2016
PHYSIOCON Conference
Evaluation of Work related musculoskeletal Disorder and
Physiological Stress during using Motorized and Pedal
threshing machines
Hiranmoy Mahata and Prakash C. Dhara
Ergonomics and Sports Physiology Division
Department of Human Physiology with Community
Health
Vidyasagar University, Midnapur -721 102
West Bengal, India
A large numbers of rural Indian populations are engaged in agriculture and exert manual
labour for the paddy cultivation activity.
There are several steps in post harvesting job, including reaping, cutting, drying, threshing
and storing.
Threshing is the process of loosening or removing grain from pods or straw.
Threshing equipment is used for separating rice grain from the straw
There are different types of threshing equipment:
 Animal operated threshing machine
Power operated threshing machine
 Manual paddle operated threshing machine
 Traditional threshing equipment
In West Bengal manual paddle threshing machine is widely used. Most of the tasks of
paddy cultivation are repetitive in nature.
Repetitive actions of certain body parts may lead to the development of musculoskeletal
disorders (MSD).
Conti…
The common occupational risk factors associated with low back pain have been identified
as poor/awkward work postures, bending, lifting and physical strenuous work.
The health problems among threshing workers could be explained by a multiple exposure
model including –
Challenging ergonomic conditions from repetitive tasks while prolonged standing
(static posture) .
 Muscular inactivity can exert tension (load) on the musculoskeletal structures.
These are the probable causes leading to musculoskeletal disorder.
The present study was aimed
 To
evaluate the occupational health hazards of the workers engaged in
threshing with motorized and pedal operated threshing machine
 To evaluate the physiological stress of the of the workers engaged in
threshing with motorized and pedal operated threshing machine.
To compare those problems with that of the motorized and pedal operated
threshing machine workers.
Selection of site and subjects:
The study was conducted on 55 female and 45 male threshing workers in the age group of 20
to 50 years, selected from different districts of West Bengal state, India.
Measurement of anthropometric dimensions:
Different anthropometric measures were taken from the subjects following standard
technique and appropriate landmarks.
 Measurement of Height:
Height was taken with the help of an anthropometric rod. At first the
subject was asked to stand straight on the floor and then the vertical distance from floor to
vertex (maximum bulge portion of the head) was measured (Weiner and Lourie, 1969).
 Measurement of Weight:
Weight of the subject was taken by a portable weighing machine.
Subject was asked to stand straight on the weighing machine in minimum clothing and
reading was taking from the scale of the machine (Weiner and Lourie, 1969).
Conti…
 Determination of BMI:
The body mass index was calculated from the collected height (mt) and weight (kg) data
(Jhonson and Nelson, 1986) using the following formula:
BMI=Weight (kg) / Height2 (mt).
Evaluation Musculoskeletal Disorder:
The musculoskeletal disorder of the subjects engaged in carpentry tasks was assessed using
modified ‘Nordic’ Questionnaire (Kuorinka et al., 1987).
Body Part Discomfort Rating:
The Body part Discomfort (BPD) rating was made for assessing pain/discomfort in a
quantitative manner in different body segments of the subjects using a 10-point scale
(Corlett and Bishop, 1976).
Conti…
0
Fig. 1: Different segments of the body
1
2
The 10 point scale:
0 : No pain
1 : Discomfortness
2 : Very mild pain
3 : Mild pain
4 : Numbness
5 : Average pain
3
4
5
6
7
8
9
10
6 : Moderate pain
7 : Severe pain
8 : Very much severe pain
9 : Very Very much severe pain
10: Intolerable
Fig 2 : Modified ten point scales to rate the discomfort experienced by the
workers
Conti…
Assessment of physiological stress:
 Heart Rate :
The cardiovascular status of the subjects were evaluated by measuring the heart rate of the
workers that was recorded in resting as well as in working condition.
The heart rate monitor (Polar S610i) was used to determine the resting heart rate and heart
rates throughout the working period.
The works pulse was also computed from resting and working heart rate.
 Cardio-vascular Stress Index (CSI):
The Cardiovascular Stress Index of the subjects were determined by the following formula
(Trites et al., 1993).
CSI
100 (Heart rate during work – Heart rate during rest)
=
----------------------------------------------------------------------------Heart rate maximum – Heart rate at resting
Where, Heart rate max = 220 – Age (years).
Statistical Analysis:
The differences between groups (motorized and pedal threshing workers) were examined by
Student's t-test (for continuous variables) and a χ2 test (for categorical variables).
Table-1: Comparison of body composition between male and female paddy threshing
workers
Parameters
Male Threshing
Workers (n=45)
Female Threshing
Workers (n=55)
t value
Height (cm.)
164.9 ± 5.68
162.0 ± 6.52
2.121 (p<0.05)
Weight (kg.)
68.85 ± 9.57
59.0 ± 8.64
4.832 (p<0.001)
BMI
25.32 ± 3.24
22.48 ± 3.35
3.852 (p<0.001)
It was observed that there was a significant (p<0.05) difference between the height of male
and the female workers. Whereas, weight and BMI were significantly higher (p<0.001) in
male workers than that of female threshing workers .
 Weight and BMI were low in female may be due to unhealthy lifestyle like irregularity of
meals, women's problems and various gastro-intestinal problems .
 Other reasons are the female have to go through more physical work ( beside these home
work) than the male worker.
Conti…
Table 2: Frequency, Percentage and Comparison of musculoskeletal disorders (MSD)
between pedal and motorized threshing workers.
Pedal Threshing
Body
Segments
Male
(n=27)
f
%
Motorized Threshing
Female
(n=23)
f
%
Male
(n=28)
f
%
χ2 value
Female
(n=22)
f
%
Male
Female
Neck
14
51.85
13
56.52
12
42.86
15
68.18
2.523
4.495*
Shoulder
23
85.19
15
65.22
25
89.29
18
81.82
1.177
10.951***
Elbow
17
62.96
15
65.22
23
82.14
18
81.82
14.415***
10.951***
Wrist
18
66.67
18
78.26
22
78.57
21
95.45
5.554*
19.881
Upper back
14
51.85
14
60.87
18
64.29
17
77.27
4.939*
9.756**
Lower back
25
92.59
22
95.65
22
78.57
19
86.36
12.293***
15.058***
Thigh
25
92.59
21
91.30
18
64.29
18
81.82
36.510***
6.052*
Knee
22
81.48
22
95.65
13
46.43
20
90.91
41.270***
2.810
Feet
17
62.96
21
91.30
14
50.00
18
81.82
5.310*
6.052*
 In case of pedal threshing the prevalence of MSD was significantly higher (p<0.05 or
lesser) in the body segments of lower extremity than that motorized threshing.
 On the contrary, in case of motorized threshing the prevalence of MSD was significantly
higher (p<0.05 or lesser) in body segments of upper extremity in comparison to that of pedal
threshing
Conti…
 In the present study the paddy threshing workers performed the work
during pedaling machine ,they were reported pain mainly in lower extremity
segments than motorized workers.
 Pedal threshing requires both hand and leg synchronization. However, little
hindrance cannot be avoided, as the pedal movement is continuous and very
fast.
 Working in the same situation for prolonged periods was the work factor
recognized as most challenging, where most respondents rated it as a most
important problem causative to musculoskeletal symptoms.
 Madeleine (2003) noted that prolonged static muscle loads have appeared
as a major risk factor in the development of load-related illnesses.
Conti…
 In case of female, the MSD was high in shoulder and elbow during motorized
threshing, its may be occurs due to the drum speed was high than the manual pedal
threshing machine, that's why the arm movement require as fast as possible.
 Kuorinka et al. (1990) also stated that there appeared to be an increased risk of
problems in the neck, shoulders and arms in monotonous and tensed work.
Conti…
Table 3: The perceived discomfort rating of (PDR) in different segments of the body of male
and female paddy threshers (N=100) during performing different paddy threshing(in a 10
point scale).
Pedal Threshing
Body Region
Neck
Shoulder
Upper arm
Lower arm
R
L
R
L
R
L
Upper back
Middle back
Lower Back
Buttock
Thigh
Calf
Feet
R
L
R
L
R
L
Male
(n=27)
Mean ± SD
Female
(n=23)
Mean ± SD
2.5±2.3
5.0±0.88
4.5±1.06
3.5±1.39
3.4±1.31
3±2.63
2.5±2.4
4.1±1.9
3±2.1
5±0.89
1.0±0.96
5.4±1.01
5.5±0.86
6±0.8
6.5±0.92
1.0±1.38
1.5±1.73
3±1.9
4±2.14
3.5±2.08
3.7±1.80
3.5±1.57
3.7±2.24
4.5±2.30
4.5±1.86
3.5±0.81
6.5±0.88
1.5±1.26
6±0.91
5.5±0.61
7±0.84
6.5±1.04
1.5±1.56
1.4±1.42
Mechanized Threshing
Male
(n=28)
Mean ± SD
2.2±1.61
5.1±1.65
4±1.49
3.6±1.87
2.5±1.65
2±1.33
1.5±1.16
4.6±1.17
1±1.22
4.5±1.26
1.0±1.25
3±1.70
2.5±1.37
4.5±1.01
4.6±1.04
2.5±1.79
2.4±1.75
Female
(n=22)
Mean ± SD
2.5±2.71
5.5±1.64
5±1.55
4±1.95
3.3±1.86
3.5±2.20
3±1.81
5.0±2.5
1.5±1.61
5.5±2.02
1.9±1.45
5±2.29
4.5±2.02
5±0.86
5.5±0.87
3.5±2.04
3.0±1.84
t-Value
Male
Female
0.559
0.714
0.282
2.646**
1.438
2.751**
0.226
0.536
2.244*
0.389
1.770
0.302
1.956
2.437*
1.170
0.759
4.298*** 5.228***
1.705
2.136*
3.001***
0.986
6.392***
1.909
9.763***
2.227*
6.117*** 7.887***
7.183***
3.504**
3.488*** 3.682***
1.918
3.255**
Conti…
 In case of male workers significant difference (p<0.05 or lesser) in PDR was observed in
upper arm, mid back, buttock, and segments of lower extremity between using pedal
threshing machine and motorized machine.
 In case female workers significant difference (P<0.05 or lesser) in PDR wad found in
lower arm, mid and lower back, and segments of lower extremities between
pedal threshing and motorized threshing
 According to Kadi et al., (2000), Upper body muscles may have more androgen receptors
than lower body muscles (Kadi et al., 2000).
 Thus, it is possible that this hormonal difference might permit greater development of
upper limb muscles in male compared to female.
 A constant repetition of movements imposes a cumulative work load which can cause pain
and weakness and impaired function of the muscles and other soft tissues (Gangopadhyay et
al.,2007).
The physiologic problems that arise from repetitive work or overuse of certain muscles,
tendons and soft-tissue structures have been addressed in terms of muscle fatigue, tissue
density changes, and tissue strain (Valachi B and Valachi K.,2003).
 Physiologic evidence shows that the rate and degree of tissue damage depends on the
amount of force, repetition and duration of exposure (Geronilla et al.,2003).
Conti…
Table 3: Physiological stress determine by the compare heart rate between pedal threshers
& mechanized threshers.
Pedal Threshing
Parameters
Male
(Mean ± SD)
(n=27)
Motorized Threshing
t value
Female
(Mean ± SD)
(n=23)
Male
(Mean ± SD)
(n=28)
Female
(Mean ± SD)
(n=22)
Male
Female
Resting HR
(beats/min)
77±7.12
75±6.29
76±4.22
75.5±4.75
0.631
0.302
Mean
Working HR
(beats/min)
134.25±4.82
148.13±4.78
121.75±4.05
126.13±4.58
9.434***
15.767***
CSI
38.53±4.48
44.03±3.75
28.12±6.34
30.12±5.77
6.336***
9.543***
w.r.t. Motorized threshing ***p<0.001
 From the results it was also noted that the mean working heart rate and CSI were
significantly higher (p<0.001) in both male and female workers during pedal threshing than
that of motorized paddy threshing.
Conti…
 Based on working heart rate as well as energy expenditure value threshing with paddy
thresher was categories heavy work and threshing by using foot was categorized very heavy
(Varghese et al. 1994).
 Increase heart rate in threshing operation was compared to assess the extent of drudgery,
as heart rate is a major parameter in quantification of drudgery (Astrand and Rodahl 1977).
 Similar findings were found in a comparative study with manual beating of paddy that
physiological responses and physiological cost of work reduced significantly in using paddy
thresher by Kwatra S. et.al.(2010).
 During pedal threshing, continuous and repetitive pedaling will inflate heart rate for a
given power output.
 In this case, the muscles are contracting and relaxing in quick succession, requiring a high
ratio of aerobic/anaerobic metabolism to energize the workload.
 Aerobic metabolism requires delivery of oxygen and glucose via blood circulation,
stimulating heart rate.
 From present study it has been concluded that the paddy threshing by pedaling method
was much stressful in both male and female workers than that of the motorized threshing.
 The findings of the present study, a significant difference was observed in MSD,BPD and
heart rate in the pedal operated and motorized threshing workers may be due to
continuous, prolonged and repetitive body segments movement.
Our sincere thanks to the paddy threshing workers for their cooperation and support.