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????? Bahrami_a_at_kaums.ac.ir
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An ounce of Prevention is worth a pound of cure !
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Designs vs Needs
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ERGONOMICS

• What it is and why you should be interested in it

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ERGONOMICS comes from

• ERGOS Greek for work
• NOMOS natural law

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Other words for Ergonomics

• Human Factors (American)
• Human Engineering

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Ergonomics is a study of work

• Word Ergonomics coined in 1949
• Focus on man-machine interaction
• Originally concerned with the military
  applications, particularly aeronautics

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• Ergo ???
• Nomos ?????? ????? ??????
  ??? ???? ??????? ?? ??? ??????????? ??????
  ???????? ?? ?? ????? ?????? ????? ???(1882-1799)
• ??? ????? ???

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Human Factors

•  Human Factors traditionally has focused on
  peoples behavior as they interact with equipment
  and their environment and on human size and
  strength capabilities.
• Human Factors has also been applied to the design
  of consumer products. Examples of products which
  have incorporated human factors principles
  include
• the Reach toothbrush
• automobile interiors/instrumentation
• adjustable chairs
• garden tools.

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Every year thousands of workers are injured while
lifting, pushing, and pulling all manner of heavy
and/or bulky objects.
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Soft-tissue injuries can occur over many weeks or
months (as with tendonitis) or can happen
instantly (as in a car accident, during a fall,
or while lifting heavy loads). Typically,
recovery is slow, and in some cases full recovery
is never realized.
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The goal of this module is to present the reader
with a number of ways to reduce soft-tissue
injuries (such as muscle strain, tendonitis and
low back pain), and to stress the importance of
injury prevention through work practice changes,
engineering solutions, and hazard awareness.
Lets start by taking a look at a common site of
ergonomic injury - the back.
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People involved in manual materials handling
often experience low back discomfort or pain in
the lumbar region of the spine.

• 7 cervical (neck) vertebrae
• 12 thoracic (middle back) vertebrae
• 5 lumbar (low back) vertebrae

Lumbar Spine
Sacrum
Coccyx (tailbone)
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This diagram depicts a herniated disk. Inner
disk material (purple) may press on spinal nerves
causing a variety of symptoms.
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The risk of low back injury can be reduced by
using the following lifting recommendations

• avoid placing objects either very high or very
  low.
• purchase supplies in containers with reduced size
  and weight.
• provide handles to improve grip.
• design the job to reduce twisting.
• eliminate bending and/or stooped postures.
• provide mechanical assistance.

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Too high
Avoid high and low object placement, especially
as the weight and/or size of the object increases.
Too high
Too low
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The use of mechanized equipment is encouraged,
but heavy equipment is not always available or
suited to the site.
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When lifting heavy and/or bulky objects manually,
be sure to

• test the objects weight before lifting it.
• keep the object close to the body.
• avoid twisting and bending.
• avoid rapid, jerky movements.
• ask for assistance from a co-worker when
  appropriate.

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Keeping loads close to the body reduces forces on
the low back.
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Rapid, jerky, and/or twisting motions, as
depicted here, should be avoided.
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Poor lifting technique
Good lifting technique
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The safest lift is no lift. Look for ways to
eliminate lifts altogether. In this case it may
be practical to slide the seed bag to the truck
tailgate, cut a hole in the bag, and let the seed
fall into the spreader.
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The lifting posture depicted at right is often
referred to as a squat lift. The squat lift is
a good choice for many lifting tasks. When using
the squat lift, keep the spine straight (use
the tail out posture), while bending at the
knees and hips.
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While a good choice for many lifting tasks and
often recommended, the squat lift (right) has
limitations and is not the best technique for
every situation. People with weak leg muscles may
not be able to use this technique and those with
bad knees may be reluctant to lift in this
manner.
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A popular alternative to the squat lift is the
power lift (near right). With the power lift,
the legs are bent, but not as much as with the
squat lift (far right). With the power lift
there is minimal spinal flexion (bending). Most
or all of the bending should occur at the knees
and hips.
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Its also perfectly acceptable to break the load
down and make several trips with more manageable
loads.
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The box at right weighs 57 pounds. The weight
and bulk of this container makes it risky to
handle manually. If a lift truck or hoist is not
practical, the container size and weight should
be reduced. Often a supplier will balk at
making such changes - only to admit after
instituting them - that the changes improved
safety and productivity at their facility.
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Occasionally lifting can be avoided by rolling or
sliding the object.
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With proper equipment, heavy loads can be easily
manipulated with little strain placed on
muscle-tendon units.
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Bulky loads are inherently awkward to lift.
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Good lifting technique can reduce the hazard.
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Good technique, combined with assistance from a
coworker, can significantly reduce the lifting
hazard.
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With any lifting task, a variety of
risk-reduction strategies should be considered.
Filling the bottom of this bin with a few inches
of solid foam would reduce the amount of bending
required.
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Some lifting tasks are quite awkward due to
object size and shape. Removing bench seats from
vans is one such task. Minimize the force of the
lift by lifting one end at a time. Let gravity
assist with the lift by letting the bench slide
over the bumper.
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When installing the bench, avoid lifting the
entire unit by sliding the bench up over the
bumper. Lift with the legs, bend at the knees
hips, and use the tail out posture. Use slow
steady motion. Jerking the object may lead to
injury. Assistance from a coworker is encouraged.
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As mentioned previously, the best lift is no
lift. The task shown is tire rotation. Both
tires are removed. Then, one at a time, the
tires are rolled along the hydraulic lift
platform. A very short lift (inset) gets the
wheel back on the wheel hub.
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Hand tools such as this drum dolly reduce
lifting demands. This in turn reduces task time,
the odds of injury, and the metabolic energy cost
of the work.
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Good housekeeping is just as important as good
ergonomics. Slips, trips and falls account for a
large percentage of workplace injuries.
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Awkward postures (inset) can be tough on the body
if they must be maintained. This oil-filling
operation is kept short by using an efficient
oil-delivery system. Task automation often
simultaneously improves task ergonomics and
reduces labor costs.
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Of jobs that are tough on the low back,
scooping is one of the worst. Straight knees
and rounded back are a recipe for trouble.
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To reduce the risk of low back injury, take small
scoops and use legs for at least some of the
lifting. Keep the spine straight (tail out)
and bend with knees and hips rather than with the
spine.
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A variety of techniques are available to reduce
the likelihood of soft-tissue injury. Back, arm
and shoulder strains can be reduced by pushing
objects vs. pulling them.
Pushing reduces risk.
Pulling increases risk.
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Human thumbs are not well suited to high forces.
The pinch grip (1 2) should be minimized or
avoided altogether. A two handed fingertip grip
(3) is an improvement, but it would be best to
place the fingers under the container (4).
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Case study Improved ergonomics results in
improved productivity for a soil media
task. Old system 1. clod busting 2. pouring
soil 3. screening soil 4. mixing media 5. moving
media 6. media clean-up
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New system 1. loading pulverizer 2.
pulverized soil 3. screening soil 4. mixing
media 5. hydraulic lift 6. unloading media
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The old system (top) involved high energy
expenditure, highly repetitive motions, and
awkward postures. The new semi-automated system
(bottom) eliminates many of these ergonomic risk
factors and has paid for itself through
productivity gains.
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Please also consider the importance of task
planning in a sound ergonomics program.
Bringing proper tools to the work site will go a
long way toward minimizing soft tissue injuries.
Additionally, task difficulty and time are
reduced.
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If you are experiencing soft tissue pain or
discomfort, be sure to seek the advice of a
health care provider. In particular, physical
therapists can provide detailed instruction in
proper body mechanics and can teach these
principles and techniques in person.
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This module has detailed ergonomic basics of
manual materials handling. For more information
please see the other ergonomics e-books on the
EHS web page at http//www.ehs.iastate.edu/ih/erg
o/ergo.htm. Additionally, EHS staff are
available for on-site consultation. Contact us
at 294-5359.
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Scope of Human Factors Engineering

• Different levels of study and intervention
• Micro-level
• Physical design of tools,
• human-computer interface,
• physical environment
• Macro-level
• Organizational design,
• job design, change management

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Thank you for your attention!