• Journal of the Ergonomics Society of Korea
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• v.23 no.4
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• pp.45-56
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• 2004

The purpose of this study is to evaluate perceived discomfort of working postures in terms of upper body (back, shoulder, and elbow) flexions when an external load varies. Eighteen subjects participated in an experiment of appraising perceived discomfort of varying upper body postures with three levels of external loads given. The ANOVA results showed that the perceived discomfort of upper body postures was significantly affected by the external load. It was also apparent that the interactions between external load and upper body posture were significant (p< 0.001). The result implies that a new posture classification scheme for workload assessment methods may be in need to reflect such interactions between external load and upper body posture. In order to support the statement, a regression model of perceived discomfort of upper body postures obtained from the experiment was developed and compared to that of perceived discomfort of seven work-related postures found in automobile assembly operations. The correlation coefficient between predicted and actual values of perceived discomfort was about 0.96. It is expected that the result help to properly estimate the body stress resluting from worker's postures and external loads and can be used as a valuable design guideline on preventing work-related musculoskeletal diseases in industry.

• International Journal of Human Ecology
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• v.14 no.1
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• pp.41-55
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• 2013

The purpose of this study was to analyze human upper body surface changes at the shoulder and back area. The body surface data were analyzed in terms of muscle and bone displacement in dynamic postures. Body surface data were collected with a 3D body scanner. The body surface was scanned at the static and four baseball batting postures. The body surface dimensions over the deltoids, scapulae and trapezius were measured. The results show that the vertical measurements of the deltoids increased by 20%. The horizontal measurements of the axilla of the back increased. The surface of the trapezius was elongated by over 10%, and the lower back musculature was elongated by about 50%. The results of this study showed that changes in back body surface caused by upper arm movements. It was influenced by the deltoid articulated with the humeri and the scapulae and trapezius. These body surface changes caused by muscle activities and ranges of motion can be used to design functional clothing.

• International Journal of Safety
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• v.10 no.1
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• pp.32-35
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• 2011

Lifting capacity and difficulty of task are influenced by body posture. In RULA and REBA, the body was divided into segments which formed two groups, A and B. Group A includes the upper and lower arm and wrist while group B includes the neck, trunk and legs. This ensures that whole body posture is recorded so that any awkward or constrained posture of the legs, trunk or neck which might influence the posture of the upper limb. This study aimed to measure MVC (maximum voluntary contraction) and subjective judgment in psychophysical method (Borg's scale) according to trunk and upper arm angle and to analyze results statistically. The results of this study were that lifting capacity was more influenced by interaction of body posture rather than angles of each part, and MVC variation according to trunk and upper arms angles should different patterns. This means that we consider the interaction of trunk angles and upper arm angles when we access risk factors of the postures. This survey would be also the basic data to evaluate difficulty of lifting tasks according to body postures ergonomically.

• Journal of the Ergonomics Society of Korea
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• v.30 no.6
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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.

• Journal of the Ergonomics Society of Korea
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• v.31 no.1
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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.

• Journal of the Ergonomics Society of Korea
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• v.33 no.2
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• pp.87-96
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• 2014

Objective: The present study is intended to objectively classify upper- & lower-body sitting strategies and identify the effects of gender and OPL type on the sitting strategies. Background: A sitting strategy which statistically represents comfortable driving posture can be used as a reference posture of a humanoid in virtual design and evaluation of a driver's seat. Although previous research has classified sitting strategies for driving postures in various occupant package layout (OPL) types, the existing classification methods are not objective and the factors affecting sitting strategies have not been identified. Method: Forty drivers' preferred driving postures in three different OPL types (coupe, sedan, and SUV) were measured by a motion capture system. Next, the measured driving postures were classified by K-means cluster method. Results: Sitting strategies of upper-body were classified as erect (33%), slouched (41%), and reclined (26%) postures, and those of lower-body were classified as knee bent (42%), knee extended (32%), and upper-leg lifted (26%) postures. Significant differences at ${\alpha}$ = 0.05 in the upper-body sitting strategy by gender and lower-body sitting strategy by OPL type were found. Application: Both the classified sitting strategies and the identified factors would be of use in ergonomic seat design and evaluation.

• International Journal of Costume and Fashion
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• v.5 no.1
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• pp.1-13
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• 2005

Two hundreds of female aged 19 years old and up were recruited to evaluate the postural changes and bilateral variation of asymmetry over age. To find out the differences among the age group, subjects were classified into 5 groups, early young age(19-29), late young age(30-39), early middle age(40-49), late middle age(50-59), and old age(60-). 35 body measurements were taken by the 3-D body scanner which allowed us to take measurements which cannot be measured using traditional methods, including the shape of a cross section, slice area surface are, and volume. Bilateral variations were observed as a function of age; Depth of scapular point level, scapular point to center back, and blade angle. Postural change of anterior cervical angle, upper anterior thoracic angle, upper posterior thoracic angle, posterior cervical angle, and center back/center front ratio were also exhibited. In each measurements, subjects were classified into normal, and abnormal group. Percentiles of abnormal in shoulder line angle, blade angle, neck point $\∼$ acromial point $\∼$ scapular point, posterior cervical angle, and upper posterior thoracic angle were increased over age group. The upper body of lateral view was classified into 3 types of posture based on the previous research; straight, erect(leaning back), and stooped(bent forward). The percentiles of subjects who have straight postures were decreased as a function of age, but those of stooped postures were increased. Subjects who have erect postures did not so. The stooped posture group shows the big cervical fossa angle, anterior cervical angle, posterior cervical angle, upper posterior thoracic angle, and the small upper anterior thoracic angle comparing to the straight and erect posture group. These results could be apply for clothing construction reflecting the changes in back, shoulder, neck, and the bilateral asymmetry according to the target age group.

• Journal of the Korean Society of Safety
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• v.24 no.2
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• pp.69-75
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• 2009

It is well-known that lifting capacity of a worker is influenced by body posture during the task. When a task analyst make use of RULA and REBA Trunk and upper arm angles are recorded in a separate item. It means that the interaction between the angles of two body segments may be ignored in a final score. The NLE(NIOSH Lifting Equation) has been used to supplement this problem. However, there is no study to validate the result of RWL (Recommended Workload Limit) under the existence of interactions between trunk and upper arm angles. The goal of this study was to assess the effect of the interaction between trunk and upper arm angles. Three responses, including NMVC(normalized maximum voluntary contraction), RWL(Recommended Weight Limit) and subjective judgment in psychophysical method (Borg's scale), were recorded according to the combinations of three trunk angles and nine upper arm angles. The results showed that lifting capacity is highly influenced by interaction of two body segments(trunk and upper arm). It means that the task workload has to be analyzed along with the interaction of trunk angles and upper arm angles when the task analyst assesses potential risk factors on the postures. This study may be able to be a fundamental study to develop an assessment method for lifting task analyses according to body postures.

• Korean Journal of Human Ecology
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• v.13 no.1
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• pp.153-158
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• 2004

With considerable development of comfortable and functional clothing in recent years, we need to evaluate the effects of garment pressure in daily wear on each parts of human body because the garment pressure is important to design the clothing. This study was designed to examine the effects of body postures on garment pressure on each parts of human body in the actual clothing conditions. All the data were collected from 50 volunteered subjects. The Garment pressure was measured in lune and December with 8 points CPMS clothing pressure system from scapular, upper am, elbow, under arm, front waist line, side waist line, abdomen, crista ilica, upper hip, middle hip, front thigh, back thigh, front knee and back knee. The postures of subjects were controlled with 3 positions such as standing (posture 1), sitting on the chair (posture 2), and sitting on the floor (posture 3) during measurement of clothing pressure. Clothing weights were more in men than in woman. It showed that clothing weights had no effects on the garment pressure. In this study, however, just the garment pressures on scapular and top of the hip increased significantly by clothing weight (p<. 05). Clothing horizontally pressed on scapular and top of hip but not on other parts. When subjects stood up, the garment pressure was the highest on the side waist. Especially, clothing pressure on the front waist point was lower than that of the left side waist. On the upper parts of the human body, the garment pressure of left side waist was the highest, and followed by front waist, crista ilica, and abdomen in order. When subjects were sitting on the chair, the garment pressure on the lower parts of the human body was the highest on the top of hip. When the subjects were sitting on the chair or on the floor, the surface area on their skin of hip and waist parts increased by postures. In addition, it showed that men felt more comfortable than women on higher clothing pressure level.

• Proceedings of the ESK Conference
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• 1997.10a
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• pp.437-440
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• 1997

The association of poor body postures with pains or symptoms of musculoskeletal discorders has been reported by many researchers. An ergonomic evaluation of postural stresses as well as biomechanical stresses is also important especially when a job involves highly repetitive or prolonged poor body postures. The human body is divided into five parts: shoulder/upper arm, lower arm/wrist, back, neck, lower extremities. A work-sampling based macropostural classification system was developed to characterize various postures in this study. Application of the posture classification schema developed in this study to 7 automobile assembly tasks showed that the schema can be used as a tool to didntify the operation and tasks involving highly stressful body postures. This posture classification schema can also be applied as a basis for quantitive evaluating the workload of manual task.