| Part 1 Influential Factors of Waist Musculoskeletal Disease in Automobile Factory WorkersObjective Occupational musculoskeletal disorders are one of the diseases that cause sickness absence in manufacturing workers,but low back pain(LBP)is the most common WMSD.In this study,the waist WMSD survey was carried out on the workers in an automobile factory in Wuhan by means of a cross-sectional survey.The lumbar prevalence of different types of work was analyzed,and the relationship between personal factors and job-related factors and lumbar WMSD was analyzed,so as to provide reference for the prevention of lumbar discomfort from the perspective of ergonomics.Methods Cluster random sampling method was used to investigate the workers in an automobile factory in Wuhan.A total of 839 workers participated in the survey,and 819 valid questionnaires were actually collected.This questionnaire is a combination of the Musculoskeletal Disorder Questionnaire of Washington State Department of Labor and the Chinese version of the Musculoskeletal Disorder Questionnaire,which includes general demographic characteristics,health status,personal factors,labor organization,physical and postural load.Univariate and multivariate regression analyses were performed using χ2 test and logistic regression model.Results(1)Demographic characteristic: Among the 819 front-line workers in this survey,808 are males,accounting for 98.7% of the effective survey number,and11 are females,accounting for only 1.3%.The average age was(25.13±5.39),the average working time was(4.27±4.49)years,the number of normal BMI was 498(60.8%),67.5% of the workers had A college degree or above,and 45.4% of the workers had A smoking history.(2)The prevalence of waist WMSD in different jobs:The prevalence of waist WMSD in 14 types of work was more than 10%,the highest prevalence was fitter,followed by foundry and welder,the prevalence was 35.48%,31.03% and 27.83%,respectively.(3)Influencing factors of waist WMSD: Logistic regression analysis showed that Smoking(OR=1.509,95%CI= 1.067-2.136),lifting weights in an uncomfortable position(OR=1.722,95%CI= 1.035-2.865),frequent neck forward(OR=1.628,95%CI= 1.117-2.375)and frequent use of hands OR arms to get objects(OR=1.755,95%CI= 1.151-2.676)were risk factors.Age “~30 years old”(OR=0.546,95%CI= 0.336-0.886),alternated work with colleagues(OR=0.607,95%CI= 0.427-0.863)and adequate break time at work(OR=0.534,95%CI=0.375~0.762)were protective factors.Conclusion Automobile factory workers have a high prevalence of WMSD waist,prevalence of each job are more than 10%,front-line workers leads to the waist of WMSD risk factors mainly related to personal factors such as age,smoking and posture load(such as moving lifting objects in uncomfortable posture,often neck forward,etc.),but reasonable labor organization,such as take turns to finish the work tasks and adequate break time at work can reduce the occurrence of the waist WMSD.Part 2 Analysis of Surface Electromyography Characteristics of Trunk ForwardPurpose: To study the measurement of lumbar muscle load and trunk forward Angle by surface electromyography(EMG).Through the analysis of the myoelectric index,a more reasonable working time and trunk forward Angle were found,and a reasonable working posture was proposed,so as to provide reference for the prevention of lumbar musculoskeletal diseases.Methods: Based on the previous epidemiological survey results of musculoskeletal disorders,combined with the actual work process of the factory,19 male college students were selected as volunteers to simulate the most common posture of the trunk forward,which is a bad posture.The forward Angle was set as30°,50° and 70°,and the working time was set as 4min,8min and 12 min.There were nine groups of experiments in total.The maximum voluntary contraction of each muscle of each subject was measured before the experiment.After the end of each experiment,they rested for 5min and performed Borg subjective fatigue evaluation.Results:(1)There was statistical difference in subjective fatigue scores among the nine groups(P < 0.001).In addition,time was a factor affecting the subjective fatigue score(F=18.827,P < 0.001),while Angle and the interaction between Angle and time had no statistical significance on the score(F=0.142,P > 0.05);(2)Angle was the influencing factor of EMG amplitude of erector spine muscle,multifidus muscle and rectus abdominis(P < 0.05).In the nine groups of experiments,the MVE% value of the left erector spinal muscle was the highest at 30°and 8min,and the lowest at 70°and 12 min,while the MVE% value of the right erector spinal muscle was the highest at 30°and 12 min,and the lowest at 70°and 8min;The MVE% value of left multifidus was the highest at 30°and 8min,and the lowest at 70°and 8min,while the MVE% value of right multifidus was the highest at 30°and 8min,and the lowest at 50°and 4min;The MVE% value of left rectus abstris was the highest at 70°and 8min,and the lowest at 30°and 8min,while the MVE% value of right rectus abstris was the highest at 70°and 4min,and the lowest at 30°and 8min;(3)Each muscle showed a decreasing trend at different forward angles,and there was a statistical difference among the three forward angles(P < 0.05),among which the erector spine muscle and multifidus muscle all declined first,and then showed an increasing trend at different time points.There was no significant correlation between erector spine muscle and rectus abdominis antagonist muscle over time(P > 0.05);(4)The slope of the MPF value fitting line showed that the erector spine muscle,multifidus muscle and rectus abdominis all decreased the slowest at 30°,the left and right multifidus all decreased the fastest at 50°,and the left and right rectus abdominis all decreased the fastest at70°;(5)The CR value of the left and right antagonist muscles decreased gradually between the nine groups,and there was a statistical difference in the left side of CR(P< 0.05),while there was no significant difference in the right side of CR(P > 0.05).The maximum and minimum values of CR in different forward angles were 30°and70°,respectively,and the maximum and minimum values of CR in different working hours were 4min and 12 min,respectively;(6)With the increase of time,CR values at different angles showed varying degrees of decreasing trend,but the right antagonist muscle showed a trend of decreasing first and then increasing at 70°,and there were statistically significant differences among the three groups(Fleft =2256.853,Fright=703.311,P < 0.001).Conclusions:(1)Ergonomic risk factors involved in trunk forward include forward Angle and working time.The results of this study showed that Angle was a risk factor in the two factors and acted independently,and had no interaction with working time;(2)With the increase of time,the coordination of antagonist muscles was better under the three types of trunk forward Angle;(3)If the continuous working time is less than 8min,the forward Angle can be set as 30°;If the continuous working duration is 9~12min,the forward Angle can be set to 70°;If continuous working time exceeds 12 min,the forward Angle can be set as 50°. |
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