Study On Musculoskeletal Disorders And EMG Characteristics Of Poor Posture Among Automobile Workers

Objective Work-related musculoskeletal disorders(WMSDs)have been known and concerned widely because of the rapid development of Chinese automobile industry and the exposure of health problems among workers in the automobile manufacturing industry.There are many occupational characteristics in the automobile manufacturing industry,such as fast-paced labor,repetitive manual labor,heavy manual operation,Local or systemic vibration,etc.,which are the main reasons of WMSDs.In this study,workers in an automobile factory in the city of wuhan were investigated.The prevalence of WMSDs in different body parts was described by cross-sectional survey.To analyze whether there is a correlation between the risk factors that are exposed in work and the musculoskeletal disorders of workers in automobile factories.To describe the exposure and contaction of the risk factors for musculoskeletal disorders of workers,and to provide scientific and effective preventive measures for muscle pain by using the data of this project in the automobile manufacturing industry.Methods A cross-sectional survey of 808 workers in an automobile factory was conducted by cluster sampling.Workers can use their mobile phones to complete the questionnaires.The musculoskeletal disorders questionnaire was used by this study,which had been accepted by international and national ergonomics researchers.The questionnaire included the personal information of the workers,the prevalence of WMSDs in different bodies' parts and the harmful ergonomic factors.The Chi-square test and Logistic regression statistical methods were used to analyze and study the data.Results(1)Demographic characteristics: the sample sizes were 808 automobile manufacturing workers,including 798 males(98.8%)and 10females(1.2%).The average age was 25.3±5.5 years,and the average work age was 4.3±4.5 years.(2)Prevalence of WMSDs: the prevalence of WMSDs which ranged from high to low in different body parts were neck(33.0%),waist(32.3%),shoulder(24.9%),wrist(21.2%),back(19.3%),ankle foot(16.8%),knee(13.2%),elbow(6.1%),hip(5.9%).(3)Logistic regressionanalysis : 1)risk factors of neck's WMSDs included age over 30 years,tilting the neck,frequent overtime work and working in uncomfortable body position.2)risk factors of waist's WMSDs include age over 30 years old,working in uncomfortable body position,tilting the neck,frequent overtime work and using upper limbs or arms to pick up objects.3)risk factors of shoulder's WMSDs include age over 30 years old,working in uncomfortable body position,tilting the neck and bending wrist for a long time.Conclusion The prevalence of neck,waist,shoulder and wrist of workers in automobile factory were in the top four.The highest prevalence of WMSDs is the neck.The main risk factors for WMSDs among the workers of automobile manufacturing were age over 30 years old,working in uncomfortable body position,tilting the neck,frequent overtime work,using upper limbs or arms to pick up objects and bending wrist for a long time.Objective To control the condition factors of using arm to pick up objects(height of platform,weight of object,the distance between hands,spinal curvature),the surface EMG and the Borg scale were used to evaluate which is the most appropriate one of different arm positions.In order to provide evidence to find out the most comfortable working position and provide data support for the prevention of work-related musculoskeletal disorders.Methods 15 male volunteers were selected in this study.There were three ways to use arms to pick up objects for the 15 volunteers.The first way is in the condition of long distance and low frequency(the distance of using arm to pick up is 60 cm,the frequency of swing arm is 15 times /min,Posture a for short).The second way is in the condition of middle distance and middle frequency(the distance of using arm to pick up is 40 cm,the frequency of swing arm is 30 times /min,Posture b for short).The third way is in the condition of short distance and high frequency(the distance of using arm to pick up is 20 cm,the frequency of swing arm is 60 times/min,Posture c for short).The volunteer held the iron bar which is 50 cm long and weighs 1kg in both hands.Swaying your both arms with keeping your body close to the edge of the workbench.The iron bar was moved from the edge of the workbench to the target distance and then it was moved back to the edge of the workbench with three ways of using arms to pick up objects.The operation time is 5min.Resting for 15 minutes between each assignment.At the end of each pose,the borg scale was used for scoring.EMG signals were recorded and marked at the beginning and end of each assignment.The start and end times of each assignment should be recorded.Results(1)The average age of the 15 volunteers was 20.1±0.7 years old,the average height was 175.1±2.6 cm,the average weight was 73±3.1 kg, and the BMI was 24±1.4.Although borg scale scores showed that there was no statistically significant difference(P > 0.05)in three kinds of the operation,postures b had the lowest scores while postures a and c had the highest scores.(2)The MVE% of volunteers' left and right erector spine were the highest in posture a;The MVE% of the left trapezius is highest in posture c,while the MVE% of the right trapezius is highest in position b.(3)Compared with the situation of rest,MF values of volunteers' left erector spine,left trapezius and right trapezius were all less than those at rest(P<0.05),while MF values of right erector spine were all more than those at rest(P<0.05).(4)Compared with the situation of rest,the MPF values of volunteers' left and right erector spine were all more than those at rest in the three positions(P<0.05).The values of MPF in both the left trapezius and the right trapezius were less than those at rest(P<0.05).(5)The JASA analysis showed that in the process of posture a,the four muscles of the volunteers showed seven times of fatigue.In the process of posture b,the four muscles of the volunteers showed six times of fatigue.In the process of posture c,the four muscles of the volunteers showed eight times of fatigue.Conclusion The MVE% value of EMG amplitude at rest was less than using arms to pick up objects in three different positions.The EMG amplitude of the left and right muscles has the characteristic of asymmetry.There were fatigue of all muscles with three different postures.The times of fatigue occurred the least in posture b.So posture b is the best postures that can reduce local muscle fatigue.