• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.4
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• pp.102-109
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• 2003

Safety and comfort are importance concepts for designers of vehicle seats and instrument panels. There have been a lot of researches on comfortable sitting postures, however, relatively a few researchers have tried to find a desirable driving posture in consideration of both comfort and safety. This study investigates a relationship between comfort and safety of sitting posture of a driver. Since a seat is closely related to comfort, the angular data of comfortable sitting posture were obtained through the correlation between the seat and the driver. In order to acquire the data of safe sitting posture, computer simulations were performed for various seatback angles. Based on comparing and analyzing the data obtained, the optimal sitting posture is suggested for both comfort and safety aspects.

• Journal of the Korean Society of Safety
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• v.15 no.3
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• pp.108-114
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• 2000

The work posture impose additional stress upon human workers so that it should be carefully considered in designing works. However, we have a lot of manufacturing plants which convert their standing workplace to sedentary one. To confirm the validity of that trend, the authors conducted an experimental study, and compared the results. The results of the EMG and the self-cognitive symptoms, in general, showed a correspondent trend that the sedentary work posture was rated more comfortable. At the beginning of the work, complaint of the lowerback was higher whereas that of the lower leg and the feet went higher as the time elapsed. If the weight of workpiece were heavier than 500g, increasing rate of bodily discomfort in the sedentary posture were greater than that of the standing posture. In the meanwhile, the standing posture was consistently superior to the sedentary posture in its performance. Thus, in conclusion, for a light assembly work, sedentary work posture would be recommendable because bodily discomfort would be larger irrespective of the small increase of performance increase.

• Safety and Health at Work
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• v.7 no.4
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• pp.389-393
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• 2016

Job hazard analyses were conducted to assess exposure to musculoskeletal disorder (MSD) risk factors in seven workers of three dry-cleaning establishments. In accordance with the Washington State Ergonomics Rule, the analyses were performed in two separate steps: (1) observation and checklist approaches were made to identify a "caution zone job" in the seven workers' pressing operations across the three shops; and (2) detailed posture and motion analyses were undertaken to determine a "MSD hazard" in one worker's operation using a video technique. One "caution zone job" was identified and it was the pressing operation job in which five physical risk factors were found in the pressing operations. The detailed analyses confirmed that one "MSD hazard", i.e., awkward posture in shoulders, was prevalent in the pressing operations of the three dry-cleaning facilities. It would be desirable to reduce MSD risk factors including awkward shoulder posture in the dry-cleaning industry.

• Journal of the Korean Society of Safety
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• v.18 no.2
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• pp.119-124
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• 2003

Despite rapid technological advance and increased automation facilities, many jobs and activities in our living require manual materials handling(MMH). These include wide variety of activities such as moving things, lifting bags. boxes or cartons, etc. Many studies found that handle could affect on maximum acceptable weight of lifting, but there were few studies f3r the effects of work posture and coupling in lifting tote box. This study performed that ten male college students were required to lift a tote box with and without handle for three postures (bending, straight, right angle posture). From the experiment, following results were obtained. (1) MVC reduced maximum 23% by type of handle. (2) MVC was highest in straight posture, but was lowest in right angle posture. (3) As a result of ANOVA, MVC paid attention to posture and coupling. (p<0.01) (4) To all handle types, biceps brachii activity was increased in right angle posture. but reduced in straight posture. (5) To all posture, biceps brachii activity was most lively in no handle. The results of MVC measurement, subjective rating, EMG analysis, statistic analysis showed that maximum acceptable weight of lifting was influenced by type of handle and straight posture was more comfortable than other postures. Based on these results, it was concluded that acceptable weight of lifting has to differ for work posture and coupling.

• 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.32 no.1
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• pp.145-152
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• 2013

Objective: The aim of this study is to develop an ergonomic office chair that has an alarm function for the unbalanced sitting postures. Background: Contrary to expectation, it is reported that office workers sit on their chairs much more in unbalanced postures during daily work. Even though an office worker uses an ergonomically good-designed chair and begins their work in a good sitting posture, his/her posture is likely to shift to the unbalanced bad posture. Therefore, a posture alarm system would be very helpful in keeping office workers' good postures. Method: We developed a prototype chair with four load cells under a seat pan and one load cell beneath a backrest. Through some experiments, we set the criteria for unbalanced bad postures then implemented the criteria into the alarm system of the prototype chair. The chair called e-BASE chair could detect unbalance postures and show alarms for chair users. We also enhanced back support by developing a step-wised folding backrest. Results: The e-BASE chair showed better performance in interface pressure distributions and balanced posture ratio in VDT work. Conclusion: The ergonomic chair with posture alarm function(e-BASE chair) was developed. It showed better performance in seat pressure distribution and in keeping good posture during office work. Application: The posture alarm system and folding backrest can be applied to the new models of office chair.

• Safety and Health at Work
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• v.5 no.1
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• pp.27-31
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• 2014

Background: Carpal tunnel syndrome (CTS) is a common work-related peripheral neuropathy. In addition to grip force and repetitive hand exertions, wrist posture (hyperextension and hyperflexion) may be a risk factor for CTS among workers. However, findings of studies evaluating the relationship between wrist posture and CTS are inconsistent. The purpose of this paper was to conduct a meta-analysis of existing studies to evaluate the evidence of the relationship between wrist posture at work and risk of CTS. Methods: PubMed and Google Scholar were searched to identify relevant studies published between 1980 and 2012. The following search terms were used: "work related", "carpal tunnel syndrome", "wrist posture", and "epidemiology". The studies defined wrist posture as the deviation of the wrist in extension or flexion from a neutral wrist posture. Relative risk (RR) of individual studies for postural risk was pooled to evaluate the overall risk of wrist posture on CTS. Results: Nine studies met the inclusion criteria. All were cross-sectional or case-control designs and relied on self-report or observer's estimates for wrist posture assessment. The pooled RR of work-related CTS increased with increasing hours of exposure to wrist deviation or extension/flexion [RR = 2.01; 95% confidence interval (CI): 1.646-2.43; p < 0.01: Shore-adjusted 95% CI: 1.32-2.97]. Conclusion: We found evidence that prolonged exposure to non-neutral wrist postures is associated with a twofold increased risk for CTS compared with low hours of exposure to non-neutral wrist postures. Workplace interventions to prevent CTS should incorporate training and engineering interventions that reduce sustained non-neutral wrist postures.

• Journal of the Korean Society of Safety
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• v.26 no.3
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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.

• Journal of Auto-vehicle Safety Association
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• v.15 no.4
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• pp.48-57
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• 2023

With the advance of autonomous vehicle technology various sitting posture is possible like relax position (inclined seating posture). Parametric study was done with MADYMO, a mutibody dynamics solver, to investigate the effect of sitting posture in different frontal crash modes, full frontal, 40% offset, and angled rigid barrier crash as well as various impact speeds. Hybrid III 50th male and 5th female dummies were used to figure out the difference induced by occupant weight and dimension. Restraint system parameters complying to current safety protocols like NCAP are studied if they still work effectively in relax position which is feasible with autonomous vehicles.

• Journal of the Korean Society of Safety
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• v.24 no.2
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• pp.83-88
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• 2009

The objective of this paper was to evaluate the effectiveness of horizontal, vertical, asymmetric and coupling multipliers for manual material handling. Lifting tasks with 5 different horizontal distances ($30{\sim}70cm$) for 6 vertical distances(ankle, knee, waist, elbow, shoulder and head height) were experimented. The muscle activity and muscle exertion level during asymmetric load handling(without trunk flexion) was experimented. Lifting tasks with and without handle tote box for three postures(straight, bending, right angle posture) were experimented. The degrading tendency did not appeared almost in $60{\sim}70cm$ interval's horizontal distance. As a result of ANOVA, MVC paid attention to horizontal and vertical distance but cross effect was insignificant(p<0.01). The change of the MVC according to the horizontal, vertical distance appeared similar from of RWL. The results of normalized MVC measurement were decreased about 16%, 24%, 34% respectively as the asymmetry angle was $30^{\circ}$, $60^{\circ}$, $90^{\circ}$. RMS EMG values of right erector spinae muscles were decreased as the work posture went to $90^{\circ}$ and those of left erector spinae muscles were increased until the asymmetry angle was $40^{\circ}$ but decreased continually over $40^{\circ}$. 7 subjects, activities of left and right latissimus dorsi muscles were maintained constantly, while for remainer, those were irregular. MVC reduced maximum 23% by type of handle. MVC was highest in straight posture, but was lowest in right angle posture. As a result of ANOVA, MVC paid attention to posture, coupling(p<0.01). To all handle types, biceps brachii activity was increased in right angle posture, but reduced in straight posture. Based on the results of this study, it is suggested that the NIOSH guideline should not be directly applied to Korean without reasonable reexamination. In addition, we need to afterward study through an age classification.