In recent years inves

EVALUATION OF RISK FACTORS ASSOCIATED WITH WORK-RELATED MUSCULOSKELETAL DISORDERS OF UPPER LIMBS EXTREMITY AMONG PRESS WORKERS Mohammad Pourmahabadian1, Kamal Azam2 ABSTRACT Obj ect ive: Exposure assessment of individual press workers t o risk f act ors associat ed wit h work-relat ed upper ext remit y muscoluskelet al disorders (UEMSDs). Design: This was a workplace f ield based, descript ive and analyt ical st udy. Place and durat ion: The st udy was conduct ed in presswork shops of an aut omobile manufact uring indust ry in Tehran, Iran during 2004-2005. Pat ient s and Met hods: Nordic Musculoskelet al Quest ionnaire (NMQ) and Rapid Upper Limb Assessment (RULA) ergonomics post ure based met hod were applied among 50 workers who work in bending, impact and hydraulic press shops. Then RULA and NMQ result s were analysed and compared against each ot her t hrough SPSS st at ist ical package. Result s: The result s of t his st udy showed t hat among all 50 press workers high and low prevalence of pain exist ed in low back (60%), shoulder and back (16%-18%), respect ively. Whilst in ot her part of body such as t highs and legs, wrist and neck it varies f rom 22%-44%. In addit ion, RULA and NMQ result s were comparable f or bending press workers only and it revealed t hat 75% of workers have score t hree f or arm, f orearm and wrist and 63% of workers have score t wo f or neck, t runk and f oot . Also, signif icant dif f erences were observed bet ween RULA body part scores (1 or >I) and t he report ed pain in neck and t runk (1df p=0. 011 and p=0. 026, respect ively). Conclusion: Press workers are involved in musculoskelet al disorders in perf orming t heir j ob and RULA met hod can be considered a usef ul met hod f or evaluat ion of WRMSDs in presswork shops of aut omobile manuf act uring indust ry. KEY WORDS: Ergonomics, Upper ext remit y muscol uskel et al disorders, RULA, NMQ, Press workers, Risk f act ors. Pak J Med Sci October - December 2006 INTRODUCTION In recent years investigations of work-related musculoskeletal disorders (WRMSDs) has attracted considerable attention because of its 1. Mohammad Pourmahabadian PhD, Assist ant Prof essor, Occupat ional Heal t h Depart ment 2. Kamal Azam PhD, Assist ant Prof essor, Epidemiol ogy & Biost at ist ics Dept . 1-2: School of Public Healt h and Inst it ut e of Public Healt h Research, Tehran Universit y of Medical Sciences, P. O. Box 14155-6145, Tehr an, Ir an. Cor r espondence: Dr. Mohammad Pourmahabadian, Email: poor mahm@si na. t ums. ac. i r pour maha@spht ums. com * Received f or Publicat ion: January 24, 2006 * Accept ed: May 22, 2006 Vol. 22 No. 4 379-384 importance in assessing ergonomics risk factors involved in industrial workplaces. WRMSDs have been found to be associated with numerous occupational ‘risk factors’, including physical work load factors such as force, posture, movement and vibration,1-3 psychosocial stressors, 4-6 and individual factors.7 The level of exposure to physical workload can be normally assessed with respect to intensity (or magnitude), repetitiveness and duration. Various methods are now available for assessing exposure to the risks associated with work-related musculoskeletal disorders, or identifying potentially hazardous jobs or risk factors within a job. These include observational methods, instrumental or direct methods, self-reports and other psycho Pak J Med Sci 2006 Vol. 22 No. 4 www.pjms.com.pk 379 Mohammad Pourmahabadian et al. physiological methods and recently the application of these techniques was reviewed critically.8 However, only several risk factors of WRMSDs are known and it was found that they are highly dependent to occupations. Further studies are needed for better understanding of these factors in detail. In this paper exposure assessment of individual workers to risk factors associated with work-related upper extremity musculoskeletal disorders (UEMSDs) were examined through Nordic Musculoskeletal Questionnaire 9 and Rapid Upper Limb Assessment10 in presswork shops of an automobile manufacturing industry in Tehran, Iran during 2004-2005. SUBJECTS AND METHOD Fifty male press workers (in bending, impact and hydraulic press shops) were enrolled in the study as case group and 50 administrative staffs as control group in an automobile manufacturing industry in Tehran during 2004-2005. Nordic Musculoskeletal Questionnaire (NMQ) and Rapid Upper Limb Assessment (RULA) method were applied for both case and control groups. In NMQ method period prevalence (12 months), point prevalence (7 days) and intensity of musculoskeletal troubles (i.e. aches, pain, discomfort, numbness or tingling) in different anatomical areas (i.e. neck, shoulders, elbows, wrist/hands, upper back, lower back, hips/thighs/buttocks, knees and ankles/ feet) were identified and questioned from individuals or workers. Optional, more details were included as part of the NMQ on the neck, shoulder and/or low back. It includes participant’s lifetime prevalence of and sickness absence due to such ‘trouble’, and the effects (if any) on work/leisure activities. Additional questions were added to the NMQ based on the literature regarding other possible risk factors for low back pain such as age, gender, cigarette smoking, and work and leisure activities. The RULA method uses diagrams of body postures and three scoring tables to provide evaluation of exposure to risk factors. The risk factors under investigation were described as external load factors.11 These 380 Pak J Med Sci 2006 Vol. 22 No. 4 www.pjms.com.pk factors include: numbers of movements; static muscle work; force; work postures determined by the equipments and furniture; and time worked without a break. In addition to these factors that was cited, 11 other important factors which may influence the load, but may vary between individuals included: the work postures adopted, unnecessary use of static muscle work or force, speed and accuracy of movements, the frequency and the duration of pauses taken by the operator. In addition, there are factors that altered an individual’s response to a particular load, individual factors (such as age and experience), workplace environmental factors and psychosocial variables.11 In RULA method, the body is divided into segments, which formed two groups of A (includes the upper and lower arm and wrist) and B (includes the neck, trunk and legs). The range of movement for each body part is divided into sections according to criteria derived through interpretation of relevant literature. These sections are numbered so that the number one is given to the range of movement or working posture where the risk factors present are minimal. Higher numbers are allocated to parts of the movement range with more extreme postures indicating an increasing presence of risk factors causing load on the structures of the body segment. This system of scoring each body part posture provides a sequence of numbers that is logical and easily remembered. According to RULA method10 a score is calculated for the posture of each body part. Score one indicates the most neutral posture and score four shows the worst position. The combined individual scores for shoulder, elbow and wrist give score A, and those for neck, trunk and legs give score B. These scores are added to scores A and B to obtain scores C and D, respectively. Combination of scores C and D, called grand score (ranging from 1 to 7), shows the musculoskeletal loading associated with the mender’s posture. Low grand scores (1 or 2) indicate acceptable working posture (action level 1). For grand scores of 3 or 4, further investigation is needed and changes may be required (action Evaluation of UEMSDs risk factors among press workers level 2). Prompt investigation and changes are required soon for scores of 5 or 6 (action level 3). Finally, immediate investigation and changes are required for grand score of 7 (action level 4). Job analysis indicated that press-working operations consisted of 4 tasks and they include: ‘‘Transportation of metal pieces from storage box into press feeding table’’, ‘‘Transportation of metal pieces from press feeding table into press operational zone’’, ‘‘Pushing press running buttons with two hands’’ and ‘‘Transportation of pressed metal pieces into collecting box’’ In this study NMQ and RULA results were recorded, analysed and compared statistically by, Fisher and t test through using SPSS computer software package for all case and control groups under this study. RESULTS Table-I shows some personal details of press workers that participated in the study. The daily working hours of press workers were long; 60% of press workers worked more than 8 h/day. Fig-1 presents the prevalence of musculoskeletal complains during the last 12 months among 50 press workers and clearly shows that the prevalence of low back pain, and shoulder and back pain in press workers are 60% and 16%-18%, respectively, but in other parts of the body such as thighs and legs, wrist and neck it varies from 22%-44%. Comparison between reported pain prevalence in both body parts groups of A and B is presented in Fig-2. It was observed that reported pain 70% Table-I: Personal details of the metal press workers (n = 50) Age (year) Work experience (year) Weekly working hours Mean SD Range 29 8.5 20–55 Mean SD Range 4.9 7.3 1–12 Mean 61.1 SD 7.7 prevalence in hydraulic press workers (in body part groups of A and B, 34%, 48%, respectively) compared with bending and impact press workers is higher. The results of Rula final posture score together with frequency and action level among press workers is tabulated in Table-II. It showed that most press workers are categorised in final posture of 3 and less than 40% of them are classified in action levels of 3 and 4. The relationship between the subject’s score defined by grouping and any reported pain, ache or discomfort from that body part region as tabulated in Table-III clearly shows that there are significant differences between RULA body part scores (1 and >1) and the NMQ results in neck and trunk ( = 6.41(1df), p = 0.011 and = 4.94 (1df), p= 0.026, respectively). DISCUSSION In this study, a Rapid Upper Limb Assessment (RULA) was selected for use as a quick and systematic objective assessment of the posture, forces and activities undertaken by the automobile press workers. RULA is a tool that assesses biomechanical and postural loading bending press Hydraulic press pnum atic press 60% 48% 50% 60% 50% 44% 40% 40% 32% 30% 18% 20% 22% 24% 22% 16% Prevalence, % Prevalence, % 60% 40% 34% 30% 20% 16% 16% 12% 10% 10% 10% 0% Neck Back Shoulders Knee legs 0% Bod y part Gro up A Body parts Fig-1: The prevalence of musculoskeletal complains among press workers during the last 12 months (n=50). Bo d y p art Gro u p B Rep o rted Pain Fig-2: Comparison of the reported pain in body part group A and B of press workers. Pak J Med Sci 2006 Vol. 22 No. 4 www.pjms.com.pk 381 Mohammad Pourmahabadian et al. Table-II: Rula posture score, frequency and action level among press workers (n=50) Job title Final A Final B Exerted Muscle Final posture group score group score force score use score score Hydraulic press 3 4 1 1 7 Hydraulic press 3 4 1 1 7 Hydraulic press 4 4 2 1 7 Hydraulic press 4 4 2 1 7 Hydraulic press 4 4 3 1 7 Hydraulic press 4 4 3 1 7 Bending press 3 5 0 1 6 Impact press 3 3 1 1 6 Impact press 3 3 1 1 6 Hydraulic press 3 3 1 1 6 Hydraulic press 3 3 1 1 6 Hydraulic press 3 3 1 1 6 Impact press 4 2 1 1 6 Impact press 4 2 1 1 6 Impact press 4 2 1 1 6 Hydraulic press 4 4 0 1 6 Bending press 3 4 0 1 5 Hydraulic press 3 2 1 1 5 Hydraulic press 3 2 1 1 5 Hydraulic press 3 2 1 1 5 Hydraulic press 3 2 1 1 5 Bending press 4 2 0 1 4 Impact press 4 2 0 1 4 Impact press 4 1 0 1 4 Impact press 4 1 0 1 4 Hydraulic press 2 2 0 1 4 Bending press 3 2 0 1 3 Bending press 3 3 0 1 3 Bending press 3 2 0 1 3 Bending press 3 2 0 1 3 Impact press 3 2 0 1 3 Impact press 3 1 0 1 3 Impact press 3 1 0 1 3 Impact press 3 2 0 1 3 Impact press 3 1 0 1 3 Hydraulic press 2 1 0 1 3 Hydraulic press 2 1 0 1 3 Hydraulic press 2 2 0 1 3 Hydraulic press 2 2 0 1 3 Hydraulic press 3 2 0 1 3 Hydraulic press 3 2 0 1 3 Hydraulic press 3 2 0 1 3 Hydraulic press 2 2 0 1 3 Hydraulic press 3 1 0 1 3 Hydraulic press 2 1 0 1 3 Hydraulic press 2 1 0 1 3 Hydraulic press 2 1 0 1 3 Supervisor 2 1 0 0 2 Supervisor 2 1 0 0 2 Supervisor 2 1 0 0 2 382 Pak J Med Sci 2006 Vol. 22 No. 4 www.pjms.com.pk Action level 4 4 4 4 4 4 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1 1 1 Evaluation of UEMSDs risk factors among press workers Table-III: Statistical analysis of the RULA body part scores (1 or >1) and the reported pain, ache or discomfort in the region. Body part Reported Posture pain score 1 >1 Neck Trunk Arm Wrist Group B Pain No pain Pain No pain Pain No pain Pain No pain Pain No pain 7 19 6 10 6 10 4 5 7 7 Type of test X2 15 6.41(1 df) 9 24 4.96 (1 df) 10 2 Fisher exact test 32 12 Fisher exact test 29 29 Fisher exact test 7 p value 0.011 0.026 0.009 0.442 0.042 on the whole body with particular attention to the neck, trunk and upper limbs and also a survey method developed for use in ergonomic investigations of workplaces where work related upper limb disorders are reported.10 Furthermore, RULA assessment requires little time to complete and the scoring generates an action level which indicated the level of intervention required to reduce the risks of injury due to physical loading on the automobile press workers.11 Although, the experience of the observer play an important role in postural analysis, but using RULA by untrained people in ergonomics can provide accurate, rapid initial assessments of jobs that may result in upper limb disorders.12 The results of this study showed that the RULA body scores in group A are higher than those in group B for all press workers and a good agreement observed between NMQ and RULA results for bending press workers, only. Statistical tests ( χ 2 and Fishers exact tests) showed that there are significant relationship between reported pain and RULA scores in neck and trunk, arm and body part in group B (p<0.05) but this was not for wrist (see TableIII) for all press workers. In addition, the prevalence of the reported musculoskeletal disorders (NMQ) for impact press workers for both body part groups (A, B) were found to be same, whilst for hydraulic press workers body part group B was higher than group A. It can be concluded that differentiate in NMQ and RULA results may be due to firstly; there was no space for sitting chair (as observed by author) for impact and press workers in the field and they have to bend frequently during their work. Secondly, hydraulic press workers have been worked in standing posture for the whole shift and in spite of their posture scores for their legs were found to be but due to the factor that they had pain in feet, NMQ results have been affected by their claim. However, musculoskeletal disorders are mostly prevalent in studied automobile press workers and RULA method could be considered as a useful method for the evaluation of risk factors associated with WRMSDs as investigated by previous researchers.10,11,13-16 It is suggested that other MSDs risk factors assessment should be tested for hydraulic press workers and validated by NMQ as well as medical test ACKNOWLEDGEMENT The authors are grateful to M. Ghafouri, A. Rahimi and B. Zahed for their valuable cooperation’s in this study. REFERENCES 1. 2. 3. 4. 5. 6. Gerr F, Letz R, Landrigan PJ. Upper-extremity musculoskeletal disorders of occupational origin. Annual Rev Pub Health 1991; (12): 543-66. Burdorf A. Exposure assessment of risk factors for disorders of the back in occupational epidemiology. Scandinavian J Work, Environment Health 1992; (18): 1-9. Kilbom AÊ. Repetitive work of the upper extremity: Part II - The scientific basis (knowledge base) for the guide. 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