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 operator‘s 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:1—Circumference of hand2—Breadth of hand3—Circumference of wrist4—Maximum 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 hand’s 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 worker’s 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 Quervain’s Disease. In De Quervain’s 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. Raynaud’s Syndrome Raynaud’s 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
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 worker’s 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 worker’s 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 back’s 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 o’clock 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.