• 대한산업공학회지
• /
• 제24권2호
• /
• pp.167-173
• /
• 1998

Many workers like welders work in squatting postures with the object on the ground during an entire work shift. It is suspected that such prolonged squatting without any supporting stool would gradually cause musculoskeletal injuries to workers. This study is to examine the physical stress caused by the prolonged squatting and to recommend a safe work/rest schedule for a welding task with squatting posture based on the lab experiments. In this study, 8 healthy student subjects participated in the experiment. They maintained a squatting work posture for 16 minutes with 4 different stool height conditions: no stool; 10cm height; 15cm height; and 20cm height. Every 2 minutes, the discomfort was subjectively assessed with the magnitude estimation method for the whole body, lower back, upper leg and lower leg. Based on discomfort ratings, we found that a 10cm height stool relieved the workload most. Discomfort rating results also indicated that a 20cm height stool showed the highest workload, and the there were no difference in workload between a 15cm height stool and no stool. We recommend to use low height stools and to maintain such working postures no longer than 6 minutes for prolonged squatting tasks.

• 대한인간공학회지
• /
• 제29권4호
• /
• pp.465-471
• /
• 2010

Work-related musculoskeletal disorders (WMSDs) have been the most common health problem covered by worker's accident compensation insurance for several years in Korea. Korean government has strengthened related regulations since 2003. People looked forward to decreasing the incidence and prevalence of WMSDs. At first, the expectation could be realized. However, we were bumped against to limit at present. The authors think it is due to the negligence of psychosocial factors for WMSDs. Many researchers reported that the various psychosocial factors were associated with WMSDs or symptoms. Job demand, social support, job satisfaction and decision latitude are the major risk factors in job stress aspect. Work pressure, lack of rest, qualified workload, workload variability and monotonous job are the significant risk factors in work context of work organization. Employment flexibility, downsizing, lean production, contingent work and pay for by the piece are also the risk factors in an organizational context. Furthermore, these risk factors are associated with each other across different dimensions of work organization. Suggestive possible pathways between these risks and WMSDs have been taken note of increasing muscle strain or ergonomic stress and of a cognitive aspect. The authors suggest these risk factors could explain the limitation of the regulation system for WMSDs. In conclusion, the strategy to manage psychosocial factors is the one of the essential approach to prevent WMSDs.

• 대한인간공학회:학술대회논문집
• /
• 대한인간공학회 1997년도 추계학술대회논문집
• /
• pp.437-440
• /
• 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.

• The Journal of Korean Physical Therapy
• /
• 제21권3호
• /
• pp.119-124
• /
• 2009

Purpose: The National Institute for Occupational Safety and Health (NIOSH) lifting equation (NLE) is a useful tool to ergonomically analyze a workload. The NLE has high reliability and it can assess tasks by analyzing the work process. The purpose of this case study was to try using the NLE to analyze the workload of transferring patients by physical therapists in the hospital setting. Methods: We observed a physical therapist (PT) transferring patients from a wheelchair to a tilt table and a therapeutic table in one day. Two types of patient transferring methods were evaluated; (1) the manual single person method of stand, pivot and transfer, and (2) manual two person lifting under the thigh and grasping the waist for totally dependent patients. Results: The NIOSH lifting indexes of a person grasping the waist during the manual two person lifting were 5.52~4.48 according to the patient's weight. The NIOSH lifting indexes were 3.34 and 4.48 for the tasks performed by the manual single person method. Conclusion: Because transferring patients is not done very frequently, patients transferring tasks by a PT are not included as one of the musculoskeletal disorder related risky work criteria of the Korea Ministry of Labor. But the NIOSH lifting indexes of a person grasping the waist during the manual two person lifting and the manual single person method were over the NIOSH recommended weight limit threshold.

• 대한인간공학회지
• /
• 제30권4호
• /
• pp.525-534
• /
• 2011

This paper describes the current status of musculoskeletal disorders(MSDs) and its ergonomic risk factors, including the preventive intervention in terms of the working conditions and health promotion among agricultural workers. Korean agricultural workers have been exposed to the poor working condition. They have suffered from a variety of work-related injury and diseases more than the general population or the other occupational group. MSDs are one of the most prevalent problems threatening the agricultural worker's health and quality of life. Low back pain, osteoarthritis of hip and knee joint and carpal tunnel syndrome are well known MSDs that was found easily and frequently among agricultural workers. MSDs are worsened by poor ergonomic working conditions such as heavy weight lifting, repetitive movement and awkward posture which involves squatting with long sitting work on the ground, long working hours and heavy workload which are inherent in the greater part of agricultural works. Even though Korean agricultural workers are very weak population in terms of occupational safety and health, no many studies were conducted in the past and no many social and institutional supports were provided sufficiently. We need more interests and efforts in agricultural fields to improve its working condition and to promote health status of agricultural workers.

• 대한한의학회지
• /
• 제33권1호
• /
• pp.136-147
• /
• 2012

Objectives: The purpose of this study was to evaluate work-related risk factors of musculoskeletal disorders (MSDs) in various departments and tasks at an oriental medicine hospital. Methods: 269 hospital workers were selected for the study. The questionnaire survey included general characteristics, work-related characteristics and MSDs. Cross-tabulation analysis, multiple logistic regression, adjusted for age, work time, job demand and workload, were used to evaluate the effects of work-related factors on MSDs. Results: There were differences in MSDs depending on gender, age, occupation, and work-related factors. Prevalence rates of MSDs were 23.79% shoulder, 14.13% back, 10.41% neck. Risk factors for MSDs was packaging of drugs, transfer, and exercise therapy of physical therapist. Shoulder pain was significantly influenced by using power tools, over-reaching, and job demand while back pain was significantly influenced by weight-lifting operations and keyboard typing. Conclusions: The results of this study suggest that consideration of MSDs characteristics of workers in oriental medicine hospital is necessary to change unsuitable work environments and educate on preventing MSDs.

• 대한인간공학회지
• /
• 제31권2호
• /
• pp.281-289
• /
• 2012

Objective: The purpose of this study is to evaluate the potential risk of shoulder muscle at particular working postures in sitting. Background: The cause of shoulder pain needs to be specifically studied in relation with particular shoulder postures to prevent shoulder MSDs in workplace. Method: In this study MVC, fatigue and subjective workload were investigated depending on the change of shoulder posture. An experiment was designed to evaluate the six shoulder muscles at nine shoulder postures including the combination of 30(adduction), 0, 30(abduction) degrees and 60, 90, and 120 degrees of shoulder flexion. Surface electrodes were attached to the middle trapezius, inferior middle trapezius, anterior deltoid, posterior deltoid, serratus anterior and teres major. Thirteen subjects participated in the experiment. Dependent variables were RPE (rating of perceived exertion), MVC(maximum voluntary contraction) and MPF(mean power frequency) shift by EMG (electromyography). Results: The middle trapezius and inferior middle trapezius were not significantly fatigued at all postures. The decline of MPF slope was less than 10% at all postures. The anterior deltoid was significantly fatigued all postures. The decline of MPF slope was more than 10% at all postures. The posterior deltoid was significantly fatigued 30 degrees of adduction and 90 degrees of flexion. And, neutral and 30 degrees of abduction postures were fatigued more than 90 degrees of flexion. The serratus anterior was significantly fatigued except for 30 degrees of adduction and 60 degrees of flexion posture. The teres major was significantly fatigued except for neutral and 60 degrees of flexion, 30 degrees of abduction and 60 degrees of flexion posture. Conclusion: It was found that a certain muscle was fatigued fast at particular posture compared to other muscles, which would mean that a certain shoulder muscle at particular posture could be easily exposed to the risk of musculoskeletal disorders than other muscles. Application: It is expected that the result can be applied to design workplace using shoulder muscles.

• 대한인간공학회지
• /
• 제26권2호
• /
• pp.157-165
• /
• 2007

The Work-Related Musculoskeletal Disorders (WMSDs) can be occurred by various factors such as repetition, forceful exertions and awkward postures. Especially, occurrences of the WMSDs on the waist and lower limb are reported in workplaces, demanded standing postures for a long time, in service and manufacturing industry. The static and standing postures without movement for a long time increase work loads to the lower limb and the waist. Accordingly, anti-fatigue mat or anti-fatigue insole is used as a preventing device of the WMSDs. However anti-fatigue mats are limited in space and movement. In this study, multi-elastic insoles are designed and shown the effects of the workload reduction for a long time under the standing work. The foot pressures and EMG (Electromyography) are measured at 0 hour and after 2 hours by 6 health students in their twenties. The 6 prototype insoles are designed with three elastic (Low, Medium and High). These insoles are compared with no insole (insole type 7) as control group. The EMG measurement was conducted to waist (erector spinae muscle), thigh (vastus lateralis muscle) and calf (gastrocnemius muscle). The foot pressure is analyzed by mean pressure value and the EMG analysis is investigated through MF (Median Frequency), MPF (Mean Power Frequency) and ZCR (Zero Crossing Rate). The results of the foot pressure show that the multi-elastic insoles had smaller foot pressure value than that of no-insole. Moreover, Insole 2 and Insole 3 have the smallest increasing rate in foot pressure. The EMG results show that the multi-elastic insoles had smaller EMG shift value than that of no-insole in 2 hour, and then shift value shows the smallest value in Insole 2. Therefore, this study presents that the multi-elastic insoles have reducing effects of the work load for a long time standing work in both side of foot pressure and EMG.

• 대한치과기공학회지
• /
• 제33권4호
• /
• pp.379-390
• /
• 2011

Purpose: This study was conducted to improve the working conditions of dental technicians, through survey for working conditions related to perform one's duty, the extent of personal exposure to substances hazardous and complaint rate and factor of job stress and subjective symptom on musculoskeletal disorders. Methods: Using four types of structured questionnaires: social and demographic factor; the actual conditions of working space; working conditions; and characteristics of dental technicians, respondents filled in the questionnaires and the results were analyzed statistically. Results: The evaluation of comfort in working place found that satisfaction level on indoor noise was the lowest with 2.6 on a five-point scale and privacy space followed 2.8 point. In reasons for dissatisfaction with job, over workload ranked the highest by 25.4% and role overload had the highest by 39.5% in job stress factors. Based on the results, we could draw conclusion that dental technicians were unsatisfied with role overload and heavy workload a day. In reasons for musculoskeletal symptom prevalence, long-patient work was the highest by 24.1%. It was thought to cause dental technicians need deep procession and long-patient work due to the nature of their job. Conclusion: In conclusion, noise reduction and privacy space are required to improve job efficiency of dental technicians. In addition; we need to think of ways to increase the job satisfaction with adequate rest while deep procession and long-patient working.

• 대한인간공학회지
• /
• 제25권2호
• /
• pp.119-124
• /
• 2006

The present study evaluated the accuracy of MSD-related work criterion of Korea Ministry of Labor by using ergonomic workload evaluation methods. 1,948 manufacturing works in automobile industry were divided into 1,286 MSD-related risky works and 662 risk-free ones by using RULA, ANSI Z-365 and perceived discomfort evaluation. Then, the two types of works were evaluated by Labor Ministry work criterion to analyze the classification accuracy of the work criterion. The work criterion of Korea Labor Ministry had low hit and false alarm ratio(20 and 11%) and high miss and correct rejection ratio(80 and 89%), and the odd ratios of hit and correct rejection were 0.2 and 8.3, respectively. It can be concluded that the work criterion of Korea Labor Ministry is a conservative evaluation method which tends to evaluate a target work as risk-free.