PHYSIOLOGICAL MEASURES TO DETERMINE THE
RECOMMENDED WEIGHT LIMIT USING NIOSH
LIFTING EQUATION
1
GARIMA MISRA
M.Tech( ME)
IFTM University
Moradabad, India
2
garimamisra17@gmail.com
Dr.VISHAL SAXENA
HOD of ME
IFTM University
Moradabad, India
3
hodme@iftmuniversity.ac.in
ahmad.nadeem61@gmail.com
ABSTRACT
In industrial workplaces, many workers
perform processes jobs in standing position
for a long period of time. Working in
standing position can be linked to versatility
because the mobility of legs position and
having
large
degree
of
freedom.Measurement
of
energy
expenditure of the worker during manual
material handling (MMH) task depends
upon various parameters that can be used to
assign the task to particular worker.[1]
The present study follows a approach to
evaluate physical work capacity during
manual material handling (MMH) tasks on
Indian male workers. This study involves six
independent variables such as lifting
frequency, lifting load, vertical height,
horizontal distance. The selected two
responses variables were heart rate and
blood pressure.
The National Institute for Occupational
Safety and Health (NIOSH) recognize the
growing problem of work related back
NADEEM AHMED
Assistant Professor in ME
IFTM University
Moradabad, India
injuries and published a summary of lifting
related literature. The components of the
original and revised lifting equation were
defined
by
using
three
criteria
(Biomechanical,
Physiological
and
Psychophysical).
The NIOSH lifting equation consists of two
primary products, the recommended weight
limit (RWL) and lifting index (LI). The
RWL is defined for a specific set of task
condition as the weight of the load that
nearly all healthy workers could perform
over a substantial period of time( e.g. up to 8
hours) without an increased risk of
developing lifting related low back pain by
healthy workers. Physiological measures
including heart rate and blood pressure have
also been considered reliable tool to identify
a safe workload, especially concerning
manual works. Heart rate is usually used as
a primary indicator of physical and mental
stress reflecting a marked linear connection
with effort experienced by a healthy worker.
KeywordsRevised
NIOSH
Lifting
Equation, Lifting Index, Manual Lifting,
Low Back Pain, Energy Expenditure.
1.INTRODUCTION
Manual Material Handling (MMH) is a
general process in all types of manufacturing
industries under which the workers are
working in different type of manufacturing
task like lifting or lowering, carrying and
holding etc. Basically industrial activities
involve lifting/ lowering of objects or
moving material from one place to another
is termed as Manual Material Handling
(MMH). In developing and under developed
countries, MMH is associated with nearly all
types of industries as manual labor is cheap
in these countries and is available in plenty.
During the manual material handling task
the risk factors leading to musculoskeletal
disorders (MSDs) are always present.
Physiological measures for assessing
physicalstresses are necessary for measuring
the expenditure of workers energy during
the task.
MMH is an expensive public health
problem. The governments and industries of
many industrialized nations, including USA,
UK, Germany pay not only for workman’s
compensation, but also spend billions on
their treatment, employee insurance claims
etc. due to loading workers suffer from
cardiovascular
and
musculoskeletal
disorders. Various short and long term
health effects can be attributed to MMH.[2]
Manual material handling (MMH) tasks play
a vital role in a various manufacturing
industries. Many jobs and activities in
industries require manual material handling.
This includes a wide variety of activities
such as loading and unloading boxes and
carbons, removing materials from a
conveyor belt, stocking items in a
warehouse, etc. as a result, and workers may
suffer
from
cardiovascular
and
musculoskeletal disorders (MSDs). Various
short term and long term health effects can
be attributed to MMH. Some of these are
(National Institute for Occupational Safety
and Health) fractures, cardiovascular strain,
such as increased heart rate and oxygen
intake, musculoskeletal injury, especially to
the spine and back pain. [2]
The National Institute for Occupational
Safety and Health (NIOSH) developed a
lifting equation in 1981 to indicate safe
occupational lifting limits. This equation
was revised in 1991.In 1981, National
Institute for Occupational Safety and Health
(NIOSH) recognize the growing problem of
work related back injuries and published a
summary of lifting of lifting related
literature. It also provides a lifting equation
for calculating a recommended weight for
specific two handed, symmetrical lifting
task, an approach foe controlling the hazard
associated with low back injury from
manual lifting.
The components of the original and revised
lifting equation were defined by using three
criteria (Bio mechanical, Physiological and
Psychophysical).Threecriteria
biomechanical,
physiological
and
psychophysical were used to define the
components of the original and revised
lifting equation. The present document
describes the rationale for selecting these
criteria and demonstrates how they were
used to determine the equation values. The
document also discusses the limitations of
the lifting equation and the use of a lifting
index for identifying hazardous jobs. [6]
The NIOSH guidelines for Psychophysical
criteria were based on the maximum
acceptable weight of load that can
accommodate 75% of the women and 99%
of the men. In the workforce for the RWL
criteria. The guidelines for physiological
criteria were based on an assumed aerobic
capacity of 15 Kcal/ min for men and 10.5
Kcal/min for women. These aerobic
capacities are average values for males and
females. The biomechanical criteria of
NIOSH lifting equation were based on the
maximum amount of compression that can
be tolerated by the lumbar spine, estimated
from a axial loading compression tests.
Heart rate and oxygen intake are used to
assess the state of health, identify status of
general health. Physiological measures,
including heart rate and blood pressure have
also been considered as reliable tool to
identify a safe workload, especially
concerning manual works. [ 5]
Heart rate is usually used as a primary
indicator of physical and mental stress
reflecting a marked linear connection with
effort experienced by a healthy person.
Physiological reactions of a person to
different lifting techniques, frequency and
distances was investigated and it was
determined that changes is consumed
metabolic energy are in line with
characteristics of different lifting methods
and help in identifying changes in ability to
lift weights..[7]
2.RELATED WORK
It can be observed that there are two
fundamentals rules to be observed while
lifting, keep the load as close as to the body
and avoid twisting. [3]
Another type of lifting job is defined as a
sequential lifting job where a worker may
rotate
between
different
specific
workstations for a fixed period of time
(either single or multi task), and then
transfer or rotate another workstation to
perform a different series of specified lifting
tasks.[4]
The 1981 equation could only be applied to
a limited number of lifting tasks, the 1981
equation was revised and expanded in 1991
to apply to a larger percentage of lifting
tasks. [5]
3.PROPOSED WORK
The main components related to the study
were as follows:
(i) Selection of manual lifting job
(ii) Measurement of data needed to calculate
the RWL and LI for the selected job.
 Weight of the load lifted
 Horizontal and vertical location of
hand with respect to midpoint
between ankles.
 Angle of symmetry
 Frequency of lift
 Lifting duration.
 Coupling type.
(iii) Measurement of physiological response.
The revised lifting equation for calculating
the recommended weight limit (RWL) was
based on multiplicative model that provided
a weighing for each of six task variables.
The weights were expressed as coefficient
that serve to decrease the load constant,
which
represent
the
maximum
recommended load weight to be lifted under
ideal conditions. The NIOSH lifting
equation is a method to assess risk of low
back disorders in jobs with repeated lifting.
It consists of two primary products, the
recommended weight limit (RWL) and the
lifting index (LI).
The RWL is defined 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 (up to 8
hours) without an increased risk of
developing lifting related low back pain. It is
calculated as a product of the weight that is
considered safe for an ideal lift( load
constant equal to 23 kg) and six weighted
task variables, which include the (1)
horizontal distance of the load from the
worker( H), (2) vertical height of the lift(V),
(3) vertical displacement during the lift( D),
(4) angle of asymmetry (A), (5)
Frequency(F) and duration of lifting and (6)
quality of the hand to object coupling ( C)
RWL= H * V* D* A*F*C......(i)
The LI is defined by the following equation:
LI = Load Weight/ RWL = L/ RWL.......(ii)
4.EXPERIMENTS & RESULTS
This
study
explored
the
workers
performances as subjects lifted from a
sagitally symmetric lift origin and three
asymmetric origins to a sagitally symmetric
lifting destination. Subjects were asked to
perform all lifts using a two handed lifting
technique. The experiment involved the
lifting of rectangular box from the ground
level to a platform of height of 100 cm from
the ground for 10 minute duration
symmetrically as well as asymmetrically.
Then various parameters as defined by
revised NIOSH lifting equation were
measured.
The heart rate and the oxygen intake were
measured using cosmed pulmonary function
equipment. It measured the responses
simultaneously. It produces two curves one
for heart rate and other uptake vs. time span.
Two kinds of face masks were provided
with the instrument. Face oxygen mask was
put on the subjects with the help of belt to
ensure that no leakage of oxygen take place.
The mask was connected through a wire to
the main instrument. A belt provided with
the instrument was put around the chest of
the subject. A heart rate probe was clamped
to the belt, the other end of the probe was
connected to the main unit to measure the
variation in heart rate vs time. Time of
experiment was noted on the stop watch.
The effects of five lifting parameters (lifting
frequency, load weight, horizontal distance
from object, angle of asymmetry and the
vertical distance of lifting) and the operator
with their interactions were evaluated. It has
been found that when the participants
performed lifting tasks, there was increase in
oxygen intake.
The effects of five lifting parameters (lifting
frequency, load weight, horizontal distance
from object, angle of asymmetry and the
vertical distance of lifting) and operator with
their interactions were evaluated. It has been
found that when the participants performed
lifting tasks, there was increase in heart rate.
5. CONCLUSION
The results of the experiment showed that
lifting loads and higher lifting frequencies
increases the physiological workloads. The
tasks become more stressful when the
vertical distance of the lift is above the
shoulder level. The effect of the load weight
and frequency of lift was found to be most
significant factors leading to the increased
oxygen intake and heart rate.
6. FUTURE WORK
In future a detailed work guide should be
created fixing the higher levels of lifting
parameters to lower the cardiovascular risks
of the workers. Further investigations are
also necessary to identify the strenuous
levels of lifting parameters which stresses
the cardiovascular system of the workers.
We have focused in this work on male
population which could be analyzed further
for the female population. Also we can
extend this work for larger age groups.
Proper training such as proper handling,
proper posture etc, should be instructed
while lifting tasks.
7. REFERENCES
[1] ZenijaRoja., 2005.Mrasures to overcome
health problems of Latvian road builders
created by ergonomical risks.
[2] Isa Halim, Abdul Rahman Omar., 2012.
A review on health effects associated with
prolonged standing in the industrial
workplaces. IJEAT .Vol 2
[3] ICMR Bulletin, 2000. Ergonomics in
manual materials handling tasks.Vol .30,
No. 8, ISSN 0377-4910
[4] CHUNG, M.K., Kee,D.,2000. Evaluation
of lifting tasks frequently performed during
fire brick manufacturing processes using
NIOSH lifting equation. International
journal of Industrial Ergonomics. Vol. 25,
423-433
[5] Astrand, P., Rodahl,K., 1977. Textbook
of work physiology, McGraw Hill, New
York.
[6] Putz-Anderson, v., and Waters, T.R.,
1991. Revisions in NIOSH guide to manual
lifting. Paper presented as national
conference entitled” A national strategy for
occupational
musculoskeletal
injury
prevention.
[7] Jaswinder ,Singh., P.Kalra., R.S.Walia.
2012. Study of manual material handling
tasks using Taguchi technique.
[8] Maiti,R.,Ray, G.G., 2004. Manual lifting
load limit equation for abult Indian women
workers based on physiological criteria.
Ergonomics, Vol.47, No, 1, 59-74.
[9] Batish, A., Bhattacharya,A.,Singh,B.,
2011. Multi response optimization and
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responses during manual lifting tasks.
Human factors and Ergonomics in
manufacturing and service industries. Vol.
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[10] Balderrama, C., Ibarra, G.,Riva, J.,
Lopez,S., 2010. Evaluation of three
methodologies to estimate the VO2 max in
people of different ages. Applied
Ergonomics. Vol.42, 162-168.
[11] Ceriello, V.M.,2007. The effects of
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[12] Singh,S.,Kumar,S.,2010. The effect of
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using revised NIOSH lifting equation.
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