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Ergonomic exposure is one of the important causes of work-related musculoskeletal disorders (WMSDs). Accurate measurement and evaluation of ergonomic exposure level and implementation of ergonomic intervention are of great significance to the prevention and control of WMSDs. Ergonomic exposure can be divided into external exposure and internal exposure, and its evaluation methods include subjective judgment method, systematic observation method, and direct measurement method. This paper summarized the internal exposure assessment methods based on musculoskeletal dynamics and biomarkers, introduced the overall design concept of ergonomic exposure assessment system, used the Ergonomic Assessment Worksheet (EAWS) as an example, and discussed the development trend of automation, intelligence, and compounding of ergonomic exposure assessment methods and the factors considered in the selection of ergonomic exposure assessment methods.
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Background Work-related musculoskeletal diseases (WMSDs) occur in a variety of occupational populations. Because of their various discomfort and serious disease burden, they have become an important issue worthy of attention in the field of occupational health. The prevention and control of WMSDs is one of the public health problems to be solved. Objective To evaluate the intervention effect on WMSDs among assembly workers in a railway vehicle manufacturing enterprise, so as to provide scientific basis for the prevention and control of WMSDs. Methods A total of 250 assembly workers in a railway vehicle manufacturing enterprise were selected using convenience sampling from August to December 2017. The Chinese Musculoskeletal Questionnaire was used for epidemiological investigation, and the Ergonomic Checkpoints was used for ergonomic inspection and worker interview. According to the above survey results, a six-month intervention plan including stepladder improvement and ergonomics training were implemented in the assembly workshop from September 2018 to February 2019. The intervention effects including the awareness of WMSDs, the exposure level of ergonomic load, and the occurrence of WMSDs symptoms were evaluated with relevant cross-sectional survey results before and after the intervention. The scores of WMSDs symptom intensity, symptom duration, and symptom frequency from low to high were 0-10, 1-4, and 1-5, respectively. Results After the intervention, the awareness rates of assembly workers on WMSDs types, affected body sites, influencing factors, preventive measures, and symptoms all increased from 52.3%, 51.9%, 25.5%, 19.1%, and 51.5% to 68.5%, 61.3%, 48.1%, 40.9%, and 61.3%, respectively (P<0.05). After the intervention, the proportion of assembly workers who "often" bend their head backwards frequently decreased from 34.6% to 21.8%, the proportion who "often" keep their trunk backward for a long time decreased from 26.6% to 15.0%, and the proportion who "never" raise their arms frequently increased from 3.4% to 9.0% (P<0.05). After the intervention, the scores of WMSDs symptom intensity in neck, shoulders, upper back, low back, elbows, hands/wrists, hips/thighs, knees, and ankles/feet all decreased, and the medians were mostly decreased from 6 to 3 (P<0.05); the scores of WMSDs symptom duration only decreased in neck (P<0.05) and there was no significant difference in the other body sites before and after the intervention; the median scores of WMSDs symptom frequency in low back, hands/wrists, and hips/thighs decreased from 3 to 2 (P<0.05). Conclusion The six-month intervention of stepladder improvement and ergonomics training among assembly workers in a railway vehicle manufacturing enterprise can improve workers' awareness of WMSDs, and reduce the exposure frequency of awkward postures and the intensity, duration, and frequency of WMSDs symptoms.
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Background China's manufacturing industry is still labor-intensive, and assembly employees in manufacturing industry are facing a great risk of work-related musculoskeletal disorders (WMSDs). Objective To investigate and analyze the prevalence and distribution of WMSDs among assembly workers in manufacturing enterprises and explore the relationship between WMSDs and ergonomic exposure factors such as posture load and mental load. Methods From July to September 2017, by convenient sampling, a cross-sectional survey was conducted to select 670 workers engaged in electronic accessories assembly and railway vehicle manufacturing in three manufacturing enterprises in two cities in northern China as the research participants. The posture load assessment was based on the Chinese Musculoskeletal Questionnaire independently developed by our research group. The mental load assessment was based on a revised Chinese version of the Subjective Workload Assessment Technique. An unconditional logistic regression model was used to explore the relationship between ergonomic exposure and WMSDs. Results The overall prevalence rate of WMSDs was 39.6% (265/670) with 43.8% in males and 25.2% in females; the highest prevalence rate was 47.7% in the group aged 40 years and over. The prevalence rate of WMSDs in the electronic accessories assembly workers was 16.9%, that in the railway vehicle manufacturing workers was 57.3%, and the difference was statistically significant (\begin{document}$ {\chi
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Background The prevalence rate of work-related musculoskeletal disorders (WMSDs) among manufacturing workers is relatively high and has been widely concerned. However, research on the prevalence and risk factors of multi-site WMSDs is still insufficient. Objective To explore the prevalence and risk factors of multi-site WMSDs of assembly workers in four manufacturing enterprises. Methods The "Chinese Musculoskeletal Questionnaire" was used to conduct a cross-sectional survey among 1401 assembly workers selected by convenient sampling in four manufacturing enterprises, and their demographic characteristics, the prevalence of WMSDs in various body parts, and the information about biomechanical factors, work organizations, work environment, and psychosocial factor exposure were collected. The prevalence of WMSDs and multi-site WMSDs were estimated, Pearson χ2 test was used for univariate analysis of multi-site WMSDs risk factors, and logistic regression was used for multi-factor analysis. Results The total prevalence rate of WMSDs was 54.9% (769/1 401). The top three affected sites were neck (41.4%), shoulders (30.7%), and wrist/hand (25.1%). The prevalence rate of multi-site WMSDs was 41.9% (587/1 401). The prevalence rates of multi-site WMSDs in railway vehicle assembly and riveting workers were higher than those in electronic parts processing and glass manufacturing workers (P<0.001). The results of logistic regression analysis showed that individual factors such as female (OR=2.09, 95%CI: 1.48−2.97) and drinking (OR=1.52, 95%CI: 1.05−2.18), biomechanics factors such as keeping head down for a long time (OR=1.37, 95%CI: 1.22–1.53), keeping bending frequently (OR=1.18, 95%CI: 1.03–1.34), and keeping arms up for a long time (OR=1.25, 95%CI: 1.10–1.41), work organizational factors such as electronic parts processing, railway vehicle assembly, and riveting (OR values were 3.23, 5.70, and 13.83, respectively), environmental factors such as temperature a little cold (OR=4.84, 95%CI: 1.90–12.37), noise seriously affecting work (OR=2.25, 95%CI: 1.23–4.11), and psychosocial factors such as high job demands (OR=1.47, 95%CI: 1.04–2.08), fatigue after work (OR=1.92−2.61) were risk factors of multi-site WMSDs. Conclusion The prevalence rate of multi-site WMSDs in assembly workers is high, and the main influencing factors include individual factors, awkward work postures, environmental factors, and psychosocial factors.
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OBJECTIVE: To analyze the prevalence of work-related musculoskeletal disorders(WMSDs) among dentists and explore its influencing factors. METHODS: A total of 455 dentists from 9 medical organizations of Beijing and Fuzhou cities were selected as study subjects. The disease occurrence and mental workload were investigated using China Musculoskeletal Disorders Questionnaire and Subjective Workload Assessment Technique. The influencing factors of WMSDs were analyzed by multivariate logistic regression. RESULTS: The total prevalence of WMSDs was 58.9%(268/455) among dentists. The top three body parts of WMSDs were neck(41.5%), shoulder(33.6%) and lower back(28.1%). The median of mental workload score was 58. Multivariate logistic regression analysis results indicated that female dentists showed a higher risk than male dentists(P<0.01) after excluding the influence of confounding factors. The higher the length of service, the higher their risk for WMSDs(P<0.01). Dentists who hold their heads sideways for long time, bent frequently, and use vibrating tools had relatively high risks of developing WMSDs(P<0.01). Dentists who use armchairs had a relatively low risk of WMSDs(P<0.01). There was no correlation between the mental workload and the prevalence of WMSDs in dentists(P>0.05). CONCLUSION: The prevalence of WMSDs among dentists is high. Individual factors, awkward posture and using vibrating tools are risk factors of WMSDs among dentists.Armchair use can help reduce the risk of WMSDs.
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OBJECTIVE: To investigate the prevalence of lower extremity work-related musculoskeletal disorders(WMSDs) among manufacturing workers, and to explore the association of lower extremity WMSDs and different types of working. METHODS: A total of 7 908 workers were selected as study subjects from four manufacturing factories in China using the cluster sampling method. The Musculoskeletal Disorders Investigating Questionnaire was adopted to investigate the prevalence of lower extremity WMSDs and the distribution of types of working. The prevalence ratio(PR) of WMSDs, calculated by log-binomial model, was used to estimate the correlation of WMSDs in different parts of lower extremity. The multi-factor logistic regression was used to analyze the association of lower extremity WMSDs and different types of working. RESULTS: The total annual prevalence of lower extremity WMSDs was 41.0%(3 241/7 908) among manufacturing workers. The annual prevalence of WMSDs of different parts in lower extremity from high to low were knee(29.5%), ankle/foot(23.9%) and hip/thigh(16.7%). The correlation of WMSDs of the three parts in lower extremity was close, and the range of PR values was 2.21-3.88. The result of logistic regression analysis showed that the workers who frequently sat for long periods had higher risk of lower extremity WMSDs than those who never/rarely sat for long periods(odds ratio=1.39, P<0.01). The higher the frequency of standing, kneeling/squatting for long periods, carrying heavy loads ≥5 kg and driving, the higher the risk of lower extremity WMSDs(the odds ratios were 1.33, 1.41, 1.16 and 1.12, respectively, P<0.01). CONCLUSION: The prevalence of lower extremity WMSDs was relatively high among manufacturing workers. There is a dose-effect relationship between the types of working and lower extremity WMSDs.
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OBJECTIVE: To compile the Chinese Musculoskeletal Questionnaire(CMQ) and test its reliability and validity. METHODS: The initial CMQ was formed through studying literatures, interviewing professional workers who have work-related musculoskeletal disorders(WMSDs) and investigation with occupational health and ergonomics experts. Then, 436 and 443 manufacturing workers were selected as prediction and verification samples respectively by convensence sampling method. The reliability and validity of the CMQ were tested by item analysis, exploratory factor analysis and confirmatory factor analysis. RESULTS: i) The CMQ composed of 48 items with item analysis. ii) Nine common factors of CMQ were extracted using exploratory factor analysis, which explained 70.721% of WMSDs variance. iii) The results of confirmatory factor analysis showed that the ratio of chi-square to degree of freedom was 3.380, the comparative fit index was 0.781, the Tucker-Lewis index was 0.764, the root mean square error of approximation was 0.073, and the standardized root mean square residual was 0.068. iv) The results showed that the item reliabilities of the 9 common factors of CMQ such as upper and lower limbs posture load, neck posture load, back posture load, job demand, social support, job control, job environment, job system and job facilities were 0.205-0.841, the composite reliabilities were 0.545-0.894, and the convergence efficiencies were 0.377-0.834. The correlation coefficients between the common factors were less than its square root of the convergence validities. CONCLUSION: The CMQ has good reliability and validity, and is a reliable and effective tool for evaluating WMSDs.
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OBJECTIVE: To explore the occurrence pattern of work-related musculoskeletal disorders( WMSDs) in electronic parts processing workers. METHODS: A total of 498 workers from an electronic parts processing factory were selected as study subjects by judgement sampling method. The prevalence of WMSDs in the past 1 year was investigated by using the China Musculoskeletal Questionnaire. The potential category model was used to classify the categories of WMSDs. RESULTS: The incidence of WMSDs in the past 1 year was 46. 8%( 233/498). Among them,the incidence of WMSDs involving only one site was 13. 1%( 65/498),and those involving at least 2 sites were 33. 7%( 168/498). The multi-site WMSDs were about 6-58 times of the single-site WMSDs. According to potential category analysis,the occurrence patterns of WMSDs were divided into three categories: i) cervical and shoulder occurrence group( 135 persons,27. 1%); ii) all parts group( 31 persons,6. 2%); iii) few or no site group( 332 persons,66. 7%). CONCLUSION: The occurrence of multi-site WMSDs in electronic parts processing workers were more common than the single-site. Analysis of potential category can be used to explore the occurrence pattern of WMSDs.
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OBJECTIVE: To analyze the prevalence and influencing factors of multisite work-related musculoskeletal disorders(WMSDs) of workers in a railway vehicle manufacturing enterprise. METHODS: A total of 366 male workers in the assembly and riveting workshop of a railway vehicle manufacturing enterprise were selected as the research subjects using the cluster sampling method. The Chinese Musculoskeletal Questionnaire was used to investigate the prevalence of multiple sites of WMSDs. Multiple logistic regression analysis was used to analyze the influencing factors. RESULTS: The total prevalence of WMSDs was 56.3%(206/366). The prevalence of WMSDs in all parts from high to low was as follows: lower back(35.5%), hand and wrist(27.6%), neck(23.2%), shoulder(21.0%), knee(19.9%), upper back(18.6%), hip and leg(18.0%), ankle/foot(15.8%) and elbow(12.3%)(P<0.01). The total prevalence of multisite WMSDs was 38.0%(139/366). The prevalence of WMSDs in different numbers of parts from high to low was as follows: 6 or more parts(12.0%), 2 parts(10.7%), 3 parts(6.6%), 5 parts(5.5%) and 4 parts(3.3%)(P<0.01). Multiple logistic regression analysis results showed that the overweight and obese workers had higher risk of multi site WMSDs than those with normal body mass index(P<0.05).Those with long-term low heads, frequent bending, long bending of the elbows, and higher frequency of work requirements, and less frequently communicated with the leader had higher risk of multi site WMSDs(P<0.05). CONCLUSION: The prevalence of multisite WMSDs in railway vehicle manufacturing enterprise is relatively high. The influencing factors include individual factors, adverse ergonomic factors and psychosocial factors.