Ergonomics, A seminar presentationMade by : Subhi sanchali
Gupta 080909460 (192)
What is Ergonomics? Ergonomics, also known as human factors, is
the scientific discipline that seeks to understand and improve
human interactions with products, equipment, environments and
systems. Drawing upon human biology, psychology, engineering and
design, ergonomics aims to develop and apply knowledge and
techniques to optimise system performance, whilst protecting the
health, safety and well-being of individuals involved. The
attention of ergonomics extends across work, leisure and other
aspects of our daily lives. Basically, Ergonomics is a science
concerned with the fit between people and their work. It puts
people first, taking account of their capabilities and limitations.
Ergonomics aims to make sure that tasks, equipment, information and
the environment suit each worker.
Factors taken into account: body size and shape fitness and
strength posture the senses, especially vision, hearing and touch
the stresses and strains on muscles, joints, nerves. mental
abilities personality knowledge experience. the job being done and
the demands on the worker the equipment used (its size, shape, and
how appropriate it is for the task) the information used (how it is
presented, accessed, and changed) the physical environment
(temperature, humidity, lighting, noise, vibration) the social
environment (such as teamwork and supportive management).
1. Applied AnthropometryIntroduction The workplace should be
designed to accommodate the body size of the user. Anthropometry is
the measure of physical human traits that is applied to determine
allowable space and equipment size and shape used for the work
environment. Factors that are considered include agility and
mobility, age, sex, body size, strength, and disabilities.
Engineering anthropometry applies these data to tools, equipment,
workplaces, chairs and other consumer products, including clothing
design.
Example In the design of controls, the size of the operators
hand must be considered. Important hand dimensions include the
circumference of the hand, breadth of the hand, circumference of
the wrist, and the maximum grip. Knobs, for example, must consider
these dimensions so they fit the hand comfortably and turn
easily.1. Important Hand Dimensions:1Circumference of hand2Breadth
of hand3Circumference of wrist4Maximum grip (circumference of thumb
and forefinger)
2. BiomechanicsIntroduction Biomechanics is the study of the
structural elements of the human body in relation to how the body
functions and how much stress, acceleration and impact it can
stand. Simply defined, it is the application of the principles of
mechanics to living biological material. Today, the total energy
demanded from a person in the performance of an industrial task has
often been drastically reduced through better engineering and
technology.
Equipment Improperly designed chairs or other poorly designed
equipment may obstruct the blood flow to body tissues. It is
essential that designers as well as the evaluators of tools and
equipment be familiar with the location of blood vessels vulnerable
to compression. Of special importance is the knowledge of the
location of blood vessels and other pressure sensitive anatomical
structures in the hand. For example, poorly designed or improperly
held hand tools may squeeze the hands ulnar nerve, which can lead
to numbness and tingling of the fingers. The simplest of hand
tools, if designed without due consideration to biomechanical
principles, can adversely affect the health of people as well as
their performance and productivity.
3. Illumination Lighting of a sufficient intensity is essential
to adequately perform visual tasks and to reduce worker fatigue.
How a space is used and what it is used for influence how lighting
should be applied. Other factors that influence lighting design for
a task include appearance, economics, building costs, energy
consumption and the quality of lighting desired. Factors affecting
the visual environment include lighting fixtures, visual tasks,
lighting maintenance, lighting system design and the individuals
eyesight.
The quantity of illumination relates to the amount of light
that exists or is required at a workplace. The amount of light
necessary for effective work depends on the nature of the work, the
sharpness of a workers vision and the environment in which the work
is done. In the design of good lighting, safety and welfare should
be taken into account as well as visual efficiency. In some jobs
where visual demands are not great, it is normal for recommended
levels of illumination to be based on safety, welfare and amenity
(creation of a pleasant environment). Too much light can be as
damaging as too little.
Measures taken: The best ergonomic solution for these varying
needs is to provide general workplace lighting and supplement it
with specific task lighting. Lighting systems should be designed to
provide a uniform distribution of light over the entire work area.
To ensure that a given illumination level will be maintained, give
more light initially than is minimally required. The reason for
this is that such factors as dirt, use and time deteriorate
lighting. Lighting should be directed to the work, or special local
lighting should be provided to match the needs of the work and the
general lighting levels.
Cumulative Trauma Disorders Introduction Musculoskeletal
injuries caused by working are common. The majority of these
injuries are not accident-related broken bones or strained
ligaments. They usually develop over a period of time as a result
of repeated stress on a particular body part. The condition is
often ignored until the symptoms become chronic and permanent
injury occurs. Cumulative trauma disorders (CTDs) and repetitive
motion injuries are terms used to refer to certain musculoskeletal
injuries.
A key reason for the increase in CTDs is the increase in
production due to automation. The assembly line, computerized
office machines and electronic checkout stations in grocery stores
are examples of workstations that require a high volume of output.
One simple, strain-producing task may be repeated several thousand
times a day. High production demands do not allow much time for
rest and recovery. The aging workforce relates to the incidence of
CTDs because the ability to withstand shock, chronic strain and
stress decreases as an individual ages.
A. Carpal Tunnel Syndrome Carpal Tunnel Syndrome (CTS) is a
common nerve CTD. It is a progressively disabling and painful
condition of the hand. CTS results from injury to the median nerve,
which is located in the wrist. It is a nerve entrapment that
develops from the build-up of pressure on the median nerve as it
passes through the carpal tunnel. This is a dime size passage
between the carpal (wrist) bones and the anterior transverse carpal
ligament. Since musculoskeletal strain from repeatedly flexing the
wrist or applying arm-wrist-finger force does not cause observable
injuries, it often takes months or years for workers to detect
damage.
Symptoms of CTS include weakness, clumsiness, numbness, pain,
tingling and a lack of sweating in parts of the hand innervated by
the median nerve. The condition is progressive and can lead to
compensable hand disabilities. CTS is considered an occupational
disease, as it is often associated with the performance of
particular repetitive tasks.
Tenosynovitis. Tenosynovitis is the inflammation of the tendons
and sheaths. It is often associated with tasks demanding extreme
wrist deviation. For example, wrist deviation is required to hold
an in-line nut-runner in a horizontal position. Trigger finger.
Trigger finger is a form of tenosynovitis that results when any
finger must be frequently flexed against resistance. It may be
avoided by designing tool handles for operation by the thumb, by
more than one finger, with lower force requirements, or by not
requiring constant pressure. De Quervains Disease. In De Quervains
disease, the tendon sheath of both the long and the short abductor
muscles of the thumb narrows. The disease is common among women,
particularly those who perform repetitive manual tasks involving
radial or inward hand motion and firm grips.
Tennis Elbow. Also called epicondylitis, this form of
tendinitis is an inflammatory reaction of tissues in the elbow
region. In an industrial environment, tennis elbow may follow
effort requiring palm-upward hand motion against resistance, such
as using a screwdriver, the violent upward extension of the wrist
with the palm down. The condition may be avoided by ensuring that
the rotation axis of the tool or machine coincides with the
rotation axis of the forearm. Raynauds Syndrome Raynauds syndrome
occurs when blood vessels and nerves in the hands constrict from
conditions such as cold temperature, vibration or emotion. The
hands, fingers or finger tips may become cold, blue, numb, and lose
fine manipulative ability. Upon recovery, the hands become red,
accompanied by a burning sensation. It can be confused with the
one-sided numbness of carpal tunnel syndrome.
CORRECTIVE ACTIONS: Corrective actions to prevent CTDs include
adjusting the height of work tables, conveyors and seats;
automating tasks to eliminate manual handling; reducing the
frequency of tasks or increasing the frequency to a point where
automation is necessary; reducing the size or weight of loads;
providing arm rests; redesigning hand tools so that the axis of
rotation or application of force coincides with the axis of
rotation of the arm; providing operator training; using careful
pre-placement screening to identify high risk employees; changing
load positions in relation to the body or hands; minimizing the
time that a load is held in the hands; and eliminating gloves if
they cause a problem or trying different gloves.
Among recommendations to help prevent the development of CTS5
are these: Low frequency vibration in hand tools should be
eliminated or reduced. Wrist deviation from the straight position
should be minimized especially where a great deal of force must be
exerted. Where possible, a closed fist (rather than a pinch) should
be used to reduce tendon tension
1. Hand tool corrections Each year, hand tools are the source
of approximately 6 percent of all compensable injuries.6 Improper
use of hand tools and defective tools can cause biomechanical
stress and injuries. Types of injuries frequently reported include
broken bones, contusions, loss of eyes and eyesight, and puncture
wounds. Additionally, fingers, tendons and arteries are severed
from the use of cutting tools. Basic safety precautions mandate
that tools always be kept in good condition and be used properly.
Workers should be careful to use the proper tool for the job
performed. Figure illustrates particular hand tools with
ergonomically designed features
Hand Tools with ErgonomicFeatures
2. Hand and Wrist Postures Some hand tools may force the wrist
to assume awkward postures. The wrist position affects the
effective strength of the contracting muscles. Therefore, as the
angle of the joint increases or decreases from the neutral
position, there is more stress on the tendons. Ulnar deviation is
the bending of the wrist toward the little finger, and radial
deviation is the bending of the wrist toward the thumb. Extension
is bending the wrist up and back, and flexion is bending of the
wrist down towards the palm
3. Finger and Hand Grips The grips used most frequently to hold
objects are shown in Figure. The tip grip (pinching) is a position
grasp used for precise manipulations. The side grip is also
classified as a precision grip. Repeated use of these grips creates
stress on the two tendons controlling the thumbs and fingers. The
power grip requires the thumb to align with the long axis of the
forearm and the wrist assumes a slight ulnar deviation. The posture
may be stressful when combined with high repetition and extreme
force.
4. Seating Almost 50 percent of workers in the industrial world
are thought to suffer from back problems. Many back problems
originate from improper sitting positions. Complications that may
arise from poor seating conditions include: Lumbar damage from lack
of support in the lumbar region. Damage to the erector spinae
muscles due to sitting without back support. Damage to the knees,
legs, and lumbar region, from sitting without footrests of the
proper height. Damage to various muscle groups
A. Proper Sitting Positions Proper sitting contributes to the
physical well-being of a worker. It may also add as much as 40
minutes of production to each workers day if the chair is properly
selected and customized to support the lower back. The ideal
position for sitting at work exists when there is a slight curve in
the lumbar region of the back, as is found in the standing
position. The workers shoulders should be relaxed, with the upper
arms hanging down loosely. During work, the neck should not be bent
too much
B. Guidelines to Chair Adjustment The human body dimension that
provides a starting point for determining correct chair height is
the popliteal height. Figure illustrates the popliteal height. This
is the height from the floor to the point at the crease behind the
knee. The chair height is correct when the entire sole of the foot
can rest on the floor or footrest and the back of the knee is
slightly higher than the seat of the chair. This allows the blood
to circulate freely in the legs and feet. The back of the chair
should be adjusted so that it catches the concave portion of the
backs lumbar region.
5. Physical Space Arrangements For workspace to be functional,
both the user of the space and the work to be performed must be
considered. Workspace arrangements should consider worker comfort,
physical constraints and performance requirements. Four basic
considerations regarding the worker that must be taken into account
are: What the worker needs to see. The amount of communication
needed with co-workers and supervisors. Equipment and material that
the worker must be able to work with and reach. Body clearances
that are needed by the worker.
6. Driving The goal of ergonomics is to fit your car so you can
drive in a way that maximizes the natural ability of your body to
move and respond to physical stress. This minimizes exposures to
risk factors that may result in injury or illness.
Here are 10 easy things to look for before youstart your next
drive: Remove items from your pockets, such as a wallet or keys,
which may press on soft tissue as you sit down. This compression
can reduce circulation or press on nerves and other soft tissues.
2. Position items that you may need during your drive : sunglasses,
tissue, if you have allergies like the rest of us, throat lozenges
or mints, etc. Place these in a location so you do not have to
reach for them while driving. If you have to reach for an item,
take the time to pull over in a safe place instead of risking an
accident and/or injury due to awkward reaching. 3. Buckle up! If
the seat belt strap is uncomfortable, take a short piece of large
diameter soft pipe insulation or foam and place it on the part of
the strap that is not comfortable against your body. If you like to
spend money, purchase a shoulder strap cushion at your favorite
store where car accessories are sold.
4. Adjust your mirrors so that you do not have to crane your
neck to see. If you have a blind spot in your car you can attach a
small mirror your dashboard to improve your view. 5. Lumbar support
the lower part of your back sho uld feel supported. If it is not
supported by your car seat you can roll up a small towel and place
it in the curve of your lower back. A lumbar roll is a cylindrical
shaped pillow sold at back stores and physical therapy offices.
This is more expensive but some people like the support of foam and
they also like to spend money. 6. Back tilt The least amount of
pressure on the back occurs when your seat back is at 100-110
degrees so that you are slightly reclined. The seat back should
fully support your back. If you cannot recline your seat back, take
frequent breaks from your upright posture by shifting your weight
side to side and using small upper body motions to relax the back
(see the Wellness Center staff for more ideas on exercises and
stretches while driving). 7. Seat cushion length when seated in
your car, scoot your tale bone as far back to the seat back as
possible. After doing this, you should be able to place your hand
comfortably between the back of your knee and the front of the
seat. If you cannot do this, add a pillow or back cushion to your
car seat to move you forward.
8. Seat pan tilt the seat of your car should allow for your
knees to be slightly lower than your hips. This opens up your hip
flexors and increases circulation to the back and decreases
pressure on the lower back. 9. Stepping up and stepping out If you
drive one of those large vehicles with a high step up/down add an
extra step or slowly step in and out of your vehicle versus jumping
down. Over time, the jumping down can cause compression to your
spine. Straps and other hand assist devices for holding on to
should be checked frequently for wear and tear. 10. Steering wheel
grip the best posture is the next posture. It is advisable to keep
two hands on your steering wheel except when shifting gears. Change
your hand postures frequently to improve circulation and reduce
fatigue.
There are common postures that should beavoided : The death
grip this grip results in decreased circulation and muscle tension.
Your grip should be light. If your knuckles are white, you are
gripping too hard! The one arm cool dude You know the one: the
wrist rests at 12 oclock on the steering wheel and the fingers flop
over the top. Not only does this cause compression of soft tissue
of the wrist, but it reduces circulation at the neck and shoulder,
too. Arms straight out in front to reach the steering wheel you
should be able to drive with your shoulders relaxed and your arms
close to the sides of your body. If you have to reach too far
forward your steering wheel maybe too far away. You can try tilting
the steering wheel upwards and using a light grasp lower on the
steering wheel. One arm propped on your window this posture
decreases circulation at the neck and shoulder and may compress
soft tissue on the arm/wrist.
SummaryThis report: mentions the significance of ergonomic
design of environment glances upon the various negative health
effects of improper postures, arrangements and positions, and lists
the various methods which if taken into consideration; increases
the harmony, ergonomical stability in a system, and significantly
reduces the work, or mechanically related injuries.
