PG Thesis Sample

INVESTIGATIONS ON WORK-RELATED
MUSCULOSKELETAL DISORDERS AMONG HAND
SCREEN PRINTING WORKERS
A PROJECT REPORT (PHASE-II)
Submitted by
MOHANKUMAR P
13MMR011
in partial fulfilment of the requirements
for the award of the degree
of
MASTER OF ENGINEERING
IN
MECHATRONICS
DEPARTMENT OF MECHATRONICS ENGINEERING
SCHOOL OF BUILDING AND MECHANICAL SCIENCES
KONGU ENGINEERING COLLEGE
(Autonomous)
PERUNDURAI, ERODE – 638 052
MAY 2015

ii
DEPARTMENT OF MECHATRONICS ENGINEERING
KONGU ENGINEERING COLLEGE
(Autonomous)
PERUNDURAI ERODE – 638052
MAY 2015
BONAFIDE CERTIFICATE
This is to certify that the Project report entitled INVESTIGATIONS ON WORK-
RELATED MUSCULOSKELETAL DISORDERS AMONG HAND SCREEN
PRINTING WORKERS is the bonafide record of project work done by
MOHANKUMAR P (Register no: 13MMR011) in partial fulfilment of the requirements
for the award of the Degree of Master of Engineering in Mechatronics of Anna University,
Chennai during the year 2014 – 2015.
SUPERVISOR HEAD OF THE DEPARTMENT
(Dr. S. SHANKAR) (Signature with seal)
Date:
Submitted for the end semester viva voce examination held on_________
INTERNAL EXAMINER EXTERNAL EXAMINER

iii
DECLARATION
I affirm that the Project Report titled INVESTIGATIONS ON WORK-
RELATED MUSCULOSKELETAL DISORDERS AMONG HAND
SCREEN PRINTING WORKERS being submitted in partial fulfilment of
the requirements for the award of Master of Engineering is the original work
carried out by me. It has not formed the part of any other project report or
dissertation on the basis of which a degree or award was conferred on an
earlier occasion on this or any other candidate.
Date: MOHANKUMAR P
(Reg.No:13MMR011)
I certify that the declaration made by the above candidate is true to the best of
my knowledge.
Date: SUPERVISOR
(Dr. S. SHANKAR)

iv
ABSTRACT
Work-related Musculoskeletal disorders (WMSD) are pain or disorder in muscles
and skeletal systems due to the work. WMSD is one of the major problems in working
environment and resulted in productivity loses. Along with those other major factors such
as high repetitiveness, awkward posture, force, prolonged standing, vibration and
temperature etc., also supports to cause MSD. Several studies inferred about WMSD and
its risk factors among different working environment around the world. Yet there is no
specific study to analyze work-related musculoskeletal disorders among Hand screen
printing (HSP) industry workers. The current study continues the investigation of work-
related upper extremity and low back disorders among the hand screen printing industry
workers. The people with minimum 1 year experience in the hand screen printing industry
and without any medical history were considered for the study. Analysis were done
through SPSS and statistical analysis reports 75.1% had Low back pain and 66.2% had
atleast one upper extremity pain in past 1 year. Risk factors such as gender, age
experience, BMI, job tenure, and stressfulness in job tenure were significantly (p<0.05)
were significantly associated with low back disorders. For upper extremities, job tenure
avail sick leave, stress in job, marital status and age were significantly (p<0.05) associated
with the upper extremity disorders. Statistical analysis reported shoulder and lower back
were the mostly affected areas among HSP industry workers. Among the three different
works, printing work had higher risks and more intend to cause pain among workers. So,
Experimental analyses were conducted during printing work on targeted muscles such as
Deltoid, Tres Major and Subcapularis on shoulder region and RES, LES on Lower back
region. Among the three muscles in the horizontal flexion movement, EMG analysis report
Deltoid (0.130mV-0.255 mV) shares the major load then followed by Tres major (0.023
mV-0.217mV) and Subcapularis (0.037 mV-0.089 mV). In Erector spinae region, RES
shares major load to withstand the posture (0.037 mV-0.107 mV) followed by LES (0.031
mV- 0.081 mV). The experimental results vary accordingly with Age, Experience and
Body mass Index (BMI).

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ACKNOWLEDGEMENT
First and foremost, I deeply thank my God for his blessings. I thank our beloved
correspondent Thiru. V.K.MUTHUSAMY, B.A.,B.L., and all the members of Kongu
Vellalar Institute of Technology Trust at this high time for providing us with plethora of
facilities to complete my project successfully.
I take privilege to express my profound thanks to our beloved principal
Prof. S. KUPPUSWAMI, B.E., M.Sc (Engg.), Dr.Ing (France) who has been a support
of moral strength and a source of incessant encouragement to me.
I express my sincere thanks to Dr. K. KRISHNAMURTHY, M.E., Ph.D., FIV.,
Dean, School of Building and Mechanical Sciences, for his expensive guidance and
suggestions.
I express my sincere thanks to Dr. R. PARAMESHWARAN, M.E., Ph.D., Head
of the Department Mechatronics Engineering, for his priceless guidance and suggestion.
I take immense pleasure to express my heartfelt thanks to my beloved project
guide, Dr. S. SHANKAR, M.E., Ph.D., for his valuable teaching and encouragement that
always led me to make a right decision whenever I face difficulties in project work.
I also thank our project coordinator Dr. R. PARAMESHWARAN, M.E., Ph.D.,
for her valuable suggestions for completing the project successfully.
Last, but not the least, I deeply thankful to all the teaching and non-teaching staff
members of Mechatronics Engineering Department and all our fellow students who stood
with me to complete my project successfully. I also extend warm thanks to my beloved
Parents.

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TABLE OF CONTENTS
CHAPTER No. TITLE PAGE No.
ABSTRACT iv
LIST OF TABLES ix
LIST OF FIGURES x
LIST OF ABBREVATIONS xi
1 INTRODUCTION
1.1 INVESTIGATION BACKGROUND
1.2 NEED FOR STUDYING MSDs
1.3 WORK-RELATED MUSCULOSKELETAL DISORDERS
1.4 MUSCLE ANATOMY AND PHYSIOLOGY
1.4.1 Neuromuscular junction
1.4.2 Rest potential
1.4.3 Action potential
1.4.4 Motor unit
1.5 ELECTROMYOGRAPHY AND MUSCLE LOAD DETECTION
1.6 STRUCTURE OF THE THESIS
1
1
1
2
2
3
4
5
5
6
7
2 LITERATURE SURVEY
2.1 LITERATURE REVIEW OF STATISTICAL ANALYSIS
2.2 LITERATURE REVIEW OF EXPERIMENTAL ANALYSIS
2.3 SUMMARY OF THE LITERATURE REVIEW
2.4 OBJECTIVES
8
8
10
11
11
3 METHODOLOGY
3.1 WORK AND WORKPLACE
3.1.1 Printing process in hand screen printing industry
3.2 STUDY PROTOCOL FOR STATISTICAL ANALYSIS
3.2.1 Questionnaire study
12
12
12
13
13

vii
3.2.2 Data collection
3.2.3 Data analysis
3.3 STUDY PROTOCOL FOR EXPERIMENTAL ANALYSIS
3.3.1 Electrode placement
3.3.2 Data Acquisition and Instrumentation
3.3.3 Data analysis
13
14
15
15
16
17
4 RESULTS AND DISCUSSIONS
4.1 STATISTICAL ANALYSIS
4.1.1 Overall discomfort by Questionnaire study
4.1.2 Prevalence of MSD on Low back and its associated risks
4.1.3 Prevalence of MSD on upper extremities and its risk factors
4.1.3.1 Probability ratio by gender
4.1.3.2 Association of UEDs and relative risk factors
4.2 EXPERIMENTAL ANALYSIS (sEMG study)
4.2.1 Muscular load study
4.2.2 Angle movement study
4.3 DISCUSSION
4.3.1 Discussion about statistical analysis results
4.3.2 Discussion about experimental analysis results
19
19
19
20
22
22
22
26
26
27
27
27
33
5 CONCLUSION AND FUTURE SCOPE
5.1 CONCLUSION
5.2 FUTURE SCOPE
REFERENCES
34
34
34
35
LIST OF PUBLICATIONS 39

ix
LIST OF TABLES
TABLE No. TITLE PAGE No.
4.1 Prevalence of low back pain with individual risk factor 21
4.2
4.3
4.4
Association of upper extremity disorder and its risk actors
EMG RMS (mV) values of targeted muscles
Joint movements (Goniometer readings)
24
26
27

x
LIST OF FIGURES
FIGURE No. TITLE PAGE No.
1.1 Neuromuscular junction 3
1.2 Muscle contraction process by Action potential 4
1.3
1.4
3.1
Motor unit
sEMG based muscle load detection systems
HSP work environment
6
6
13
3.2
3.3
3.4
3.5
3.6
Targeted muscles for electrode placement
sEMG Sensors and systems
Field recordings using sEMG kit during printing work
Front panel view of Customized LabVIEW program
Block diagram view Customized LabVIEW program
15
16
16
17
18

xi
LIST OF ABBREVATIONS
BMI
CI
CTS
LBP
LLDs
MSD
OR
SPSS
UEDs
WMSDs
Body Mass Index
Confidence Interval
Carpal Tunnel Syndrome
Low Back Pain
Lower limb disorders
Musculoskeletal Disorder
Odds Ratio
Statistical Package for Social Sciences
Upper Extremity Disorders
Work-related Musculoskeletal Disorders
sEMG Surface Electromyography
RMS Root Mean Square
MPF Mean Power Frequency
MDF Median power Frequency
RES Right Erector Spinae
LES Left Erector Spinae

1
CHAPTER 1
INTRODUCTION
1.1 INVESTIGATION BACKGROUND
This work aimed to investigate the work related musculoskeletal disorders
(WMSD) among hand screen printing (HSP) workers in western part of Tamil Nadu. Hand
screen printing industries are majorly concentrated on the western part of Tamil Nadu and
people employed for the works are mostly belong to rural areas. The workers employed in
the particular work were easily affected by musculoskeletal disorders. This cross sectional
research analyzes the each and every postures and risk factors associated with the hand
screen printing work. So, this type of research and Ergonomics intervention may be
provide good solution to reduce the musculoskeletal disorders among HSP workers.
1.2 NEED FOR STUDYING WMSDs
The study of WMSDs is very essential since it provides better understanding of
anatomical sites of the human body and the various internal and external forces that affects
the health conditions during work. Most of the people across the world wide depend on
any one of the occupation as a livelihood. Each and every work has its own risk factors
that support to cause musculoskeletal disorder (MSD). MSD for workers resulted in people
to quit their job, productivity loss and long time sick for workers. Moreover it gives better
understanding of forces and postures that affects the health conditions of workers during
work. The hand screen printing work is fully manual and its work nature constitute of
prolonged standing, repetitiveness, force and awkward postures. Due to the risk factors,
poor Ergonomics and poor work practices the HSP workers were affected with Work-
related musculoskeletal disorders. The workers reported discomforts were majorly at lower
back, shoulder, knees, and ankle/feet. Thus this study is very important for HSP workers to
reduce the WMSD risks by implementing proper ergonomic workstation in hand screen
printing industry.

2
1.3 WORK-RELATED MUSCULOSKELETAL DISORDERS
Work-related musculoskeletal disorders (WMSDs) are pain or disorders on muscles
and joints linked with skeletal systems due to work. The MSD mostly concentrated on
tendons, nerves, ligaments, cartilages, and joints. Osteoarthritis, Rheumatoid arthritis,
Osteoporosis, Myasthenia gravis, Carpal tunnel syndrome, and Tendonitis are some
examples. Work which involves repetitive motions, awkward posture and prolonged
standing causes these disorder and results pain during work and rest time. This HSP work
mostly involves all upper and lower extremity regions resulted disorders in both upper and
lower arms. The prolonged and repetitive motion cause severe pain in legs. The repetitive
awkward posture causes pain in lower back and repetitive force cause pain shoulder in
manner.
1.4 MUSCLES ANATOMY AND PHYSIOLOGY
Muscle is an organ that contains muscle tissue, nerves, connective tissue and blood
vessels. Muscle cells contain protein filaments of actin and myosin that slide past one
another, producing a contraction that changes both the length and the shape of the cell.
Muscle cells are cylindrical in nature with diameter varies from 50 to 100 µm. Muscles
function to produce force and motion. They are primarily responsible for maintaining and
changing posture, locomotion, as well as movement of internal organs. Muscle tissues are
derived from the mesodermal layer of embryonic germ cells in a process known
as myogenesis. There are three types of muscle, skeletal or striated, cardiac, and smooth.
Muscle action can be classified as being either voluntary or involuntary. The electrolyte
ion displacement on the cell membranes primarily sodium and potassium are responsible
for the organism-specific information system.
Muscle spindles are muscle sensory receptors and are located within the body of a
muscle. Spindles primarily detect changes in the length of the muscle. They convey length
information to the central nervous via sensory neurons. This information can be processed
by the brain to determine the position of body parts. The responses of muscle spindles to
changes in length also play an important role in regulating the contraction of muscles, by
activating motoneurons via the stretch reflex to resist muscle stretch. Renshaw cells are
physically located in the central nervous system. They receive collateral branches from the
motoneurons themselves and have an inhibitory effect. Renshaw cell inhibition represents

3
a negative feedback mechanism. The rate of discharge of the Renshaw cell is broadly
proportional to the rate of discharge of the motor neuron is inversely proportional to the
rate of the Renshaw cell. Renshaw cells therefore act as “limiters” or “governors” on the
alpha motor neuron system, thus helping to prevent muscular damage from tetanus.
1.4.1 Neuromuscular junction
The neuromuscular junction connects the nervous system to the muscular
system via synapses between efferent nerve fibers and muscle fibers, also known as muscle
cells as shown in figure 1.1. As an action potential reaches the end of a motor
neuron, voltage-dependent calcium channels open allowing calcium to enter the neuron.
Calcium binds to sensor proteins (synaptotagmin) on synaptic vesicles triggering vesicle
fusion with the plasma membrane and subsequent neurotransmitter release from the motor
neuron into the synaptic cleft. In vertebrates, motor neurons release acetylcholine (ACh), a
small molecule neurotransmitter, which diffuses through the synapse and binds nicotinic
acetylcholine receptors (nAChRs) on the plasma membrane of the muscle fiber, also
known as the sarcolemma.
Figure 1.1 Neuromuscular junction (Source: Wikipedia)

1.4.2 Rest potential
The relatively static
membrane potential (or resting voltage), as opposed to the specific dynamic
electrochemical phenomena called
the cell membrane is polarized, maintaining a negative interior charge of
forming called as electrical gradient. In rest condition a concentration gradient is present
with 10 times more sodium (Na
inside. The membrane is semi
usually cannot cross it. Certain ions, potassium (K
the membrane at specialized gates
Figure 1.2 Muscle contraction process by Action potential
The relatively static membrane potential of quiescent cells is called the
(or resting voltage), as opposed to the specific dynamic
electrochemical phenomena called action potential and graded membrane potential
the cell membrane is polarized, maintaining a negative interior charge of
with 10 times more sodium (Na+
) on the outside and 20 times more potassium (K
inside. The membrane is semi-permeable and electrically charged ions and molecules
usually cannot cross it. Certain ions, potassium (K+
), chloride (cl-
), and sodium (Na
the membrane at specialized gates as depicted in figure 1.2.
Figure 1.2 Muscle contraction process by Action potential (Source: Wikipedia)
4
cells is called the resting
(or resting voltage), as opposed to the specific dynamic
membrane potential. At rest
the cell membrane is polarized, maintaining a negative interior charge of -70mV and
sium (K+
) on the
permeable and electrically charged ions and molecules
), and sodium (Na+
) cross
(Source: Wikipedia)

5
1.4.3 Action potential
An action potential is a short-lasting event in which the electrical membrane
potential of a cell rapidly rises and falls, following a consistent trajectory. The action
potential starts from the central nervous system, impulses propagate through the axons to
reach the muscle cells. The impulse propagation through the muscular junction is described
in the following four steps. When the impulse reaches the muscle, an action potential starts
the propagation through the muscle (I) to (IV).
 Impulse arrives at the motor end plate causing release of Acetilcholin (ACH) from
vesicles in the axon terminus. Ca2
+
act as intermediate in causing exocytosis by
ACH vesicles into the synapse.
 ACH diffuses across the synapse to bind to receptors on the sarcolemma.
 Binding of ACH to the receptors opens chemically regulated ion gates. This causes
Na+
to enter the cell producing depolarization as shown in figure 1.2.
I. As depolarization reaches the threshold of -55mV, the action potential is triggered
off and Na+
rushes into the cell. The membrane potential reaches +30mV and a new
impulse (action potential) move along the sarcolemma.
II. The propagation of the action potential occurs with a velocity of 100 m/sec.
III. The sarcolemma repolarizes: K+
leaves the cell (potassium channels open as sodium
channels close) and the positive ions are going back to the outside of the
sarcolemma (return to -70mV). More K+
than necessary leaves and the membrane
is hyperpolarized briefly. This causes the relative refractory period.
IV. Return of ions (Na+
and K+
) to their extracellular and intracellular sites by the
sodium potassium (Na+
K+
) pump.
 ACH is broken down by ACH-E (cholinesterase). This allows the receptors to
respond to another stimulus.
1.4.4 Motor unit
A motor unit is made up of a motor neuron and the skeletal muscle fibers
innervated by those motor neurons axonal terminals. Groups of motor units often work
together to coordinate the contractions of a single muscle; all of the motor units within a
muscle are considered a motor pool. When the muscle fibers of a motor unit are stimulated,
muscles start to contract as shown in figure 1.3.

6
Figure 1.3 Motor unit (Source: Wikipedia)
1.5 ELECTROMYOGRAPHY AND MUSCLE LOAD DETECTION
Electromyography (EMG) is the best technique to study the muscle activity during
contraction and expansion of muscles as shown in figure 1.4. It is kind of non-invasive
type of neuromuscular assessment. Muscle activities are detected by fixing the electrode
on the surface of the skin. sEMG (surface electromyography) is the algebraic summation
of all MU action potentials spread over the muscles. sEMG is user-friendly and suitable
method for measuring muscle activities under movement in prolonged time.
Figure 1.4 sEMG based muscle load detection systems (Source: Biometrics ltd)

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1.6 STRUCTURE OF THE THESIS
Chapter 1 introduces background information relevant to the current research and
discussed about the electromyography and detection of the muscle load.
Chapter 2 summarizes the existing analyses of the work-related upper extremity,
low back disorders and risk factors associated with the disorders for different working
environment. A survey of methods available to analyze the muscle load and signal
analyses techniques to find the muscle fatigue. This chapter concludes by providing
motivation for continuation of the future research work.
Chapter 3 describes the methodology of the research work which contains the study
protocol for statistical analysis and experiment analysis, Data analysis of the experimental
data using LabVIEW and SPSS.
Chapter 4 provides the results of the work-related upper extremity, low back
disorders and risk factors associated with the WMSDs among HSP workers. It also
provides experimental results of muscles present in upper extremity and lower back region
during the printing work which were concluded from the statistical study. Finally, the work
was discussed with the various studies done related to analyze the disorders and
fatigueness.
Chapter 5 summarizes the major conclusion of the research work and suggests the
scope of the future work. Various sources pertaining to this research work are listed in the
references.

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CHAPTER 2
LITERATURE SURVEY
Clothes are one of the basic needs of our human lives. The outcomes of
manufacturing clothes are majorly from spinning and hand screen printing industries. In
India, south region is famous for the textile business and manufacturing. For textile
manufacturing, spinning and hand screen printing plays a major role to produce required
cloth designs. The hand screen printing industries are running without proper ergonomic
design and air circulations. Though, the work is simple due to some ergonomic and
psychosocial factor present in the work leads to suffer workers by musculoskeletal
disorders easily. The literature survey related to musculoskeletal disorders provides
sufficient evidence between WMSDs, psychosocial and workplace factors. The literatures
related to experimental analysis provides sufficient method to analyze fatigue among the
hand screen printing workers.
2.1 LITERATURE REVIEW OF STATISTICAL ANALYSIS
A case control study conducted by Das and Gangopadhyay (2012) displayed the
prevalence of MSD and Physiological stress among male potato cultivators. They
displayed, the potato cultivators were suffered mostly pain on lower back, knee, ankle and
feet regions when performing different works in potato cultivation. The prolonged work
activity, high repetitiveness and awkward posture for long duration had major risk factors
for causing MSD for those potato cultivation workers. The investigation by Hanklang et al.
(2014) among construction workers shows that Lower back and shoulder is the maximum
body parts affected. The risk factors include prolonged working hours and awkward
posture were major reasons for causing WMSDs. The pattern study done by the Henry et
al. (2013) among palm plantation occupation observed that back (40%) and shoulder
region (19%) as commonly reported region, followed by neck pain (56%). 58% of palm
plantation workers reported pain in single region and nearly 10.7% of people reported pain
in two various sites. The WMSDs report by Saxena et al. (2013) discussed 83.10% dentists
having any one musculoskeletal pain in past 12 months. The dentists working with direct
vision, without assistant and in standing positions were mostly affected with

9
Lower back (57.75%) and neck pain (31.17%). The cross-sectional study done by Phajan
et al. (2014) among sugarcane farmers in North-Eastern Thailand evaluated that 82.96%
and 88.70% having musculoskeletal disorders in last 7 days and 12 months. Repetitive
motions, work related awkward posture, forceful exertions and stress about future income
were the major factors of causing MSDs in sugarcane farmers. The WMSD were asses by
using MSD Questionnaire and 2 expert physiotherapists.
The study related to upper extremity disorders conducted by Sandra Bot et al.
(2007) discussed there is positive relation between psychosocial risk factors and sick leave
for the patients visiting hospitals. The people who performing work with heavy physical
load and standing for long time during working are risk factors for taking more sick leave.
An Ergonomic intervention study reported that, a change in work station set-up for the
long time computer usage workers, there is significant difference between the reducing
MSD in ergonomic intervention group and controlled group. There was also significant
difference in pain by the physical and mental health for intervention and controlled group.
They concluded ergonomic intervention might be resulted in reduced MSDs Esmaeilzadeh
et al. (2014). The cross-sectional study conducted among the weaving industries workers
reported that female weavers were more prone to developing pain in upper and lower back;
male workers were mostly affected with knee and hand pain. The high job duration,
manual material handling and poor machinery safety were main contributing factor to
cause MSDs among power loom industry workers. Poor machinery design, mental
overload, skill requirement to perform job were significant factors for causing MSD in
handloom industry workers Nag et al. (2010).
The survey conducted on hospital for workers using the Hand 20 assessment tool
reported that women had more upper extremity disorders than men. They also reported that
workers with age greater than 25 and work involving heavy physical load were more prone
to cause MSDs. They concluded that workers with proper training would result in reduced
MSDs. The occupational hazards such as manual material handling, high stress and
working postures are some of the common issues of causing MSD. (Mattioli et al. (2009),
Waters et al. (2007), Smith et al. (2004)).A work-related upper extremity musculoskeletal
disorders survey conducted among newspaper employees by Bernard et al. (1994) showed
that 41% having upper extremities problem. They also reported that greater time working
with the video display units resulted in increasing hand/wrist problems. The survey

10
conducted on the general working population by De Zwart et al. (2000), reported that
women were higher risk of complaining high neck, shoulder, elbow, and wrist pain.
Furthermore, there were various study conducted to analyze the musculoskeletal disorders
for various occupational workers, but few work done related to ergonomics with
Biomechanics with suitable suggestions to reduce musculoskeletal pain.
2.2 LITERATURE REVIEW OF EXPERIMENTAL ANALYSIS
Balasubramanian et al. (2008) evaluated the variations of dynamic standing
postures over the static standing postures in reducing the physical stress using sEMG
analysis. The Ergonomic cycle designed for aerobic cyclist by analyzing the cyclist with
non-ergonomic cycle using sEMG assessment on reporting pain causing areas like
trapezius medial, brachii medial, latissimus dorsi medial and erector spinae muscles
bilaterally during 30 minutes of cycling. So, the ergonomic study with biomechanics
design (ergonomic design) will create WMSD free environment. Muscle fatigue analysis
for various bicycle design by Balasubramanian et al. (2014) reported RMS and MPF
values of sEMG signal is best method to analyze the sEMG signal in time domain and
frequency domain. A review on surface EMG based muscle fatigue evaluation reported,
the current trend signal acquisition and signal processing provides sufficient support to
analyze the EMG signals. The different signal analysis methods such as estimates of
sEMG amplitude, Zero-crossing rate of the signal, spike analysis are comes under time
domain methods. In frequency domain methods, Fourier-based spectral estimators,
parametric based spectral estimators, joint analysis of EMG spectrum and amplitude,
Wigner distribution and wavelets methods. Other mathematical methods such as
Frequency-band method, Logarithmic power-frequency representation, fractal analysis are
some kind of other mathematical methods for analyzing the EMG signals Cifrek et al.
(2009).
Meyland et al. (2014) analyzed muscular load sharing among the male and female
house painters using Electromyography technique inferred female house painters had
higher relative muscular loads than male colleagues without exerting ore force. Un-paired
double-sided t-test and Pearsons correlation coefficients are used to infer the result and
pain variation between the genders.

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2.3 SUMMARY OF THE LITERATURE REVIEW
From the literature survey, the high prevalence of work-related musculoskeletal
disorders were present on different occupational categories and work-related risk factors
such as awkward posture, repetitiveness, excess force and prolonged standing was mostly
reported risk factors. The high prevalence was found on lower back and shoulder. For the
analysis, researchers used various tools to find prevalence and its risk factors. But
moreover the variations in using tools couldn’t affect the findings. sEMG method was a
feasible method to analyze muscle fatigue among workers. In experimental analysis, RMS
and MPF values were the best method to analyze the signal in both time domain and
frequency domain method.
2.4 OBJECTIVES
The objectives of the present study are:
1. To investigate the relation between job related factors, psychosocial
factors and lower back disorders.
2. To identify the relation between factors associated with the upper
extremity disorders.
3. To examine the significant difference in muscle fatigue among hand
screen printing workers on upper extremity areas by variation in age and
experience by experimental analysis( sEMG).

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CHAPTER 3
METHODOLOGY
3.1 WORK AND WORKPLACE
This study was conducted among the hand screen printing workers from various
districts in western part of Tamil Nadu, India. The daily work for hand screen printing
workers is to print various designs ordered by the customers. This work is regular and
workers don’t have rest except Sunday. The workers would print 400-900 meters per day
depending on the size of the industry. The table length lies between 50-100 meter and
width more or less equal to 3 meter. During the work period, the working method and
work nature was evaluated, the risk factors were also observed.
Hand screen printing is one of the textile based work. Plain cloth materials are
purchased from weaving industry by the managers and supervisors in the printing industry.
Mostly, the work in the industry was shared with 10-15 workers. Work hours on hand
screen printing industry are ≥ 10 hours. Three rest times were provided to the workers, two
tea breaks and one lunch break. Tea break at fore noon session is from 11.00 am- 11.15 am
and after noon is from 4.00pm-4.15pm.Lunch break is 1.00pm-2.00pm.
3.1.1 Printing process in hand screen printing
The printing is done with the aid of screen. The screen consists of rectangular steel
frame and the steel frame is fitted with a woven mesh type stencil. The stencil has the
desired pattern. The stencil frame is 1m in length and 3m in width, weighs around 5-10 kg.
During printing, subjects lift the frame and place it at a desired position and they use the
rubber squeegee to force the ink on the cloth. During this printing work, workers
frequently lift and place the frame alternatively at the desired position and move the rubber
squeegee with force which causes pain in shoulder. The squeegee movement makes the
worker to stand in an awkward posture as shown in Figure 3.1. So, it causes pain to lower-
back of the workers and repetitive movements cause knee and foot pain to the workers.

13
Figure 3.1 Printing process in HSP work
3.2 STUDY PROTOCOL FOR STATISTICAL ANALYSIS
3.2.1 Questionnaire study
A total of 385 Hand screen printing workers with different age and experience
groups were considered for the investigation. The workers included male (54.8%), female
(45.2%) with marital status married (81.8%) and unmarried (18.2%). The workers
participated in the study were full time workers and all of them work more than 10 hours
per day. The wages for the subjects were based on contract basis and permanent monthly
wages. There is no higher increment depends on the experience. The workers perform
different tasks such as attaching clothes with table, printing the cloth material with the aid
of stencil, dye and squeegee. Finally dry the printed material by hanging the printed
clothes on rope tied over the printing table. This work was performed throughout the year.
3.2.2 Data collection
The sample size for the cross-sectional study 385 was determined using Cochran’s
sample size for infinite population with 95% confidence interval and 5% margin error
Kotrlik and Higgins (2001). The data were collected by Modified Nordic Musculoskeletal
Questionnaire and direct observations. The first section of the questionnaire were related to
workers background such as age, gender, body mass index (BMI), work experience, and
personal habits such as smoking and alcohol consuming were discussed. In the second
section Questionnaire consists of Psychological factors such as willingness in job, personal
satisfaction in job, comfortableness and stressfulness. In medical section chronic diseases,

14
respiratory problems, sick leave, surgery and bone dislocation were discussed. In work-
related information’s rest time, work hours, cloth meters, standing hours, awkward posture,
frame weights, and repetitive work were discussed. For analyzing MSD symptoms each
and individual sites such as neck, shoulder, elbow, wrist/hands, upper back, lower back,
hip/thighs, knees and ankle/feet were analyzed individually by asking questions. Eg. “Have
you ever suffered from neck pain for last 12 months? 1) Yes 2) No”. The frequency and
severity for different anatomical sites were analyzed by asking questions like, “How
frequent you realize the pain in particular part?” with options as ‘1) 1-2 times per year’, ‘2)
1-2 times per month’, ‘3) 1-2 times per week’, ‘4) Everyday’ were displayed. The workers
were supposed to reply anyone of the option for that question. If the workers reported there
is no pain in any site, for that particular site the frequency and severity was skipped. The
severity of the pain in anatomical sites were analyzed by, “Rate the severity of pain”, for
which the options disclosed as 1) mild pain/discomfort, 2) moderate pain with no reduction
in activity, 3) severe pain with reduction in activity, 4) unbearable pain requiring time off
work for severity rating. Finally, the question discussed about how far the pain affecting
the work efficiency. The Questionnaire for the musculoskeletal disorders was related to
studies done by De Zwart et al. (2000), Bot et al. (2007) for upper extremity disorders and
lower extremity disorders.
3.2.3 Data analysis
Statistical analysis was performed using Statistical Package for Social Sciences
SPSS (v20.0). Descriptive statistics were performed to determine mean, frequency,
standard deviation of the variables. Under the descriptive statistics Chi-Square test were
used to find the association between MSDs and various risk factors. Prevalence (%) and
95% confidence interval (95% CI) were used to describe the pain in each anatomical site
by different age and experience group. The Bonferroni correction method was added to
adjust the p-values for reducing the chance of false positive findings. The upper extremity
and lower extremity disorders were described using, Chi-square test for association and
Prevalence ratio to define which group receive the increased amount of MSD. A 2-tailed
test for all variables at p<0.05 was considered as statistically significant.

15
3.3 STUDY PROTOCOL FOR EXPERIMENTAL ANALYSIS
From the SPSS statistical report, the major pain was found on the shoulder and
lower back region. Among the various work in hand screen printing industry, workers
reported printing work printing work is more prone to cause MSD in upper extremity and
lower back region. So, the experimental study is conducted during the printing work.
3.3.1 Electrode placement
Figure 3.2 Targeted muscles for electrode placement
The muscles responsible for shoulder movement and lower back were targeted for
the study. The muscles such as Pectorallis major, Subcapularis, Tres Major,
Coracobrachialis, Deltoid muscles are responsible for arm horizontal movement as shown
in figure 3.2. The muscles present in the right erector spinae and left erector spinae are
responsible for the lower back movement.
Subcapularis
Deltoid
Tres Major
Erector Spinae

16
3.3.2 Data Acquisition and Instrumentation
Data acquisition was done through the accurate and precision Electromyography kit
Biometrics Data LOG MWX8 as depicted figure 3.3 (a). The electrode provided by the
biometrics is Gel-free attached with aid of stickers with low input impedance as displayed
figure 3.3 (b). Goniometer is a device used to measure the angle movement of any joints.
There are different types of Goniometers are available for example elbow Goniometer,
wrist Goniometer, Ankle Goniometer are some types of Goniometer to measure the angle
between the various joints as shown in figure 3.3 (c).
a) Data LOG MXW8 b) sEMG sensor c) Goniometer
Figure 3.3 sEMG Sensors and systems
Figure 3.4 Field recordings using sEMG kit during printing work

All EMG signals were recorded
LOG sEMG system as shown figure 3.4
and also in our laptop through Bluetooth
recoded into Engineering units and frequency values.
order Butterworth filter with a pass band of 20
period of 60 seconds during the dynamic
3.3.3 Data analysis
Root Mean Square (RMS) of sEMG signal
parameter in the time domain
Luca (1985). The RMS value was calculated along with the
signal of the fatigued muscles can be
sEMG signal (Basmajian and De Luca (1985)
accordingly with the fatigue (
frequency decreases with the increase in the fatigue of the muscles. Decrease in MPF from
sEMG profiles was a recognized method of determining fatigue in an isometric muscle
action (Allison and Fujiwara (2002)
Figure 3.5 Front panel view of
All EMG signals were recorded at the sampling frequency of 1000 Hz using a Data
as shown figure 3.4. The signal acquired was directly stored in the kit
nd also in our laptop through Bluetooth as shown in figure 3.4. After that the signals are
recoded into Engineering units and frequency values. The data was filtered using second
order Butterworth filter with a pass band of 20-450 Hz. The recording was don
period of 60 seconds during the dynamic sprinting work.
Root Mean Square (RMS) of sEMG signal was considered as the most reliable
parameter in the time domain (Balasubramanian and Jayaraman (2009), Basmajian and De
The RMS value was calculated along with the normalized signal.
muscles can be assess in frequency domain by power spectrum of the
Basmajian and De Luca (1985). The power spectrum of the muscles varies
accordingly with the fatigue (Van der Hoeven et al. (1993). The amplitu
recognized method of determining fatigue in an isometric muscle
Allison and Fujiwara (2002), Srinivasan and Balasubramanian (2007)
Front panel view of Customized LabVIEW program
17
at the sampling frequency of 1000 Hz using a Data
. The signal acquired was directly stored in the kit
. After that the signals are
The data was filtered using second
450 Hz. The recording was done for a
s considered as the most reliable
Basmajian and De
d signal. The sEMG
assess in frequency domain by power spectrum of the
The power spectrum of the muscles varies
The amplitude of the higher
recognized method of determining fatigue in an isometric muscle
(2007).
program

Figure 3.6 Block diagram view Customized LabVIEW program
Customized LabVIEW program were used to analyze and find out the RMS and
MPF values. The Front panel shows the RMS and
depicted in figure 3.5. The block diagram shows the virtual connections with the process
icons as shown in 3.6. The Biomedical tool kit reads only the signal in the form of .wav
format. The RMS, MPF and MDF icons process
in numerical indicator and also with that Excel file through the write to the measurement
file options. The final values from the LabVIEW results
the EMG recordings.
MPF values. The Front panel shows the RMS and MPF values in graph as an indicator
. The block diagram shows the virtual connections with the process
The Biomedical tool kit reads only the signal in the form of .wav
format. The RMS, MPF and MDF icons process the user required and displayed as va
values from the LabVIEW results were considered as the results of
18
MPF values in graph as an indicator
. The block diagram shows the virtual connections with the process
The Biomedical tool kit reads only the signal in the form of .wav
ired and displayed as values
considered as the results of

19
CHAPTER 4
RESULT AND DISCUSSION
4.1 STATISTICAL ANALYSIS
4.1.1 Overall discomfort by Questionnaire study
The survey was conducted for 385 Hand screen printing workers. Among them 54.8%
were male and 45.2% were female. Out of 385 workers 315 (81.8%) were married and 70
(18.2%) were unmarried. The mean age of the Hand screen printing workers in the study was
35.08 (SD: 8.11 range 20-60) and majority of them fall under >40 years age group (35.8%).
The subjects participated in the study mostly completed elementary level education (44.6%).
But percentage of workers present in the lower education was higher than the higher
education. Most of the workers were present in middle experience group as 6-15 years. The
majority of the workers reported moderate stressfulness present in the job (73.2%). And
moreover 74.8% reported job satisfaction as ‘moderate’. Among the workers participated in
the study, about 264 (68.5%) were in normal weight and 108 (28%) were present in
underweight, very few of them present in the overweight category.
The results obtained from the survey reported that 62.5% has musculoskeletal
disorders in last 12 months. The workers reported musculoskeletal disorder in at least any one
anatomical site. The prevalence found on various anatomical sites is displayed as Neck
(27.8%), Shoulder (66.2%), Elbow (29.6%), Wrist (24.7%), Upper back (28.8%), Lower back
(75.1%), Hip (27.8%), Knee (58.7%) and Ankle/Feet (55.6%) were displayed in Figure 4.2.
The highest prevalence was found on Lower back (75.1%), and Shoulder (66.2%) followed by
Knees (58.7%) and Ankle/Feet (55.6%). The prevalence of WMSDs among Hand Screen
Printing workers was depicted in figure 4 1.

Figure 4.1 Pain
4.1.2 Prevalence of MSD on
Table 3 shows the relationship between various independent risk factors and low back
pain obtained by multiple logistic regression method using SPSS 20.0. In the 75.1% (n=289)
of workers who reported having low back pain, 38.2% (n
were female workers. Within the gender, the female
back pain (OR-1.932, CI 1.192
18.2% of workers within the age of <30 years we
within the age group of 31-
the age group of >40 years
age group of >40 years we
of getting low back pain compared to workers of other age gr
The workers were grouped into four categories based on the years of experience they
had in hand screen printing industries. In that
experience in hand screen industry
75.1
66.2
0
10
20
30
40
50
60
70
80
Prevalence(%)
4.1 Pain prevalence(%) on different anatomical sites
Prevalence of MSD on Lower back and its associated risk factors
by multiple logistic regression method using SPSS 20.0. In the 75.1% (n=289)
of workers who reported having low back pain, 38.2% (n=147) were male and 36.9% (n=142)
re female workers. Within the gender, the female workers were prone to have high low
1.932, CI 1.192-3.313) compared to male workers. In the sampling population,
rs within the age of <30 years were having low back pain, 26.5% of workers
-40 years were reported low back pain and 28.8% of wor
the age group of >40 years were affected with low back pain. In that, workers belonging
age group of >40 years were having nearly 3 times (OR-2.898, CI 1.630-
of getting low back pain compared to workers of other age group.
re grouped into four categories based on the years of experience they
had in hand screen printing industries. In that, 28.3% of workers having more than 15 years of
erience in hand screen industry reported having severe low back pain
58.7 55.6
29.6 28.8 27.8 27.8
Anatomical sites
Prevalence of MSD in various sites
20
anatomical sites
and its associated risk factors
by multiple logistic regression method using SPSS 20.0. In the 75.1% (n=289)
re male and 36.9% (n=142)
re prone to have high low
sampling population,
re having low back pain, 26.5% of workers
re reported low back pain and 28.8% of workers within
re affected with low back pain. In that, workers belonging to the
-5.151) more chance
re grouped into four categories based on the years of experience they
28.3% of workers having more than 15 years of
reported having severe low back pain (OR-1.548, CI
24.7
MSD
sympt
oms

21
0.934-2.563) compared with other three categories. From the result, it was found that height of
the workers had greatly influenced by the occurrence of low back pain among the workers.
Table 4.1 Prevalence of Low back pain with individual risk factor identified using multiple
logistic regression method
Independent risk
factors
LOW BACK PAIN (75.1%)
N % OR 95% CI
Gender-
Male
Female
147
142
38.2
36.9
0.518
1.932
0.319-0.839*
1.192-3.313*
Age-
< 30
31-40
>40
70
102
111
18.2
26.5
28.8
0.340
1.260
2.898
0.210-0.552*
0.766-2.074*
1.630-5.151*
Experience-
Less than 5 years
6-10 years
11-15 years
More than 15
years
46
70
64
109
11.9
18.2
16.6
28.3
0.510
0.959
1.153
1.548
0.294-0.883*
0.562-1.637*
0.649-2.046*
0.934-2.563*
Height-
Less than 150 cm
151-160 cm
161-170 cm
More than 170 cm
81
149
38
21
21.0
38.7
9.9
5.5
2.103
0.863
0.704
0.674
1.145-3.862*
0.543-1.373*
0.376-1.315
0.305-1.487*
Education-
Illiterate
Elementary
High school
Degree
95
132
64
11
24.7
34.3
16.6
2.9
1.861
1.283
1.153
1.860
1.073-3.226*
0.802-2.053*
0.649-2.046*
0.405-8.543
Smoking-
Smoker
Non smokers
50
238
13.0
61.8
1.050
0.993
0.567-1.947*
0.504-1.728*
Stressfulness -
Low
Very low
Moderate
High
Very high
12
30
211
32
4
3.1
7.8
54.8
8.3
1
0.551
0.996
1.005
1.370
1.333
0.210-1.442*
0.468-2.122*
0.598-1.690*
0.608-3.084*
0.147-12.07*
*- Statistically Significant (p<0.05), 95% CI- 95% confidential interval, OR- Odds Ratio

22
Since the workers having height of <150cm (OR-2.103, CI 1.145-3.862) were highly
affected with low back pain compared to the workers with height more than 150cm. Workers
with smoking habit reported severe low back pain (OR-1.050, CI 0.567-1.947) compared with
non-smokers (OR-0.993, CI 0.504-1.728). Also workers having job-related stress were
suffering from severe low back pain (OR-1.370, CI 0.608-3.084) compared with workers
having low job oriented stress.
4.1.3 Prevalence of MSD on upper extremities and its associated risk factors
4.1.3.1 Probability ratio by gender
Table 4.2 displays the odds ratio of pain for gender variance in upper extremity
regions. The working hours and work done by individual were same. From the table, it was
well justified that the female gender had high morbidity and pain in upper extremity areas than
male. The highest prevalence rate of complaints in upper extremities for both male (57.34%)
and female (77.01%) were on shoulder region. Next to the shoulder, females reported neck
(42.52%) as high prevalent area but only 15.63% of males reported pain in neck region(OR;
CI 1.92; 1.57-2.35). Pain prevalence in elbow and upper back region reported by females were
same as 35.63%, whereas 24.64% and 23.22% for males.
4.1.3.2 Association of upper extremity disorders and relative risk factors
Table 3 shows the result of psychosocial and job related risk factors supports to cause
MSD’s on upper extremity areas. The statistical analysis displays, there was significant
relation (p<0.05) between age and neck, elbow pain. The odds ratio displays the shoulder,
elbow and wrist had higher probability to cause pain when increase in age but middle age
group had high probability to cause pain in neck and upper back region (ref. table 4.2). For
other socio-demographical factors (marital status), subjects who were get married had
suffering more on upper extremity disorders. The upper back pain and shoulder pain were
significantly(p<0.05) associated with the subjects who got married and the odds ratio also
reported that subjects who were married had high risk or high probability to undergone upper
extremity disorders.

23
The risk factors related to physical and mental health resulted that there was no
significant relationship between the cigarette smoking and upper extremity disorders. The
upper extremities pain reported by the smokers was moreover same as non-smokers. Few of
the male subjects participated in the current study consume alcohol before going to sleep for
reliving their pain during sleeping. The logistic regression analysis reports that pain reported
by non-consumers in upper extremity areas were more than the alcohol consumers. (Ref. table
4.2)
In the current study, there were some work related factors such as job satisfaction,
stressfulness in job, job tenure and sick leave availed due to the work. Chi-square test reported
that there was no significant relation between reporting job satisfaction and upper extremities
pain. But, the subjects who reported low satisfaction in job had high risk to cause pain in neck
(OR, 95%CI; 1.05, 0.60-1.83), elbow (OR, 95%CI; 1.36, 0.81-2.30), and upper back region
(OR, 95%CI; 1.48, 0.87-2.52). Next, the workers reported high stressfulness in job having
high probability to cause pain in neck (OR, 95%CI; 1.13, 0.63-2.04), elbow (OR, 95%CI;
1.67, 0.97-2.88) and wrist areas (OR, 95%CI; 1.96, 1.13-3.38). There was significant (p<0.05)
relation between moderate stressfulness and reporting shoulder pain.
From the descriptive analysis, the Chi-square test reported that there was significant
(p<0.05) positive relation between the upper extremity disorders and work related variable
sick leave. Binary logistic regression analysis displays that, subjects who reported sick leave
had high probability to cause pain in upper extremity areas such as neck(OR, 95%CI; 1.96,
1.13-3.38), upper back(OR, 95%CI; 1.79, 1.11-2.89), shoulder(OR, 95%CI; 2.13, 1.14-3.97),
elbow(OR, 95%CI; 1.72, 1.07-2.78) and wrists(OR, 95%CI; 2.94, 1.85-4.69). The upper
extremities pain increases with increase in age. Descriptive statistics reported there was a
significant relationship between higher experience group and the upper back, shoulder and
elbow pain. The logistic regression analysis identified higher age group significantly
experiences high risk on upper back (OR, 95%CI; 1.48, 1.06-2.08), shoulder (OR, 95%CI;
1.83, 1.20-2.79), and elbow region (OR, 95%CI; 1.83, 1.32-2.54).

24
Table 4.2. Association of Upper Extremity disorders and its risk factors for previous 12 months among HSP workers (n=385)
Factors n Rep.
Neck
pain (%)
Odds Ratio
(95 % CI)
Rep.
UBP
(%)
Odds Ratio
(95 % CI)
Rep. SP
(%)
Odds Ratio
(95 % CI)
Rep.
Elbow
pain (%)
Odds Ratio
(95 % CI)
Rep.
Wrist
pain(%)
Odds Ratio
(95 % CI)
Gender
Male 211 33(15.6) Ref. 49(23.2) Ref. 121(57.3) Ref. 52(24.6) Ref. 37(17.5) Ref.
Female 174 74(42.5) 1.92
(1.57-2.35)**
62(35.6) 1.36
(1.09-1.70)*
134(77.0) 1.70
(1.28-2.26)
62(35.6) 1.31
(1.05-1.64)*
58(33.3) 1.52
(1.23-1.89)
Age
< 30 117 20(17.0) Ref. 22(18.8) Ref. 55(47.0) Ref. 22(18.8) Ref. 22(18.8) Ref.
30-40 131 44(33.5) 1.31
(0.98-1.74)*
44(33.5) 1.24
(0.93-1.66)
92(70.2) 1.20
(0.88-1.63)
42(32.0) 1.12
(0.83-1.50)
35(26.7) 1.11
(0.81-1.51)
>40 137 43(31.3) 1.18
(0.89-1.57)
45(32.8) 1.20
(0.91-1.59)
108(78.8) 1.89
(1.33-2.69)
50(36.4) 1.36
(1.04-1.79)*
38(27.7) 1.17
(0.87-1.57)
Marital
status
Single 70 7(10.0) Ref. 12(17.1) Ref. 31(44.2) Ref. 13(15.5) Ref. 9(12.8) Ref.
Married 315 100(31.7) 1.20
(1.11-1.31)
99(31.4) 1.13
(1.03-1.23)*
224(71.1) 1.12
(1.02-1.22)**
101(32.0) 1.12
(1.02-1.22)
86(27.3) 1.14
(1.05-1.25)
Cigarette
smoking
Yes 66 10(15.1) Ref. 21(31.8) Ref. 42(63.6) Ref. 19(28.7) Ref. 17(25.7) Ref.
No 319 97(30.4) 1.13
(1.04-1.23)*
90(28.2) 0.97
(0.87-1.07)
213(66.7) 1.02
(0.92-1.13)
95(29.7) 1.0
(0.90-1.11)
78(24.4) 0.98
(0.88-1.10)
Alcohol
consuming
Yes 72 13(18.0) Ref. 24(33.3) Ref. 42(63.6) Ref. 21(29.1) Ref. 19(26.3) Ref.
No 313 94(30.0) 1.11
(1.01-1.22)*
87(27.7) 0.95
(0.85-1.06)
213(66.7) 1.08
(0.97-1.21)
93(29.7) 1.0
(0.90-1.11)
76(24.2) 0.97
(0.87-1.08)
Table 4.2 con.

25
Factors n Rep.
Neck
pain(%)
Odds Ratio
(95 % CI)
Rep.
UBP (%)
Odds Ratio
(95 % CI)
Rep. SP
(%)
Odds Ratio
(95 % CI)
Rep.
Elbow
pain (%)
Odds Ratio
(95 % CI)
Rep.
Wrist
pain (%)
Odds Ratio
(95 % CI)
Job
Satisfaction
High 45 13(28.8) Ref. 20(44.4) Ref. 25(55.6) Ref. 16(35.5) Ref. 15(33.3) Ref.
Moderate 288 79(27.4) 0.98
(0.86-1.12)
79(27.4) 0.93
(0.81-1.06)*
195(67.7) 1.06
(0.94-1.21)
79(27.4) 0.89
(0.78-1.03)
63(21.8) 0.85
(0.73-0.99)
Low 52 15(28.8) 1.05
(0.60-1.63)
12(23.0) 0.74
(0.40-1.47)
35(67.3) 1.05
(0.61-1.80)
19(36.5) 1.36
(0.81-2.30)
17(32.6) 1.48
(0.87-2.52)
Stress in
job
Low 57 15(26.3) Ref. 25(43.8) Ref. 32(56.1) Ref. 19(33.3) Ref. 18(31.5) Ref.
Moderate 282 78(27.6) 0.99
(0.86-1.13)
75(26.5) 0.89
(0.77-1.03)
194(68.7) 1.12
(0.98-1.28)*
76(26.9) 1.12
(0.98-1.28)*
59(20.9) 0.80
(0.68-0.95)
High 46 14(30.4) 1.13
(0.63-2.04)
11(23.9) 0.77
(0.40-1.47)
29(63.0) 0.87
(0.49-1.52)
19(41.3) 0.87
(0.49-1.52)*
18(39.1) 1.96
(1.13-3.38)
Sick Leave
No 328 83(25.3) Ref. 87(26.5) Ref. 209(63.7) Ref. 90(24.7) Ref. 67(20.4) Ref.
Yes 57 24(42.1) 1.89
(1.17-3.04)*
24(42.1) 1.79
(1.11-2.89)*
46(80.7) 2.13
(1.14-3.97)*
24(42.1) 1.72
(1.07-2.78)
28(49.1) 2.94
(1.85-4.69)*
Job tenure
< 5 years 137 30(21.8) Ref. 32(23.3) Ref. 67(48.9) Ref. 26(18.9) Ref. 18(13.1) Ref.
6-15 years 147 45(30.6) 1.14
(0.87-1.50)
41(27.8) 0.95
(0.71-1.27)
109(74.1) 1.46
(1.08-1.98)*
44(29.3) 1.01
(0.77-1.34)
45(30.6) 1.34
(1.03-1.75)
15 years 101 32(31.6) 1.20
(0.84-1.71)
38(31.4) 1.48
(1.06-2.08)*
79(78.2) 1.83
(1.20-2.79)*
44(43.5) 1.83
(1.32-2.54)**
32(31.6) 1.41
(0.99-2.00)
*p<0.05; **p<0.001; Rep. UBP, Reported Upper Back pain; Rep. SP,Reported Shoulder Pain.

26
4.2 EXPERIMENTAL ANALYSIS (sEMG study)
4.2.1 Muscular load study
The muscle exerts some force to withstand the load on the shoulder and lower back
during the printing work. From the statistical analysis, the study narrows down the work to
analyze pain on shoulder and lower back region. The Data LOG kit provides the values in the
form of mV and results of the Goniometer in the form of degrees. Table 4.3 displays the
results in mV of muscular load on targeted muscles.
Table 4.3 EMG RMS (mV) values of targeted muscles on shoulder and lower back during
printing work on Age basis
S.
No.
Age
(Years)
Experience
(Years)
Deltoid
(mV)
RES
(mV)
LES
(mV)
Tres Major
(mV)
Subcapularis
(mV)
1 20 3 0.161 0.093 0.031 0.079 0.044
2 20 4 0.176 0.107 0.075 0.103 0.046
3 24 5 0.194 0.089 0.080 0.091 0.056
4 26 4.5 0.130 0.021 0.081 0.065 0.058
5 26 11 0.190 0.035 0.031 0.023 0.047
6 32 5 0.151 0.045 0.060 0.054 0.037
7 45 24 0.170 0.042 0.054 0.055 0.089
8 46 25 0.162 0.045 0.052 0.058 0.067
9 50 15 0.180 0.046 0.045 0.206 0.067
10 50 20 0.255 0.030 0.050 0.061 0.081
11 55 21 0.200 0.021 0.053 0.217 0.040
The table clearly shows the force level present in the shoulder and lower back regions
during the printing work. The Deltoid, Tres major, Subcapularis were the muscles that action
for the horizontal flexion movement. Awkward posture for the lower back primarily affects
the muscles present in the right erector spinae and left erector spinae. The recordings were
performed during the dynamic printing work for one minute. Among the three muscles the
Deltoid muscles had more action than the other two muscles during the printing work. Next to

27
the deltoid the Subcapularis plays second and finally the Tres major muscles. In the lower
back region the muscle present in the right erector spinae acted more than the left side.
4.2.2 Angle movement study
During the printing work, the upper extremity region had certain angle movement in
the certain time delay to perform the work in proper manner. In the upper extremity regions,
the upper arm had certain angle movement in the elbow region during the printing work. The
angle movements were measured using Goniometer.
Table 4.4 Joint movements (Elbow and Low back region, Goniometer readings).
Joint area Work
Movement in Angle
(Minimum)
Movement in Angle
(Maximum)
Elbow Printing 5.5 18.4
Elbow Lifting 2.1 24.9
Lower Back Printing 70.6 90.4
Lower Back Lifting 40.3 60.6
The elbow joint movement during the printing work varies from -12.5 to 10.4 degrees.
And also lifting works goes parallel to move the frame from printed place to the desire place.
Elbow undergoes angle movement from 2.1 to 24.9 degrees during the lifting process. As
same the lower back under goes awkward posture during the printing and lifting work. During
the printing work lower back involves bending of 70.6 to 90.4. And during the lifting work
lower back involves 40.3 to 60.6 degrees as shown in table 4.4. Workers involves that much
bending causes heavy pain on the lower back region.
4.3 DISCUSSION
4.3.1 Discussion about statistical analysis results
The present study found that the low back pain was the most prevalent (71.5%)
disorder which was consistent with work done on commercial male kitchen workers in south

28
India and LBP among non-working women in Kanpur city, India Shankar and Shanmugam
(2014 (accepted), Gupta and Tiwari (2014). Leaning the body forward, prolonged standing,
frequent and repetitive motion around the table without micro breaks associated with the job
were the major job risk factors influencing the occurrence of low back pain.
The study conducted with the dentist in Madhya Pradesh reported that 57.75% of study
population was suffered from low back pain because of maintaining the standing position for
prolonged period of time during their work Saxena et al. (2013). A research found that
workers who were standing throughout the day without the freedom to sit during their work
were having more chance for occurring low back pain Tissot et al. (2009). A study revealed
that the crane operators maintaining sedentary position during the work were suffered from
severe low back pain BURDORF and ZONDERVAN (1990). In a similar study conducted
with the constructional workers found that, remaining in static position for longer time
influences the low back pain Merlino et al. (2003). In hand screen printing industry, the
workers were standing and moving across the table throughout the day without micro breaks
was one of the main risk factor influencing the occurrence of low back pain.
The study conducted with the workers of concrete manufacturing industry found that
bending and twisting position of back during the work was highly influencing the occurrence
of low back pain Burdorf et al. (1991). A cross sectional study revealed that non neutral trunk
position during the work was the major reason for low back pain among the port machinery
operators Bovenzi et al. (2002). Another work found that male potato cultivators of West
Bengal were suffering from low back pain because of repetitive motion Das and
Gangopadhyay (2012). Similarly sugar cane farmer in Thailand were suffering from the low
back pain because of high repetitiveness and remaining in the awkward position involved in
the work Phajan et al. (2014). Also in carpet mending industry, workers reported severe low
back pain because of remaining in awkward position for the long period of time during carpet
mending operation Choobineh et al. (2007, Choobineh et al. (2004). Brick field workers were
prone to have high low back pain compared to other parts of the body because of working in
different uncomfortable posture for prolonged period of time Das (2014). In the present work,
the occurrence of low back pain was more common among workers because of frequently

29
bending and leaning the upper body (awkward position) during the work. This also supports
the previous study results on low back pain Rufa'i et al. (2013).
A cross sectional study conducted with the textile workers found that increasing age of
workers influence the low back pain Tiwari et al. (2003). Another study with commercial
kitchen workers (male), shown that the risk for low back pain increases with the increase in
age Shankar et al. (2014 (accepted)). A study conducted with Thai construction workers found
that high numbers of old age group workers were reported to have low back pain compared to
young and middle age workers Hanklang et al. (2014). Also, the study conducted among the
Iranian dentists reported that Musculoskeletal disorders changes with job tenure and year of
work practice Shadmehr et al. (2014, Chamani et al. (2012). The present study also reveals the
same, as the workers with age group of >40 years had nearly three times more chance of
getting low back pain(OR-2.898, CI 1.630-5.151) compared to young (< 30 years) and middle
age group (31-40 years).
Workers with the height less than 150cm were prone to had two times more chance of
getting low back pain compared to other three categories of height. This was, because the tall
workers need not bend their body fully to pass the squeegee to the worker in the other end of
the screen table. But the workers of shorter height need to bend their body fully to pass the
squeegee while applying the color in the cloth fabric. The study conducted with staffs in
specialized healthcare centre reports that female staff in all the department were having high
WMSDs Ibrahim and Mohanadas (2012). A pilot study conducted among the post graduate
dental students reported prevalence of low back pain was higher among female students than
male Kursun et al. (2014). It was also found to be the same for the present case. When
compared to male workers, female workers were reported higher prevalence with low back
pain and this may be due to the physical strength which differs for male and female.
A study conducted with garment workers revealed that workers in high demand were
prone to had severe low back pain Byrns et al. (2002). A cross sectional study conducted with
Danish female nursing professionals reports that job related stress and low back pain was
strongly associated with each other Gonge et al. (2002). In similarly study conducted with
college students proves that there was a significant relationship between the psychological

30
variables and occurrence of low back pain Kennedy et al. (2008). Another research work
found that increase in psychological factor increases the risk of WMSDs among nursing
professions Heiden et al. (2013). It becomes evident, that the workers had high job related
stress were having more chance of getting affected with low back pain (OR-1.370, CI 0.608-
3.084).
Few studies found that smoking habit was one of significant risk factor for the
occurrence of low back pain Tiwari et al. (2003, Pinar et al. (2013). In the present study, the
smoking habit of the workers was associated with the low back pain. Previous researchers
found that the longer job tenure would increase the risk of WMSDs among the workers Coury
et al. (2002, Tiwari et al. (2003). Here also, 28.3% of workers with more than fifteen years of
experience reported with low back pain which was nearly three times more chance of getting
low back pain (OR-2.898, CI 1.630-5.151) compared to others. It was also found that literacy
doesn’t have significant influence on low back pain.
The study also confirmed the association between the job, psychosocial factors and
upper extremity disorders among hand screen printing workers for previous 12 months. The
hand screen printing work was spread over the western part of Tamil Nadu. None another
study analyzed pain prevalence and risk factors among HSP workers. Totally 385 workers
were recruited from 41 hand screen printing industries and data were collected through
modified Nordic musculoskeletal questionnaire. The study comprised of 211 male and 174
female workers and 315(81.8%) were got married. The working hours and work for all
workers were same ≥ 10 hours. The workers did not perform any other activities like playing,
agricultural work and any other occupational activities. The morbidity report had some
limitations as the workers reported up to memory recall level. Out of 385 workers 27.8%
reported neck pain, shoulder 66.2%, elbow 29.6%, wrist 24.7% and upper back 28.8%. The
risk factors displayed in the study were reported by subjects and by direct observations. In the
current study, there is significant difference in MSD by age and gender difference like various
studies related to age, gender and MSD Collins and O'Sullivan (2010).
In the current study out of 385, 107(27.8%) subjects reported neck pain in past 12
months. Here the major contributors were female 74(44.5%). The study conducted among

31
female nurses in Greek hospital reported 47% nurses having neck pain in past 12 months
Roquelaure et al. (2006) and a study conducted among the female employees in administrative
region of France reported, 50% employees having neck pain Alexopoulos et al. (2003).
Reviews of upper quadrant musculoskeletal disorders reported female workers were mostly
affected in the working and general population Long et al. (2012). Recent review on
longitudinal epidemiological studies reported heavy physical work, awkward posture and
frequent lifting supports to cause MSD in neck regions da Costa and Vieira (2010). The HSP
work didn’t have awkward posture for neck but there contains frequent lifting and heavy
physical work. This load might be heavy for female gender that’s why they reported high. The
MSD on neck changes with the psychosocial and physical factors such as marital status and
age. The subject’s undergone married (OR, 95%CI; 1.20, 1.11-1.31) and higher age (OR,
95%CI; 1.31, 0.98-1.74) were suffered from neck pain.
The workers exposed to both physical and psychosocial risk factors were suffered lot
from upper limb disorders Devereux et al. (2002) and work which undergone with heavy
physical work and repetitive movement for upper limbs resulted in shoulder pain da Costa and
Vieira (2010). The HSP workers reported pain in shoulder area was more prevalent among the
various upper extremity regions. The female genders were suffered more shoulder pain (OR,
95%CI; 1.70, 1.28-2.26) than male. Also, there is significant relation between prolonged work
hours and pain in shoulder region among female workers Baran et al. (2011). Because, the
women working in the HSP industry mostly home makers they daily perform kitchen work
and dress washing. The washing work involves awkward posture and repetitive movement and
heavy physical work and combination of those works for women leads to high MSD’s on
shoulder region Lortie (1986). The study conducted among male kitchen workers by Shankar
and Shanmugam) reported shoulder was the second high prevalent area. The study done by
Mayer et al. found the association between the manual material handling and shoulder
complaints (OR: 1.4-1.9) and working with hand above shoulder level Mayer et al. (2012).
Smedley reported the physical task which involves pushing and pulling with help of arm and
shoulder outstretched resulted shoulder symptoms Smedley et al. (2003). The HSP work
involves repetitive pushing and pulling of arms during the printing work. The psychosocial
factors and demographical factors such as job stress, co-worker support and marital status

32
were related with upper extremity disorders Marcus and Gerr (1996) which supports the
present study.
The HSP work involves many frequent lifting and placing of steel stencil frame in
awkward posture which impart pain on elbow region. Descriptive statistics reported 29.6%
having elbow pain in last 12 months. Elbow was the second high pain prevalence area
reported by the HSP workers. Chi-square test reports there was strong association between the
elbow pain and marital status and subjects reported married having high elbow pain. The
elbow pain increases with increase in age as higher age group having high pain prevalence
(OR, 95%CI; 1.36, 1.04-1.79). The psychosocial factor, stress in job was significantly
associated with the elbow pain and multivariate analysis results subjects reporting high stress
in job had high elbow pain (OR, 95%CI; 1.67, 0.97-2.88). Significant association was found
between the job tenure (psychosocial factor) and reported elbow pain and higher experience
group reported elbow pain in higher level. This was consistent with study conducted by
NIOSH among office workers Hurrell et al. (1996).
Wrist pain was one of the major problems in occupational environment. A 5 year
follow-up study conducted on Denmark employees(3900) predicted pain in wrists due to stress
symptoms and bending Feveile et al. (2002). The HSP work involves high repetition and force
exertion for wrist hands during printing work. The present study supports the epidemiological
study done by Silverstein et al. (1986)on wrist disorders reported, risk increases when exposed
to high force or high repetition alone. The same relation was found on the epidemiological
study done by Moore et al. on manual materials handling process Moore et al. (1991). The
work with often lifting, with awkward and dynamic wrist postures lead to discomfort in wrist
region Devereux et al. (1998, van der Beek et al. (1993). So, the present study also had
frequent lifting of steel stencil frame with dynamic wrist postures causes’ pain. Also, there
was significant association between the wrist pain and job related risk factor sick leave
(P<0.05).
The upper back region was more over linked with the upper extremity areas. So,
subjects who reported pain in upper back region were same as reported with the neck region.
The upper back pain significantly (p<0.05) associated with the demographic factors as marital

33
status and job related factors sick leave and job tenure. Binary logistic regression analysis
reported physical, psychosocial and job related factors had great impact on WMSD among
HSP workers and it was consistent with study performed among weaving industry workers in
Gujarat Nag et al. (2010). From the above discussions, the present study provided the
justifications related with the similar studies on upper extremity disorders and its
consequences among working population.
4.3.2 Discussion about experimental analysis results
The experimental analyses were done among the hand screen printing volunteers. The
muscles targeted for the experimental analysis were Deltoid, Subcapularis and Tres Major on
upper extremity areas and right erector spinae and left erector spinae on lower back region.
The current study analyses muscle which had undergone on the shoulder region and lower
back region during the printing work. The experimental procedures for analyzing the muscle
fatigue were followed as per work done by Balasubramanian and Srinivasan (2009). From the
experimental results of hand screen printing workers, deltoid shared the major load in the
upper extremity areas followed by the tres major and the Subcapularis. In the lower back
region, right erector spinae shares the major load as compared to the left erector spinae region.
As for the particular horizontal flexion movement present in the hand screen printing work
deltoid muscle share more load to give the proper work force. As all workers were intimated
to do the same work there was many variations in the results of the muscles readings. The
variations might be due to experience, age and its body mass index.
The angle movements of the elbow joint were calculated using goniometer and from
the results during the printing work degrees 5.5 to 18.4 degrees and during the lifting work
degrees 2.1 to 24.9 degrees. These angles were varying within the 20 seconds. The goniometer
readings from the Hip joint reported 70.6 to 90.4 degrees during the printing work and during
the lifting work it varies from 40.3 to 60.6 degrees within the delay of 20 seconds.
Further analysis among hand screen printing workers on lower and upper extremity
regions, lower back during all other tasks performed in the hand screen printing industries.
Based on the muscular load reported by EMG kit on the various anatomical sites further
Ergonomic based actions will take to reduce the MSDs among workers.

34
CHAPTER 5
CONCLUSIONS AND FUTURE SCOPE
5.1 CONCLUSIONS
Hence the present study concludes with the results of various risk factors associated
with the low back and upper extremity disorders. From the statistical report, independent
risk factors such as age, experience, height with lower than 160 cm, smoking and
stressfulness in job were significantly (p<0.05) associated with the LBP among HSP
workers. Meanwhile, the factors such as gender, age (30-40), non-smokers, non-alcohol
consumers had significantly (p<0.05) associated with the neck, wrist pain and elbow pain.
Gender, avail sick leave and marital status were significantly (p<0.05) associated with the
shoulder and upper back pain.
The experimental analysis were conducted on the targeted muscles such as Deltoid,
Subcapularis, Tres major on shoulder region and RES, LES on the lower back region.
Among the three muscles in the horizontal flexion movement, EMG analysis report Deltoid
(0.130mV-0.255 mV) shares the major load then followed by Tres major (0.023 mV-
0.217mV) and Subcapularis (0.037 mV-0.089 mV). In Erector spinae region, RES shares
major load to withstand the posture (0.037 mV-0.107 mV) followed by LES (0.031 mV-
0.081 mV). The experimental results vary accordingly with age, experience and body mass
index (BMI).
5.2 FUTURE SCOPE
In future, the study could include experimental analysis on lower extremity region,
and upper neck region to find the discomfort in overall regions among hand screen printing
industry workers. Also with that, the current study does not consider any female workers
for the experimental analysis they may be considered in future. Finally the study can also
extends to find the angle movement on upper extremity, lower back and lower extremity
areas.

35
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60. Tiwari R. R. Pathak M. C. and Zodpey S. P. (2003). 'Low back pain among textile
workers' Indian journal of occupational and environmental medicine Vol. 7 No.1 pp.27-29.
61. van der Beek A. J. Frings-Dresen M. H. van Dijk F. J. Kemper H. C. and Meijman T. F.
(1993). 'Loading and unloading by lorry drivers and musculoskeletal complaints'
International Journal of Industrial Ergonomics Vol. 12 No.1 pp.13-23.

41
62. Van der Hoeven J. Van Weerden T. and Zwarts M. (1993). 'Long‐lasting supernormal
conduction velocity after sustained maximal isometric contraction in human muscle'
Muscle & nerve Vol. 16 No.3 pp.312-320.
63. Waters T. R. Nelson A. and Proctor C. (2007). 'Patient handling tasks with high risk for
musculoskeletal disorders in critical care' Critical care nursing clinics of North America
Vol. 19 No.2 pp.131-143.

42
LIST OF PUBLICATIONS
INTERNATIONAL JOURNALS
1. Shankar S, Naveen Kumar R, Mohankumar P and Karthik J. Work-related
physical and psychosocial risk factors for upper extremity musculoskeletal
complaints among Hand screen printing workers: a cross sectional approach.
Human factors and Ergonomics in manufacturing and service industries. 2015
(Under Review)
2. Shankar S, Naveen Kumar R, Mohankumar P and Karthik J. Prevalence of
Lowback pain and associated risk factors among fulltime hand screen printing
workers. Journal of Musculoskeletal pain. 2015 (Under Review)
3. Shankar S, Naveen Kumar R and Mohankumar P. Job factors, psychosocial stress
and Prevalence of Musculoskeletal disorders among garment related workers of
South India. Slovenian journal of public health. 2015 (Under Review)
4. Shankar S, Naveen Kumar R and Mohankumar P. Prevalence of work related
musculoskeletal disorders on lower extremity among hand screen printing industry
workers. Work place Health & Safety. 2015 (Under Review)
INTERNATIONAL CONFERENCE
1. Shankar S, Mohankumar P and Prabu M. Work related musculoskeletal pain and
risks factors variation for male and female workers in Hand screen printing
industry. International conference on contemporary research tends in Diagnostics
and Therapeutics, 2015. Anna University, Chennai.18 FEB. 2015.

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