Keywords

8.1 Introduction

8.1.1 Musculoskeletal Disorders

Musculoskeletal disorders (MSDs) are a foremost health problem among the workers in both developed and developing countries (Widanarko et al. 2014). Work-related MSD issues have always been an area of examination and enhancement especially for industries involving work-intensive operations and techniques (Spasojević Brkić et al. 2015). MSDs are more common among women than among men (Dahlberg et al. 2004). Work-related MSDs have been recognized as a significant problem within the European Union in terms of individual ill health and economic factors such as the impact on production and revenues (Buckle and Jason Devereux 2002) and another part of the world also (Oh et al. 2011). Prevention of MSDs is most important factors that can have a major impact on productivity improvement and on the upgradation of health and safety at workplace (Kogi et al. 2003). Work-related musculoskeletal disorders (WMSDs) are a major anxiety in the industry which can also compromise competitiveness due to costs related to worker compensation, labor turnover, absenteeism, poor quality, and reduced productivity (Andersson 1992). There are various factors which can cause musculoskeletal disorders, such as low temperature and humidity. Improper work posture and repeated tasks in such an environment may harm the musculoskeletal system (Oksa et al. 2002; Piedrahíta et al. 2004). And also the fatigue failure plays an important role in the etiology of MSDs (Gallagher and Schall 2016). Finally some psychosocial and organizational factors and also some individual factors were associated with prevalence of MSDs (Piranveyseh et al. 2016).

8.1.2 Sewing Machine Operators (SMO)

The possible ergonomics deficiencies have been identified and described in the workstation of sewing machine operators in a textile industry in Botswana as well as their insight of workload and discomfort and also with specific reference to sewing machine operators, this is an occupational group that may experience a high occurrence of MSDs (Sealetsa and Thatcher 2011). The poor working postures of the workers have to be maintained during the whole working period as well as to repetitive hand and arm movements. Their posture is constrained by the task and the design of the sewing machine and table have a considerable influence on the posture adopted (Li et al. 1995). The sewing machine operators use both hands to handle workpieces, or feel objects, and tools; control by leg; sit and repeat the same motions for working periods of time. The sewing machine operation includes tasks that involve operating power sewing machines to sew, alter or repair wearing apparel, linens, blankets, and other fabric. This includes the operation of automatic sewing machines when the operator must know how to thread the machine, wind bobbins, adjust tension, and oil parts (Kaergaard and Andersen 2000). For this reason, a high occurrence of musculoskeletal symptoms of neck, shoulder, back, hand/fingers, and lower extremities have been found in studies of female SMOs (Kaergaard and Andersen 2000; Brisson et al. 1989; Kilroy and Dockrell 2000). Typically, sewing machinists perform piecework activities, assembling component parts of a final garment or product. The fragmentation of work in this way means that the task is often highly repetitive, potentially dangerous and complex task involving the coordination of both hands, usually performed in a seated working posture for a long period of time. The operation usually requires the operator to lean forward, with a forward inclined posture of both head and trunk, to focus their attention and have better visual control of the task. In many ways, given the fixed nature of the sewing machine, the machinists have to adapt their posture and viewing angle so that they can conduct this form of ‘precision work’ and this can lead to the development of MSDs, particularly in the back, neck, and upper limbs.

8.1.3 Modular Sewing Production

The decision to move straight-line assembly systems to U-shaped assembly lines systems constitutes a major layout design change and huge investment for assembly operations. U-shaped assembly systems offer several benefits over traditional straight-line layouts including an improvement in labor productivity, quality of the product, traceability, reduced WIP and reduced lead time and changeover time. The workers can move between the two legs of the U-line to perform combinations of tasks (Aase et al. 2004). The operators are standing and operating the machines to convenient to move from machine to machine and also it reduces the long-term static posture of the workers. The MSDs are the major health problem among the sewing machine operators working in the textile industries. Several ergonomic researches have been done for SMOs, who are all working in sitting position. Most of the aches are recorded in the upper body, hand, and arm and very less on the lower body (Oh et al. 2011; Sealetsa and Thatcher 2011; Li et al. 1995; Dianat et al. 2015). In the MSP, the SMOs are standing, operating and controlling the machine with the foot. There is no ergonomics studies have reported on standing modular SMOs.

Prolonged standing at workstations can cause muscle fatigue and mental stress. Furthermore, an insufficient rest period during the standing time coupled with improper footwear can lead to discomfort and fatigue in the lower extremities, causing occupational injuries in the long term. When workers work in a prolonged standing posture , static contraction occurs particularly in their back and legs, resulting in impaired functioning of calf muscles (Krijenen et al. 1997). Prolonged standing transfers the weight of upper body parts to lower parts and results in lower back pain. 83% of industrial workers in the USA experience foot or lower leg pain and discomfort associated with prolonged standing (Zander et al. 2004).

8.1.4 Rationale

Witd an overview of the modular sewing production in textile industries and the potential of this work to lead to MSDs provided, research was conducted to investigate the following factors:

  • To determine MSD prevalence among the SMOs working in the lean environment by using Cornell Musculoskeletal Discomfort Questionnaire.

  • To examine the level of ergonomic workplace risk factors by using the rapid entire body assessment.

  • To develop the productivity by eliminating the ergonomic risks in lean environment.

8.2 Materials and Methods

8.2.1 The Workplace

This ergonomic study was conducted in a textile industry that manufactures children wear, and which is located in Sri Lanka. The main customers for the company are USA, Europe, and UK and suppliers from India, China, and Sri Lanka. To meet the market demand and agility, the industries have to adopt lean manufacturing system . Lean sets out a methodology for being highly responsive to customers’ demands whilst constantly challenging costs and wastes throughout supply networks (Bhamu et al. 2014; Shah and Ward 2007). So, it would appear that Lean can be applicable to all sizes of enterprise in their endeavors to become more competitive to sustain, and possibly enhance, their position in the modern marketplace. The industry started to follow the standing MSP system, which consists of U-shaped layout, Multi-skilled operators, standing operations machines and single piece flow. The totals of 896 female SMOs are working in both shifts and shift duration is 8 h which includes half an hour total break time. The sewing floor consists of 32 modules and 14 SMOs for each. Each SMO sews the ready-to-sew cut panels coming from the cutting department. The full garment packed at the end of the layout and send to quality audit than Finished Goods Storage (FGS) through metal detectors. There were no ergonomic programs being conducted at all.

8.2.2 Participants

The study samples are paid based on their years of employment, an average of 100 USD per month. Based on their performance, incentive money also paid with their monthly salary. The participation was on a voluntary basis and the operators were under no compulsion to complete the study. The operators were not paid for their participation. The primary task is the ‘sewing ’ and the secondary task is trims and accessories handling apart from these tasks thread changing and cleaning tasks have to carry out by these SMOs. The sewing process carried out by flexed left and right side, standing by the left leg and operating the machine pedal with right leg throughout the shift (Fig. 8.1). The SMOs standing on the floor, leans forward at an angle of 25°–30° and head around 35°, and moves her hands backward and forward and to the left and right (Average 150 times per hour) to perform the sewing process. Most of the operators are not using footwear on the floor while sewing.

Fig. 8.1
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Standing modular sewing machine operators

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8.2.3 Research Design

The proposed research methodology is shown in Fig. 8.2. Initially the data collection about demographic and job characteristics among the sample SMOs (n = 557) working in the case industry. The chi-square test was conducted to identify the significant factors for the discomfort among the demographic and job characteristic factors. The operators (n-336), who were all felt discomfort demographic and job characteristic survey, were considered to further discomfort survey CMDQ and posture analysis REBA and who did not feel discomfort were not considered for further study (n-221). The CMDQ and REBA validated by test–retest and reliability test, respectively. These study outcomes have analyzed and discussed further.

Fig. 8.2
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Research methodology

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8.2.4 Tools and Data Collection

In this study, the data were obtained with a questionnaire and by direct observation, done by the trained management trainees. The management trainees are undergraduate fresher working in the case company and properly trained about these survey and tools. The data collection process consists of three parts; one is about demographic and job characteristics , the second one is about discomfort survey, and the final one is posture analysis. The 557 SMOs from both shift (Out of 896 SMOs), have selected for demographic and job characteristics study based on their years of employment in the case organization.

8.2.4.1 Demographic and Job Characteristics

In the first part the questionnaires, information was collected about age, weight, height, Body Mass Index (BMI) , education, marital status, daily walking distance, SMO experience, job satisfaction, job stress, and finally the discomfort of the SMOs. The information has collected by interviews with the SMOs. The age (in years) considered as a factor and BMI, based on the height and body weight, the BMI (kg/m2) was calculated. Marital status included because of married SMOs have to contribute their household works and for daily walking distance included because of a lot of SMOs have to walk (2–3 km) to reach the transport boarding place or to the company. The SMOs experience is considered only on standing operation in MSP. The discomfort of the SMOs was answered ‘Yes or No’ and job satisfaction and job stress, in “low, medium & high” scale.

8.2.4.2 Cornell Musculoskeletal Discomfort Questionnaire (CMDQ)

The list of SMOs, all who felt discomfort in the previous study, have been considered for further discomfort survey and REBA analysis. The CMDQ consists of three sectional parts and each consists of a different scoring part (i), shows in Fig. 8.3. Respondents indicated the frequency of discomfort on an ordinal scale (R) from 0 (Never) to 4 (Several times everyday) and severity of discomfort from 1 (slightly uncomfortable) to 3 (very uncomfortable). The level at which the discomfort interfered with work was scored from 0 (Not at all) to 2 (substantial interference). Total discomfort score was calculated by using the following formula (Jansen et al. 2012) (2). Here, the interference score starts from 1 (Not at all) to 3 (substantial interference) proposed. The frequency (F), severity (S) and interference (I) score of a particular body part were calculated (1) as the addition of the number of SMOs multiplied by corresponding ordinal scale score.

$$F \left( {or} \right)S \left( {or} \right)I = \mathop \sum \limits_{i = 1}^{r} n_{i} R_{i}$$
(8.1)

where n i is the number of operators (n) in ith scoring part and Ri is the corresponding score in ordinal scale.

$$Total\;Discomfort\,score = Frequency \times Severity \times Interference$$
(8.2)
Fig. 8.3
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Cornell musculoskeletal discomfort questionnaire (CMDQ), female version (http://ergo.human.cornell.edu/ahmsquest.html)

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The total discomfort score of different body parts will be calculated from the above Eq. (8.2). Test–retest reliability for CMDQ at a one-month interval found a 3% difference in responses for upper body parts and a 7% difference for lower body parts. This study was done among 30 SMOs. The questionnaires were filled in at the workplace. This CMDQ survey was conducted among the SMOs who were answered ‘Yes’ for discomfort question in previous (demographic and job) characteristics survey. The 336 SMOs have answered that feeling discomfort.

8.2.4.3 Rapid Entire Body Assessment (REBA)

The REBA was used to evaluate the SMOs full body working postures at their workstations. The body parts were grouped into two categories. “Group A” included the trunk, neck and legs and “group B” included upper arms, lower arms, and wrists. Each body part was evaluated depending on the angle of parts and load/force. The scores were calculated to get the final score, which was then assessed according to the proposed action categories shown in Table 8.1 (Hignett and McAtamney 2000).

Table 8.1 REBA—Action Categories
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The observations and recordings of postures were performed by ten trained management trainees. The investigators made sure to study the longest adopted posture of the SMOs. A separate REBA sheet (Fig. 8.4) was used for each operator for recording the REBA scores.

Fig. 8.4
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REBA Work sheet (‘REBA-Worksheet-v-2.0.pdf’, 15 July 2015)

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8.2.4.4 REBA Reliability

To establish how much homogeneity or consistency in the REBA score, which collected by the management trainees. The reliability of the REBA scores, observed by each management trainees, using Cronbach’s Alpha was found to be ‘good’ (0.9 > α ≥ 0.8) (with Cronbach’s Alpha 0.86 for REBA scores).

8.2.5 Data Analysis

Statistical analysis was performed with Minitab 16. The analytical statistics were carried out using chi-square test (Öztürk and Esin 2011) and used to assess relationships between demographic (Age, BMI, education, marital status, daily walking distance,) with job-related characteristics (SMO experience, job satisfaction & job stress) and the discomfort. The CMDQ survey also analyzed in terms of individual body parts of total SMOs and frequency, severity and work interference of case industry. The REBA score was analyzed in terms of percentage of operators in risk level. For all statics test the P values below 0.05 were considered statistically significant (Dianat et al. 2015).

8.3 Results

8.3.1 Demographic and Job Characteristics

Table 8.2 presented the demographic and job characteristics details of the study participants. The study sample comprised of 557 SMOs. The ages of the SMOs were ranges from 18 to 36 (Mean-25.9, Standard Deviation (SD)-4.4) and the majority of them were in the range of 21–25(37.2%), next one in 26–30(37%) and, above 30 and below 21-year-old was very minimum (<14%). The BMI of the SMOs were varied from 15.6 to 28.9 kg/m2 (Mean-21.6, SD-2.7), the 58% of SMOs had healthy body, 25.5% overweight body, underweight (15%) and very less in obese (1.4%). The 57.8% of the operators were primary school level, 25.3% were secondary school level and higher secondary very less (16.7%). The 79.7% of the workers were married (Unmarried-20.3%) and operators daily walking distance to reach boarding place or company below 1 km (56.9%), 1–2 km (19.4%) and 2–3 km (23.7%). The experience only in MSP was considered in the study as a factor and ranges from 0.5 to 3 years. Most of the operators have below one year (49.9%) and 33.4% has 1–2 years and very fewer operators (16.7%) has 2–3 years. The most of the SMOs were satisfied with their job in medium level (50.8%) and fewer in high level (27.3%) and low level (21.9%). The stress due to job demand among the SMOs was medium (36.8%), low level (36.1%) and less in high level (27.1%).

Table 8.2 Demographic and job characteristics and their relationship to discomfort (n: 557)
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8.3.2 CMDQ Discomfort Survey

Table 8.3 shows the discomfort, severity, and interference of SMOs with respect to different body parts and in terms of percentage of operators (n = 336). Among 336 SMOs, 85.4% (287) of them never felt discomfort in their hip/buttocks and very fewer SMOs felt comfort with their left foot (3.6%, n = 12) and left knee (7.4%, n = 25). The maximum number of the SMOs sense the discomfort in their foot (Left (29.2%, n = 98) and Right (27.1%, n = 91)) several times in a day and the severity (Left (35.4%, n = 119) and Right (32.4%, n = 109)) of the discomfort substantially interfered (Left (37.2%, n = 125) & Right (35.4%, n = 119)) with their work.

Table 8.3 Discomfort, severity and interference of SMOs with respect to different body parts (n = 336)
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Table 8.4 shows the sectional score and total discomfort score with the percentage of different body parts of SMOs (n = 336). The frequency, severity, and interference score of the different body parts were calculated by using the Eq. (8.1) and the total discomfort score by Eq. (8.2). Finally, the discomfort score has presented in terms of percentage for the different body parts. Figure 8.5 shows the graphical representation of discomfort score (%) of different body parts. Based on the discomfort score percentage, the body parts arranged in descending order (Table 8.5).

Table 8.4 Total discomfort score of different body parts
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Fig. 8.5
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Graphical representation of discomfort score (%) of different body parts

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Table 8.5 Priority of body parts based on discomfort
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8.3.3 REBA

The body posture of the participants during sewing tasks was observed in accordance with the REBA form and the scores were recorded. A separate REBA form was used for each operator and observation. The observations were carried out without disturbing the regular task of the operators. The operators’ mean score A, score B, and grand score were found to be 5.4 (SD: 1.3, range: 3–8), 3.8 (SD: 1.3, range: 2–6) and 7.98 (SD: 2.2, range: 5–12) respectively (Table 8.6).

Table 8.6 Mean, SD and range of REBA score
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Score A included the trunk, neck and legs and score B included upper arms, lower arms, and wrists. The grand score includes the activity score too. The mean score A of 5.4 indicates that the operators’ trunk, neck, and leg were in medium risk level and need to change soon. The risk scores of the legs and neck were determined to be within normal limits. But, due to standing operation the leg has to bear the stress created by the upper body. The score B found to be 3.8 (≈4) indicates that the operators’ upper arms, lower arms, and wrists were in medium risk level and need to change soon.

The final mean REBA score of 7.98 (≈8) indicates that the operators’ postures at high risk and their workstations need to be investigated and required changes are required immediately. There were no operators who received REBA scores of 1–3, which indicates an acceptable posture (Table 8.7). A maximum number of the operators (Score A ~ 88%, Score B ~ 53% and Grand score ~ 49%) were in the medium risk level and action necessary. The graphical representation of the percentage of operators in different risk level of the REBA analysis shown in Fig. 8.6.

Table 8.7 Risk level and action of the observed REBA score
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Fig. 8.6
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Graphical representation of percentage of operators in REBA risk level

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8.4 Discussion

This study conducted to determine MDSs and ergonomic risks in female SMOs is the first of standing modular sewing production in Sri Lanka. Women are the principal workers in the textile sector. The result of the demographic and job characteristics survey presented that the factors like age, education, marital status, and experience in MSP were not significantly affected with the operators discomfort. But, the factors like BMI, daily walking distance to boarding place or company, job satisfaction, and job stress were significantly influenced with operators’ discomfort. In several studies, psychosocial factors, such as high job strain, less job satisfaction and to feel less passionate about work, have been reported to increase the MSD prevalence (David 2005; Denis et al. 2008; Choobineh et al. 2009). The similar studies of sitting sewing operators’ discomfort were significantly influenced by the factors like medical history of systemic illness, use of scissors and work pressure, but BMI was not a significant factor (Öztürk and Esin 2011). The results of the present study provide further evidence that both physical and psychosocial job factors are associated with increased discomfort among workers involved in sewing activities.

The CMDQ discomfort survey result presented that the influence of discomfort among the different body parts of the operators (Table 8.5). A maximum number of operators have felt more discomfort in their foot, knee, lower leg, thigh, lower back, and shoulder than upper back, upper arm, neck, forearm, wrist and hip/buttocks. Comparatively, the operators’ discomfort was more in left than right in the body parts of foot, lower leg, knee, and thigh but reverse in shoulder, upper arm, fore arm, and wrist. The left leg bear the total weight of the body and most of the repetitive activities carried out by right hand with flexed left side. In the present study in the lower body more discomfort was felt than upper body. But in the sitting sewing operation, upper body gets more strain than lower body. The sitting operation studies reported that the overall prevalence of complaints was surprisingly low (15.5%), with the back (8.9%) and knee (4.9%) the most commonly noted sites of pain (Lombardo et al. 2012) and high in neck, shoulder and back (Nazari et al. 2012; Roquelaure 2012). Öztürk and Esin (2011), reported that the areas identified by most women as complaint more discomfort than lower body (trunk (62.5%, 34.8% upper back, 23.9% lower back), neck (50.5%), shoulders (50.2%), and upper limbs (22.3%)). These findings provide evidence that more discomfort in lower body than upper body in standing sewing operation.

In this study, the operator’s ergonomic risks were determined by REBA scores and presented the result (Table 8.6) with SD and range of the score with respect to different body parts, score A and B, and grand score. The leg (REBA) score was below low risk level but felt maximum discomfort (CMDQ). The leg score indicates that the discomfort was not due to awkward posture and due to stress created by upper body weight. The score A (Range-3–8, Mean-5.4) indicates that the 88.39% of the operators’ trunk, leg, and neck were in medium risk level and necessary to change. The score B (2–6, 3.8) indicates that the 52.98% of the operators’ upper arm, lower arm and wrist were also in medium risk level and necessary to change. Finally, the grand score (5–12, 7.98) indicates that the 49.11% of the operators were in medium risk level, 32.44% were in high risk level and need to change soon and 18.45% of operators were in high risk level (Tables 8.7). The most of the operators were in medium risk level in the MSP operators in lean environment.

8.4.1 Managerial Implications

The study exposed to management that the operators’ ergonomics risks level and interference with work in the lean environment sewing production floor. The posture analysis exposed that the most of the operators were in medium risk level in the floor. The study motivates that the awareness of the ergonomic aspects in MSP floor. The result of the study motivates the management to provide the necessary action and resources to overcome the ergonomic issues in the floor. Once the management commitment ensures the development project cost, the development projects can be initiated in the MSP floor. An initial investment has to be made by management to provide resources. Once the development projects were done, a study can compare the ergonomics benefits in terms of cost.

8.5 Conclusions

The CMDQ survey indicates that the high occurrence of musculoskeletal ache and discomfort (mostly in the foot, knee, lower leg, thigh, low back, and shoulders) among the standing sewing machine operators emphasizes the need for ergonomic interventions for improving the working conditions of the lean environment. The relatively medium REBA scores in the study highlight that the operators were in medium risk level and the work station redesign and ergonomic awareness programs. The demographic characteristics like BMI and daily walking distance were a significant factor for MSD and job characteristics factors including job stress and job satisfaction were also found to be associated with the occurrence of musculoskeletal symptoms in different body regions. The ergonomic solutions like fixing the proper height of sewing machine, inclined work table, providing anti-fatigue mats, job rotation, stretching exercises and short-break approach is suggested for minimizing the absenteeism and turnover due to body ache and to increase the efficiency and quality of the product and process.

There is further research scope to consider more demographic and job characteristics and more levels in discomfort answering part. Comparative study can between standing and sitting operation of sewing production among female operators, and before/after ergonomic development in terms of performance metrics.