به نام خدا. بنام خدا عباس بهرامی عضو هیات علمی گروه بهداشت حرفه ای . دانشکده بهداشت دانشگاه علوم پزشکی کاشان Bahrami_a@kaums.ac.ir. اهداف یادگیری : انتظار میرود دانشجویان در پایان جلسه بتوانند: 1- ارگونومی را تعریف کنند. 2- اهداف ارگونومی را بیان کنند. 3- اجزای ارگونومی را توضیح دهند.
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What it is and why you should be interested in it
ERGONOMICS comes from
ERGOS = Greek for work
NOMOS = natural law
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:
Every year thousands of workers are injured while lifting, pushing, and pulling all manner of heavy and/or bulky objects.
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.
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.
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
Inner - disc material
This diagram depicts a herniated disk. Inner disk material (purple) may press on spinal nerves causing a variety of symptoms.
The risk of low back injury can be reduced by using the following lifting recommendations:
Avoid high and low object placement, especially as the weight and/or size of the object increases.
The use of mechanized equipment is encouraged, but heavy equipment is not always available or suited to the site.
When lifting heavy and/or bulky objects manually, be sure to:
Keeping loads close to the body reduces forces on the low back.
Rapid, jerky, and/or twisting motions, as depicted here, should be avoided.
Poor lifting technique
Good lifting technique
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.
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.
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.
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.
Its also perfectly acceptable to break the load down and make several trips with more manageable loads.
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.
Occasionally lifting can be avoided by rolling or sliding the object.
With proper equipment, heavy loads can be easily manipulated with little strain placed on muscle-tendon units.
Bulky loads are inherently awkward to lift.
Good lifting technique can reduce the hazard.
Good technique, combined with assistance from a coworker, can significantly reduce the lifting hazard.
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.
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.
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.
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.
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.
Good housekeeping is just as important as good ergonomics.
Slips, trips and falls account for a large percentage of workplace injuries.
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.
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.
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.
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.
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).
Case study: Improved ergonomics results in improved productivity for a soil media task.
1. clod busting
2. pouring soil
3. screening soil
4. mixing media
5. moving media
6. media clean-up
1. loading pulverizer
2. pulverized soil
3. screening soil
4. mixing media
5. hydraulic lift
6. unloading media
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.
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.
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.
This module has detailed ergonomic basics of manual materials handling.
For more information please see the other ergonomics e-books on the EH&S web page at http://www.ehs.iastate.edu/ih/ergo/ergo.htm.
Additionally, EH&S staff are available for on-site consultation. Contact us at 294-5359.
job design, change management
Thank you for your attention!