• Safety and Health at Work
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• v.11 no.2
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• pp.187-192
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• 2020

Background: This study investigated the relationship between verbal aggression against school teachers and upper extremity (neck, shoulder, upper limb, and/or upper back) musculoskeletal pain. Methods: This was a cross-sectional study of 525 elementary school teachers from Jaboatão dos Guararapes, Northeast Brazil. Results: The prevalence of upper extremity musculoskeletal pain among teachers who reported verbal aggression in the past six months (67.7%) was higher than that among those who did not report verbal aggression (51.7%): (prevalence ratio = 1.21; 95% confidence interval = 1.04-1.40). The prevalence of upper extremity musculoskeletal pain was associated with verbal aggression, sex, and common mental disorders, controlled by skin color, age, monthly income, teachers' education, years working as a teacher, workload, and obesity. Furthermore, the measure of the association between verbal aggression and upper extremity musculoskeletal pain was modified by sex and common mental disorders, considered altogether. Teachers who suffered verbal aggression, of the feminine sex, and also having common mental disorders reported high prevalence (85.4%) of upper extremity musculoskeletal pain. Conclusion: The association between verbal violence in the school and complaints of upper extremity musculoskeletal pain was strong and modified by teachers' sex and common mental disorders.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.19 no.2
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• pp.156-169
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• 2009

In this study, the authors introduced DASH (Disabilities of the arm, shoulder, and hand), which had been developed for evaluating the functional impairment in the movement of upper extremities in regular daily activities, work ability and sports/performing arts ability. It is an ergonomic risk assessment tool used for industrial workers and also a disability measurement tool for upper extremity disorders arising from musculoskeletal disorders and symptom. This study intended to examine the applicability of DASH in occupational health field. Firstly, DASH development process and composition were reviewed through The DASH outcome measure user's manual and early articles. Secondly, reliability, validity, and responsiveness of the DASH in various languages at the application stage as well as its reliability and validity at the early stage of development were investigated. Thirdly, focusing on the application of DASH to clinical cases, workers with musculoskeletal symptoms, healthy workers, workers with other diseases, and general population were discussed besides workers with major musculoskeletal disorders. Lastly, DASH questionnaire was examined for its potential as a reference for assessing the functional impairment in the movement of upper extremities of workers with musculoskeletal symptoms in industrial workers in Korea.

• Safety and Health at Work
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• v.1 no.1
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• pp.37-42
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• 2010

Over years it has been increasingly concerned with how upper extremity musculoskeletal disorders (UEMSDs) are attributed to psychosocial job stressors. A review study was conducted to examine associations between UEMSDs and psychosocial work factors, and to recommend what to consider for the associations. For studies in which the job demand-control-support (DCS) model or its variables were specifically employed, published papers were selected and reviewed. A number of studies have reported relationships between UEMSDs symptoms and psychosocial exposure variables. For example, the findings are: higher numbness in the upper extremity was significantly attributed to by less decision latitude at work; work demands were significantly associated with neck and shoulder symptoms while control over time was associated with neck symptoms; and the combination of high psychosocial demands and low decision latitude was a significant predictor for shoulder and neck pain in a female working population. Sources of bias, such as interaction or study design, were discussed. UEMSDs were shown to be associated with psychosocial work factors in various studies where the job DCS model was addressed. Nonetheless, this review suggests that further studies should be conducted to much more clarify the association between UEMSDs and psychosocial factors.

• Journal of the Ergonomics Society of Korea
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• v.24 no.2
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• pp.65-70
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• 2005

Evaluation of repetitiveness for upper extremity intensive tasks is essential to determine the level of risk for upper extremity musculoskeletal disorders at the workplace. However, experimental data available to establish the acceptable levels of repetitiveness for various postures and forces is lacking. The present study examined the maximum acceptable frequencies(MAFs; motions/min.) of shoulder, elbow, wrist, and index finger motions at different forces(1kgf and 4kgf for shoulder, elbow, and wrist; 0.25kgf and 1 kgf for index finger) in sitting. Seventeen right-handed males in 20s without having any history musculoskeletal disorders participated in the MAF experiment. The participants determined their MAFs for the upper extremity motions by using the self-adjustment method and their work pulse(increase in heart rate; beats/min.) and rating of perceived exertion(RPE) were measured when working at MAF. The MAFs of elbow, wrist, and index finger motions for each force level were about 2, 3, and 6 times the corresponding MAF(9 at the high force and 24 at the low force) of shoulder motion and the MAFs at the low force increased about 2 times those at the high force. The work pulses of elbow, wrist, and index finger motions for each force level were 70%, 50%, and 30% of the corresponding work pulse(17 at the high force and 12 at the low force) of shoulder motion and the work pulses at the low force were about 70 % of those at the high force. Lastly, the RPEs of the upper extremity regions were about level 3(moderate) or below.

• Journal of the Ergonomics Society of Korea
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• v.29 no.3
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• pp.311-320
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• 2010

This study aimed to examine the development and characteristics of the workers with upper limb musculoskeletal symptoms and disorders and to analyze the upper limb musculoskeletal symptoms and disorders for its relationship with the individual socio-demographic characteristics. This study investigated the effect on the limitations of physical activities using standardized surveillance tool and clinical diagnosis. Musculoskeletal symptoms and the limitations of physical activities were examined. The clinical diagnosis of musculoskeletal disorders were carried out by physical examination, radiological examination and electromyography-electroneuronography for 22 workers in kitchen hood assembly process and 50 workers in toggle process of leather product manufacturing. The proportion of workers with musculoskeletal disorders was higher and the DASH score was also statistically higher in female and aged workers with longer working hours, longer household working hours, less leisure/hobby activity and higher physical load. Physical activities component score increased in the following order: workers in normal health, workers with musculoskeletal symptoms, and workers with musculoskeletal disorders as clinically diagnosed. Score for each DASH component increased in the following order: sports/performing arts ability, social activities, specific physical functional activities, work or other regular daily activities, work ability, psychological activities, insomnia and upper limb symptoms. The overall and each component DASH scores were higher in workers with symptoms of status praesens and of more severity, and receiving medical intervention. Musculoskeletal symptoms and disorders are associated with individual socio-demographic characteristics, and DASH score for physical activities of upper limb was higher in workers with musculoskeletal disorders. Musculoskeletal symptoms and disorders have a remarkable epidemiological significance for physical activities, social activities, work or other regular daily activities, upper limb symptoms and insomnia, where work ability, sports/performing arts ability and preventive measure is needed.

• Journal of the Ergonomics Society of Korea
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• v.29 no.4
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• pp.405-422
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• 2010

Occupational musculoskeletal disorders currently account for the largest proportion of the occupational illnesses in Korea. In this research, status of musculoskeletal disorders among the occupational illnesses was examined through workers' compensation claims data. Types and characteristics of musculoskeletal disorders were looked at other data set as well. The data sets included epidemiological investigation data reported by Occupational Safety and Health Research Institute, and data collected from occupational disease surveillance reports and Korean occupational health-related scientific journals. Number of cases, incidence rate and insurance benefits for occupational musculoskeletal disorders in Korea are increasing every year. In addition, musculoskeletal disorders occurrence is shifted from large enterprises group to small-and-medium group, from manufacturing to service sector, and from production workers to office and professional workers. Although low back pain is still most common, its occurrence characteristics is gradually shifted from traumatic to cumulative while musculoskeletal disorders are somewhat seemingly moved from lumbar to upper limb body part. Musculoskeletal disorders were observed to be more diverse and prevalent in epidemiological investigations or surveillance data rather in workers' compensation claims data. Musculoskeletal disorders occurrence is related to demographic factors, occupational psychosocial factors, and ergonomic risk factors at workplace for which appropriate preventive measures needed to be made accordingly.

• Safety and Health at Work
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• v.1 no.2
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• pp.124-133
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• 2010

Objectives: This study was conducted to develop a model describing the interaction between lifestyle, job, and postural factors and parts of the upper extremities in shipyard workers. Methods: A questionnaire survey was given to 2,140 workers at a shipyard in Ulsan City. The questionnaire consisted of questions regarding the subjects' general characteristics, lifestyle, tenure, physical burden, job control, posture and musculoskeletal symptoms. The overall relationship between variables was analyzed by a structural equation model (SEM). Results: The positive rate of upper extremity musculoskeletal symptoms increased in employees who worked longer hours, had severe physical burden, and did not have any control over their job. Work with a more frequent unstable posture and for longer hours was also associated with an increased positive rate of musculoskeletal symptoms. Multiple logistic regression analysis showed that unstable posture and physical burden were closely related to the positive rate of musculoskeletal symptoms after controlling for age, smoking, drinking, exercise, tenure, and job control. In SEM analysis, work-related musculoskeletal disease was influenced directly and indirectly by physical and job stress factors, lifestyle, age, and tenure (p < 0.05). The strongest correlations were found between physical factors and work-related musculoskeletal disease. Conclusion: The model in this study provides a better approximation of the complexity of the actual relationship between risk factors and work-related musculoskeletal disorders. Among the variables evaluated in this study, physical factors (work posture) had the strongest association with musculoskeletal disorders.

• Journal of the Ergonomics Society of Korea
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• v.34 no.1
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• pp.11-18
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• 2015

Objective: The aim of this study was to understand the effects of phone weight on the typing performance and muscle recruitment in the neck and upper extremity while typing a text message with dominant hand. The iPhone4 and iPhone5 were compared due to their 28-gram differences in weight. Background: Too much use of a cellular phone can lead the musculoskeletal disorders in the upper extremity. Phone makers tend to make their new models bigger, lighter, faster and smarter. Method: Fourteen healthy volunteers without any history of neuromuscular disorders or ongoing pain who used their smartphone more than one year were recruited. A 112g phone (iPhone5) and a 142g phone (iPhone4) were used for typing the lyric of the Korean national anthem with their dominant hand. Typing duration, the typing error, the perceived fatigue, and preference was investigated. Muscle recruitment and the resting gap of neck (middle trapezius and levator scapula), shoulder (infraspinatus and mid deltoid), elbow (biceps brachii and brachioradialis), thumb (extensor and abductor policis brevis) were collected using surface electromyography. Typing error was counted and typing speed was calculated in characters per min. The data were analyzed using a paired t-test and chi-square (${\chi}^2$) analysis for the effects of phone weight on the typing performance parameters and muscle recruitment. Results: Typing text message with iPhone5 took longer but had less muscle recruitment in brachioradialis, and extensor policis brevis muscles. Lighter weight of iPhone5 made biceps brachii to rest less without increasing the mean %EMG. Conclusion/Application: Findings of this study can be valuable information for phone designers to develop more productive device and for smartphone users to prevent the musculoskeletal disorders in the upper extremities.

• Safety and Health at Work
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• v.1 no.2
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• pp.158-166
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• 2010

Objectives: This study aimed to find gender distinctions in terms of the sociology of the population; to determine work-related factors; to analyze gender differences in daily living, work, sports, and art performances; and to identify gender-related factors that limited performance of daily living and work activities. Methods: A questionnaire was designed that included disabilities of the arm, shoulder, and hand (DASH), accident history, disease history, work duration at current workplace, marital status, job satisfaction, job autonomy, and physical demands of the job. Out of 1,853 workers surveyed, 1,173 questionnaires (63.3%; 987 males, 186 females) included responses to DASH disability and DASH optional work and were judged acceptable for analysis. Results: Upper extremity functional limitation during work and daily living was higher for females than males. The limitations for males increased according to their household work time, accident history, work duration, job satisfaction, physical demand, and job autonomy. Meanwhile, female workers' upper extremity discomfort was influenced by their disease history, job satisfaction, and physical demands. In addition, the size of the company affected male workers' upper extremity function, while marriage and hobbies influenced that of female workers. Conclusion: This study addressed sociodemographic factors and work-related factors that affect each gender's upper extremity function during daily living and working activities. Each factor had a different influence. Further studies are needed to identify the effect that role changes, not being influenced by risks at work, have on musculoskeletal disorders.

• Journal of the Korean Society of Safety
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• v.31 no.4
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• pp.111-119
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• 2016

This study aimed to analyze postures that were frequently conducted in manufacturing industry. To find grip strength and muscle activities of each posture, Maximum Voluntary Contraction (MVC) and ElectroMyoGraphy (EMG) were measured. Based on the results of this study, the most appropriate posture could be suggested and used as a basic information for preventing musculoskeletal disorders. Most work-related musculoskeletal disorders have been occurred in the fields of manufacturing industry. According to previous studies, it was reported that the rate of musculoskeletal diseases of upper extremity was higher than that of other body parts. Accordingly, there were many studies about discomfort and grip strength of upper extremity. However, these studies dealt with single selection of wrist, elbow and shoulder. So, it was insufficient for comprehensive studies about upper extremity. And in order to improve the work posture, the physiological changes being generated by the combination of wrist, elbow and shoulder postures should be observed and analyzed. In order to conduct this study, thirty university students who had no records of MSDs involved were recruited. Independent variables were postures of wrist(pronation, neutral, supination), postures of elbow(flexion $45^{\circ}$, $90^{\circ}$) and postures of shoulder(flexion $0^{\circ}$, $90^{\circ}$). And dependent variables were MVC values and EMG values. Jamar dynamometer and TeleMyo 2400T G2 was used to measure MVC and EMG. MVC and EMG for 12 postures were measured for three second and for three times. Experiment was performed randomly. A 10 minutes rest period was provided after each t. To measure muscle load, the EMG signals of eight muscles (Biceps, Medial triceps, Lateral triceps, Brachioradialis, Extensor carpi ulnaris, Extensor carpi radialis, Flexor carpi ulnaris and Flexor carpi radialis) were evaluated. MVC values and EMG values were analyzed using Minitab ver. 14. The results showed that MVC value was the highest at shoulder $0^{\circ}$, elbow $45^{\circ}$ and wrist supination. In case of wrist postures, MVC of supination is the highest. In case of elbow and shoulder postures, MVC of flexion $45^{\circ}$ and $0^{\circ}$ was the highest. It was found that there were interaction between wrist and elbow posture under shoulder flexion and between shoulder and wrist under elbow flexion $45^{\circ}$. In case of the angle of shoulder $0^{\circ}$, elbow $45^{\circ}$ and wrist supination, the EMG values of four muscles(Medial Triceps, Extensor carpi ulnaris, Extensor carpi radialis, Flexor carpi ulnaris) were the highest. Based on this study, it is worth to note that the combination postures of upper extremity have a large impact on the MVC and EMG. The optimal condition upper extremity was shoulder flexion $0^{\circ}$, elbow flexion $45^{\circ}$ and wrist supination for preventing work-related musculoskeletal disease.