Abstract
Introduction
Musculoskeletal disorders are the most common causes of occupational injury and disability in industrialized countries and developing countries [1]. Musculoskeletal disorders are nearly half of all work-related diseases and are the major cause of lost work time, increased labor costs and human injuries [2]. One of the main causes of absenteeism in the workplace is musculoskeletal injuries, and according to reports about 40 percent of the compensations paid to workers are associated with musculoskeletaldisorders [3, 4]. These disorders begin with muscles feeling tired and achy and progress to a disease in which restricted movement of limbs or loss of muscles’ strength and power can be observed [5]. Prevention of musculoskeletal disorders has become particularly important in recent years, as such the goal of occupational ergonomics is preventing of these disorders [6].
If a workplace and working-tasks cause the occurrence of musculoskeletal disorders, they are called work-related disorders [7]. Among the risk factors for work-related musculoskeletal disorders, the major risk factor is poor posture [8–10]. Improved working posture will reduce the risk of musculoskeletal disorders, enhance health, reduce stress and discomfort and lead to increased efficiency and performance [11, 12].
In the semiconductor industry, the assembly of electronic circuits can be done in a sitting position. During the work shift, workers assemble electronic circuits that require high precision while in static postures, for long duration [13]. Due to the sensitivity and accuracy requirements, assembly workers’ heads and necks are bent forward to provide optimum visual conditions. These conditions cause poor posture and the occurrence of musculoskeletal disorders in the neck and back [14, 15].
A few studies related to MSDs have been accomplished on electronics assembly workers. A study conducted on Malaysian electronic assembly workers found that musculoskeletal disorders of the upper limb, including shoulder, neck, arms and hands were highly prevalent [16]. The results of another study conducted by Chandrasakaran et al. also found that musculoskeletal disorders of the neck, shoulders, hands and back were prevalent in electronic assembly workers [15]. Further, it was shown that the risk factors for musculoskeletal disorder included working in a sitting position with head and shoulders bent forward and raised [15].
In light of the above findings further ergonomics intervention is required in this industry. The purpose of this research is to further evaluate ergonomics intervention to reduce pressure on neck and trunk, and reduce musculoskeletal discomfort while working, in the semiconductor industry.
Materials and methods
This study was conducted on 105 electronic circuits assembly workers in a semiconductor industry in Tehran province based on subjective assessments methodologies. All assembly workers in this industry were male. Data collecting tools of the study were as followings:
Demographic data and Nordic questionnaire
Data were collected via anonymous questionnaires, which covered (a) personal details (including age, weight, height, job tenure, education, health, and medical background); and (b) musculoskeletal problems in different body regions. The general Nordic musculoskeletal questionnaire of musculoskeletal symptoms was used to examine reported cases of MSDs among the study population [17]. Reported MSD symptoms were limited to the 12 months prior to the study. All workshops were visited; the questionnaires were completed on the basis of an interview with each worker.
Assessment of body discomfort before the intervention
The first symptoms of musculoskeletal injuries include fatigue, pain or discomfort in the limbs [5], Corlett and Bishop’s body part discomfort scale was applied to evaluate body discomfort before and after the intervention [18]. The numeric scale was a 10-point with body map. Body discomfort was assessed at the beginning and end of the working shift such that the amount of discomfort during the working shift could be calculated. For example, if assembly workers reported a neck pain scoreof 7 at the end of working shift, and a score of 2 at the beginning of working shift, then the discomfort score during the work shift, was equal to 5. Calculation of total body pain intensity was accomplished by adding together the different areas severity discomfort.
Ergonomic intervention
Ergonomic intervention in this study was the optical magnification loupes for increased visual clarity for electronic circuits assembly workers. Figure 1 shows a magnification loupes used in this study. The loupes were Hires flip-ups, com–plete with head straps and side shields. The frames were all standard titanium frames, slate in color. The head–bands and standard frames had interchangeable working lengths to allow for portability within the group. The magnification for all assembly workers was 3.5x. Early in the session, workers were measured for their visual working distances, and each was fitted with either the standard frames or headbands, depending on his visual needs. Due to increased magnification and clarity of vision of the lenses, they improve their working postures such that postural deviation of the back, head and neck were lessened. In previous studies on dentists magnification lenses used to enhance the clarity from vision and reduce poor postures [19–22] interventions were provided for each person, with a magnification lenses at the beginning of the work shift. The time for use of the devices for each person was a full working shift (7 to 8 hours). Since, this study was done in a private sector industry use of picture-based methods for posture evaluation were not permitted. Observations showed that the majority of job activities were characterized by a sitting posture with the workers head and trunk flexed forward and shoulders flexed and abducted. The back became straight, shoulders became relaxed and assumed a balanced position, forearms became parallel, and the trunk assumed a neutral position. Consequence use of magnification loupes improved posture for assembly workers in the study. After the intervention, the benefit of using the magnification loupes wasexamined.
Assessment of body discomfort after intervention
After the intervention, discomfort intensity was assessed at the beginning and end of the work shift similar to before the intervention. Finally, assembly workers were asked to consider about the usefulness and comfort using of the magnification loupes.
Data analysis
Statistical analyses were performed using SPSS (version 22). Data analysis was performed by using independent t-test and central statistical indicators.
Results
Demographic data
Table 1 shows assembly workers demographic characteristics. The age mean of the study population 34.35 years and average work experience is 9.7 years. Thus, the study population is young and experienced.
Prevalence of musculoskeletal disorders
The prevalence of MSDs symptoms that assembly workers experienced over recent 12 month are presented in Table 2. The prevalence of symptoms in the neck, back, shoulders and arms is high and includes a high percentage of study subjects. (More than75%).
Body discomfort intensity before and after intervention
Results of the discomfort assessment in different areas of the body and whole body at the beginning and end of the working shift before the intervention are presented in Table 3. The results revealed that the discomforts of assembly workers is most pronounced in the neck, shoulders and arms and back. Also, results of the discomfort assessments in different areas of the body and whole body at the beginning and end of the work shift after the intervention are presented in Table 4. Results showed discomfort intensity increases in neck, back, shoulder and arm, at the end of work shift even after intervention. However, the discomfort intensity increased in this stage is far less than before the intervention.
Variations of discomfort intensity after intervention
Table 5 shows the results of the discomfort intensity before and after intervention. The results show a significant reduction in discomfort intensity in the neck, shoulders and arms, back, elbow and forearm, and whole body (p < 0.05). On the other hand, no significant effects were observed in reducing discomfort in hand and wrist, buttocks, thighs and knees, and feet (p > 0.05).
Judgments about the usefulness of optical magnification loupes
The results showed 93 percent of assembly workers believed that the magnification loupes facilitated their work. Also, 92 percent of them reported using these loupes comfortably. And 90 percent believed using the magnification loupes made working conditions better than before.
Discussion
Demographic data
Based on age mean and experience the study population are relatively young and experienced. Thus their opinion expressed about working conditions and ergonomics intervention are reliable. Average working hours are over than 8 hours per day. It can increase the risk factors of musculoskeletal disorders.
Prevalence of musculoskeletal disorders
The results showed MSDs symptoms are highly prevalent among the assembly workers, with thehighest rate in the neck, back, shoulder and arms. This finding is consistent with the findings of other studies [16, 23]. Therefore in ergonomics intervention programs eliminating the risk factor of musculoskeletal disorders, in these areas are very important.
Body discomfort intensity before and after intervention
The results found discomfort among assembly workers are highest in the neck, shoulders and arms and back. These findings are in accordance with the general prevalence of musculoskeletal disorders among assembly workers. Assessment of discomfort in different areas of the body before the start of work showed highest levels of discomfort is in the back area at the beginning of work shifts. This finding could indicate that the discomfort in the back area is a chronic problem among assembly workers. In a study conducted in the semiconductor industry, a significant relationship was reported between the prevalence of musculoskeletal disorders symptoms in the upper limbs and pressure condition [16, 23]. This finding agrees with the results of the discomfort assessment using a numerical rating scale in this study. The results showed the highest accumulation of discomfort in the neck, back, shoulders and arms after the intervention at the end of the work shift. Of course this increase was less than the increase in discomfort intensity before the intervention. These results imply that ergonomic intervention (using a magnification loupes) had a significant effect in reducing the severity of discomfort in these body areas. Therefore, it appears to be effective in reducing the incidence of musculoskeletal disorders in these areas. Several studies on the effect of magnification loupes on improving dentists’ posture also demonstrated these lens had a significant impact on improving posture, neck and trunk [19–22]. The results of these studies are in correlate with the findings of the present study. In addition, the mean intensity of the whole body discomfort is significantly reduced after the intervention. This shows that the intervention had a positive effect on reducing musculoskeletal stresses in the assembly workers body.
Variations of discomfort intensity after intervention
After the intervention, there was a significant reduction in discomfort intensity of the neck, shoulders and arms, back, elbow, forearm, and whole body. This suggests that the intervention has the potential in reducing prevalence of MSD in assembly workers in the long term.
Judgments about the usefulness of optical magnification loupes
The results showed workers liked the magnification loupes. The findings also showed the use of these loupes led to better working conditions and facilitate the work. These findings suggest consensus of assembly workers regarding effectiveness of its application in production operations. These results are in accordance with Branson & Maillet studies on dentists[19, 21].
Conclusions
Results of this study showed a high prevalence of musculoskeletal disorders among electronic circuits assembly workers in the semiconductor industry. It also was determined, these disorders are more common in the neck, back, shoulder and arm. The study found that ergonomic interventions (using a magnification loupes) had a significant effect in reducing the severity of discomfort in these body areas. Therefore they appear to be effective in reducing the incidence of musculoskeletal disorders. Assembly workers agreed that using these loupes improved work conditions. So can be concluded that use of the magnification loupes with electronics industry assembly workers is an effective intervention. In this study, the short-term effects of using magnification loupes were studied (during a work shift). Obviously use the magnification loupes should be done for longer time period to achieve for more accurate comments. (For example, a month or even more).
Conflict of interest
The authors have no conflict of interest to report.
Footnotes
Acknowledgments
This article is related the thesis written by Naser Dehghan PhD. student at Occupational Medicine Research Center and was financially supported by Iran University of Medical Sciences, grant No. 94-01-127-25814.