An ergonomic intervention to relieve musculoskeletal symptoms of assembly line workers at an electronic parts manufacturer in Iran

Abstract

Background:
Prolonged, awkward postures among assembly line workers can lead to work-related musculoskeletal disorders (WMSDs).

Objective:
This study determined the prevalence of WMSDs and ergonomic risk factors among assembly line workers at an electronic parts manufacturer, and introduced a low-cost ergonomic intervention.

Methods:
Data were gathered by means of a questionnaire. The Rapid Upper Limb Assessment (RULA) technique was used to determine ergonomic risk factors. A low-cost intervention, designed to improve working postures was introduced.

Results:
Most musculoskeletal symptoms were associated with the lower back (73.6%), wrist/ hands (71.7%), and neck (67.9%). Most (80%) of the working postures analyzed using the RULA were at action levels 3 or 4.

Conclusions:
The ergonomic intervention resulted in a significant reduction in posture scores for the neck and trunk. This indicated that the intervention helped to improve workplace ergonomics.

Full text

AUTHOR COPY
Work 61 (2018) 515–521
DOI:10.3233/WOR-182822
IOS Press
515
An ergonomic intervention to relieve
musculoskeletal symptoms of assembly
line workers at an electronic parts
manufacturer in Iran
Hadi Daneshmandia, Dohyung Keeb, Mojtaba Kamaliniac,∗, Mohammad Oliaeic
and Heidar Mohammadid
aResearch Center for Health Sciences, Institute of Health, Shiraz University of Medical Sciences, Shiraz, Iran
bDepartment of Industrial and Management Engineering, Keimyung University, Dalseo-gu, Taegu,
South Korea
cDepartment of Occupational Health Engineering, School of Health, Shiraz University of Medical
Sciences, Shiraz, Iran
dDepartment of Occupational Health and Safety Engineering, School of Health, Larestan University
of Medical Sciences, Larestan, Iran
Received 10 January 2018
Accepted 6 September 2018
Abstract.
BACKGROUND: Prolonged, awkward postures among assembly line workers can lead to work-related musculoskeletal
disorders (WMSDs).
OBJECTIVE: This study determined the prevalence of WMSDs and ergonomic risk factors among assembly line workers
at an electronic parts manufacturer, and introduced a low-cost ergonomic intervention.
METHODS: Data were gathered by means of a questionnaire. The Rapid Upper Limb Assessment (RULA) technique was
used to determine ergonomic risk factors. A low-cost intervention, designed to improve working postures was introduced.
RESULTS: Most musculoskeletal symptoms were associated with the lower back (73.6%), wrist/ hands (71.7%), and neck
(67.9%). Most (80%) of the working postures analyzed using the RULA were at action levels 3 or 4.
CONCLUSIONS: The ergonomic intervention resulted in a significant reduction in posture scores for the neck and trunk.
This indicated that the intervention helped to improve workplace ergonomics.
Keywords: Electronic manufacturer, musculoskeletal disorders, posture, risk factor, RULA
1. Introduction
Work-related musculoskeletal disorders (WM
SDs) are a serious concern in industries in many
∗Address for correspondence: Mojtaba Kamalinia, Department
of Occupational Health Engineering, School of Health, Shiraz Uni-
versity of Medical Sciences, Shiraz, Iran. Tel.: +98 7137256001;
Fax: +98 7137260225; E-mails: kamalinia@sums.ac.ir and
mokamalinia@gmail.com.
countries, as they can reduce working time, lower
productivity and increase the health costs of indus-
trial labor [1–6]. WMSDs also are a leading cause of
sick leave, occupational injuries and disabilities in
both industrially developed and developing countries
[4, 7–10]. The situation is particularly critical in
developing countries, where only cases that are
serious enough to lead to disability are recorded
[4]. For example, in Colombia, the estimated total
1051-9815/18/$35.00 © 2018 – IOS Press and the authors. All rights reserved

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516 H. Daneshmandi et al. / Ergonomic intervention in a manufacturing company
cost of WMSDs relative to workers’ productivity
was US$171.7 million, representing around 0.2% of
the country’s gross domestic product in 2005 [11].
Prevention is now a national priority [9].
WMSDs are associated with various physical
factors, including the exertion of force, repetitive
movements, awkward postures and vibration [1, 12,
13]. One of the most important risk factors that
ergonomists focus on is the posture or position of
the body while working [7, 14]. A review of the sci-
entific evidence of a relationship between physical
workplace factors and WMSDs found strong evi-
dence that an awkward posture was a risk factor for
disorders of the neck, shoulders, back and wrists/
hands [9, 14]. The adoption of a posture that deviates
from the body’s neutral position for a long period of
time creates tension in the limbs and causes adverse
health effects such as discomfort, fatigue and pain
[7]– eventually leading to musculoskeletal disorders
[7, 15].
WMSDs — resulting from repetitive movements,
standing for long periods, and awkward postures
— are the most prevalent occupational diseases
among assembly line workers in the automotive,
telecommunication, electronics industries [1, 8, 12,
13]. Many adopt static postures for long periods of
time, creating effects that include increased fatigue,
pain and stiffness in active muscles [7, 16, 17].
According to Aghilinejad [7] more than 75% of dis-
comfort experienced by assembly line workers is
linked to back, neck and shoulder regions. Another
study showed that 83.4% of workers had experienced
WMSD symptoms in their back, leg and shoulder
regions [18].
Various studies have examined the effectiveness
of ergonomic interventions designed to prevent
WMSDs. Some confirm that the prevalence of
WMSDs noticeably decreased post-intervention [7,
13, 19]. Aaras [15] reported that sick leave due to
WMSDs reduced from 5.3% to 3.1%, and turnover
fell from 30.1% to 7.6%, after the implemen-
tation of ergonomic interventions at workstations
in the telecommunications industry. This suggests
that ergonomics may be an effective support for
good working conditions, and consequently reducing
WMSDs [7].
In developing countries, such Malaysia and
Iran, electronics is one of the largest revenue-
generating industries. However, businesses struggle
to achieve high levels of quality and productivity
and to provide good working conditions for their
workers. At the same time, costs must be kept
low to remain competitive in the global market
[8, 20].
In Iran, in particular, no studies have been car-
ried regarding the design of the workstation for
an assembly unit in the electronics industry. The
aims of the present study were, therefore, to deter-
mine the prevalence of WMSDs, to quantify the
ergonomic risk factors, and to introduce and evalu-
ate a low-cost ergonomic intervention. The company
that took part in the study produces fixed and mobile
telephones, telecommunications equipment, digital
switches, base transceiver stations, etc.
2. Method
2.1. Participants
This cross-interventional study was conducted
with assembly line workers who assembled electronic
boards for a parts manufacturer in Iran. These boards
were a major part of the company’s finished products.
Our preliminary study had established a high base-
line rate of musculoskeletal symptoms in the lower
back (78.3%), neck (63.8%), and shoulders (60.9%)
among workers [9].
The sample was based on the census method, and
consisted of 53 assembly line workers of the visual
inspection unit, with at least one year’s experience
in the position (Table 1). The assembly line itself
consisted of four processes: through-hole technol-
ogy, surface-mount technology, visual inspection
and functional testing. Participants consisted of 44
women and 9 men with average age of 38.75 years.
Table 1
Demographic statistics of assembly line workers and working
conditions (N = 53)
Characteristics Mean (SD)
Age (years) 38.75 (6.2)
Weight (kg) 68.2 (2.14)
Height (cm) 159 (9.4)
Job tenure (years) 16 (5.5)
Weekly working time (hours) 34 (2.7)
No. (%)
Gender
Female 44 (83.0)
Male 9 (17.0)
Marital status
Married 9 (17.0)
Single 44 (83.0)
Working posture
Standing 32 (60.4)
Sitting 3 (5.7)
Sitting–Standing 18 (34.0)

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H. Daneshmandi et al. / Ergonomic intervention in a manufacturing company 517
Most assembly line tasks were performed in sitting
(through-hole technology and visual inspection
units), standing (functional testing unit), and sitting-
standing (surface-mount technology unit) positions.
The study was conducted in accordance with the
2008 revision of the Helsinki Declaration of 1964.
All subjects voluntarily participated in the study, after
receiving information about its objectives, and signed
written informed consent forms before it began.
2.2. Instruments
The General Nordic Questionnaire was used to
determine the initial prevalence of WMSDs. The
validity and reliability of the Persian version has been
evaluated by Choobineh et al. [21]. The questionnaire
consisted of two parts: 1) demographic characteris-
tics (i.e., gender, age, job tenure, body weight, marital
status); and 2) questions about any WMSDs in var-
ious parts of the body over the past 12 months. The
questionnaire was completed in the workplace during
face-to-face interviews that lasted 30 minutes, with an
occupational hygienist.
The Rapid Upper Limb Assessment (RULA) was
employed to assess the physical exposure of employ-
ees to WMSD risks [22]. RULA is a survey method
developed for use in ergonomic investigations of
workplaces where work-related upper limb disorders
are reported. This tool requires no special equipment
and provides a quick assessment of the posture of
the neck, trunk and upper limbs, along with the mus-
cle function and external loads experienced by the
body in seated jobs, such as those undertaken by the
assembly line workers [22]. In the RULA technique,
the total risk score would be extracted from relevant
matrix and table. Total score can be in four action
levels as follows:
Action level 1 (the total risk score is 1–2: no changes
are required).
Action level 2 (the total risk score is 3–4: fur-
ther investigation is needed/and changes may be
required).
Action level 3 (the total risk score is 5–6: investigation
and changes are required soon).
Action level 4 (the total risk score is 7≤: investigation
and changes are required immediately).
For the RULA analysis, videos were made of work-
place scenes for each individual task cycle. The visual
inspection unit consisted of five similar workstations,
and approximately ten workers worked in each work-
station. While performing various tasks in the unit
(visual inspection unit), a video file from the working
postures was recorded. After reviewing the recorded
video, 20 most repetitive/awkward/static postures
were selected and analyzed using the RULA method.
2.3. Ergonomic intervention
Following the RULA analysis, the visual inspec-
tion was selected as object of the ergonomics
intervention due to the awkward postures of the neck
and lower back. In this task, the inappropriate view-
ing angle means that workers may have to bend
their head forward to check the electronic boards,
which puts pressure on the neck and shoulder area. To
improve the situation, a small, forward-tilted mount
was designed to hold the boards (Fig. 1). First, a 3-
dimensional schema of the board holder was designed
in Solid Works software (ver. 2014). A prototype was
built and assessed, then improved. Next, the final
sample was made. Its dimensions were 70 ×50 cm
(width ×height), with two moving parts (parts 1 and
2). The angle of part 1 could be adjusted from 0◦to
45◦(towards or away from the user) (Fig. 1a). Sim-
ilarly, part 2 could be slid towards or away from the
user over a distance of 0 to 30 cm (Fig. 1b).
Participants used the board holder for two months
(Fig. 2). After this period, the working postures of
participants were assessed using the RULA tech-
nique.
2.4. Statistical analysis
Statistical analysis was performed using Statisti-
cal Package for the Social Sciences (SPSS) version 16
(SPSS Inc, Chicago, IL, USA). The aim was to assess
the effectiveness of the corrective actions offered by
the board holder. Because the data did not appear to
follow a normal distribution, the Wilcoxon nonpara-
metric test was used to compare RULA scores before
and after the intervention.
3. Results
3.1. Prevalence of WMSDs
Table 2 indicates the prevalence of musculoskele-
tal disorders symptoms as a function of body part for
assembly line workers over the preceding 12 months.
This shows that the lower back was the most com-
monly affected body region (73.6%), followed by the
hand/ wrist (71.7%), neck (67.9%), shoulder (62.3%)
and knee (62.3%).

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518 H. Daneshmandi et al. / Ergonomic intervention in a manufacturing company
Fig. 1. a. Adjustability range of part 1 of the board holder (0 to 45◦). b. Adjustability range of part 2 of the board holder (0 to 30 cm).
3.2. Ergonomic intervention
Table 3 and Fig. 3 present the posture scores of
assembly line workers evaluated by the RULA tech-
nique before and after the intervention. Before the
intervention, the trunk had the highest score (3.25),
while the upper arm and forearm were in second
place (2.65). Table 3 reveals that the board holder
reduced scores for the trunk and neck from 3.25 and
2.55 to 1.6 and 1.5, respectively. These reductions
were significant based on the Wilcoxon nonparamet-
ric test (p< 0.01). Scores for the upper arm and wrist
only changed a little: from 2.65 and 2.0 to 2.60 and
1.90, respectively (p> 0.70). However, the score for
the lower arm increased slightly (by 0.05) after the
intervention (p< 0.01). Scores for the feet were iden-
tical before and after the intervention.
Before the intervention, 80% of the analyzed pos-
tures were rated at an action level of 3 or over, with
an average of 3.15. This indicates that investigation
is required and changes must be made quickly or
immediately [22]. However, post-intervention only
one posture was rated 3; one posture was rated 1 and
18 postures were rated 2 (Fig. 4). The average rat-
ing was 2.0, which indicates either that the posture is
acceptable, or that further investigation is needed and
changes may be required [22]. The Wilcoxon non-
parametric test showed that there were appreciable
differences in total scores and action levels before
and after the intervention (p< 0.01).

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H. Daneshmandi et al. / Ergonomic intervention in a manufacturing company 519
Fig. 2. Workplace arrangement before and after the introduction of the board holder.
Table 2
Prevalence of musculoskeletal disorders by body part in the past
12 months (N = 53)
Body part Yes No
No. (%) No. (%)
Neck 36 (67.9) 17 (32.1)
Shoulders 33 (62.3) 20 (37.7)
Upper back 24 (45.3) 29 (54.7)
Lower back 39 (73.6) 14 (26.4)
Elbow 17 (32.1) 36 (67.9)
Hand/wrist 38 (71.7) 15 (28.3)
Legs 18 (34.0) 35 (66.0)
Knee 33 (62.3) 20 (37.7)
Feet/ankle 25 (47.2) 28 (52.8)
4. Discussion and conclusions
This study shows that WMSDs symptoms are com-
mon among assembly line workers in an electronics
parts manufacturer in Iran. In the 12 months pre-
ceding the study, their prevalence was highest in the
back (73.6%), followed by the hand/wrist (71.7%)
and the neck (67.9%). These findings are consis-
tent with previous studies which report a high rate
of WMSDs in assembly line workers in commu-
nications companies, semiconductor industry and
television manufacturers [5, 7, 9, 13]. The high preva-
lence rate of WMSDs symptoms in the present study
may be attributed to: 1) low number of participants
who included in the study, and 2) the high proportion
of young women workers (83.0%), as the findings are
consistent with the results of Kamalinia et al. [9], who
found that WMSD symptoms were frequently found
in female and young workers.
The RULA analysis showed that 80% of the pos-
tures examined in this study were at levels 3 or 4,
meaning that the need for corrective action is urgent.
This is similar to the results of Choobineh et al.
[23], which indicated that more than 88% of postures
adopted in the telecommunications industry were at
action level 3 or 4. It is known that a correctly- posi-
tioned workstation can be a safe and effective way to
reduce awkward postures [7, 17]. In this study, the
Table 3
RULA scores and action levels for assembly line workers pre- and post-intervention
Body part Pre-intervention Post-intervention P-value
Max Min Mean Max Min Mean
Upper arm 4 1 2.65 4 1 2.60 0.94
Forearm 3 1 2.65 4 2 2.70 0.01
Wrist 3 1 2.00 3 1 1.90 0.71
Neck 4 1 2.55 3 1 1.50 0.001
Trunk 4 2 3.25 3 1 1.60 <0.001
Feet 1 1 1.00 1 1 1.00 1.00
Total 7 2 5.85 5 2 3.65 <0.001
Action level 4 1 3.15 3 1 2.00 0.001

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520 H. Daneshmandi et al. / Ergonomic intervention in a manufacturing company
Fig. 3. Mean RULA scores for different body areas before and
after intervention.
Fig. 4. Distribution of action levels before and after the
intervention.
board holder was selected as the way to ergonomi-
cally improve the situation. This tilted, square plate
was mounted on the worktable used to support the
electronic board during the inspection. It reduced the
need for assembly line workers to bend their neck and
trunk forward while working, and provided a good
viewing angle for it to be inspected.
This study found that the ergonomic intervention in
the form of the electronic board holder significantly
reduced the average action level (from 3.15 to 2.0),
while 95% of analyzed postures were 2 or less. The
significant decrease in the action level was related to
improvements in the posture of the trunk and neck.
This was confirmed by the result of the Wilcoxon
nonparametric test, which showed that posture scores
for the trunk and neck before and after the interven-
tion were significantly different. On the other hand,
the posture score for the lower arm slightly increased
after the intervention. This was because, although the
holder reduced the need to bend the trunk and neck
forward to inspect the board, its forward-tilted angle
increased the flexion of the lower arm in order to hold
the board on the worktable during the inspection. An
ergonomic chair, with an armrest to support the fore-
arm and wrist, was proposed as a way to solve this
problem.
Aghilinejad et al. [7] showed that optical magni-
fication loupes enhance visual clarity of electronic
circuit assembly workers and improve their work-
ing postures such that the postural deviation of the
head, neck and back are reduced. All these results
are consistent with our findings and demonstrate the
effectiveness of ergonomic interventions in reduc-
ing the incidence of WMSDs. Also, another study
conducted by Motamedzade et al. [13] supports our
findings.
Many studies have also suggested that the
ergonomic interventions can have positive effects on
several factors, such as musculoskeletal discomfort
and disorders, working postures and conditions, pro-
ductivity, product quality and cost, etc. [8, 12, 13, 23,
24]. The present study is consistent with this earlier
research, and it confirms that working postures were
significantly improved due to the ergonomic interven-
tion. However, this study did not address any other
effects. Further work on the effects of ergonomic
interventions that vary the factors mentioned above
is needed.
4.1. Limitations
In this study, working postures were assessed using
a pen and paper observational method (RULA) —
instrumental methods such as electromyography, and
electrogoniometry may yield different results. Sec-
ondly, the number of the studied subjects was low.
This may affect the discomfort and prevalence rates
reported by Nordic questionnaire. Thus, the findings
related to WMSD symptoms derived from Nordic
questionnaire are to be interpreted cautiously. More-
over, the sample was limited to assembly line workers
in an electronics parts manufacturer. Therefore, the
results of the study may not be generalizable to other
workplaces and working groups.

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H. Daneshmandi et al. / Ergonomic intervention in a manufacturing company 521
Acknowledgments
The authors would like to thank the managers and
assembly line workers at the Iranian Telecommu-
nication Manufacturing Company for their valuable
cooperation.
Conflict of interest
None declared.
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