• Safety and Health at Work
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• v.7 no.1
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• pp.49-54
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• 2016

Background: Prolonged sitting leads to low back discomfort and lumbopelvic muscle fatigue. This study examined the characteristics of body perceived discomfort and trunk muscle fatigue during 1 hour of sitting in three postures in office workers. Methods: Thirty workers sat for 1 hour in one of three sitting postures (i.e., upright, slumped, and forward leaning postures). Body discomfort was assessed using the Body Perceived Discomfort scale at the beginning and after 1 hour of sitting. Electromyographic (EMG) signals were recorded from superficial lumbar multifidus, iliocostalis lumborum pars thoracis, internal oblique (IO)/transversus abdominis (TrA), and rectus abdominis muscles during 1 hour of sitting. The median frequency (MDF) of the EMG power spectrum was calculated. Results: Regardless of the sitting posture, the Body Perceived Discomfort scores in the neck, shoulder, upper back, low back, and buttock significantly increased after 1 hour of sitting compared with baseline values ($t_{(9)}=-11.97$ to -2.69, p < 0.05). The MDF value of the EMG signal of rectus abdominis, iliocostalis lumborum pars thoracis, and multifidus muscles was unchanged over time in all three sitting postures. Only the right and left IO/TrA in the slumped sitting posture was significantly associated with decreased MDF over time (p = 0.019 to 0.041). Conclusion: Prolonged sitting led to increased body discomfort in the neck, shoulder, upper back, low back, and buttock. No sign of trunk muscle fatigue was detected over 1 hour of sitting in the upright and forward leaning postures. Prolonged slumped sitting may relate to IO/TrA muscle fatigue, which may compromise the stability of the spine, making it susceptible to injury.

• Proceedings of the ESK Conference
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• 1997.04a
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• pp.90-94
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• 1997

Many workers like welders are working in squat sitting postures with te object on the ground for an entire work shift. It is suspected that such prolonged squat sitting without any supporting stool would gradually cause musculoskeletal injuries to workers. This study is to quantitatively evaluate the physical stress caused by the prolonged squat sitting and to recommend a safe work/rest schedule for the task with squat sitting posture based on the lab experiment. In this study, 8 healthy student subjects participated in the experiment. They maintained a squat sitting posture for 16 minutes with 4 different stool height conditions: no stool, 10cm hight, 15cm height, 20cm height. Every 2 minutes, the discomfort was subjectively assessed using the magnitude estimation method for the whole body, lower back, upper leg and lower leg. Based on discomfort rating, we found that 10cm height stool relieved the workload most. Discomfort rating results also indicated that 20cm height stool showed the heghest workload, and that there was no difference in workload between 15cm height and no stool. We recommend to provide the workers with 10cm height stool for prolonged squat sitting tasks.

• Safety and Health at Work
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• v.8 no.2
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• pp.212-219
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• 2017

Background: Low back pain (LBP) is a major problem for office workers. Individuals adopting poor postures during prolonged sitting have a considerably increased risk of experiencing LBP. This study aimed to investigate seat pressure distribution characteristics, i.e., average pressure, peak pressure ratio, frequency of postural shift, and body perceived discomfort (BPD), during 1 hour of sitting among office workers with and without chronic LBP. Methods: Forty-six participants (chronic LBP = 23, control = 23) typed a standardized text passage at a computer work station for an hour. A seat pressure mat device was used to collect the seat pressure distribution data. Body discomfort was assessed using the Body Perceived Discomfort scale. Results: Office workers with chronic LBP sat significantly more asymmetrically than their healthy counterparts. During 1-hour sitting, all workers appeared to assume slumped sitting postures after 20 minutes of sitting. Healthy workers had significantly more frequent postural shifts than chronic LBP workers during prolonged sitting. Conclusion: Different sitting characteristics between healthy and chronic LBP participants during 1 hour of sitting were found, including symmetry of sitting posture and frequency of postural shift. Further research should examine the roles of these sitting characteristics on the development of LBP.

• Journal of Korean Institute of Industrial Engineers
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• v.39 no.3
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• pp.192-197
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• 2013

In this study, it is investigated the relationship between sitting discomfort and major design variables of lumber support, such as prominence, height and width through volunteer tests. Korean $50^{th}$ percentile males and American $50^{th}$ percentile males are recruited among 36 to 45 years old peoples who have driving experiences and have no back pain during the past 12 months. Subject ratings are asked by changing design variables randomly. Body pressure and lumber position changes are also measured as object measures. And correlation among subject ratings, object measures and three design variables are analyzed using statistical analysis. As a result, it is revealed that prominence is the most dominant factor that correlates to the discomfort strongly for both-Koreans and Americans and contribution of other two variables are very low.

• Proceedings of the ESK Conference
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• 1995.04a
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• pp.124-133
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• 1995

A field study was conducted to assess the preferred height and the range of discomfort recognition of school desks and chairs for students from elementary school to high school. For this study 43 male subjects and 44 female subjects in Taejon area were surveyed. The result shows that the preferred height of chairs is about 1.7cm higher than the popliteal sitting height, while the preferred height of desks shows no significant difference with the elbow sitting height which is known to be the ergonomically proper desk height. The threshold value between comfort and discomfort recognition of chair height is 1.88cm below the most prefeered height and 1.79cm about it. The threshold value between comfort and discomfort recognition of desk height is 1.76cm below the most prefeered height and 2.62cm about it.

• Journal of the Ergonomics Society of Korea
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• v.14 no.2
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• pp.41-50
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• 1995

A field study was conducted to assess the preferred height and the range of discomfort recognition of school desks and chairs for students from elementary school to high school. For this study 43 male subjects and 44 female subjects in Taejon metropolitan area were surveyed. The result showed that the preferred height of chairs were found to be about 1.7cm higher than the popliteal sitting height, while the preferred height of desks showed no significant difference with the elbow sitting height which is known to be the ergonomically proper desk height. The threshold value between comfort and discomfort recognition of chair heigth was 1.88cm below the most preferred height and 1.79cm above it. The threshold value between comfort and discomfort recognition of desk height was 1.76cm below the most preferred height and 2.62cm above it.

• Korean Journal of Human Ecology
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• v.19 no.4
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• pp.655-665
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• 2010

This study analyzed the effects of skinny jean on women's health by questionnaire survey and measuring the pressure experienced under the clothing and participants' subjective view of the pressure level. The average size women in their 20s' waists is 26 inches and so three pairs of jeans were prepared and worn by 4 female participants. A survey was conducted to investigate how often participants wear skinny jeans and whether they had had any feelings of discomfort as a result of this. Participants responded that they hadexperienced middle to high levels of discomfort due to the high pressure inside skinny jeans. For the maximum value of clothing pressures, jean f2 at the part of buttocks showed $48.7gf/cm^2$. The pressure inside the clothing was found to be highest around the buttocks followed by the knees and finally the belly. The mean values of 7 measuring parts are different according to the jean type; f3 $20.8gf/cm^2$ > f2 $16.4gf/cm^2$ > f1 $15.5gf/cm^2$, which is corresponding to the order of pressure sensation, but not corresponding to the order of ease amount of clothing pattern: f2 > f3 > f1. Mean pressure values were also measured according to the body posture: they were found to by highest when sitting on a chair (21.3gf/$cm^2$), second highest when sitting on the floor ($19.2gf/cm^2$) and lowest when standing ($15.0gf/cm^2$). This is not always same to the order of participants subjective perceptions of the pressure, which is, they estimated pressure to be highest when sitting on the floor followed by sitting on a chair and lowest in a standing position.

• Safety and Health at Work
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• v.11 no.2
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• pp.207-214
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• 2020

Background: Prolonged sitting at work can lead to adverse health outcomes. The health risk of office workers is an increasing concern for the society and industry, with prolonged sitting work becoming more prevalent. Objective: This study aimed to explore the variation in muscle activities during prolonged sitting work and found out when and how to take a break to mitigate the risk of muscle symptoms. Methods: A preliminary survey was conducted to find out the prevalence of muscle discomfort in sedentary work. Firstly, a 2-h sedentary computer work was designed based on the preliminary study to investigate the variation in muscle activities. Twenty-four participants took part in the electromyography (EMG) measurement study. The EMG variations in the trapezius muscle and latissimus dorsi were investigated. Then the intervention time was determined based on the EMG measurement study. Secondly, 48 participants were divided into six groups to compare the effectiveness of every break type (passive break, active break of changing their posture, and stand and stretch their body with 5 or 10 mins). Finally, data consisting of EMG amplitudes and spectra and subjective assessment of discomfort were analyzed. Results: In the EMG experiment, results from the joint analysis of the spectral and amplitude method showed muscle fatigue after about 40 mins of sedentary work. In the intervention experiment, the results showed that standing and stretching for 5 mins was the most effective break type, and this type of break could keep the muscles' state at a recovery level for about 30-45 mins. Conclusions: This study offers the possibility of being applied to office workers and provides preliminary data support and theoretical exploration for a follow-up early muscle fatigue detection system.

• International conference on construction engineering and project management
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• 2022.06a
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• pp.426-432
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• 2022

HVAC systems play a critical role in reducing energy consumption in buildings. Integrating occupants' thermal comfort evaluation into HVAC control strategies is believed to reduce building energy consumption while minimizing their thermal discomfort. Advanced technologies, such as visual sensors and deep learning, enable the recognition of occupants' discomfort-related actions, thus making it possible to estimate their thermal discomfort. Unfortunately, it remains unclear how accurate a deep learning-based classifier is to recognize occupants' discomfort-related actions in a working environment. Therefore, this research evaluates the classification performance of occupants' discomfort-related actions while sitting at a computer desk. To achieve this objective, this study collected RGB video data on nine college students' cold discomfort-related actions and then trained a deep learning-based classifier using the collected data. The classification results are threefold. First, the trained classifier has an average accuracy of 93.9% for classifying six cold discomfort-related actions. Second, each discomfort-related action is recognized with more than 85% accuracy. Third, classification errors are mostly observed among similar discomfort-related actions. These results indicate that using human action data will enable facility managers to estimate occupants' thermal discomfort and, in turn, adjust the operational settings of HVAC systems to improve the energy efficiency of buildings in conjunction with their thermal comfort levels.

• Journal of the Ergonomics Society of Korea
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• v.33 no.2
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• pp.143-153
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• 2014

Objective: The aim of this study is to investigate the effects of trunk-forearm supported sitting on trunk flexion angle, trunk extensor fatigue and seat contact pressure. Background: The relationship between sitting posture and musculoskeletal disorders of the trunk extensor fatigue and seat contact pressure has been documented. The trunk-forearm support type ergonomic chair was devised from the fact that trunk-forearm support has been reported to reduce trunk extensor activity and discomfort. Method: Using three different sitting postures, upright ($P_1$), trunk-forearm supported ($P_2$) and normal sitting ($P_3$), six healthy subjects participated in the study. Motion capture system was used to collect head and trunk flexion angle, and surface electromyography (sEMG) was used to collect myoelectric signal of upper trapezius, lower trapezius, erector spinae, multifidus, and pressure mat system was used to measure seat contact pressure. Results: When trunk and forearm were supported by the ergonomic chair, higher head flexion angle showed upright > trunk-forearm supported > normal in order, and muscle fatigue showed less than upright and normal sitting. Mean seat contact pressure decreased 19% than upright sitting. But muscle fatigue was not affected by each condition. Conclusion: Trunk-forearm supported sitting of the ergonomic chair showed positive effect in respect of trunk and head flexion angle, trunk extensor fatigue, seat contact pressure. To acquire comprehensive understanding of the effectiveness of the ergonomic chair, further studies such as anatomical effects from measurement of external applied loading effect to the body from interface pressure analysis are required. Application: The results of the publishing trend analysis might help physiological effects of trunk-forearm support type chair.