Objective:To investigate the incidence of shoulder work-related musculoskeletal disorders (WMSDs) among occupational population in China, and to explore their intrinsic association with personal and work-related factors.Methods:In April 2024, 73497 valid questionnaires of the Chinese version of the Musculoskeletal Disorders Electronic Questionnaire were retrospectively analyzed from June 2018 to December 2023 in 22 provinces and 29 key industries in China, and the general information, occurrence of WMSDs and related risk factors of key occupational populations in different regions in China were collected. By using Chi-square test and confirmatory factor analysis, the relationship between shoulder fatigue and pain in key occupational groups and individual factors, work type, work posture and work organization was discussed, and the internal relationship was analyzed based on structural equation model.Results:Higher incidence of shoulder fatigue and pain were associated with female, lack of physical exercise, uncomfortable working posture and neck leaning forward ( P<0.05). Structural equation model analysis showed that work type, work posture and work organization were strongly correlated ( r=0.58, 0.55). Work organization and work type were strongly correlated with shoulder fatigue ( r=0.65) and moderately correlated with shoulder fatigue ( r=0.21). Shoulder fatigue was moderately associated with shoulder pain ( r=0.40). Individual factors, work type, work posture and shoulder fatigue could directly affect shoulder pain ( OR=0.07, -0.09, 0.17 and 0.40), and work type and work posture could also indirectly affect shoulder pain through shoulder fatigue ( OR=0.08, 0.03). Work organization only indirectly affected shoulder pain through shoulder fatigue ( OR=0.26) . Conclusion:The main influencing factor of shoulder pain is shoulder fatigue, followed by work posture and individual factors. Structural equation model can better reflect the complex relationship between work type, work posture and work organization and shoulder WMSDs. Improving work posture and work organization may be an effective way to control the influence of shoulder fatigue on shoulder pain.

Objective:To explore the structural equation model to explore the levels of work-related musculoskeletal disorders (WMSDs) and various risk factors in the feet and ankle of China's occupational population, providing scientific basis for for preventing WMSDs in feet and ankles.Methods:Data of 73497 national occupational epidemiological cases were selected from June 2018 to December 2023 used the Chinese version of the Electronic Questionnaire on Musculoskeletal Disorders. The adverse ergonomic factors and their source classification standard and confirmatory factor analysis were used to investigate foot and ankle WMSDs and their related risk factors (including individual factors, work organization, work posture, work type, fatigue, etc.) in key occupational groups in China, and structural equation model hypothesis, fitting, verification, and path and intermediary effect analysis were carried out. The model fit evaluation indexes included Chi-square specific degrees of freedom ( χ2/ df), gauge fit index (NFI), Tucker Lewis index (TLI), goodness of Fit index (GFI), adjusted Goodness of Fit index (AGFI) and approximate root mean square error (RMSEA) . Results:A total of 73497 occupational workers were surveyed, with local muscle fatigue and WMSDs incidence rates in the feet and ankles being 17.17% and 12.06%, respectively. The fitting index of the adjusted structural equation model basically meets the standard (GFI=1, AGFI=1, RMESA=0.042, NFI=0.716, TLI=0.663). The top three factors affecting feet and ankle WMSDs are feet and ankle muscle fatigue, work type, and work organization, with standardized path coefficients of 0.221, 0.105, and 0.095, respectively. The top two factors affecting feet and ankle muscle fatigue are work organization and work type, with standardized path coefficients of 0.548 and 0.383, respectively. Feet and ankle muscle fatigue, work type, work organization, and work posture have a direct effect on feet and ankle WMSDs, with effect values of 0.221, 0.105, 0.095, and 0.077, respectively. The organization and type of work can also have indirect effects through feet and ankle muscle fatigue, with effect values of 0.121 and 0.084, respectively.Conclusion:Feet and ankle muscle fatigue has a direct impact on WMSDs, and plays a mediating role between ankle and ankle WMSDs caused by work organization and work type. Feet and ankle muscle fatigue is an important pathway leading to feet and ankle WMSDs. It is recommended that employers and managers detect job fatigue early and take corresponding prevention and intervention measures, which can play a key role in preventing feet and ankle WMSDs.

Objective:To explore the structural relationship between WMSDs in the upper limbs and various risk factors in the occupational population in China, based on a large sample epidemiological survey and structural equation analysis, and to establish a structural equation model, so as to lay a foundation for the prevention and control of such diseases.Methods:The Chinese version of the Musculoskeletal Disorders Electronic Questionnaire was used to conduct a nationwide survey on the prevalence of WMSDs in the upper extremity. Six factors related to WMSDs in the upper extremity were extracted by the classification standard of adverse ergonomic factors and their source and confirmatory factor analysis, including work organization, work type, upper extremity work posture, individual factors, upper extremity fatigue and upper extremity WMSDs. The structural equation analysis was carried out and the structural equation model was established.Results:The incidence of WMSDs and fatigue in the upper limbs was 24.44% and 43.76%, respectively. The adjusted structural equation model fitting indicators were generally up to the standard (GFI=1.000, AGFI=1.000, RMSEA=0.043, NFI=0.808, TLI=0.784) . The four exogenous latent variables of work organization, work type, upper limb work posture and individual factors were correlated. There was a strong positive correlation between job type and upper limb work posture ( r=0.865) , a moderate positive correlation between work organization and job type and upper limb work posture ( r=0.570, 0.490) , and a weak negative correlation between individual factors and the other three exogenous latent variables. Upper limb work posture and individual factors had direct effects on upper limb WMSDs, and the effect coefficients were 0.10 and 0.06, respectively. Upper limb fatigue played a mediating role between work organization, work type, upper limb work posture and upper limb WMSDs. The effect coefficient was 0.46, and the composition ratios of indirect effects were 100.0%, 100.0%, and 38.3%, respectively. The direct path effect of upper limb work posture, individual factors and upper limb WMSDs was weaker than the mediating path through upper limb fatigue. Conclusion:When carrying out the prevention and control of upper limbWMSDs, it is necessary to comprehensively consider the pathogenesis path of upper limb muscle fatigue and upper limb WMSDs caused by work organization, work type, and upper limb work posture, so as to provide theoretical reference for improving the prevention and control level of such diseases.

Objective:To analyze the impact of occupational health management assistance for small and micro enterprises in Suzhou on employers, exploring the assistance model for occupational health management in small and micro enterprises.Methods:From 2020 to 2022, a total of 318 small and micro enterprises with serious occupational disease hazards, weak occupational health management, and strong subjective improvement were selected as assistance objects annually by means of territorial recommendation and active registration of employers. The basic information of the enterprise and the status of occupational health management were obtained by means of questionnaire survey, archives review, workplace field investigation and occupational disease hazard factors detection. Pearson χ2 test was used to analyze the changes of occupational health management before and after helping enterprises. Results:The small and micro enterprises receiving assistance were mainly private enterprises (51.26%, 163/318) and limited liability companies (27.99%, 89/318). The occupational health training rates for enterprise leaders, management personnel, and workers increased from 77.36% (246/318), 82.08% (261/318) and 72.44% (4554/6287) before assistance to 90.57% (288/318), 95.28% (303/318) and 94.40% (5905/6255), the differences were statistically significant ( χ2=20.60, 27.63, 1092.67, all P<0.001). After the assistance, the distribution and wearing of personal protective equipment for workers, the detection of occupational hazard factors in the workplace and occupational health examination by enterprises increased by 3.34%, 18.39%, 13.21% and 15.10%, respectively. In terms of occupational health management, the comprehensive establishment rate of occupational health management system increased from 21.70% (69/318) before assistance to 64.47% (205/318). Compared with before assistance, the comprehensive notification rate/setting rate of warning signs and notification cards, labor contracts for occupational disease hazard positions, occupational health bulletin boards, and occupational health examination results were significantly increased after assistance ( χ2=120.08, 77.40, 149.18, 86.76, all P<0.001) . Conclusion:Suzhou adopts a model led by the health administrative department and supported by technical support from service institutions to assist small and micro enterprises, resulting in a significant improvement in the occupational health management level of small and micro enterprises.

Objective:To construct a rat model of osteoporosis induced by lead exposure, simulate the effects of lead exposure on the skeletal system of rats, and provide reliable basic data support for subsequent research.Methods:In July 2021, 40 eight-week-old SPF-grade SD rats were selected and randomly divided into 5 experimental groups according to body weight stratification randomization: blank control group, positive control group, low-dose, medium-dose and high-dose groups, with 8 rats in each group. Continuous intragastric administration (1 ml/100 g) for 60 days was performed respectively with ultrapure water, 0.4 g/L prednisone acetate, 2.0 g/L, 4.0 g/L, and 8.0 g/L lead acetate (PbAc). During the experiment, the general condition and weight changes of the rats were recorded in detail. After model establishment, biological samples of rats were collected. The levels of blood lead, serum calcium, phosphorus, tartrate-resistant acid phosphatase (TRAP) and bone alkaline phosphatase (BALP) in rats were determined. Additionally, micro-computed tomography (Micro-CT) was used to perform 3D reconstruction of the rat femurs and examine ultrastructural changes. One-way analysis of variance was used to compare multiple groups of data, and LSD or SNK methods were used for pairwise comparisons between groups.Results:During the experiment, there were no obvious abnormalities in feeding and drinking, behavioral activities, and fur color of rats in each group, and the body weight maintained normal and gentle growth. Compared with the blank control group, the levels of blood lead, serum calcium, phosphorus, TRAP and BALP in each dose group of PbAc were significantly increased ( P<0.05), while the femoral bone mineral density, bone volume/total volume and trabecular thickness were significantly decreased ( P<0.05). Compared with the blank control group, the trabecular separation of the femur in the high-dose group was significantly increased, and the trabecular number was significantly decreased ( P<0.05). Compared with the blank control group, the bone mass loss of the femur in each dose group of PbAc was severe in rats. Conclusion:PbAc can cause osteoporosis in rats, and osteoporosis assessment indicators such as bone resorption and bone formation markers in rats, femoral bone mineral density and its ultrastructure can all evaluate the success of model construction.

Objective:To analyze the impact of occupational health management assistance for small and micro enterprises in Suzhou on employers, exploring the assistance model for occupational health management in small and micro enterprises.Methods:From 2020 to 2022, a total of 318 small and micro enterprises with serious occupational disease hazards, weak occupational health management, and strong subjective improvement were selected as assistance objects annually by means of territorial recommendation and active registration of employers. The basic information of the enterprise and the status of occupational health management were obtained by means of questionnaire survey, archives review, workplace field investigation and occupational disease hazard factors detection. Pearson χ2 test was used to analyze the changes of occupational health management before and after helping enterprises. Results:The small and micro enterprises receiving assistance were mainly private enterprises (51.26%, 163/318) and limited liability companies (27.99%, 89/318). The occupational health training rates for enterprise leaders, management personnel, and workers increased from 77.36% (246/318), 82.08% (261/318) and 72.44% (4554/6287) before assistance to 90.57% (288/318), 95.28% (303/318) and 94.40% (5905/6255), the differences were statistically significant ( χ2=20.60, 27.63, 1092.67, all P<0.001). After the assistance, the distribution and wearing of personal protective equipment for workers, the detection of occupational hazard factors in the workplace and occupational health examination by enterprises increased by 3.34%, 18.39%, 13.21% and 15.10%, respectively. In terms of occupational health management, the comprehensive establishment rate of occupational health management system increased from 21.70% (69/318) before assistance to 64.47% (205/318). Compared with before assistance, the comprehensive notification rate/setting rate of warning signs and notification cards, labor contracts for occupational disease hazard positions, occupational health bulletin boards, and occupational health examination results were significantly increased after assistance ( χ2=120.08, 77.40, 149.18, 86.76, all P<0.001) . Conclusion:Suzhou adopts a model led by the health administrative department and supported by technical support from service institutions to assist small and micro enterprises, resulting in a significant improvement in the occupational health management level of small and micro enterprises.

Objective:To construct a rat model of osteoporosis induced by lead exposure, simulate the effects of lead exposure on the skeletal system of rats, and provide reliable basic data support for subsequent research.Methods:In July 2021, 40 eight-week-old SPF-grade SD rats were selected and randomly divided into 5 experimental groups according to body weight stratification randomization: blank control group, positive control group, low-dose, medium-dose and high-dose groups, with 8 rats in each group. Continuous intragastric administration (1 ml/100 g) for 60 days was performed respectively with ultrapure water, 0.4 g/L prednisone acetate, 2.0 g/L, 4.0 g/L, and 8.0 g/L lead acetate (PbAc). During the experiment, the general condition and weight changes of the rats were recorded in detail. After model establishment, biological samples of rats were collected. The levels of blood lead, serum calcium, phosphorus, tartrate-resistant acid phosphatase (TRAP) and bone alkaline phosphatase (BALP) in rats were determined. Additionally, micro-computed tomography (Micro-CT) was used to perform 3D reconstruction of the rat femurs and examine ultrastructural changes. One-way analysis of variance was used to compare multiple groups of data, and LSD or SNK methods were used for pairwise comparisons between groups.Results:During the experiment, there were no obvious abnormalities in feeding and drinking, behavioral activities, and fur color of rats in each group, and the body weight maintained normal and gentle growth. Compared with the blank control group, the levels of blood lead, serum calcium, phosphorus, TRAP and BALP in each dose group of PbAc were significantly increased ( P<0.05), while the femoral bone mineral density, bone volume/total volume and trabecular thickness were significantly decreased ( P<0.05). Compared with the blank control group, the trabecular separation of the femur in the high-dose group was significantly increased, and the trabecular number was significantly decreased ( P<0.05). Compared with the blank control group, the bone mass loss of the femur in each dose group of PbAc was severe in rats. Conclusion:PbAc can cause osteoporosis in rats, and osteoporosis assessment indicators such as bone resorption and bone formation markers in rats, femoral bone mineral density and its ultrastructure can all evaluate the success of model construction.

Objective:To investigate the incidence of shoulder work-related musculoskeletal disorders (WMSDs) among occupational population in China, and to explore their intrinsic association with personal and work-related factors.Methods:In April 2024, 73497 valid questionnaires of the Chinese version of the Musculoskeletal Disorders Electronic Questionnaire were retrospectively analyzed from June 2018 to December 2023 in 22 provinces and 29 key industries in China, and the general information, occurrence of WMSDs and related risk factors of key occupational populations in different regions in China were collected. By using Chi-square test and confirmatory factor analysis, the relationship between shoulder fatigue and pain in key occupational groups and individual factors, work type, work posture and work organization was discussed, and the internal relationship was analyzed based on structural equation model.Results:Higher incidence of shoulder fatigue and pain were associated with female, lack of physical exercise, uncomfortable working posture and neck leaning forward ( P<0.05). Structural equation model analysis showed that work type, work posture and work organization were strongly correlated ( r=0.58, 0.55). Work organization and work type were strongly correlated with shoulder fatigue ( r=0.65) and moderately correlated with shoulder fatigue ( r=0.21). Shoulder fatigue was moderately associated with shoulder pain ( r=0.40). Individual factors, work type, work posture and shoulder fatigue could directly affect shoulder pain ( OR=0.07, -0.09, 0.17 and 0.40), and work type and work posture could also indirectly affect shoulder pain through shoulder fatigue ( OR=0.08, 0.03). Work organization only indirectly affected shoulder pain through shoulder fatigue ( OR=0.26) . Conclusion:The main influencing factor of shoulder pain is shoulder fatigue, followed by work posture and individual factors. Structural equation model can better reflect the complex relationship between work type, work posture and work organization and shoulder WMSDs. Improving work posture and work organization may be an effective way to control the influence of shoulder fatigue on shoulder pain.

Objective:To explore the structural equation model to explore the levels of work-related musculoskeletal disorders (WMSDs) and various risk factors in the feet and ankle of China's occupational population, providing scientific basis for for preventing WMSDs in feet and ankles.Methods:Data of 73497 national occupational epidemiological cases were selected from June 2018 to December 2023 used the Chinese version of the Electronic Questionnaire on Musculoskeletal Disorders. The adverse ergonomic factors and their source classification standard and confirmatory factor analysis were used to investigate foot and ankle WMSDs and their related risk factors (including individual factors, work organization, work posture, work type, fatigue, etc.) in key occupational groups in China, and structural equation model hypothesis, fitting, verification, and path and intermediary effect analysis were carried out. The model fit evaluation indexes included Chi-square specific degrees of freedom ( χ2/ df), gauge fit index (NFI), Tucker Lewis index (TLI), goodness of Fit index (GFI), adjusted Goodness of Fit index (AGFI) and approximate root mean square error (RMSEA) . Results:A total of 73497 occupational workers were surveyed, with local muscle fatigue and WMSDs incidence rates in the feet and ankles being 17.17% and 12.06%, respectively. The fitting index of the adjusted structural equation model basically meets the standard (GFI=1, AGFI=1, RMESA=0.042, NFI=0.716, TLI=0.663). The top three factors affecting feet and ankle WMSDs are feet and ankle muscle fatigue, work type, and work organization, with standardized path coefficients of 0.221, 0.105, and 0.095, respectively. The top two factors affecting feet and ankle muscle fatigue are work organization and work type, with standardized path coefficients of 0.548 and 0.383, respectively. Feet and ankle muscle fatigue, work type, work organization, and work posture have a direct effect on feet and ankle WMSDs, with effect values of 0.221, 0.105, 0.095, and 0.077, respectively. The organization and type of work can also have indirect effects through feet and ankle muscle fatigue, with effect values of 0.121 and 0.084, respectively.Conclusion:Feet and ankle muscle fatigue has a direct impact on WMSDs, and plays a mediating role between ankle and ankle WMSDs caused by work organization and work type. Feet and ankle muscle fatigue is an important pathway leading to feet and ankle WMSDs. It is recommended that employers and managers detect job fatigue early and take corresponding prevention and intervention measures, which can play a key role in preventing feet and ankle WMSDs.

Objective:To explore the structural relationship between WMSDs in the upper limbs and various risk factors in the occupational population in China, based on a large sample epidemiological survey and structural equation analysis, and to establish a structural equation model, so as to lay a foundation for the prevention and control of such diseases.Methods:The Chinese version of the Musculoskeletal Disorders Electronic Questionnaire was used to conduct a nationwide survey on the prevalence of WMSDs in the upper extremity. Six factors related to WMSDs in the upper extremity were extracted by the classification standard of adverse ergonomic factors and their source and confirmatory factor analysis, including work organization, work type, upper extremity work posture, individual factors, upper extremity fatigue and upper extremity WMSDs. The structural equation analysis was carried out and the structural equation model was established.Results:The incidence of WMSDs and fatigue in the upper limbs was 24.44% and 43.76%, respectively. The adjusted structural equation model fitting indicators were generally up to the standard (GFI=1.000, AGFI=1.000, RMSEA=0.043, NFI=0.808, TLI=0.784) . The four exogenous latent variables of work organization, work type, upper limb work posture and individual factors were correlated. There was a strong positive correlation between job type and upper limb work posture ( r=0.865) , a moderate positive correlation between work organization and job type and upper limb work posture ( r=0.570, 0.490) , and a weak negative correlation between individual factors and the other three exogenous latent variables. Upper limb work posture and individual factors had direct effects on upper limb WMSDs, and the effect coefficients were 0.10 and 0.06, respectively. Upper limb fatigue played a mediating role between work organization, work type, upper limb work posture and upper limb WMSDs. The effect coefficient was 0.46, and the composition ratios of indirect effects were 100.0%, 100.0%, and 38.3%, respectively. The direct path effect of upper limb work posture, individual factors and upper limb WMSDs was weaker than the mediating path through upper limb fatigue. Conclusion:When carrying out the prevention and control of upper limbWMSDs, it is necessary to comprehensively consider the pathogenesis path of upper limb muscle fatigue and upper limb WMSDs caused by work organization, work type, and upper limb work posture, so as to provide theoretical reference for improving the prevention and control level of such diseases.