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International Journal of Engineering Research ISSN:2319-6890)(online),2347-5013(print)
Volume No.3, Issue No.4, pp : 190-195 01 April 2014
IJER@2014 Page 190
Analysis on the Work-Related Musculoskeletal Disorders (WMSD’s) Based on
Ergonomic Study in Case of Industry Study
Khairul Akmal Shamsuddin1, a, Mohd Norzaimi Che Ani2, b, A.R. Ab-Kadir2, c, Mohd Hairizal Osman2, d
1Mechanical Section, Universiti Kuala Lumpur - Malaysian Spanish Institute, Kulim Hi-Tech Park, 09000
Kulim, Kedah, Malaysia.
2Manufacturing Section, Universiti Kuala Lumpur - Malaysian Spanish Institute, Kulim Hi-Tech Park, 09000
Kulim, Kedah, Malaysia.
akhairulakmal@msi.unikl.edu.my, bmnorzaimi@msi.unikl.edu.my, cahmadrazlee@msi.unikl.edu.my
dmhairizal@msi.unikl.edu.my
Abstract —Musculoskeletal disorders (MSDs) can affect the
body's muscles, joints, tendons, ligaments and nerves. Most
work-related MSDs develop over time and are caused either
by the work itself or by the employees' working environment.
The paper presents a case study on the analysis of the Work -
related musculoskeletal disorders (WMSD’s) occur when
there is a mismatch between the requirements of the job and
the physical capacity of the human body. Risk factors linked
with WMSD’s include repetitive motion, heavy lifting,
forceful exertion, awkward posture, and rapid hand and wrist
motion. In a review of loss-based data (1993), ergonomic-
related injuries are the single greatest source of lost-time in
the workplace today. Currently, these injuries account for
between 33% and 40% of total worker compensation
spending. This statistics compiled by the Occupational Safety
and Health Administration (OSHA), the National Institute for
Occupational Safety and Health (NIOSH).
Keywords— Musculoskeletal disorders (MSDs), Work-related
mus culoskeletal disorders (WMSD’s), Occupational Safety and
Health Administration (OSHA), National Institute for
Occupational Safety and Health (NIOSH).
1. INTRODUCTION
In a review of loss-based data (1993), ergonomic-related
injuries are the single greatest source of lost-time in the
workplace today. Currently, these injuries account for between
33% and 40% of total worker compensation spending. As the
work force ages and healthcare cost continue to rise, these
percentages are expected to hit 50% by the end of the century.
The study has been conducted at small medium industry (SME)
is in the beverage industry where it produces, bottles, and
distributes a variety of products. The Bottle House Department
of contains a de-palletizing workstation, which is the starting
point of the bottling process. Employees at this workstation are
complaining of physical distress that may be associated with
exposure to the potential material handling-based risk factors as
they manually unload pallets of new cases of bottles from a
pallet to a conveyor. Consequently, 8 employee complaints of
lower back or elbow pain indicate that ergonomic risk factors
may exist at the de-palletizing workstation.
This company is in the beverage industry producing,
bottling,
and distributing a variety of products. The starting point of
the bottling process begins at the de-palletizing workstation
where employees manually
unload new cases of bottles from a pallet onto a conveyor.
Workers at this station were complaining of discomfort in the
shoulders, neck, elbows, hands, wrists, and lower back from
excessive overhead reaching at the beginning of a new pallet
and forward bending toward the end of the unloading process.
2. BACKGROUND AND SIGNIFICANT
According to the National Occupational Research Agenda,
lower back pain is one of the most common and significant
musculoskeletal problems in the world. Thirty percent of
American workers are employed in jobs that routinely require
them to perform activities that may increase risk of
developing low back disorders. The Occupational Safety and
Health Administration reports over one million workers each
year are affected by back pain. Economically, lower back
disorders in the United States cost between $50 and $100
billion each year. An estimated $11 billion of those costs are
covered by worker compensation, with an average back injury
claim costing the employer $8,300, which is more than twice
the average cost of all other types of compensable claims
combined (NORA). Lower back and elbow pain complaints
from employees have alerted upper management that
ergonomic risk factors may be present. If a WMSD injury
occurs, the company will have direct costs including medical
and indemnity payments as well as indirect costs such as
paying overtime, decreased employee morale, lost production,
or missed production schedules, etc. The company
has recognized that the de-palletizing workstation may pose
extraordinary ergonomic risk factors. Therefore, the company
prefers to reduce or eliminate the potential risk factors before
the employees become symptomatic. The purpose of this
study is to identify, via ergonomic assessment, if workstation
design and work practice risk factors are currently exposing
employees to injuries and illness es at company’s de -
palletizing workstation.
The goals of this study include:
• Identify to what extent that employees are suffering
from WMSD symptoms.
• Analyze and quantify the extent that ergonomic risk
factors may be present at de-palletizing workstation.
International Journal of Engineering Research ISSN:2319-6890)(online),2347-5013(print)
Volume No.3, Issue No.4, pp : 190-195 01 April 2014
IJER@2014 Page 191
3. ASSUMPTIO NS AND ASSESSMENT
Assumptions made for this study include:
• The employees at case study industry are earnest in
their complaints about back and elbow pain they are
experiencing from the de-palletizing workstation
• The employees at case study industry fill out the
WMSD Signs and Symptom Surveys with integrity and without
bias
• The employees at case study industry perform
consistently the methods and practices they use to de-palletize
while the workstation is being videotaped.
The purpose of this study was to identify, via ergonomic
assessment, if workstation design and work practice risk factors
were exposing employees to injuries and illnesses at case study
Company’s de-palletizing workstation. This ergonomic
assessment was performed in three steps. First, the researcher
began by identifying the extent of the 3 employees discomfort
by utilizing work-related musculoskeletal d isorder symptom
surveys. These results indicated the severity and location of the
employee’s distress and informed the researcher of the extent of
the problem. In the second step, the researcher video-recorded
an employee’s bodily postures while per forming job duties at
the de-palletizing workstation. The body angles and posture
measurements were incorporated into three ergonomic
methodologies to reveal the severity and amount of intervention
required by company. The results from the symptom surveys
and products of the methodologies revealed that the de-
palletizing wor kstation is in fact expos ing the employee’s to
risk factors that lead to the onset of work-related
mus culoskeletal disorders (WMSD’s). The final step in this
process was to recommend suitable engineering controls that
will reduce or eliminate those risk factors, while protecting and
preserving employees and preventing future worker
compensation expenditures.
4. DATA COLLECTION AND ANALYSIS
Once the Super-8 video recorder is positioned, the researcher
will count the number of individual cases, measure its height,
width, and weight and then determine the overall dimensions of
one full pallet. The researcher and subject can begin video
recording.
During the taping session, some data needs to be collected
on-site to complete the NIOSH Lifting Equation.
Measurements for the horizontal, vertical, and distance
multipliers will be made with a conventional tape measure,
while the asymmetric value will be projected with the
goniometric. The hand to-object interface (coupling) of the
cases and subject will be rated according to the NIOSH Lifting
Equation criteria. The researcher will also be timing the lifts per
minute for the frequency multiplier of the NIOSH Lifting
Equation 48 and the repetition criteria for the R.U.L.A. and
BRIEF Survey. Another component of the NIOSH Lifting
Equation is the conveyor (destination) height which will be
measured and documented. Any additional observations made
regarding workstation design, safe work practices, and
environmental concerns will be documented and taken into
consideration while analyzing the data. Data analysis will be
completed in several steps. First, the researcher will review
the symptom surveys to reveal if the employees are indeed
experiencing any pain or discomfort from working at the de-
palletizing station. The surveys will identify the symptom
locations and to what extent the employees are feeling
distress from potential WMSD risk factors. The main areas of
concern are the lower back, the elbows (Epicondylitis),
shoulders (TOS), and the wrists (CTS). This information will
be charted in table form and expressed as a percentage of the
population surveyed.
The second step will be to complete the R.U.L.A. and Brief
Survey by utilizing the jog shuttle VCR, goniometric, and a
water-based felt tip marker. This instrumentation will allow
the researcher to analyze the subject’s postures frame-by-
frame as they unload the pallet of cases. The felt tip marker
will allow the researcher to draw lines on the television screen
to assist in measuring the body postures and joint angles with
the goniometric. Specifically, the researcher will be looking
for the most severe instances of flexions/extensions and
ulnar/radial deviations of the hands and wrists, pronation /
supination of the forearms and elbows, shoulder
abduction/adduction, trunk twisting, forward bending, and
feet location and support. Observations for the more severe
postures and joint angles will be made while the employee is
unloading the top, 49 middle, and bottom layers of the pallet.
For example, the first section of group A in the R.U.L.A.
examines as to what degree the shoulders are raised and/or
abducted. The researcher will be able to extract those
measurements needed through a thorough examination of the
video recording and correlate the results with the criteria in
the R.U.L.A. or the Brief Survey. The product of the
R.U.L.A. is a grand score, while the results of the BRIEF
Survey are in the form of a high-risk summary.
The NIOSH Lifting Equation is the third step in this
analysis. All the data that was collected during the taping
session will be incorporated into the Recommended Wight
Limit (RWL) equation yielding the RWL. Furthermore, the
RWL will be included in the Lifting Index (LI) equation to
calculate the LI score that will be used to determine the
severity and the amount of intervention required to reduce the
risk factors that contribute to the onset of WMSD’s.
At the conclusion of the data collection process, the
information extracted from methodologies and symptom
surveys will be used by the researcher to compare and
contrast the similarities, dissimilarities, and interpret the final
results. In combination, these ergonomic assessment tools
will assist the researcher in determining whether or not the
International Journal of Engineering Research ISSN:2319-6890)(online),2347-5013(print)
Volume No.3, Issue No.4, pp : 190-195 01 April 2014
IJER@2014 Page 192
employees at case study industry are being exposed to WMSD
risk factors at the de-palletizing workstation.
5. ERGO NOMIC RISK ASSESSMENT
The employees at de-palletizing workstation are unloading
pallets of beverage cases that contain 24 new bottles per case at
an average rate of 18 cases per minute. One pallet consists of
one hundred and eight cases that weigh 12.02 pounds each.
The dimensions for an individual case (figure 1) and the overall
dimensions of one full pallet are illustrated in Figure 1.
Figure 1: Case Dimensions
Figure 2: Pallet Dimensions
The employees at this workstation have to extend their reach
over seven feet to remove the top layer of cases from a pallet.
As the pallet is unloaded, the employees at this station have to
bend forward and reach down to pick up the last row of cases
and place them on a conveyor that’s approximately 32 1/2
inches off the ground. The repetitive and awkward postures of
this nature are what the employees at the de-palletizing
workstation have to deal with on a daily basis. More
information on the employees who work at the de-palletizing
workstation and the results of the symptom surveys are in the
next sections.
A. Demographic Information
The workstations has on average has 10 employees on two
shifts that rotate in and out of the de-palletizing workstation
every half hour. Of those, six people agreed to participate in
the study by filling out the symptom surveys, therefore
representing 60% of the total possible participants. Of the
six, two (33.3%) were female and the remaining 4 (66.7%)
were male. Four (66.7%) of the six employees have been
working at the de-palletizing workstation for one year or
more, while the remaining 2 (33.3%) have less than one
year at this position. The overall results of the symptom
survey these employees filled out are discussed in the next
section.
B. Symptom Survey Analysis
The symptom surveys revealed that all 6 employees
participating in this study have in the last year experienced
some type of discomfort from working at the de-palletizing
station. Specifically, the areas of concern for this study
included the lower back, elbows/forearms, shoulders/neck,
hands and wrists. The areas of discomfort for each of the
six employees are charted in Table 1.
Table 1: Discomfort Locations
Employee
Shoulders
/ Neck
Lower
Back
Elbows /
Forearms
Hands
/Wrists
1
X
---
X
---
2
X
X
X
X
3
X
---
---
---
4
X
X
---
---
5
X
X
X
---
6
---
X
---
X
Totals
5
4
3
2
Percentage
83.3
66.6
50
33.3
As indicated in Table 1, nearly 84% of the participants
have encountered or are currently experiencing discomfort in
the shoulder and neck region. Almost 67% have encountered
lower back pain during their employment at this workstation.
Discomfort in the elbows and forearms have affected or are
currently inflicting pain on 50% of the employees, while 33%
claim distress in the hands and wrists. Nearly all of the
employees have attributed their aches and pains from the
excessive amount of overhead reaching at the beginning of a
new pallet and bending down to remove the last row of cases
at the end of a pallet. The signs and locations of discomfort
the participants specified in the symptom surveys are the
same types of work-related musculoskeletal disorders.
Several of the e mployee’s claim that their d iscomfort includes
pain, tingling, and numbness when sleeping, while the
remainder of the participants state their discomfort arises in
the form of stiffness, swelling, and a burning sensation in the
affected areas. Evidence from the symptom surveys reveal
that the de-palletizing workstation is exposing the employees
to the potential risk factors that lead to the onset of WMSD’s.
In the next section the researcher will evaluate the results of
the ergonomic analysis to better determine the causes of the
problem
International Journal of Engineering Research ISSN:2319-6890)(online),2347-5013(print)
Volume No.3, Issue No.4, pp : 190-195 01 April 2014
IJER@2014 Page 193
C. Methodology Analysis
In conjunction with the symptom surveys, the researcher will
use the results from the ergonomic methodologies to better
determine the extent of the problem at de-palletizing
workstation. The data extracted from the NIOSH Lifting
Equation, Rapid Upper Limb Assessment (R.U.L.A.), and the
Baseline Risk Identification of Ergonomic Factors (BRIEF
Survey) will help the researcher determine the severity and
amount of intervention required to eliminate the risk factors
that lead to the onset of WMSD’s.
D. NIOSH Lifting Equation
The NIOSH Lifting Equation is a methodology the
researcher used in this study to help determine to what extent
the employees are being exposed to WMSD risk factors. The
lifting equation is comprised of two parts. The first is the
Recommended Weight Limit (RWL) and the other is the
Lifting Index (LI). The researcher will calculate and discuss
the two components in the next section.
The NIOSH Lifting equation is expressed as:
RWL = LC x HM x VM x DM x AM x FM x CM (1)
The measurements required to complete this equation were
taken during the data collection process. The measurements are
documented in table 2.
Table 2: NIOSH Equation Components
Components
On-site
Measurements
Calculations
Load Constant (LC)
51 pounds
51 pounds
Horizontal Multiplier(HM )
12”
0.83
Vertical Multiplier (VM)
14.5”
0.891
Distance Multiplier (DM)
18”
0.92
Asymmetric Multiplier
(AM)
45°
0.856
Frequency Multiplier (FM)
Less than 1
hour
---
Coupling Multiplier (CM)
Poor
0.90
The RWL was calculated using the following equation of
numbers.
RWL = 51 * .83 * .891 * .92 * .856 * .90
= 26.73 pounds
RWL = 26.73 pounds
NIOSH defines the RWL for a specific set of task conditions
as the weight of the load that nearly all healthy workers could
perform over a substantial period of time without an increased
risk of developing lifting related lower back disorders. The
RWL is then required to complete the LI equation, which can
be utilized to estimate the relative magnitude of physical
stress for a lifting task. The greater the LI score, the smaller
the fraction of employees that are capable of safely sustaining
that particular level of physical exertion. A Lifting Index
score greater than 1.0 indicates a need for immediate
attention, as the lifting task has the increased potential for
accumulat ing WMSD’s, especially lower back disorders. The
Lifting Index formula is:
LI = Load Weight (L) / RWL
LI = 12.02 pounds (L) / 26.73 pounds (RWL)
LI = 0.45
The Lifting Index for the de-palletizing workstation is 0.45,
which indicates there is very little need to intervene with the
workstation. However, the results from this equation are not
consistent with the symptom surveys and employee
complaints. To obtain a better understanding of the extent the
problem, the researcher will complete the Rapid Upper Limb
Assessment.
E. Rapid Upper Limb Assessment (R.U.L.A)
R.U.L.A. is an ergonomic methodology that examines the
postures of the upper extremities, trunk, and legs. The
researcher used this methodology to capture the upper
extremity angles on the subject as they unloaded one full
pallet of cases. The next section will reveal the step-by-step
results and the grand score.
The Rapid Upper Limb Assessment is divided into three
sections, group A, group B, and a grand score table. The
results for each of the groups and the grand score are
presented in Table 3.
Table 3: R.U.L.A Score Sheet
Group A: Arm and Wrist Analysis
Score
Step 1: Upper Arm Position
5
Step 2: Lower Arm Position
1
Step 3: Wrist Position
3
Step 4: Wrist Twist
1
Step 5: Posture Score A
5
Step 6: Add Muscle Use Score
1
Step 7: Add Force / load Score
2
Step 8: Final Wrist / Arm Score
8
Group B: Arm and Wrist Analysis
Score
Step 9: Neck Position
4
Step 10: Trunk Position
5
Step 11: Leg
2
Step 12: Posture Score B
7
Step 13: Add Muscle Use Score
1
Step 14: Add Force / Load Score
2
Step 15: Final Neck, Trunk and
Leg Score
10
International Journal of Engineering Research ISSN:2319-6890)(online),2347-5013(print)
Volume No.3, Issue No.4, pp : 190-195 01 April 2014
IJER@2014 Page 194
Table 4: Grand Score Table
1
2
3
4
5
6
7+
1
1
2
3
3
4
5
5
2
2
2
3
4
4
5
5
3
3
3
3
4
4
5
6
4
3
3
3
4
5
6
6
5
4
4
4
5
6
7
7
6
4
4
5
6
6
7
7
7
5
5
6
6
7
7
7
8+
5
5
6
7
7
7
7
Grand Score = 7
Group A of the R.U.L.A. analyzed the arms and wrist postures.
The angle criteria for each of the steps were scored according to
the subject’s postures on screen. Steps one and two located the
degrees of upper and lower arm extensions, while three and
four identified the amount of wrist flexion and twisting. The
scores combined are utilized in table A of the R.U.L.A. to yield
a posture score of five. The muscle use and force/load numbers
are then added to the posture score to result in a final wrist and
arm score of eight. The final wrist and arm score (8) is inputted
into the grand score table.
Group B of the R.U.L.A. analyzed the neck, trunk, and leg
positions. Steps nine, ten, and eleven measured the degrees of
neck extension, bending and twisting of the trunk, and support
from the legs, which yielded a posture B score of seven. Added
to the seven, is the muscle use and force/load score to result in
the final neck, trunk, and leg score of ten. The ten is
incorporated into the grand score table to result in a final
overall score of seven. Seven indicates the need for further
investigation and immediate intervention at the workstation.
Seven is the highest score allotted for this assessment therefore
the results are significant.
The Baseline Risk Identification of Ergonomic Factors
(BRIEF Survey) is another ergonomic methodology that
examines the postures of the upper extremities, neck, back, and
legs. This assessment process is similar to the R.U.L.A. method
as it assists in determining the severity and amount of
intervention required to reduce or eliminate the risk factors
associated with WMSD’s. The results of the BRIEF Survey
will be discussed in the next section.
F. Result and Recommendation
The BRIEF Survey analyzes the posture, force, duration, and
frequency for the left and right hands, wrists, elbows, and
shoulders. It also examines the posture, force, duration, and
frequency for the neck, back, and legs. The results for the
applicable criteria for the BRIEF Survey are illustrated in Table
5. The posture analysis for the left and right hands and wrists
indicated that the subject was using a pinch grip to grasp the
cases and their wrist flexion was greater than 45 degrees. The
force of the pinch grip was estimated at greater than two
pounds, therefore scoring a two for the hand and wrist
category. The posture rating for the elbows includes.
Table 5: High Risk Summary
Left
Right
◄Hand / Wrist
◄Hand / Wrist
◄Elbow
◄Elbow
◄Shoulder
◄Shoulder
Each grouping has a total number score. If the number is
two or greater, then the area of the body that’s affected gets
marked in the High Risk Summary Box. (Table 5) All of the
body parts in this survey have been marked with a red triangle
in the High Risk Summary Box. These results indicate the
need for intervention with some type of controls to
reduce/eliminate the WMSD risk factors. The R.U.L.A.,
BRIEF, and symptom surveys indicated significant potential
for WMSD’s at de-palletizing workstation. These results are
consistent with the employee complaints that the excessive
overhead reaching and awkward bending to pick up cases is
the overall cause of their distress. In contrast, however, the
NIOSH Lifting Equation did not indicate substantial problems
in that the product of this methodology yielded a Lifting
Index Score of only 0.45. A disadvantage of this equation 60
is that it only accounts for the perfect lifting tasks that are
directly from the pallet or floor to the destination spot. The
lifting tasks at this workstation often require employees to
shuffle their feet or walk around the pallet to gain access to all
sides of the pallet of cases. The NIOSH Lifting Equation is
not applicable to those types of conditions. Whereas, the
R.U.L.A. and Brief Survey measure the full body including
the upper extremities, back, legs, and trunk.
The researcher’s first reco mmendation is to fully automate
the de-palletizing workstation. Alvey Systems, Inc.
(Packexpo.com, 2002) manufactures the Accu-Flow De-
palletized, which removes cases from the pallets and
unscrambles them onto a single conveyor line. The Accu-
Flow is capable of handling 3000 pounds with an output rate
of up to seventy cases per minute. The benefits of this system
are that it is 3-4 times faster than manual de-palletizing,
reduces product damage, and eliminates the WMSD risk
factors that currently cause the employees discomfort. Other
benefits of the Accu-Flow De-palletized include built-in
control functions such as oversized load protection and a
complete diagnostics system in the event of a malfunction
Final
Arm
and
Wrist
Score
= 8
Final
Neck,
Truck
and
Leg
Score
= 10
High Risk Summary
◄Neck
◄Back
◄Legs
International Journal of Engineering Research ISSN:2319-6890)(online),2347-5013(print)
Volume No.3, Issue No.4, pp : 190-195 01 April 2014
IJER@2014 Page 195
(Packexpo.com, 2002).
If the fore-mentioned reco mmendation is not feasible due to
cost, space limitations, or applicability to the current process at
case study industry, the researcher has provided a second
recommendation. This option for engineering the risk factors
out of the workstation involves a hydraulic lift table provided
by Advance Lifts, Inc. (Avancelifts.com, 2002). This lift table
has a fifteen hundred pound capacity and a travel distance of 96
inches. Currently, the overall pallet height is 91 inches. This lift
table can be utilized by submerging it into the floor where the
workstation currently exists. The de-palletized operator would
be able to place the pallet on the lift table at floor level and then
lower it 64 until the top layer is at roughly waist height on the
employee. An additional option is adding an Advance Lift’s
work positioned (turn-table) to the hydraulic table. The benefit
of adding the turn-table is that as employee unloads the layers
of cases, the table can be raised and then rotated to keep the
cases directly in front of them. The overall benefits of this
system would include relieving the amount of awkward
postures such as excessive overhead reaching and forward
bending that is currently causing the distress the employee’s are
experiencing. Also, once the operators are familiar with using
the lift table, this control could possibly reduce the amount of
product loss and increase product output per minute.
Overall, the goal of utilizing the engineering controls is to
reduce or eliminate the excessive reaching and bending
associated with working at the current manual de-palletizing
workstation. The employees are currently and will continue in
the future to suffer discomfort in the upper extremities and
lower back if the workstation design is not automated. The net
effect of the above options would be to relieve the workers
from risk factors that lead to the onset of WMSD’s which
plague the nation’s industries today.
6. Conclusion
The combined results of the R.U.L.A., BRIEF, and symptom
surveys reveal that de-palletizing workstation does expose the
employees to the risk factors that lead to the onset of work-
related musculoskeletal disorders. The scores for the
R.U.L.A. and BRIEF Survey were as high as the
methodologies would allow, which indicates the need for
immediate intervention. The researcher has concluded the
best way to reduce or eliminate the risk factors is by utilizing
some form of engineering controls. The current workstation is
inadequately designed, rendering safe work practices,
personal protective equipment, and administrative controls
that no applicable. Consequently, the best practice to
eliminate the excessive overhead reaching 63 at the beginning
of a new pallet and the forward bending when the pallet is
nearly empty is to engineer the risk factors out of the
workstation. In the next section, the researcher will provide
some possible engineering controls to reduce or eliminate the
risk factors that lead to the employee’s distress.
7. Acknowledgement
THIS PAPER WAS PARTIALLY SUPPORTED BY FINANCE FROM
UNIVERSITI KUALA LUMPUR (UNIKL) AND THE CASE STUDY
AND ANALYSIS HAS BEEN DONE IN BEVERAGE INDUSTRY IN
PRAI, PENANG.
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iii. Heizar, Jay and Render,Barry (2008). Operation
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iv. Liker, J.K and Hoseus, Michael (2008). Toyota Culture:
The Heart and Soul of the Toyota Way. McGraw Hill
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White, T and Tanchoco, B (2003), Facilities Planning (3rd
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