Empirical Suitability of Scoring Systems of Observational Techniques for Repetitive Movements Based on Discomfort.

This study empirically investigated the effects of repetitive movements of body parts through an experiment, and evaluated the suitability of the scoring systems of the existing observational methods for repetitive movements, based on the experimental results. Eighteen healthy college students participated in the experiment to assess discomfort, wherein joint movement, its repetition, and external load were used as independent variables. Postural loads for 16 postures used in the experiment were assessed using rapid upper limb assessment (RULA) and loading on the entire body assessment (LEBA). Three independent variables, joint motion, its repetition, and external load, as well as the interaction between motion repetition and external load, had significant effects on discomfort. Joint motion and external load significantly affected the RULA grand score, whereas all three independent variables affected the LEBA score. This finding may indicate that LEBA more accurately reflects the effect of repetitive body part movements. Additionally, the scoring systems for repetitive back motions by quick exposure check (QEC) and for repetitive wrist motions via a risk assessment and management tool for manual handling proactively II (RAMP II) may be reasonable based on the results of this study. The findings of this study can be used as reference information for better evaluation of postural loads assessed using the existing observational techniques, and as useful baseline data for the development of a new observational method to accurately assess stress caused by repetitive movements.

Characteristics of Work-Related Musculoskeletal Disorders in Korea.

This study aimed to analyze trends for work-related musculoskeletal disorders (WMSDs) from 1996 to 2020 in Korea and to investigate characteristics of WMSDs, including WMSD approval rates, distribution by WMSD names, and the effects of industry type and size, and workers' age and gender on WMSD occurrence. The data included those obtained from the official yearbooks for industrial accidents published by the Ministry of Employment and Labor and those obtained personally from the Korea Workers' Compensation & Welfare Service. The results showed that although the incidence of WMSDs differed by year, approximately 9500 cases of WMSDs occurred in 2019 and 2020, the incidence rate of WMSDs was approximately 5.0 per 10,000 workers, and the proportions of WMSDs among industrial accidents were almost 9%. Low back pain was the leading cause of WMSDs; WMSDs occupied 9.5−71.5% of total occupational diseases by year and occurred most frequently in the manufacturing industry, followed by construction, transportation/warehouse and communication, and mining industries, and nearly 60% of WMSDs occurred in small business with <50 workers. Among chronic WMSDs, rotator cuff syndrome in the shoulder ranked first, intervertebral disc disorders second, and rotator cuff and tendon injuries third. By body parts, the shoulder was most susceptible to chronic WMSDs, followed by the low back, leg, and elbow/lower arm. The chi-square test and logistic regression analysis showed that industry type and size and workers' gender and age were significantly associated with WMSD approval. It can be concluded that the WMSD preventive efforts should focus on low back pain and rotator cuff syndrome by WMSD name, manufacturing by industry, small business by industry size, men by gender, and aged workers by age.

Comparison of LEBA and RULA Based on Postural Load Criteria and Epidemiological Data on Musculoskeletal Disorders.

Various observational methods have been developed and applied in industrial settings with the aim of preventing musculoskeletal disorders (MSDs). This study aimed to compare the Rapid Upper Limb Assessment (RULA), a representative observational method, and the Loading on the Entire Body Assessment (LEBA), a newly developed tool for assessing postural loads and their association with MSDs. The two methods were compared in various categories, including general characteristics, risk levels, postural load criteria, association with MSDs, influencing factors, and inter- and intra-rater reliabilities based on relevant previous studies. The results showed that compared to the RULA, the LEBA was better at evaluating various factors affecting postural loads and assessing musculoskeletal loadings, was better correlated with various postural load criteria, could predict the association with MSDs more accurately, and had higher inter- and intra-rater reliabilities. Based on these comparisons, it seems that the LEBA may be better than the RULA for estimating postural stress and predicting the association with MSDs.

Systematic Comparison of OWAS, RULA, and REBA Based on a Literature Review.

This study aimed to systematically compare three representative observational methods for assessing musculoskeletal loadings and their association with musculoskeletal disorders (MSDs): Ovako Working Posture Analysis System (OWAS), Rapid Upper Limb Assessment (RULA), and Rapid Entire Body Assessment (REBA). The comparison was based on a literature review without time limitations and was conducted on various factors related to observational methods. The comparisons showed that although it has a significant limitation of comprising only two classifications for the leg postures, (1) the RULA is the most frequently used method among the three techniques; (2) many studies adopted the RULA even in evaluation of unstable lower limb postures; (3) the RULA assessed postural loads as higher risk levels in most studies reviewed in this research; (4) the intra- and inter-reliabilities for the RULA were not low; and (5) the risk levels assessed by the RULA were more significantly associated with postural load criteria such as discomfort, MHTs and % capable at the trunk, and MSDs.

Development and evaluation of the novel postural loading on the entire body assessment.

This study aimed to develop and evaluate a novel observational technique for postural Loading on the Entire Body Assessment (LEBA). The technique was developed based on discomfort and epidemiological data from previous research, from which posture classification and scoring systems of representative observational methods were adopted and modified. The LEBA score reflected the effects of posture, external load, motion repetition, static loading, and coupling. The LEBA score for a given posture was obtained by summing the scores for these factors (except coupling) and multiplying the sum by the coupling multiplier. LEBA scores were classified into four action categories, depending on the urgency of corrective actions. Correlation analyses between LEBA scores and postural load criteria yielded confirmative results, with correlation coefficients of >0.60. Application to epidemiological cases of work-related musculoskeletal disorders indicated that LEBA action categories aided in determining whether musculoskeletal disorders were work-related. Acceptable reliability and usability were also observed. Practitioner summary: This study developed and evaluated a novel observational technique for postural loading on the entire body assessment (LEBA), based on perceived discomfort and epidemiological data from previous studies. LEBA scores aided in determining risk levels and urgent indications for more detailed assessments and/or interventions and the work-relatedness of musculoskeletal disorders.

An empirical comparison of OWAS, RULA and REBA based on self-reported discomfort.

This study aimed to compare three observational techniques, the Ovako working posture analysis system (OWAS), rapid upper limb assessment (RULA) and rapid entire body assessment (REBA), based on whole-body discomfort. Fifteen college students participated in the experiment measuring discomfort. Hand height, hand distance and external load were used as independent variables. The results showed that while just the two independent variables of hand height and distance significantly affected the OWAS action category, all three independent variables including external load were significant for the discomfort, RULA grand and REBA scores. The grand score was more linearly correlated to discomfort, compared to the OWAS action category and REBA score. RULA generally assessed postural loads for the postures tested more highly than OWAS and REBA. Based on these findings, it was concluded that, of the three methods, RULA may be the best for estimating postural stress under the conditions of this study.

Prevalence of work-related musculoskeletal disorders in agriculture workers in Korea and preventative interventions.

BACKGROUND: Work-related musculoskeletal disorders (WMSDs) are estimated to be the most common and frequent of all occupational diseases in agriculture in Korea, but the full extent of the problem has yet to be surveyed. OBJECTIVE: This paper presents the results of a survey investigating the extent of WMSDs among self-employed farmers in Korea. It also describes ergonomics based preventive interventions initiated by the Korean government. METHOD: The prevalence of WMSDs was surveyed among 358 farmers using a questionnaire adapted from the Nordic questionnaires, employing three case definitions. RESULTS: The results showed that the overall prevalence rates of WMSDs by case definition 1 (any symptoms), 2 (symptoms with a pain intensity of moderate or greater), and 3 (symptoms with a pain intensity of high or greater) were 97.2%, 83.2%, and 39.7% respectively and that the shoulder, knee and lower back disorder rates were higher than those of other body parts. Compared to the prevalence rates of WMSDs for workers in other industries in Korea as well as USA farmers, the overall rates for farmers in Korea were much higher. The interventions, which adopted a participatory approach involving government, farmers, ergonomics, technical and industrial hygiene experts, showed benefits in terms of work efficiency, safety and farmer satisfaction. CONCLUSIONS: The high WMSD symptom prevalence showed that agriculture is one of the most hazardous industries in Korea, and the Korean government's interventions were effective and successful.

An ergonomic intervention to relieve musculoskeletal symptoms of assembly line workers at an electronic parts manufacturer in Iran.

BACKGROUND: Prolonged, awkward postures among assembly line workers can lead to work-related musculoskeletal disorders (WMSDs). OBJECTIVE: This study determined the prevalence of WMSDs and ergonomic risk factors among assembly line workers at an electronic parts manufacturer, and introduced a low-cost ergonomic intervention. METHODS: Data were gathered by means of a questionnaire. The Rapid Upper Limb Assessment (RULA) technique was used to determine ergonomic risk factors. A low-cost intervention, designed to improve working postures was introduced. RESULTS: Most musculoskeletal symptoms were associated with the lower back (73.6%), wrist/ hands (71.7%), and neck (67.9%). Most (80%) of the working postures analyzed using the RULA were at action levels 3 or 4. CONCLUSIONS: The ergonomic intervention resulted in a significant reduction in posture scores for the neck and trunk. This indicated that the intervention helped to improve workplace ergonomics.

A systemic analysis of South Korea Sewol ferry accident - Striking a balance between learning and accountability.

The South Korea Sewol ferry accident in April 2014 claimed the lives of over 300 passengers and led to criminal charges of 399 personnel concerned including imprisonment of 154 of them as of Oct 2014. Blame and punishment culture can be prevalent in a more hierarchical society like South Korea as shown in the aftermath of this disaster. This study aims to analyse the South Korea ferry accident using Rasmussen's risk management framework and the associated AcciMap technique and to propose recommendations drawn from an AcciMap-based focus group with systems safety experts. The data for the accident analysis were collected mainly from an interim investigation report by the Board of Audit and Inspection of Korea and major South Korean and foreign newspapers. The analysis showed that the accident was attributed to many contributing factors arising from front-line operators, management, regulators and government. It also showed how the multiple factors including economic, social and political pressures and individual workload contributed to the accident and how they affected each other. This AcciMap was presented to 27 safety researchers and experts at 'the legacy of Jens Rasmussen' symposium adjunct to ODAM2014. Their recommendations were captured through a focus group. The four main recommendations include forgive (no blame and punishment on individuals), analyse (socio-technical system-based), learn (from why things do not go wrong) and change (bottom-up safety culture and safety system management). The findings offer important insights into how this type of accident should be understood, analysed and the subsequent response.

Effect of external load at varying hand positions on perceived discomfort.

The purpose of this study was to assess the effect of external load at varying hand positions on discomfort, and to provide a new classification of external load. An experiment was carried out in which 16 postures with an external load of 0, 1.5, 3 kg were tested. The postures were controlled by 2 independent variables of hand distance and hand height. The subjects were instructed to rate their perceived discomfort with magnitude estimation after holding a given posture for 1 min. Analysis of variance (ANOVA) exhibited that the main effects of the 3 independent variables were statistically significant for discomfort. Discomfort increased linearly with external load and hand distance. Hand height showed a quadratic relation with discomfort, which exhibited a slightly different trend from hand distance and external load. Based on the results, a new classification of external load was proposed with 3 classes grouped by perceived discomfort.

Postural loading assessment in assembly workers of an Iranian telecommunication manufacturing company.

BACKGROUND: Changes in industries and work practices have coincided with work-related musculoskeletal disorders (MSDs). This study was conducted to determine the prevalence of MSDs and to assess postural loading in assembly workers of an Iranian telecommunication manufacturing company. METHODS: Data were collected from 193 randomly selected workers in 4 units of the company. The Nordic musculoskeletal disorders questionnaire and the UBC ergonomic checklist were used as data collection tools. Loading on the upper body assessment (LUBA) was used to assess postural loading. RESULTS: Lower back symptoms were the most prevalent problems among the workers (67.9%). LUBA showed that most assembly workers (94.3%) had experienced considerable and high postural loading (postural load index, PLI > 5). Regression analyses revealed that lighting, rotation, contact stress, repetition, gender and age were factors associated with symptoms. CONCLUSION: Work-related MSDs occurred at a high rate among workers. Postural loading requires consideration. Any ergonomic intervention should focus on eliminating ergonomic factors associated with symptoms.

Relationships between subjective and objective measures in assessing postural stresses.

The purpose of this study is to investigate the relationships between subjective measures of discomfort and objective measures related to the assessment of postural stresses based on literature survey. Objective measures included posture holding time, maximum holding time (MHT), torque at joints, lifting index (LI) and compressive force (CF) at L5/S1. The major relationships identified in this literature survey were the following: 1) postural discomfort linearly increased with increasing holding time, and holding force, 2) whole body discomfort was inversely linearly proportional to the MHT, 3) body-part discomfort was related to objective measures such as torque at the relevant joint, 4) discomfort was strongly linearly related to LIs and CFs, and 5) the discomfort measured with the magnitude estimation was linearly related to that measured with Borg CR10. Thus, it is thought that discomfort might be used as a measure for quantifying postural stresses.

A comparison of three observational techniques for assessing postural loads in industry.

This study aims to compare 3 observational techniques for assessing postural load, namely, OWAS, RULA, and REBA. The comparison was based on the evaluation results generated by the classification techniques using 301 working postures. All postures were sampled from the iron and steel, electronics, automotive, and chemical industries, and a general hospital. While only about 21% of the 301 postures were classified at the action category/level 3 or 4 by both OWAS and REBA, about 56% of the postures were classified into action level 3 or 4 by RULA. The inter-method reliability for postural load category between OWAS and RULA was just 29.2%, and the reliability between RULA and REBA was 48.2%. These results showed that compared to RULA, OWAS, and REBA generally underestimated postural loads for the analyzed postures, irrespective of industry, work type, and whether or not the body postures were in a balanced state.

Quantitative postural load assessment for whole body manual tasks based on perceived discomfort.

Many Korean workers are exposed to repetitive manual tasks or prolonged poor working postures that are closely related to back pain or symptoms of musculoskeletal disorders. Workers engage in tasks that require not only handling of heavy materials, but also assuming prolonged or repetitive non-neutral work postures. Poor work postures that have been frequently observed in the workplaces of shipbuilding shops, manufacturing plants, automobile assembly lines and farms often require prolonged squatting, repetitive arm raising and wrist flexion and simultaneous trunk flexion and lateral bending. In most manufacturing industries, workers have to assume improper work postures repetitively, several hundreds of times per day depending on daily production rate. A series of psychophysical laboratory experiments were conducted to evaluate the postural load at various joints. A postural load assessment system was then developed based on a macro-postural classification scheme. The classification scheme was constructed based on perceived discomfort for various joint motions as well as previous research outcomes. On the basis of the perceived discomfort, postural stress levels for the postures at individual joints were also defined by a ratio scale to the standing neutral posture. Laboratory experiments simulating automobile assembly tasks were carried out to investigate the relationship between body-joint and whole-body discomfort. Results showed a linear relationship between the two types of discomfort, with the shoulder and low back postures being the dominant factor in determining the whole body postural stresses. The proposed method was implemented into a computer software program in order to automate the procedure of analysing postural load and to enhance usability and practical applicability.

Joint angles of isocomfort for female subjects based on the psychophysical scaling of static standing postures.

This study investigated the joint angles of isocomfort (JAIs) for females based on the psychophysical scalings for static standing postures held for 60 s, which were obtained in a laboratory experiment. The subjects were instructed to rate their comfort levels for varyious joint postures by using the free modulus method of magnitude estimation. The comfort scores for the joint postures and the related verbal comfort categories were subjected to regression analysis in order to obtain the JAIs corresponding to verbal categories. The results showed that the JAIs were significantly different depending upon the joints and joint postures investigated (p < 0.01), and that the JAIs for female subjects were significantly different than those for males (p < 0.01) which had been obtained in an earlier study (Kee and Karwowski, 2001). Compared to the corresponding range of joint motion values, the JAIs for hip postures were the smallest of all joint postures dealt with in this study, while those for the neck were the largest of all postures, which means that hip postures are more stressful than any other joint posture. Based on this study, it is recommended that the gender-based JAI values should be used for design applications.

Ranking systems for evaluation of joint and joint motion stressfulness based on perceived discomforts.

This study aims to develop ranking systems for evaluation of the stressfulness of joints and joint motions based on perceived discomforts measured through an experiment. Twenty healthy male subjects participated in the experiment, where discomforts for varying joint motions in the sitting and standing postures were measured using the magnitude estimation. The results showed that the perceived discomforts were affected by the type of joint motions, size of joint motions, and joints. The joints and joint motions were classified into several distinct classes according to perceived stresses. Three ranking systems based on the perceived discomforts were developed, including classification by the joint motions and joints, by types of joint motions, and by the joints only. The ranking systems revealed that while hip and back motions exhibited higher discomfort ratings than any other joint motion, elbow motions were the least stressful of all joint motions. The ranking systems can be used as a valuable design guideline when ergonomically designing or evaluating workplaces, or as a helpful tool for understanding adverse effects of poor working postures.

A method for analytically generating three-dimensional isocomfort workspace based on perceived discomfort.

The purpose of this study was to develop a new method for analytically generating three-dimensional isocomfort workspace for the upper extremities using the robot kinematics. Subjective perceived discomfort scores in varying postures for manipulating four types of controls were used. Fifteen healthy male subjects participated in the experiment. The subjects were asked to hold the given postures manipulating controls for 60 s in the seated position, and to rate their perceived discomfort during the following rest of 60 s using the magnitude estimation. Postures of the upper extremities set by shoulder and elbow motions, types of controls, and left right hand were selected as experimental variables, in which the L32 orthogonal array was adopted. The results showed that shoulder flexion and adduction-abduction, elbow flexion, and types of controls significantly affected perceived discomfort for postures operating controls, but hand used for operating controls did not. Depending upon the types of controls, four regression models predicting perceived discomfort were presented. Using the models, a sweeping algorithm to generate three-dimensional isocomfort workspace was developed, in which the robot kinematics was employed to describe the translational relationships between the upper arm and the lower arm/hand. It is expected that the isocomfort workspace can be used as a valuable design guideline when ergonomically designing three-dimensional workplaces.

Analytically derived three-dimensional reach volumes based on multijoint movements.

The main objectives of this study were to quantify the range of reaching for the upper body with eight degrees of freedom (the trunk and shoulder, elbow, and wrist joints) and the lower body with six degrees of freedom (the hip, knee, and ankle joints). A sweeping algorithm that included trunk and foot motions was used to generate the analytical total reach volume of the human body for young men. Three types of reach volume--unconstrained arm reach, shoulder-restricted arm reach, and foot reach--were generated depending on the joint involved in reach activities. The robot kinematics methodology was employed to represent the human body as a multilink system, which was needed for calculating three-dimensional coordinates of the involved joints. The statistical test results showed that the total reach volume analytically generated in this study was nearly identical to that obtained from the direct human body measurements. Applications of this research include generating the human body's reach volume for the purpose of designing work spaces and products.