ERGONOMICS

"Ergonomics is the scientific discipline concerned with the understanding of the interactions among humans and other elements of a system . . . that applies theory principles, data and methods to design in order to optimize human well-being . . . ergonomists contribute to design and evaluation of tasks, jobs, products, environments and systems in order to make them compatible with the needs, abilities, and limitations of people."— International Ergonomics Association

Ergonomics means fitting the workplace to the worker by modifying or redesigning the job, workstation, tool, or environment. Ergonomics draws from the fields of engineering, and medical and health sciences to optimize the work environment. By identifying ergonomic hazards that can result in an injury or illness, and correcting these hazards, employees can be provided a healthier workplace. Some of the factors evaluated in an ergonomic analysis are:

·  Repetitiveness of a task

·  Posture and movement of the limbs and whole body as a task is performed

·  Physical strength required for a task

·  Design and use of tools

·  Design and layout of the work area or equipment

While the primary goal of ergonomics is to minimize employee exposure to ergonomic hazards that lead to Cumulative Trauma Disorders (CTDs) and related injuries and illnesses, the benefits of ergonomics are:

·  Improved safety and health in the workplace

·  Improved employee morale and job satisfaction

·  Improved productivity

·  Improved quality of work

·  Improved competitiveness in the marketplace

·  Reduced probability of accidents and errors

·  Reduced absenteeism and employee turnover

·  Reduced medical and workers' compensation costs associated with cumulative trauma disorders

Ergonomics is an ongoing process, not just a quick fix. Continued awareness and cooperation among responsible groups is essential to an effective ergonomics program.

This chapter offers a combination of resources and tools to help maximize your comfort and safety. Ergonomics is a combination of good habits, work practices and optimizing the environment. There is no magic bullet and every person and situation possesses unique challenges for making all the pieces fit together.

Cumulative Trauma Disorders

Cumulative trauma disorder (CTD) is not a diagnosis, but a group of health problems with similar characteristics. CTDs are soft tissue disorders (e.g., muscles, tendons, joints, nerves) caused by wear and tear from repetitive motion. CTDs usually occur in the upper body in the neck, shoulders, back, arms, wrists, and hands. It is important to prevent CTDs because they can lead to serious and/or permanent injuries. CTDs are also referred to as repetitive motion injuries, repetitive strain injuries, repetitive trauma disorders, and overuse injuries.

Risk Factors - Several factors, usually in combination, contribute to the risk of developing a cumulative trauma disorder due to the stress on muscles, tendons, joints, and nerves. The presence of these factors in a job, process, operation, or work environment may not necessarily cause a problem, but they do increase the risk of developing a CTD.

Repetition -Tasks that require high repetition rates require more muscle effort and less recovery time, which can lead to fatigue and stress. Examples of repetitive tasks are typing (faster than 60 words per minute), sorting, and flipping through files.

Excessive Force -Examples of tasks in which it is possible to use excessive force are stamping, stapling, grasping large file folders or books, and hammering into a hard surface.

Awkward Posture or Position -Examples of awkward postures or positions are using the shoulder and bending the neck to hold the telephone to the ear, turning the head to the side to read, bending the back in a forward/stooped position, reaching over the shoulder, and bending the wrists. Employees should always strive to maintain a neutral wrist.

Prolonged Activities - Holding a position without movement for prolonged periods causes fatigue and requires a long recovery time. Examples of prolonged activities are standing or sitting for hours at a time, computer operators grasping the mouse for long periods, holding elbows away from the body while typing, and grasping a hand tool for an extended period of time.

Localized Pressure (Mechanical Stress) - Too much pressure on muscles, tendons, and nerves can decrease blood-flow circulation. Over time, constant localized pressure can cause an injury. Examples are pressure on the median nerve in the wrist, which can cause carpal tunnel syndrome, and resting forearms and wrists on sharp or hard edges (e.g., work surface corners, hard arm rests).

Vibration - Working with vibrating tools or equipment for extended periods of time can potentially cause damage to the nerves in the arms, hands, and wrists.

Temperature (Cold) - Working in cold may also contribute to developing CTDs. Cold temperature can result in a loss of sensory feedback, which reduces manual dexterity.

Common Cumulative Trauma Disorders

Carpal Tunnel Syndrome - This condition involves compression or pinching of the median nerve that runs through the wrist. Symptoms include pain, numbness, or tingling in the first three fingers and the base of the thumb. An aching sensation and wrist pain (mostly at night) is also typical of many cases.

DeQuervain's Disease - This disorder is marked by inflammation of the extensor tendon sheath at the back of the thumb. Symptoms include pain and difficulty in movement, especially making a fist.

Lateral Epicondylitis - Also known as tennis elbow, lateral epicondylitis is an inflammation of the tendons on the outside of the elbow. Symptoms include point tenderness over the bone near the outside of the elbow. It is often caused by repetitive forceful grasping.

Hand-Arm Vibration Syndrome - This condition can result from prolonged vibration stress to the fingers and hands. Symptoms include paleness in the fingers, pain, numbness, and loss of finger dexterity.

Rotator Cuff Tendonitis - An inflammation of one or more of the four rotator cuff tendons in the shoulder. Symptoms include pain and limited movement of the shoulder.

Tendonitis - An inflammation of the tendon in the hand and wrist due to excessive use. Symptoms include pain, swelling, tenderness, and weakness when using the affected body part.

Tenosynovitis - An inflammation of the tendon and sheath surrounding a tendon upper extremity. Symptoms include pain, swelling, and tenderness in the hand or arm.

Trigger Finger - This condition results when the tendon of a finger is sufficiently swollen so that the tendon becomes locked in the sheath. This will cause a snapping and jerking movement when attempting to move the finger.

White Finger - This is also referred to as the vibration syndrome or Raynaud's Phenomenon. This disorder occurs when blood vessels in the fingers are damaged, especially from using vibrating tools in cold weather. Symptoms include paleness in the fingers, tingling, and a sense that the finger is "on fire."

Prevention of CTDs

Prevention is the key to reduce or eliminate the risk of developing a cumulative trauma disorder. Prevention includes the use of good body mechanics, good ergonomic design (engineering controls), and the use of administrative controls. Early intervention makes a difference for employees who experience symptoms such as pain, numbness, tingling, or tenderness in the fingers, hands, or arms or muscle pain in the back, shoulders, or other parts of the body from lifting or other body motions. It is important for employees to report early signs and symptoms of work-related CTDs to their supervisor and/or to the Health Services Group for evaluation.

Good Body Posture - Using good body (neutral) posture is important for minimizing the risk of developing a CTD. Equipment, tools, and furniture are an important part of the work environment. Since frequent use of these items does have a significant impact on job performance and overall health, good body posture is essential when equipment, tools, and furniture are used.

Engineering Controls - Engineering control measures should be addressed as the first line of defense to eliminate or reduce ergonomic hazards that employees are exposed to. It is important to design out the problem when this approach is feasible.

Administrative Controls - Administrative controls that can be used effectively are:

·  Job enlargement. Have employees perform more parts of a job rather than one specific task repeatedly.

·  Job rotation. Cross-train employees to perform other jobs. Rotate employees in jobs that use different muscle groups, if possible.

·  Work breaks. Have employees take frequent short breaks from repetitive tasks throughout the day.

·  Training. Training provides information for mitigating ergonomic hazards, strategies to improve a workstation layout, and stress-reduction exercises.

Principles of Ergonomics

A Neutral Wrist - It is important to maintain a neutral wrist to minimize the potential for developing a CTD, whether the operator is sitting while conducting a task (e.g., working at a computer workstation) or standing (e.g., using a hand tool). The workstation should be designed so that a neutral wrist position can be maintained.

The Work Envelope - The work envelope is the zone in which an employee performs most routine tasks, whether repetitive movements (e.g., typing at a keyboard) or less frequent movements (e.g., lifting). Work should be arranged to be within easy reach and usual work located within 30.5 cm (12 inches) of the operator. Frequently used materials should be located within 45.75 cm (18 inches) maximum of the operator. Such an arrangement reduces potential stress to the back, shoulders, and arms by avoiding awkward postures and positions.

EMPLOYEES SHOULD NEVER REACH BEHIND THE SHOULDER.

Office Ergonomics

Computer Workstation Components - A computer workstation should be designed to accommodate each user. Adjustability is the key. It allows each employee to adjust the furniture (e.g., chair, work surface, document holder) and reorganize the work area to fit individual needs. The posture employed should minimize muscle tension and body strain. Good body posture permits employees to relax while maintaining a neutral body position.

Chairs

·  Use a chair that is stable, mobile, swivels, and allows for operator movement.

·  Use a chair that provides proper lower back support. The back support should be easy to adjust backward, forward, up, and down. A properly adjusted chair is important to help reduce or prevent stress on the back.

·  Use a chair that has an adjustable seat height. Raise or lower the chair to a comfortable height such that the thighs are parallel to the floor and the knees are at a 90 degree angle. Rest the feet flat on the floor or use a footrest.

·  Use the armrests if they allow maintaining elbows between 90 to 110 degrees. If the armrests obstruct sitting posture, then adjust the armrests, or get a chair that allows proper posture, or use a chair without armrests.

Working  Surfaces

·  Adjust the work surface so that the keyboard is at the correct height to maintain proper posture (i.e., elbows at keyboard height with the forearms parallel to the floor). If possible, use a bi-level sit/stand adjustable table that has an adjustable top height: the lower level for the keyboard and mouse or trackball, and the upper level for the computer monitor. The height of each level should adjust separately.

·  Use a table large enough to hold the keyboard, monitor, wrist rest, mouse or trackball, and a document holder or all necessary documents.

·  Keep adequate clearance under the table for leg length, knee height, and thighs.

Computer Monitors

·  Position the computer monitor directly in front.

·  Position the computer monitor at a comfortable viewing distance (45-60 cm [18-24 inches] from the eyes), viewing height (top of the display screen at or slightly below eye level), and viewing angle (15 degrees below the horizontal line of sight).

·  Use a monitor that tilts and rotates.

·  Use a monitor that has adjustable contrast and brightness. Adjust the contrast to a high level and the brightness to a low level to minimize or prevent eye strain. Make sure the monitor refresh rate is set appropriately (e.g., at least 75 Hz).

·  Keep the display screen or glare shield clean because dust reduces character clarity and reflects light.

·  If work space is limited, a flat panel display may be an option.

Keyboards

·  Position the keyboard directly in front.

·  Position the keyboard approximately at elbow height.

·  Adjust the keyboard angle to a comfortable position; keep the wrists straight and in line with the forearm. The control to adjust the angle is located at the rear of the keyboard.

Other Input Devices

·  When using a mouse, trackball, another alternative pointing device or special keypads, place the wrist in a neutral position.

·  When using a mouse, trackball, or special keypads, rest the arm and hand close to the body and at a natural elevation, not reaching forward or raising the shoulder.

·  Locate the input device adjacent to the keyboard.

·  Use the whole arm to move the input device instead of just the wrist.

·  If the arm is resting on the table edge (hard work surface) when using the mouse or trackball, then use a mousepad rest to provide a cushion.

Wrist Rests/Pads

·  Use a wrist rest for support to help maintain a neutral wrist.

·  Use a wrist rest for cushioning to protect the wrist from resting on a hard or sharp work surface. Note that wrist rests are designed to be used during pauses in typing.

Document Holders

·  Use a document holder that has an adjustable height.

·  Use a document holder large enough to support the documents the operator uses.

·  Position the document holder beside and parallel to the display screen.

·  Position the document holder at the same height and distance as the display screen. Such positioning minimizes the amount the operator has to turn his/her head to look from the document to the display screen and reduces eye muscle fatigue by maintaining the same focal distance.

Footrests - A footrest may be necessary if the operator cannot rest his/her feet comfortably on the floor.

·  Use a footrest that has an adjustable height and heel stop.

·  Use a footrest that is large enough to allow for operator movement.

Eyewear - Computer users should have eye checkups on a regular basis. Some computer users who wear corrective lenses/contacts should wear lenses designed specifically for computer use.

Printers

·  Locate the paper supply where the operator can easily reach it.

Lighting Glare - To minimize eye fatigue and eyestrain:

·  Set up the computer monitor in front of you, but at right angles to windows and parallel to and between light fixtures.

·  Locate the computer monitor so that bright light sources are not in the direct visual field while viewing the display screen.

·  Use appropriate illumination level for computer-related tasks, which is usually approximately half the intensity of normal office lighting. Ambient illumination in the room should be approximately 50 footcandles (200 lux).

·  Use shades, drapes, or blinds to shield light from windows.

·  Properly adjust the monitor brightness and contrast controls to increase character resolution.

·  Get a glare screen for the monitor and keep it clean.

·  Use additional task lighting for reading copy when the room is darkened.

Exercises

·  For the eyes, look away from the work to a distant point at least every hour.

·  For the body, stretch the neck, shoulders, back, legs, arms, and fingers at least twice a day. Stand up and walk around often to increase blood flow circulation.

Computer Workstation Checklist - The following is a checklist of good practices that should be followed by employees using computer workstations.

Breaks

·  Take frequent short breaks from repetitive tasks throughout the day.

Head/Neck/Shoulders

·  The head is straight or slightly tilted forward, not tilted up or turned to one side.

·  The computer screen is directly in front.

·  The top of the display screen is at or slightly below eye level.

·  The eyes are at the proper viewing distance: 45-60 cm (18-24 inches) from the display screen.

·  The display screen is clean and free of dust.

·  The document holder is at the same height and eye distance as the display screen.

·  The document holder is beside and parallel to the display screen.

·  The shoulders are relaxed, not hunched up or pulled back.

·  If substantial time is spent writing or typing while on the phone, the employee should consider a headset phone. A headset phone will eliminate awkward and prolonged bending of the neck.

Back

·  The backrest of the chair is used. The lumbar support cushion firmly supports the lower back.

·  The employee sits up straight, not leaning forward or backward, or hunched over. A slightly reclined position is acceptable posture too.

·  Equipment (e.g., phone) and reference materials are located within easy arm reach to minimize leaning forward or reaching.

·  The body is not twisted while sitting in the chair.

Legs/Feet

·  The thighs are parallel to the floor.

·  The knees are at a 90 degree angle to the legs.

·  The legs, knees, and thighs fit under the work surface/table, not rubbing or hitting the work surface.

·  Circulation under the thighs and behind the knees is not restricted; a numbness or tingling sensation is not experienced.

·  The feet are flat on the floor or supported by a footrest. The angle or height of the footrest can be adjusted.

Arms/Wrists/Hands

·  The elbows are at a 90–110 degree angle. The keyboard is located at elbow height or slightly below. (Some people find it more comfortable to have the keyboard located slightly below elbow height.)

·  The elbows are close to the body.

·  The forearms are in a comfortable relaxed position.

·  The keyboard is directly in front, not at an angle or to one side.

·  The keys are not pressed with too much force. Only enough finger force to activate the keys should be used.

·  The wrists are in line with the forearm.

·  The wrists are supported by a wrist rest and/or mousepad rest, not resting on the work surface, keyboard, or the hard edge of the work surface.

·  The wrists are held in a straight, neutral position. The wrists are not extended, flexed, or bent to one side.

Industrial Ergonomics

When ergonomics is applied at an industrial work area (e.g., work shops, labs, manufacturing process areas) it is referred to as "Industrial Ergonomics." It encompasses all other workstations except workstations. The CTD risk factors are still relevant, only the setting is different. As mentioned previously, good body posture should always be employed to minimize muscle tension and body strain.

Manual Material Handling - Manual material handling involves sitting, lifting, lowering, and carrying objects; it may also involve getting up and down from a standing position. All of these movements involve using the back. To avoid the risk of developing back problems, ergonomic principles should be applied while using the back. If ergonomics is ignored, daily stresses on the muscles, joints, and disks in the back can eventually cause a CTD in the back. For objects that are too heavy or bulky for safe manual handling by employees, mechanical lifting devices must be used for lifting and moving.

ALTHOUGH THERE ARE NO LEGAL MAXIMUM WEIGHT LIMITS FOR OBJECTS LIFTED BY EMPLOYEES, THE NATIONAL INSTITUTE FOR OCCUPATIONAL SAFETY AND HEALTH (NIOSH) RECOMMENDS A 23-KG (51-LB) MAXIMUM WEIGHT LIMIT FOR LIFTING COMPACT OBJECTS.

To minimize the risk of developing a CTD in the back, employees should follow these guidelines:

·  Keep the back/torso erect with the natural curve of the spine intact.

·  Keep the load close to the body.

·  Avoid bending forward or backward or twisting while lifting or carrying the load.

·  Avoid lifting, pushing, or pulling a load that is too heavy. Always get assistance when needed. The maximum weight of the load that can be handled will vary for each employee.

·  Lift and carry a heavy load with two hands instead of one.

·  Do not lean forward, backward, or to either side without support.

·  Use a chair that supports the weight of the upper body when sitting for long periods. Adequate low back support should also be provided to retain the natural curve of the spine.

·  Lift loads at about waist height.

·  Store loads above knee height, but below shoulder height.

·  Bend at the knees to lift objects, not the back.

·  Stay in good physical condition.

Standing Workstations - Standing for extended periods of time places static load on the back muscles, which can contribute to a back injury. To minimize the risk of developing a CTD in the back when standing, follow these guidelines:

·  Keep the back/torso erect with the natural curve of the spine intact.

·  Stand on a rubber antifatigue mat for cushioning, not on hard floor surfaces. Footrests or footbars can also be used to change positions.

·  Tilt the work surface instead of bending continuously.

·  Adjust the work to the appropriate height whenever possible. Generally, work should be done at approximately elbow height. The optimum work height, for standing or sitting, is based on the elbow height.

·  For light duty tasks, set the work height so that the hands are positioned slightly (approximately 5 cm [2 inches]) below the elbow.

·  For tasks that require lifting or downward forces, the work height should be lower. Examples are manual material handling and heavy grinding.

·  For tasks that have extensive vision requirements, the work height should be increased. Examples are precision grinding and using a microscope.

THE WORK HEIGHT IS NOT THE SAME AS THE WORK SURFACE HEIGHT. THE WORK HEIGHT IS THE HEIGHT OF THE INTERFACE BETWEEN THE OPERATOR (GENERALLY HIS/HER HANDS) AND THE WORK. THE WORK SURFACE HEIGHT IS THE HEIGHT OF THE TABLE/BENCH THAT THE WORK IS SITTING ON.

RAISING THE WORK HEIGHT TO IMPROVE POSTURE (I.E., TO MINIMIZE STRESS TO THE NECK/SHOULDERS/BACK) APPLIES WHETHER AN EMPLOYEE IS STANDING OR SITTING. ALSO, A CUSHION/REST SHOULD BE USED TO PROTECT THE ELBOW FROM THE HARD WORK SURFACE.

·  Locate objects within easy arm reach to minimize leaning forward and awkward reaching (e.g., reaching over your head or behind your back).

·  Alternate between standing and sitting when possible. Use a sit-lean stand as an alternative to a chair stool.

Hand Tools - Improper hand tool selection or improper use of tools can cause CTDs. Hand tools should fit the employee's hand; employees with small hands or who are left-handed may need tools designed specifically for these situations. Hand and wrist posture are important because they affect how much force the muscles must produce to hold objects. When selecting and purchasing hand tools, follow these guidelines:

·  Select tools that allow the wrist to be held straight and that minimize twisting of the arm and wrist. Good working posture can be maintained when properly designed tools are used.

·  Select tools that allow the operator to use a power grip, not a pinch grip. Minimal muscle force is required to hold objects in a power grip posture. The pinch grip requires excessive fingertip pressure, and can lead to a CTD.

·  Avoid tools that put excessive pressure on any one spot of the hand (i.e., sides of fingers, palm of the hand).

·  For power or pneumatic tools, select tools with vibration dampening built in whenever possible. Provide personal protective equipment such as gel-padded gloves to reduce exposure to vibration.

Definitions & Terms

Administrative controls are procedural risk-control measures that include, but are not limited to, redesign of work duties, adjustment of work pace, use of rest periods/breaks, training, or altering work duties to interrupt activities that pose a risk to the employee.

Computer User is an employee who routinely works at a computer workstation for a cumulative total of four or more hours, inclusive of breaks, during any 12-hour period.

Cumulative trauma disorder (CTD) is the term used for health disorders arising from repeated biomechanical stress on the body due to ergonomic hazards. CTDs are disorders of the muscles, tendons, and/or nerves that develop from or are aggravated by repeated exertions or movements of the body. CTDs are also referred to as repetitive motion injuries, repetitive strain injuries, repetitive trauma disorders, and overuse injuries.

CTD risk is the presence of the following factors in work activity whereby a CTD is substantially likely to result: frequency (repetition), force, duration, posture, exposure to localized or whole-body vibration, and exposure of hands and feet to temperatures cold enough to cause discomfort.

CTD symptom is any of the following, when persisting or recurring: pain from movement, from pressure, or from exposure to cold or vibration, except when the pain is due to an acute injury; numbness or tingling in an arm, leg, or finger, especially fingertips at night; decreased range of joint motion; decreased grip strength; and swelling of a joint or part of an arm, leg, or finger.

Disorder is a physical ailment or abnormal condition.

Engineering controls are engineered risk-control measures that include, but are not limited to, devices such as adjustable workstations, tables, chairs, equipment, and tools; and physical modifications to workstations, equipment, tools, production processes, or any other aspect of the work environment.

Ergonomics is the study of human interaction with the tools workers use, the work process, and the environment workers function in. The goal is to fit the job to the person. Ergonomics recognizes the capabilities, differences, and limitations of individuals, and adjusts the tools or environment accordingly.

Ergonomic hazards refer to the workplace conditions that pose a biomechanical stress to the worker.

Health Care professional (HCP) is a licensed physician, a registered nurse, or other health care professional who has received appropriate medical training.

Manual material handling (MMH) refers to materials being moved directly by people.

Personal protective equipment (PPE) includes clothes, padding, gloves, devices, equipment, or other items worn on or attached to the body and used for the purpose of controlling CTD risk. Note: Splints or braces are not considered to be PPE.

Risk factors are conditions that contribute to the risk of developing a disorder.

Repetitive motion means to perform the same motion continuously for hours.

Surveillance is the ongoing systematic collection, analysis, and interpretation of health and exposure data for the purpose of describing and monitoring a health event. Surveillance data are used to determine the need for occupational safety and health action and to plan, implement, and evaluate ergonomic interventions and programs.

Trauma is bodily injury from mechanical stress.