• 대한인간공학회지
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• 제28권1호
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• pp.9-19
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• 2009

Repetitive movement, inadequate working posture, overuse of force, physical contact with sharp edge, vibration and temperature were well known risk factors of WMSDs (Work-related Musculoskeletal Disorders). Many researchers have investigated the relationship between inadequate working postures and incidences of WMSDs of the upper extremities, whereas relatively few researchers have tried to evaluate workload associated with the lower-body postures. The effects of lower-limb postures including various knee flexion angles on the subjective discomfort, heart rate and EMG of lower-limb muscles were investigated in this study. Thirty graduate students were asked to maintain thirteen different body postures, and heart rate and EMG data of five muscle groups (electro spine, biceps femoris, vastus medialis, gastrocnemius and tibialis anterior) from each posture were collected during fifteen minutes sustaining tasks. All participants were also asked to report their discomfort ratings of body parts. Results showed that high subjective discomfort ratings and heart rates were reported at the postures of knee angles of $60^{\circ}$ and $90^{\circ}$, whereas low discomfort ratings were founded at the postures of chair heights with 20cm, 40cm, and sitting with crossed legged. The change of median frequency for each muscle group during fifteen minutes tasks was investigated for each body posture to evaluate the relationship between muscle fatigue and body posture. It was found that the trends of changes of median frequency were different based on muscle group as well as lower-limb body posture from this study.

• 대한인간공학회지
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• 제24권4호
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• pp.15-21
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• 2005

Use of a glove made of materials with a low elasticity decreases the performance of the hand such as agility, dexterity, range of motion, and grip strength. The present study examined if the adverse effects of a low-elastic glove can be reduced by a design which accommodates the changes of hand surface lengths by hand motion. Two glove designs which provide patches of elastic cloth and pleats at the finger joints and knuckle were developed by considering the hand surface length changes, and then compared with two conditions(bare hand and conventional glove design that does not consider the dynamic characteristics of the hand dimensions) in terms of completion time in peg board insertion task, maximum grip strength, discomfort in hand motion, discomfort in force exertion, and overall discomfort by 24 right-handed participants. The test results confirmed that wearing of a glove significantly reduced the agility and grip strength capability of the hand and indicated that the novel designs were effective to lessen the performance decreases compared to the conventional design. Also, of the glove designs, the pleat glove design was found most preferred for both better hand performance and less subjective discomfort.

• 대한인간공학회지
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• 제31권1호
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• pp.165-170
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• 2012

Objective: The aim of this study is to develop new K-OWAS on the basis of the anthropometry of Koreans considering works in shipbuilding and heavy industry for evaluation whole-body working postures. Background: Work Related Musculoskeletal Disorders(WMSDs) were a leading cause of sick leaves and injuries in the industries of our country. Especially, awkward working postures and handling of heavy weight are known as a main cause of WMSDs. OWAS, RULA and REBA are much used as the method for evaluating the awkward working postures. OWAS is the working postures evaluation method that can be used for the evaluation of whole-body working postures. OWAS was the method made based on the anthropometry of the foreigner, working postures and weight does not fit our work state. Method: This method was evaluated considering the anthropometry of the Koreans, working postures and weight in shipbuilding and heavy industry work state in Korea. Results: Correlation of action level of OWAS and subjective discomfort for each body parts were not statistically significant($p{\geq}0.1$). But correlation of action level of K-OWAS and subjective discomfort for torso and waist were statistically significant($p{\leq}0.1$). Conclusion: K-OWAS was suitable in the evaluation of upper body including torso and waist. Application: New method for whole-body working postures from this study prevent WMSDs and help improvement of working environment and design of working method.

• 한국생활과학회지
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• 제10권4호
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• pp.349-355
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• 2001

The use of bed in Korea has increased steadily, however, intensive survey on the general use and consumer's evaluation of their beds have not been performed sufficiently, yet. Thus, the purpose of this study is to investigate the actual use of the consumer and their degree of evaluation for the component of the bed as well as their feeling of discomfort on the various parts of body. More than one hundred users of commercial beds were responded to the survey. The results obtained were as follows: (1) Complaint about the depression of the mattress and the noise from the bed was apparent in the current use of beds. (2) Important physical variable related to the comfortable sensation of the sleeping was the degree of support in maintaining the natural shape of the spine and waist. Durability and the degree of hardness of the mattress were also important physical parameters of bed perceived by consumer. (3) The degree of discomfort on the back and waist during sleep was closely related to the comfort evaluation of the bed.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1995년도 춘계공동학술대회논문집; 전남대학교; 28-29 Apr. 1995
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• pp.787-796
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• 1995

A man model is a useful design tool for the evaluation of man machine systems and products. An arm reach trajectory prediction for such a model will be specifically useful to present human activities and, consequently, could increase the accuracy and reality of the evaluation. In this study, a three-dimensional reach trajectory prediction model was developed using an inverse kinematics technique. The upper body was modeled as a four link open kinematic chain with seven degrees of freedom. The Resolved Motion Method used for the robot kinematics problem was used to predict the joint movements. The cost function of the perceived discomfort developed using the central composite design was also used as a performance function. This model predicts the posture by moving the joints to minimize the discomfort on the constraint of the end effector velocity directed to a target point. The results of the pairwise t-test showed that all the joint coordinates except the shoulder joint's showed statistically no differences at .alpha. = 0.01. The reach trajectory prediction model developed in this study was found to accurately simulate human arm reach trajectory and the model will help understand the human arm reach movement.

• 한국자동차공학회논문집
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• 제11권4호
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• pp.165-172
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• 2003

This study aims to find frequency weighting curves for the evaluation of drivers' discomfort by vertical and rotational steering wheel vibration. Equal sensation curves, inverse of frequency weighting curves, were determined for the two kinds of vibrations respectively by using the sinusoidal signals with reference amplitudes from 0.2 to 0.4 m/s2 in the frequency range from 5 to 100 ㎐. Twelve subjects joined at the tests, and median values of the twelve judgments were used to determine the equal sensation curves. An experiment was followed to compare the relative sensation magnitude between the two kinds of equal sensation curves, which showed discomfort by the rotational vibration was 1.5 times of that by the vertical vibration at 50 ㎐.

• 대한인간공학회:학술대회논문집
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• 대한인간공학회 2004년도 추계학술대회
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• pp.22-22
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• 2004

• 대한인간공학회지
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• 제30권6호
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• pp.695-703
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• 2011

Objective: This study was to investigate the effects of coordinated upper-limb body postures on the subjective discomfort rating, heart rate, and muscle activities. Background: Although generally many checklists such as OWAS, RULA, and REBA were applied to evaluate various body postures, the body postures were might be overestimated or underestimated because each body part(i.e., back, shoulder, and elbow etc.) was evaluated separately, and then added all rates of individual body parts to assess an overall risk level for the body posture in these methodologies. Methods: A total of 20 participants maintained 14 postures which were combinations of back, shoulder, and elbow flexion angles and then muscle activities, subjective discomfort, and heart rates were collected every three minute during a sustained 15 minute and 0.5kg weight holding task. Four muscle groups were investigated: erector spine, anterior deltoid, upper trapezius, triceps brachii. Results: Results showed that subjective discomfort was the lowest when the angle of back and shoulder were both $0^{\circ}s$, while the body posture with $45^{\circ}$ of back angle and $45^{\circ}$ shoulder angle was rated as the most subjective discomfort posture. In general, the subjective discomfort ratings increased as back and shoulder flexion angles increased. It was noted that, however, the subjective discomfort of body posture with a $45^{\circ}$ back angle and $45^{\circ}$ shoulder flexion angle was lower than that of body posture with a $0^{\circ}$ back and $45^{\circ}$ shoulder flexion angle. The research findings of heart rates and muscle activities showed similar results for the analyses of subjective discomfort ratings. Conclusions: The possible limitations of the current ergonomics evaluation techniques which assessing a body posture with summing all body part score after individually analyzed in this study. Based on the analyses of subjective discomfort, heart rate, and muscle activities, it was recommended that a use of effects of coordinated upper-limb body postures would be considered when one evaluates work-load for various working postures. Application: These findings can be used for developing a more accurate assessment checklist for working posture as well as preventing musculoskeletal disorders of workers in workplaces.

• 대한산업공학회지
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• 제31권4호
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• pp.289-296
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• 2005

This study aims to measure maximum holding times(MHTs) of symmetric and asymmetric whole body postures, and to compare three representative observational methods including OWAS, RULA, REBA, based on the MHTs. An experiment was conducted for obtaining the MHTs, in which hand position was used as experimental variable, and the MHT and subjective discomfort rating as dependent variables. The hand position was defined by the percentage of the shoulder height(%SH), the percentage of the arm reach(%AR) and rotation angle(R). The results showed that three independent variables of %SH, %AR and R significantly affected on the MHTs at ${\alpha}$=0.01, and that the MHTs were negatively linearly related to the discomfort scores of Borg CR10. It was also revealed that OWAS and REBA were less sensitive to postural stress than RULA. In addition, OWAS and REBA underestimated postural load of given postures compared to RULA. Therefore, it is recommended that among the three observational methods investigated in this study, RULA be used for a more precise evaluation of postural load.

• 대한안전경영과학회지
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• 제17권2호
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• pp.153-160
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• 2015

This study tried to investigate the difference of the legibility in different age groups (young and old) with same near visual acuity and to provide preliminary guidelines for the text sizes in the pesticides products based on the legibility experiments. To achieve the objective, legibility evaluation experiments were conducted to test the effects of different age(20s, 50-60s), gender, font type(thick gothic-type and fine gothic-type), thickness (plain and bold), and number of syllables(2 and 3 syllables) in the same near visual acuity(0.6). The results showed that legibility 50s was higher than 20s. And 20s are appealed higher discomfort than 50s. Considering these experimental results, it was recommended that the 14 pt or larger characters (100% readable size) should be used the important information such as toxicity, and the minimum character size was 7 pt (50% readable size) for other information.