrial accidents, and used to improving directions based on analyzed result.

• 대한인간공학회지
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• 제34권3호
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• pp.279-291
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• 2015

Objective: The purpose of the study is to evaluate appropriate weight for aged farmers in manually handling livestock feed in bags using ergonomic methods. Background: In the livestock industry in South Korea, despite the trend of aging of labor manpower, heavy items are still manually handled in many farms. In particular, among stockbreeding works, the handling of feed in bags weighing 25~30kg is reported as a cause of frequent injuries and musculoskeletal system diseases. However, studies on the standard for recommended weight allowed considering the physical characteristics of aged farmers older than 60 years with greatly decreased physical strength and muscle strength are insufficient. Method: To evaluate appropriate weight for handling of heavy livestock feed in bags, physical techniques for measuring recognized levels of physical work loads, the NLE (NIOSH lifting equation) a method that is an observation type technique, and an ergonomic modeling technique to predict compressive force imposed on L5/S1 were used. Subjects who participated in the experiment were organized into two groups of males/females with mean age exceeding 60 years, and lifting tasks were evaluated for nine weight levels. Results: Based on the results of psychophysical measurement, females showed a tendency of more drastic increases compared to males when weight was over 19kg. The results of estimation of regression models for the weight, 18.0 kg ($r^2=0.97$) and 15.3kg ($r^2=0.97$) were evaluated as stable load for males and females, respectively. In addition, both the observation type evaluation and ergonomic model evaluation showed stable loads in a range of 15~18kg. Conclusion: Given the results of the study, the weight of the feed in bags currently distributed to farms can become a cause of not only overexertion but also farm work related disasters such as musculoskeletal disorders and safety accidents. Providing livestock feed in bags weighing not more than 19kg for aged farmers is judged desirable, and managerial improvement for this matter is considered necessary. Application: The results of the present study can be utilized as useful data for institutional improvement of the weight of livestock feed in bags.

• 산업경영시스템학회지
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• 제27권3호
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• pp.90-96
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• 2004

The objective of this study was to develop a model for safe work load based on a physiological model of metabolic energy of manual material handling tasks. Fifteen male subjects voluntarily participated in this study. Lifting activities with four different weights, 0, 8, 16, 24kg, and four different working frequencies (2, 5, 8, 11 lifts/min) for a lifting range from floor to the knuckle height of 76cm were considered. Oxygen consumption rates and heart rates were measured during the performance of sixteen different lifting activities. Simplified predictive equations for estimating the oxygen consumption rate and the heart rate were developed. The oxygen consumption rate and the heart rate could be expressed as a function of task variables; frequency and the weight of the load, and a personal variable, body weight, and their interactions. The coefficients of determination ($r^2$) of the model were 0.9777 and 0.9784, respectively, for the oxygen consumption rate and the heart rate. The model of oxygen consumption rate was modified to estimate the work load for the given oxygen consumption rate. The overall absolute percent errors of the validation of this equation for work load with the original data set was 39.03%. The overall absolute percent errors were much larger than this for the two models based on the US population. The models for the oxygen consumption rate and for the work load developed in this study work better than the two models based on the US population. However, without considering the biomechanical approach, the developed model for the work load and the two US models are not recommended to estimate the work loads for low frequent lifting activities.

• 대한인간공학회지
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• 제29권1호
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• pp.145-153
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• 2010

Activity of lifting has been a major issue in many research area related in manual materials handling tasks. However, the opposite activity of lifting, lowering, has received much less attention. It is known that 52% of all box-handling tasks were lowering in nature. The difference in stress between lifting and lowering activity is not well understood. A simple assumption that these two activities are very similar has been established and widely used. However, this simple assumption may be questionable. The objective of this study was to compare a lifting activity and a lowering activity based on the three different ergonomic approaches; (1) biomechanical, (2) physiological, (3) psychophysical approach. It was found that the stress of lowering activity was from 65% to 93%, from 87% to 97%, and from 87% to 96% according to the biomechanical, physiological, and psychophysical point of view, respectively. It is concluded from the result of this study that the stress of lowering activity is lower than that of the lifting activity. The maximum compressive force on the lumbro-sacral joint (L5/S1) was 158% and 108% respectively, for lifting and lowering activity of which the work load is the 58% of Action Limit. It is suggested that the NIOSH AL and RWL and biomechanical criteria should be reconsidered especially for the low frequency of lifting activities.

• 한국주거학회:학술대회논문집
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• 한국주거학회 2011년도 춘계학술발표대회 논문집
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• pp.167-171
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• 2011

Managing apartments is critical not only to handling the physical deterioration over time, but also to the quality of community life, social environment and ultimately residents' satisfaction with the housing environment. Therefore, this study aims at understanding residents' awareness of apartment management, and finding the relationship between management activities and residents' satisfaction and participation by comparing an apartment with active management and an apartment without it. This study examines 1) management activities of two subject apartment complexes, and 2) how management activities affect residents' participation and satisfaction. Surveys were conducted of the residents, and SPSS statistics package was utilized to analyze the survey data. This study found that management activities of apartment complex have positive influence on residents' participation and satisfaction with their housing environment. The results of this study can be utilized as basic materials to develop effective guidelines and manual from the perspective of environmental management of apartment houses, in order to improve the participation of the residents in the apartment management.

• 대한인간공학회:학술대회논문집
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• 대한인간공학회 1995년도 춘계학술대회논문집
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• pp.106-110
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• 1995

A local manufacturing companyin which low back pain(LBP) complaints were frequently reported was selected, and regularly perfomed lifting tasks were investigated using questionnaires and the 1991 NIOSH lifting guide. Among several processes of manufacture in the company, three processes-forming, heating and packing-were studied, where most of tasks were perfomed through manual materials handling (MMH). Questionnaire surveys showed that anthropometric data such as stature, weight and someatotype did not affect and weight of load influenced significantly the incidence of LBP, and workers who expwrienced LBP was older than the inexperienced. In addition, safety education conducted at the company was found to be ineffective in preventing LBP injuries. Lifting indexes(LI) was ranged from 0.86 to 17.0 with an average of 4.49, which revealed that tasks performing in the selected factory were in danger of LBP, and should be ertonomically redesigned. The critical factor reducing LI was found to be the horizontal component in all three processes, and most of weight of load was heavier than load constant(23kg) of the 1991 NIOSH lifting equation in heating process and packing.

• 한국산업안전학회:학술대회논문집
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• 한국안전학회 2002년도 추계 학술논문발표회 논문집
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• pp.371-376
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• 2002

자동화된 생산시설에도 불구하고, 아직도 여러 현장에는 사람이 직접 bag, box, carton 등을 들고, 내리고, 옮기는 등의 인력운반 (Manual Materials Handling, MMH) 작업으로 생산활동이 이루어지고 있다. 상자 운반 작업에서 있어서 손잡이는 최대허용무게에 영향을 미친다는 연구 결과들이 많이 나왔지만, 자세에 따른 손잡이 형태의 영향에 관한 연구들은 미흡한 실정이다. 따라서 본 연구에서는 MMH 작업시 흔히 사용되는 3가지 자세(구부린 자세, 팔을 편 자세, 팔을 90$^{\circ}$로 굽혔을 때 자세)에서 손잡이 형태에 따라 tote box를 들 때, 작업자세와 손잡이 형태에 따른 Maximum Voluntary Contraction (이하 MVC)를 측정하고 MVC에 대한 작업자세와 손잡이 형태의 상관관계의 통계적 분석, 주관적 평가방법(Borg법)과 MVC와의 유의성을 검증하였다.