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American Journal of Applied Sciences 7 (8): 1087-1092, 2010
ISSN 1546-9239
© 2010 Science Publications
Corresponding Author: Baba Md. Deros, Department of Mechanical and Materials Engineering,
Faculty of Engineering and Built Environment, University Kebangsaan Malaysia, UKM, Bangi,
43600 Selangor, Malaysia
1087
Work-Related Musculoskeletal Disorders among Workers’ Performing
Manual Material Handling Work in an Automotive Manufacturing Company
Baba Md. Deros, Dian Darina Indah Daruis, Ahmad Rasdan Ismail,
Nurfarhana Abdullah Sawal and Jaharah A. Ghani
Department of Mechanical and Materials Engineering,
Faculty of Engineering and Built Environment,
University Kebangsaan Malaysia, UKM, Bangi, 43600 Selangor, Malaysia
Abstract: Problem statement: The study investigated the prevalence of Musculoskeletal Disorders
(MSD) among workers who perform the Manual Material Handling (MMH) task in an automotive
manufacturing plant in Malaysia. A cross sectional study was carried out among the workers in an
automotive manufacturing plant. Approach: Respondents were selected through random sampling.
Then, a Body Parts Symptoms Survey (BPSS) data sheets were given to the workers to obtain the
prevalence of MSD among them. Later, a few workers were selected based on the In-House Clinic
(IHC) visitations data for interviews. Results: Five hundreds workers showed that the highest
prevalence of MSD was Low Back Pain (LBP). It was found from interviews of 17 workers who had 3
or more visitation times to the IHC that the main reason of the ergonomic risk comes from the task that
they perform. It was found that the highest prevalence of MSD was lower back pain, followed by pain
at feet/ankle and pain at upper back regions. Almost one third of the study populations claimed to feel
uncomfortable to their upper back and lower back. Conclusion: It was concluded that the back pain
the workers are experiencing may be a result of their ignorance in the correct and ergonomic
techniques in materials handling.
Key words: Automotive, back pain, manual material handling, musculoskeletal disorders, prevalence
INTRODUCTION
Any job that involves heavy labor or Manual
Material Handling (MMH) may be in a high-risk
category. MMH entails lifting, but also includes
climbing, pushing, pulling and pivoting, all of which
pose the risk of injury to the back. The term
musculoskeletal disorder refers to conditions that
involve the nerves, tendons, muscles and supporting
structures of the body (Bernard, 1997). Ranging from
back strains to carpal tunnel syndrome, it is common
for employers to find MSD accounting for 40% or more
of their injury cases and 60% of their workers
compensation costs (Adams, 2005). MSD are always
being associated with MMH.
Most data concerning back pain are related to
developed countries and information about back pain in
developing and low-income countries are still lacking
(Ghaffari et al., 2006). In Malaysia, the awareness of
back pain due to study is still at a budding stage. The
issue is considered new among the workers in Malaysia
compared to other developed countries and it is still
being promoted by the professionals especially the
Occupational Safety and Health (OSH) practitioners to
enhance the awareness level of all Malaysians. Besides
affecting the workers health, back pain and MSD can
also lower productivity. As according to Punnet and
Wegman (2004), back pain is associated with
substantial financial cost and loss of quality of life.
Study of Low Back Pain (LBP) among Iranian
industrial workers by Ghaffari et al. (2006) found that
the 1-year prevalence of self-reported LBP in the
Iranian industrial population was 21%. The prevalence
rate of absence due to LBP was 5% per annum. The
multiple logistic regression models indicated that the
following remained as risk indicators for LBP in the
previous 12 months: increasing age, no regular
exercise, heavy lifting, repetitive study and monotonous
study.
A cross-sectional study was conducted by Bernard
(1997) to assess the association of upper extremity
MSD and work-related factors among employees using
Am. J. Applied Sci., 7 (8): 1087-1092, 2010
1088
video display terminals at a large metropolitan
newspaper factory. The study included 1050 randomly
selected workers from four departments. The workers
were asked to complete questionnaires on symptoms,
job tasks and psychosocial and study organization
conditions. MSD of the upper extremities were defined
by frequency, duration and intensity of symptoms not
attributable to acute injury. The results suggest a high
prevalence of MSD of the upper extremities among
newspaper factory employees and they provide
additional evidence that increased work load, time
pressure and greater hours of computer use are related
to the occurrence of work-related MSD among these
workers, particularly for disorders in the hand or wrist
area.
According to year 2007 in-house report of an
automotive manufacturing company in Malaysia, the
total number of workers suffering the back pain had
increased from the year 2005 until 2006. A total of 954
cases of back pain were reported by the in-house clinic
throughout the year. From the total number of cases
reported, 783 workers had been involved with this back
pain illness, which means that some of these workers
had visited the in-house clinic for more than one time
due to backache.
Hence, the current study was carried out to confirm
the above claims from the automotive manufacturing
company itself. The current study is to determine the
prevalence of MSD among workers who perform the
MMH before any ergonomics intervention can be
introduced into the company being studied and at the
same time to determine the ergonomics risk of MMH at
the workstation of workers with back pain.
MATERIALS AND METHODS
The study was conducted in an automotive
manufacturing company in Malaysia. Respondents were
production operators from various sections in the
production plant, such as from the Press Section, Body
Section, Paint Section, Assembly Section, Casting
Section, Machining Section, Engine Section and other
support departments. The sample size for this study was
15% from the total production operators who worked in
the same shift. Fifteen percent was thought to be
enough as to represent the total number of production
workers in the company which is around 6000 people.
There are approximately 3000 operators in each shift.
The shift rotates every week where the day shift
workers for the week will be working in the night shift
the week after and vice versa.
Therefore, for the purpose of this study, only about
500 workers were involved. However, for the
precaution in case of any missing data, more than 10%
from the calculated figures of the sample size were
added. More than 500 workers were given out the
questionnaire. Data were collected using three
approaches through the Body Parts Symptoms Survey
(BPSS), self-reported questionnaire for workstations
conditions and oral interview.
The survey of comfort level to all body parts is
crucial in an ergonomics assessment. It is a standard
and systematic way of identifying ergonomic risk
(Zavitz, 2008). For this study, BPSS was used to
determine which body part is exposed to the risk from
the study especially when dealing with MMH task. As
shown in Fig. 1, twelve body parts were identified to
be evaluated by the workers to determine the comfort
level that they feel. The survey used Likert-Scale
method where the comfort levels were numbered from
1-5, the higher number means that the more
uncomfortable they felt at that certain part of the body.
The questionnaires had been pre-tested in order to
check the reliability and validity of the questions.
Results from the pre-test enabled the real test to be
carried out, however with some changes to certain
words that were very technical to layman language as
a result from focus group discussion. Random
sampling method have been applied, where the
authors randomly select the subjects and gave them
the BPSS sheet where they need to circle the comfort
level they feel at each of the body parts.
A cross-reference was carried out through the In-
House Clinic (IHC) reports of visitations due to back
pain. For workers who had visited three times or
more to the clinic for back pain, they were selected
to fill in the self-reported questionnaire to assess
their workstation conditions in terms of ergonomics.
This was to answer the second aim of this study.
Fig. 1: Body parts symptoms survey sheet
Am. J. Applied Sci., 7 (8): 1087-1092, 2010
1089
The self-assessment by the worker involved two parts
(Part A and B) with sixteen questions. Part A was about
the worker’s background which was to determine the
current health status, previous injuries or accidents,
hobbies, lifestyles and previous job. While in Part B,
the questions were more focused on the current
workstation that they are in; the condition, the
environmental factors and also the human factors.
Interview sessions were conducted for the reason
that there might be some misunderstanding of the
questions in the questionnaire form. It was also done to
ensure the reliability of the data collected, so that what
was answered in the survey questionnaire was the same
as found from the interview.
RESULTS
A total of 525 workers were involved in this study.
From the total of respondents, only 473 workers
(90.1%) answered the working shift column, while 496
of the overall respondents (94.5%) answered the
department column. There were almost similar
percentages between respondents from Shift A and Shift
B, with only eleven workers difference. The study
populations were from Shift A workers with 39.7%
(188 workers), followed by Shift B with 37.4% (177
workers). The total of Normal Shift workers who were
involved in this study was 108, which contributed to
22.8% of the study population.
The BPSS forms were distributed at the resting
areas and at the canteen. These locations were chosen
so that workers were minimally disturbed during their
working hours. Most of the subjects participated in the
study were from the Paint Section (26.4%). The reason
might be because the section itself comprises of two
main buildings of the plant (car body paint building and
bumper paint building). The second highest percentage
of the study samples were from the Body Section
(12.9%), where their main task was to attach the cast
body parts together and welds them to make a car body.
The rest are from; engine 12.5%, logistics 10.5%, repair
and accessory 8.3%, casting 7.1%, quality control
6.9%, R&D 5.2%, maintenance 3.6%, assembly 3.2%,
machining 0.2% and others 4%.
Table 1 showed the trend of MSD among the
workers in the plant. Low back pain showed the highest
prevalence on the ‘very uncomfortable’ column, with
122 out of 500 workers (24%) claimed to feel very
uncomfortable to their lower back. The trend followed
by feet/ankle and upper back with 20% (104 workers)
and 19% (97 workers) respectively. In addition to that,
a similar MSD trend was shown under the ‘extremely
uncomfortable’ column, where 8% of 505 workers
claimed to feel it at their lower back. Meanwhile, 6%
feel extremely uncomfortable at their feet/ankle and 4%
to their upper back.
Table 2 showed the prevalence of back pain among
the workers according to their working section. The
first three columns in the BPSS were considered as
‘comfortable’, including the middle column which is
‘neutral’. The last 2 columns were considered as
‘uncomfortable’.
Table 3 showed the workers’ background on their
knowledge of ergonomics and the back pain they
suffered. Thirteen out of 17 workers did not know about
ergonomics. All of them had never heard of the word
ergonomics. Table 3 also lists out the details of the
workers’ hobbies and lifestyle.
Workers’ perception on the workstation conditions
were detailed in Table 4. The assessment of tasks
performed by the workers who were having back pain
is shown in Table 5.
Table 1: Musculoskeletal Disorders (MSD) trend
Body part EC (%) VC (%) Nt (%) VU (%) EU (%)
Eye 130 (26.0) 166 (33.2) 140 (28.0) 52 (10.4) 12 (2.4)
Neck 87 (17.4) 170 (34.0) 159 (31.8) 76 (15.2) 8 (1.6)
Shoulder 67 (13.4) 157 (31.4) 189 (37.8) 75 (15.0) 12 (2.4)
Upper back 52 (10.4) 137 (27.4) 194 (38.8) 97 (19.4) 20 (4.0)
Elbow 109 (21.8) 173 (34.6) 156 (31.2) 50 (10.0) 12 (2.4)
Lower back 48 (9.6) 110 (22.0) 179 (35.8) 122 (24.4) 41 (8.2)
Arm 95 (19.0) 163 (32.6) 169 (33.8) 65 (13.0) 8 (1.6)
Hand wrist 107 (21.4) 174 (34.8) 142 (28.4) 60 (12.0) 17 (3.4)
Thigh 91 (18.2) 156 (31.2) 187 (37.4) 58 (11.6) 8 (1.6)
Knee 64 (12.8) 157 (31.4) 166 (33.2) 88 (17.6) 25 (5.0)
Calf of leg 78 (15.6) 150 (30.0) 188 (37.6) 72 (14.4) 12 (2.4)
Feet/ankle 78 (15.6) 139 (27.8) 146 (29.2) 104 (20.8) 33 (6.6)
EC: Extremely Comfortable; VC: Very Comfortable; Nt: Neutral; VU: Very Uncomfortable; EU: Extremely Uncomfortable
Am. J. Applied Sci., 7 (8): 1087-1092, 2010
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Table 2: Prevalence of back pain
Body part
---------------------------------------------------------------------------------------------------------------------------------------
Upper back Lower back
-------------------------------------------------------------- -----------------------------------------------------------
Department/section C (%) UC (%) N C (%) UC (%) N
Body 41 (67.2) 20 (32.8) 61 42 (71.2) 17 (28.8) 59
Paint 110 (85.3) 19 (14.7) 129 95 (74.2) 33 (25.8) 128
Assembly 13 (81.3) 3(18.8) 16 10 (62.5) 6 (37.5) 16
Casting 25 (71.4) 10 (28.6) 35 21 (61.8) 13 (38.2) 34
Machining 1(100) - 1 1(100) - 1
Engine 41 (69.5) 18 (30.5) 59 36 (61.0) 23 (39.0) 59
Logistics 39 (76.5) 12 (23.5) 51 36 (70.6) 15 (29.4) 51
Maintenance 11 (61.1) 7(38.9) 18 10 (58.8) 7 (41.2) 17
Quality control 28 (82.4) 6(17.6) 34 22 (66.7) 11 (33.3) 33
Repair and accessory 26 (66.7) 13 (33.3) 39 22 (56.4) 17 (43.6) 39
R and D 22 (91.7) 2(8.3) 24 16 (66.7) 8 (33.3) 24
Others 5(71.4) 2(28.6) 7 6(54.5) 5(45.5) 11
Overall 383 (76.6) 117 (23.4) 500 336 (67.2) 163 (32.6) 500
C: Comfortable; UC: Uncomfortable
Table 3: Worker’s background
Ergonomics knowledge History of back pain Hobby
---------------------------------------------------------- ----------------------------------------------------------- -----------------------------------------------------------
Attended Back pain Involved Prolonged
Know Ergonomics limits Surgery to the previous ache until Same problem Planting/
Ergonomics class routine work back accident present in previous job gardening Sports
------------------- ------------------ ------------------- -------------------- ------------------ ------------------ -------------------- ----------------- -------------------
Yes No Yes No Yes No Yes No Yes No Yes No Yes No Yes No Yes No
Section (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%)
Body 1(25) 7(53.8) - 8(50) 4(57.1) 4(40) 1(100) 7(43.8) 5(55.6) 3(37.5) 2(50) 6(46.2) 3(50) 5(45.5) 1(50) 7(46.7) 3(30) 5(71.4)
Assembly - 4(30.8) - 4(25) 1(14.3) 3(30) - 4(25) 1(11.1) 3(37.5) 1(25) 3(23.1) - 4(36.4) - 4(26.7) 3(30) 1(14.3)
Engine 2(50) 2(15.4) 1(100) 3(18.8) 1(14.3) 3(30) - 4(25) 3(33.3) 1(12.5) 1(25) 3(23.1) 3(50) 1(9.1) - 4(26.7) 3(30) 1(14.3)
Machining 1(25) - - 1(6.3) 1(14.3) - - 1(6.3) - 1(12.5) - 1(7.7) - 1(9.1) 1(50) - 1(10) -
N 4 13 1 16 7 10 1 16 9 8 4 13 6 11 2 15 10 7
Table 4: Worker’s background (cont’d)
Lifestyle
--------------------------------------------------------------------------------------------------------------------------------------------------------
Frequent exercise Maintain good posture Taking balance diet Enough rest and sleep
----------------------------------- ------------------------------- --------------------------- ---------------------------
Yes No Yes No Yes No Yes No
Section (%) (%) (%) (%) (%) (%) (%) (%)
Body 3(27.3) 5(83.3) 3(33.3) 5(62.5) 4(40) 4(57.1) 5(50) 3(42.9)
Assembly 3(27.3) 1(16.7) 2(22.2) 3(25) 2(20) 2(28.6) 1(10) 3(42.9)
Engine 4(36.4) - 3(33.3) 2(12.5) 3(30) 1(14.3) 4(40) -
Machining 1(9.1) - 1(11.1) - 1(10) - - 1(14.3)
N 11 6 9 8 10 7 10 7
N = 17
Table 5: Workstation self-assessment-workstation conditions
Working environment
Restricted space for Insufficient --------------------------------------------------------------------------------------------
Condition Space is small movement height Ventilation Lighting Noise Temperature
-------------------- --------------------- -------------------- -------------------- -------------------- -------------------- -------------------- -----------------
OK NG Yes No Yes No Yes No OK NG OK NG OK NG OK NG
Section (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%)
Body 6(46.2) 2(50) 3(50) 5(45.5) 1(33.3) 7(50) 4(66.7) 4(36.4) 6(50) 2(40) 8(50) - 3(33.3) 5(62.5) 6(50) 2(40)
Assembly 3(23.1) 1(25) - 4(36.5) - 4(28.6) 1(16.7) 3(27.3) 3(25) 1(20) 4(25) - 2(22.2) 2(25) 3(25) 1(20)
Engine 4(30.8) - 2(33.3) 2(18.2) 2(66.7) 2(14.3) 1(16.7) 3(27.3) 3(25) 1(20) 3(18.8) 1(100) 4(44.4) - 3(25) 1(20)
Machining - 1(25) 1(16.7) - - 1(7.1) - 1(9.1) - 1(20) 1(6.3) - 1(12.5) - 1(20)
N 13 4 6 11 3 14 6 11 12 5 16 1 9 8 12 5
N = 17; NG: Not Good
Am. J. Applied Sci., 7 (8): 1087-1092, 2010
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Table 6: Workstation self-assessment-task performed
Lifting (%) Pushing (%) Pulling (%) Trunk bending (%) Head lifting (%) Twisting (%) Extended reach (%)
-------------------- -------------------- ----------------------- ---------------------- --------------------- ---------------------- -----------------------
Section Yes No Yes No Yes No Yes No Yes No Yes No Yes No
Body 7 (46.7) 1 (50) 6 (50) 2 (40) 7 (58.3) 1 (20) 7 (50) 1 (33.3) 3 (37.5) 5 (55.6) 7 (50) 1 (33.3) 6 (60) 2 (28.6)
Assembly 3 (20) 1 (50) 2 (16.7) 2 (40) 2 (16.7) 2 (40) 3 (21.4) 1 (33.3) 2 (25) 2 (22.2) 2 (14.3) 2 (66.7) 2 (20) 2 (28.6)
Engine 4 (26.7) - 3 (25) 1 (20) 2 (16.7) 2 (40) 3 (21.4) 1 (33.3) 2 (25) 2 (22.2) 4 (28.6) - 1 (10) 3 (42.9)
Machining 1 (6.7) - 1 (8.3) - 1 (8.3) - 1 (7.1) - 1 (12.5) - 1 (7.1) - 1 (10) -
N 15 2 12 5 12 5 14 3 8 9 14 3 10 7
Excessive force (%) Foot lifting (%) Excessive motion (%) Repetitive work (%) Static load (%) Static pressure (%) Vibration (%)
--------------------- -------------------- ------------------------- --------------------- -------------------- ---------------------- -----------------------
Yes No Yes No Yes No Yes No Yes No Yes No Yes No
Body 5 (55.6) 3 (37.5) 3 (50) 5 (45.5) 4 (44.4) 4 (50) 7 (53.8) 1 (25) 5 (71.4) 3 (30) 6 (50) 2 (40) 4 (50) 4 (44.4)
Assembly 1 (11.1) 3 (37.5) 2 (33.3) 2 (18.2) 2 (22.2) 2 (25) 2 (15.4) 2 (50) 2 (28.6) 2 (20) 1 (8.3) 3 (60) 3 (37.5) 1 (11.1)
Engine 3 (33.3) 1 (12.5) 1 (16.7) 3 (27.3) 2 (22.2) 2 (25) 4 (30.8) - - 4 (40) 4 (33.3) - - 4 (44.4)
Machining - 1 (12.5) - 1 (9.1) 1 (11.1) - - 1 (25) - 1 (10) 1 (8.3) - 1 (12.5) -
N 9 8 6 11 9 8 13 4 7 10 12 5 8 9
N = 17
DISCUSSION
Trend of MSD: Departments or sections with more
than 10% workers are the Paint, Body, Engine and
Logistics. Among these four, Body and Engine sections
involved with demanding MMH works such as lifting,
moving and handling heavy mostly metal parts. It is
expected that the prevalence of MSD for those workers
were back and feet discomforts or pains (Table 1).
Morken et al. (2003) suggested that MSD especially
LBP have high prevalence rate especially among the
blue-collar workers, to the point that it can be used to
predict sickness absence.
Furthermore, the production volume was high most
of the time. Therefore, with the short tact time work
plan, it was observed that there were high frequencies
of carrying out similar tasks. It might be the reason to
the pains experienced at lower and upper back. As for
the feet and ankle, it might be due to the fact that most
tasks were standing position tasks. The workers might
feel exhausted for the prolonged standing position.
Prevalence of back pain: As shown in Table 2, the
highest prevalence among the main sections for upper
back pain was found among Body section (32.8%) and
Engine section (30.5%) workers. As for the support
group, Repair and Accessory section noted the highest
percentage of upper back pain with thirteen out of 39
workers, 33.3% have an uncomfortable feeling to their
upper back. Meanwhile, for the uncomfortable feeling
to the lower back, the top three highest prevalence
among the main sections were found at Engine section
(39.0%), followed by Casting section (38.2%) and
Assembly section (37.5%). This again is expected since
all the materials were medium to large sized metal parts
of the car body and engine. Manual handling of those
parts require much force from the workers. Wrong
postures and techniques of handling the parts will
definitely cause discomfort and pains. A more detail
investigations to quantify the degree of risk by body
part need to be carried out in the next step of risk
assessment such as identifying how many degrees the
back bend or how much force exerted.
Ergonomic risks: It could be presumed that the back
pain that the workers’ are experiencing may be a result
of not knowing the correct and ergonomic techniques
and practices in MMH. As shown in Table 3, 40% of
the workers thought that back pain had limited their
routine work, nevertheless only four of them still
experiencing back pain until present. Quite alarming is
that nine of them had previously involved in accidents
while one had a surgery to the back. Six workers
claimed to have suffered the back pain since their
previous job and the back pain worsen at their current
workstations as a result of MMH. From this health
background result, it is thought that it does not
represent the ergonomic risks as a result of task that the
workers of the whole plant perform. Furthermore, the
number of workers that have been visiting the in-house
clinic for three times and more is too small to be
representative for the whole plant. The results also
showed that the workers are practicing good lifestyle
with frequent exercise, maintaining good posture, taking
balance diet and get enough rest and sleep. However,
smoking habit is another important point to be
investigate in any prevalence of musculoskeletal-disorder
studies especially if it’s involving blue-collar workers
(Inoue and Harada, 2002). This matter is not discussed
here and will be critically analyzed in future study.
Overall judgment of the workstation conditions
was good. Most of the workers answered the condition
of the workstation was acceptable, the space is not
small and did not restrict the workers for movement and
the height was also satisfactory (Table 4). About the
working environment, apart from ventilation, lighting
and temperature conditions, half of the workers (50%)
agreed that their working environment was noisy due to
Am. J. Applied Sci., 7 (8): 1087-1092, 2010
1092
the machines and tools used to perform the work.
Nearly most of the task stated including lifting,
pushing, pulling, trunk bending, twisting and extended
reach (Table 5). From the oral interview, the workers
claimed that those tasks to be the main factor of back
pain. Their claims as shown in Table 6 correlated well
with the findings showed in Table 1 and 2. In addition
to the above issues, workers also feel that the back pain
they had suffered is due to the excessive force and
motions used during work. Thirteen workers performed
the same task over and over again, repetitively.
Repetitive work, although in sitting position has been
shown to be the cause of MSD and LBP (Ghaffari et al.,
2006). Only seven workers worked in standing
positions for long durations. Half of the workers
perceive vibration effect when handling the job; this
may due to the fact that workers from Body and
Assembly sections used an impact gun which is
vibrated to perform their jobs.
CONCLUSION
A total of 500 workers were involved in the BPSS
to achieve the first objective of the study, which is to
determine the trend of musculoskeletal disorders and
the prevalence of back pain among workers who
perform the Manual Material Handling (MMH) study. It
was found that the highest prevalence of MSD was
lower back pain, followed by pain at feet/ankle and pain
at upper back regions. Almost one third of the study
populations claimed to feel uncomfortable to their
upper back and lower back. The workers claimed that
the back pain is due to the excessive force and motions
used during study. It was presumed that the back pain
the workers are experiencing may be a result of their
ignorance in the correct and ergonomic techniques in
materials handling.
ACKNOWLEDGMENT
The researchers would like to acknowledge the
financial contributions both from Ministry Of Science,
Technology and Innovation and Ministry Of Higher
Education for their grants.
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