Even when the design of the workstations is correct and environmental factors are at their best, users can face risks from task organization which can intensify the impact of other risk factors, such as repetition. Additionally, failing to recognize early warning signs could allow small problems to develop into serious injuries. Addressing task organization factors and medical awareness can help minimize the risk of developing musculoskeletal disorders (MSDs) and stop the progression to injury.

Prolonged periods of activity

Potential Hazard

Computer work, whether it's for a job or for fun, may appear to be a low effort activity when viewed from a total body perspective, but maintaining postures or performing highly repetitive tasks for extended periods can lead to problems in localized areas of the body. For example, using a mouse for a few minutes should not be a problem for most users, but performing this task for several uninterrupted hours can expose the small muscles and tendons of the hand to hundreds or even thousands of activations (repetitions). There may not be adequate time between activations for rest and recuperation, which can lead to localized fatigue, wear and tear, and injury. Likewise, maintaining static postures, such as viewing the monitor, for a prolonged period of time without taking a break can fatigue the muscles of the neck and shoulder that support the head.

Possible Solutions

• Provide variation in tasks and workstations so there is time to recover from the effects of activity. There are several ways to provide recovery time for overused muscles.
  • Utilize an adjustable workstation so users can easily change their working postures. The use of easily adjustable furniture, for example, allows you to frequently change seated postures, which allows different muscle groups to provide support while others rest.
  • Ensure that there is enough work space so you can use each hand alternately to perform mouse tasks. This allows the tendons and muscles of the free hand to rest.
  • Substitute keystrokes for mousing tasks, such as Ctrl+S to save, Ctrl+P to print. Especially if your job is highly mouse intensive.
• High repetition tasks or jobs that require long periods of static posture may require several, short rest breaks (micro breaks or rest pauses). During these breaks users should be encouraged to stand, stretch, and move around. This provides rest and allows the muscles enough time to recover.
• Alternate tasks whenever possible, mixing non-computer-related tasks into the workday. This encourages body movement and the use of different muscle groups.

Medical awareness and training

Potential Hazard

Employees who have not been adequately trained to recognize hazards or understand effective work practices designed to reduce these hazards are at a greater risk of harm. Without proper medical awareness, Musculoskeletal Disorders (MSD) signs and symptoms may go unnoticed and un-addressed. For example, users who do not understand the risk of bad body postures or techniques do not have the knowledge to actively participate in their own protection. Detection and reporting delays can result in more severe injury.

Possible Solutions

Computer users should take the time to obtain general ergonomics awareness training on the following issues:

• Factors related to specific computer components that may increase discomfort or risk of injury.
• Being aware of discomfort (signs and symptoms).
• How to correctly use and adjust components and environmental factors.

To understand the best way to set up a computer workstation, it is helpful to understand the concept of neutral body positioning. This is a comfortable working posture in which your joints are naturally aligned. Working with the body in a neutral position reduces stress and strain on the muscles, tendons, and skeletal system and reduces your risk of developing a musculoskeletal disorder (MSD). The following are important considerations when attempting to maintain neutral body postures while working at the computer workstation:

• Hands, wrists, and forearms are straight, in-line and roughly parallel to the floor.
• Head is level, forward facing, and balanced. Generally it is in-line with the torso.
• Shoulders are relaxed and upper arms hang normally at the side of the body.
• Elbows stay in close to the body and are bent between 90 and 120 degrees.
• Feet are fully supported by the floor or a footrest may be used if the desk height is not adjustable.
• Back is fully supported with appropriate lumbar support when sitting vertical or leaning back slightly.
• Thighs and hips are supported and generally parallel to the floor.
• Knees are about the same height as the hips with the feet slightly forward

Regardless of how good your working posture is, working in the same posture or sitting still for prolonged periods is not healthy. You should change your working position frequently throughout the day in the following ways:

• Make small adjustments to your chair or backrest.
• Stretch your fingers, hands, arms, and torso.
• Stand up and walk around for a few minutes periodically.
• Perform some of your tasks in standing: computing, reading, phone, meetings.

These four reference postures are examples of body posture changes that all provide neutral positioning for the body.

Upright Sitting

Upright sitting posture. The user's torso and neck are approximately vertical and in-line, the thighs are approximately horizontal, and the lower legs are vertical.

Standing

Standing posture. The user's legs, torso, neck, and head are approximately in-line and vertical with feet slightly apart. The user may also elevate one foot on a rest while in this posture.

Declined Sitting

Declined sitting posture. The user's thighs are inclined with the buttocks higher than the knee and the angle between the thighs and the torso is greater than 90 degrees. The torso is vertical or slightly reclined and the legs are vertical. This position should not inhibit the ability to easily reach the keyboard or view the monitor.

Reclined Sitting

Reclined sitting posture. The user's torso and neck are straight and recline between 105 and 120 degrees from the thighs.

A well-designed and appropriately-adjusted desk will provide adequate clearance for your legs, allow proper placement of computer components and accessories, and minimize awkward postures and exertions. The installation, setup, and configuration of comfortable and productive workstations involves the following considerations:

• Desk or work surface areas
• Areas under the desk or work surface

Desk Quick Tips

• Desk surface should allow you to place the monitor directly in front of you, at least 20 inches away.
• Avoid storing items, such as a CPU, under desks.
• Desks should be able to accommodate a variety of working postures.

Desk or work surface areas

Potential Hazard

Limited space on the work surface may cause users to place components and devices in undesirable positions. This placement may lead to awkward postures as you reach for a pointer/mouse or look at a monitor that is placed to the side.

Possible Solutions

• Work surface depth should allow you to:
  • View the monitor at a distance of at least 20 inches (50 cm).
  • Position the monitor to achieve the appropriate viewing angle, which is generally directly in front of you.
• Using a corner rather than a straight run of desk may provide additional space and depth to accommodate large monitors or multiple items.
• The location of frequently-used devices (keyboard, phone, and mouse) should remain within the repetitive access (primary work zone) (Figure 3).

Potential Hazard

Some desks and computer equipment have hard, angled leading edges that come in contact with a user's arm or wrist (Figure 4). This can create contact stress, affecting nerves and blood vessels, possibly causing tingling and sore fingers.

Possible Solutions

To minimize contact stress:

• Pad table edges with inexpensive materials such as pipe insulation.
• Use a wrist rest.
• Buy furniture with rounded desktop edges.

Areas under the desk or work surface

Potential Hazard

Inadequate clearance or space under the work surface may result from poor design or excessive clutter. Regardless of the cause it can result in discomfort and performance inefficiencies, such as the following:

• Shoulder, back, and neck pain due to users sitting too far away from computer components, causing them to reach to perform computer tasks.
• Generalized fatigue, circulation restrictions, and contact stress due to constriction of movement and inability to frequently change postures.

Possible Solutions

• Provide, to the extent possible, adequate clearance space for users to frequently change working postures (see recommended dimensions). This space should remain free of items such as files, CPUs, books, and storage (Figure 6).
• Be sure clearance spaces under all working surfaces accommodates at least two of the three seated reference working postures, one of which must be the upright seated posture.
• Limit the number of items that are stored under the work surface. There should be no items stored that will limit the space needed for workers' legs and feet.

Potential Hazard

Desk surfaces that are too high or too low may lead to awkward postures, such as extended arms to reach the keyboard, and raised shoulders.

Possible Solutions

• Raise work surfaces by inserting stable risers such as boards or concrete blocks under the desk legs if necessary.
• Remove center drawers of conventional desks to create additional thigh clearance if necessary.
• Lower work surfaces by cutting off desk legs if necessary. If the work surface cannot be lowered, raise the chair to accommodate the user. If needed, provide a footrest to support the user's feet (Figure 7).
• Provide height-adjustable desks. Clearance for the legs, under the desktop, should generally be between 20-28 inches (50-72 cm) high.

A chair that is well-designed and appropriately adjusted is an essential element of a safe and productive computer workstation. A good chair provides necessary support to the back, legs, buttocks, and arms, while reducing exposures to awkward postures, contact stress, and forceful exertions.

Increased adjustability ensures a better fit for the user, provides adequate support in a variety of sitting postures, and allows variability of sitting positions throughout the workday. This is particularly important if the chair has multiple users.

To ensure that the chair will provide adequate support, it is important that you try out different chairs before purchasing one.

The following parts of the chair are important elements to consider in creating a safe and productive workstation:

• Backrest
• Seat
• Armrest
• Base

You should adjust your chair along with appropriately placing your monitor, keyboard, and desk.

Choosing a suitable monitor and placing it in an appropriate position helps reduce exposure to forceful exertions, awkward postures, and overhead glare. This helps prevent possible health effects such as excessive fatigue, eye strain, and neck and back pain.

Consider the following issues to help improve your computer workstation:

• Viewing distance
• Viewing angle-height and side-to-side
• Viewing time
• Viewing clarity

You should choose a monitor and consider its placement in conjunction with other components of the computer workstation, including the keyboard, desk, and chair.

Monitor Quick Tips

• Put monitor directly in front of you and at least 20 inches away.
• Place monitor so top line of screen is at or below eye level.
• Place monitor perpendicular to window.

Proper selection and arrangement of the computer keyboard helps reduce exposure to awkward postures, repetition, and contact stress.

Consider the following factors when evaluating your computer workstation.

• Keyboard Placement - Height
• Keyboard Placement - Distance
• Design and Use
• Left Hand Key Usage

You should choose a keyboard and consider its placement in conjunction with other components of the computer workstation, including the pointer/mouse and wrist/palm rests.

Keyboard Quick Tips

• Put the keyboard directly in front of you.
• Your shoulders should be relaxed and your elbows close to your body.
• Your wrists should be straight and in-line with your forearms.

KEYBOARD PLACEMENT - HEIGHT

Potential Hazards:

Keyboards, pointing devices, or working surfaces that are too high or too low can lead to awkward wrist, arm, and shoulder postures. For example, when keyboards are too low you may type with your wrists bent up, and when keyboards are too high, you may need to raise your shoulders to elevate your arms. Performing keying tasks in awkward postures such as these can result in hand, wrist, and shoulder discomfort.

Possible Solutions:

• Adjust the chair height and work surface height to maintain a neutral body posture. Elbows should be about the same height as the keyboard and hang comfortably to the side of the body. Shoulders should be relaxed, and wrists should not bend up or down or to either side during keyboard use.
• Remove central pencil drawers from traditional desks if you can't raise your chair high enough because of contact between the drawer and the top of the thighs. The work surface should generally be no more than 2 inches thick.
• A keyboard tray may be needed if the work surface or chair cannot be properly adjusted. The keyboard tray should:
  • Be adjustable in height and tilt.
  • Provide adequate leg and foot clearance.
  • Have adequate space for multiple input devices (for example, a keyboard and pointer/mouse).
• The keyboard's vertical position should be maintained within the recommended range. The tilt of the keyboard may need to be raised or lowered using the keyboard feet to maintain straight, neutral wrist postures while accommodating changes in arm angles.

KEYBOARD PLACEMENT - DISTANCE

Potential Hazards:

A keyboard or pointer/mouse that is too close or too far away may cause you to assume awkward postures such as reaching with the arms, leaning forward with the torso, and extreme elbow angles. These awkward postures may lead to musculoskeletal disorders of the elbows, shoulders, hands, and wrists.

Possible Solutions:

• Place the keyboard directly in front of you at a distance that allows your elbows to stay close to your body with your forearms approximately parallel with the floor.
• A keyboard tray may be useful if you have limited desk space or if your chair has armrests that interfere with adequate positioning.

DESIGN AND USE

Potential Hazards:

A traditional keyboard may cause you to bend your wrists sideways to reach all the keys. Keyboard tilt, caused by extending the legs on the back of the keyboard or by a steep design angle, may cause the wrist to bend upward. Smaller keyboards, such as those found on laptops, may also contribute to stressful postures. These awkward wrist postures can create contact stress to the tendon sheath and tendons that must move within the wrist during repetitive keying.

Possible Solutions:

• Reduce awkward wrist angles by lowering or raising the keyboard or chair to achieve a neutral wrist posture.
• Elevate the back or front of keyboards to achieve a neutral wrist posture. For example, if the operator sits lower in relation to the keyboard, slightly elevating the back of the keyboard may help maintain a neutral wrist. Similarly, raising the front of the keyboard may help maintain neutral wrist postures for users who type with the keyboard in a lower position. Do not use keyboard feet if they increase bending of the wrist.
  • Consider alternative keyboards to promote neutral wrist postures. Alternative keyboards may be provided on a case-by-case basis. Users may need time to become accustomed to these devices. NOTE: alternative keyboards help maintain neutral wrist postures, but available research does not provide conclusive evidence that using these keyboards prevents discomfort and injury.

• Keyboards should be of appropriate size and key-spacing to accommodate most users. Generally, the horizontal spacing between the centers of two keys should be 0.71-0.75 inches (18-19 mm) and the vertical spacing should be between 0.71-0.82 inches (18-21 mm).

LEFT HAND KEY USAGE

Potential Hazards:

Most keyboards are manufactured with a 10 key keypad permanently affixed to the right side of the keyboard. This arrangement can be limiting to left handed workers or right handed workers who are recovering from injury and are attempting to remain functional during their recovery. This arrangement is also a problem if one is attempting to create work-rest regimens by alternating principle hand usage during the work day or work week.

Possible Solutions:

• Alternative left hand keyboards which have the keypad permanently affixed to the left side of the keyboard are available as are keyboards with a detached keypad. These allow the user to switch positions for either left or right hand use. These may be especially useful for applications where workers share computers.
• Programmable stand alone keypads are available which can be programmed to facilitate either right or left hand usage.

Pointing devices such as a mouse now come in many sizes, shapes, and configurations. In addition to the conventional mouse, there are trackballs, touch pads, finger tip joysticks, and pucks, to name a few. Selection and placement of a pointer/mouse is an important factor in creating a safe computer workstation.

Consider the following factors when evaluating your computer workstation.

• Pointer Placement
• Pointer Size, Shape, and Settings

Pointer/Mouse Quick Tips

• Keep the pointer/mouse close to the keyboard.
• Alternate hands with which you operate the pointer/mouse.
• Use keyboard short cuts to reduce extended use.

POINTER PLACEMENT

Potential Hazards:

If the pointer/mouse is not near the keyboard you may be exposed to awkward postures, contact stress, or forceful hand exertions while using the device. Working in this position for prolonged periods places stress on the shoulder and arm and increases the likelihood that you will assume awkward wrist and shoulder postures, which may lead to musculoskeletal disorders.

Possible Solutions:

• Position the pointer/mouse to allow you to maintain a straight, neutral wrist posture. This may involve adjustments in your chair, desk, keyboard tray, etc.
• If the keyboard tray/surface is not large enough to accommodate both the keyboard and mouse, try one of the following to limit reaching:
  • Use a mouse platform positioned over the keyboard. This design allows the mouse to be used above the 10-key pad.
  • Install a mouse tray next to the keyboard tray.
• Use a keyboard that has a pointing device, such as a touchpad, incorporated into it.
• Use a keyboard without a ten-key pad, which leaves more room for the pointer/mouse.
• Install keyboard trays that are large enough to hold both the keyboard and mouse.
• Use a mouse pad with a wrist/palm rest to promote neutral wrist posture.
• Substitute keystrokes for mousing tasks, such as Ctrl+S to save, and Ctrl+P to print.

POINTER SIZE, SHAPE, AND SETTINGS

Potential Hazards:

Inappropriate size and shape of pointers can increase stress, cause awkward postures, and lead to overexertion. For example, using a pointing device that is too big or too small may cause you to increase finger force and bend your wrist into awkward positions. Using the left hand to operate a device that is designed for right-hand use can also create force and posture issues and may create contact stress to the soft tissue areas in the palm of the hand. Contact stress can create irritation and inflammation.

Possible Solutions:

• Select a pointing device designed to fit the hand that will normally operate it. Many devices are available in right hand/left hand models and also come in sizes to fit large and small hands. A device that is designed for either hand use may be desirable, since changing from right- to left-hand operation provides periods of rest for one hand. You should test a device prior to purchase and long term use to ensure proper fit and feel.
• Select pointing devices that are appropriately sized and that require minimal force to generate movement. For example, a puck device must be small enough for single-handed operation (generally, 1.5 to 2.5 inches wide, 2.5 to 4.5 inches long, and 1 to 1.5 inches high).
• Reduce the strain on hands by reducing pointing device use. Using keyboard functions, such as page down, may reduce mouse use and provide rest for hand and arm muscles.
• Use another type of device that fits the hand better or doesn't require bending the wrist while gripping. A fingertip joystick, touchpad, or trackball may be less fatiguing for certain tasks. Always try out any new product prior to selection and long term use.

Potential Hazards:

When the sensitivity for the input device is not appropriately set, you may need to use excessive force and awkward hand postures to control the device. For example, a mouse that is too sensitive may require excessive and prolonged finger force to provide adequate control. A mouse that has insufficient sensitivity may require large deviation of the wrist to move the pointer around the screen. Exerting prolonged force or repeatedly bending the wrist can fatigue the muscles of the hand and arm and increase the risk of musculoskeletal injuries.

Possible Solutions:

• Sensitivity and speed (how fast the pointer moves on the screen when the pointing device is moved by the hand) should feel comfortable and be adjustable. The pointer should be able to cover the full screen while the wrist is maintained in a straight, neutral posture.
• Sensitivity should be set so you can control the pointing device with a light touch. Most current devices have sensitivity settings that can be adjusted through the computer control panel.
• Avoid tightly gripping the mouse or pointing device to maintain control.
• A trackball's exposed surface area should be at least 100 degrees. It should feel comfortable and rotate in all directions to generate any combination of movement.

Proper arrangement of the keyboard and mouse help create a comfortable and productive workstation. Wrist or palm rests can also increase your comfort.

Although opinions vary regarding the use of wrist/palm supports, proper use has been shown to reduce muscle activity and to facilitate neutral wrist angles.

Wrist Rest Quick Tips

Use a wrist rest to maintain straight wrist postures and to minimize contact stress during typing and mousing tasks.

Design and use

Potential Hazards

• Performing keying tasks without a wrist rest may increase the angle to which users' wrists are bent (Figure 1). Increasing the angle of bend increases the contact stress and irritation on tendons and tendon sheathes. This is especially true with high repetition or prolonged keying tasks. Keying without a wrist rest can also increase contact stress between the users wrist and hard or sharp workstation components.
• Resting the wrist/palm on a support while typing may inhibit motion of the wrist and could increase awkward wrist postures.

Possible Solutions

• Your hands should move freely and be elevated above the wrist/palm rest while typing. When resting, the pad should contact the heel or palm of your hand, not your wrist.
• If used, wrist/palm rests should be part of an ergonomically-coordinated computer workstation.
• Reduce bending of the wrists by adjusting other workstation components (chair, desk, keyboard) so the wrist can maintain an in-line, neutral posture.
• Match the wrist support to the width, height, and slope of the front edge of the keyboard (keeping in mind that the goal is to keep wrist postures as straight as possible).
• Provide wrist/palm supports that are fairly soft and rounded to minimize pressure on the wrist. The support should be at least 1.5 inches (3.8 cm) deep.

Appropriately placing lighting and selecting the right level of illumination can enhance your ability to see monitor images. For example, if lighting is excessive or causes glare on the monitor screen, you may develop eyestrain or headaches, and may have to work in awkward postures to view the screen. Ventilation and humidity levels in office work environments may affect user comfort and productivity.

• Lighting
• Glare
• Ventilation

Environment Quick Tips

• Arrange your office to minimize glare from overhead lights, desk lamps, and windows.
• Maintain appropriate air circulation.
• Avoid sitting directly under air conditioning vents that "dump" air right on top of you.

Lighting

Potential Hazard

Bright lights shining on the display screen "wash out" images, making it difficult to clearly see your work. Straining to view objects on the screen can lead to eye fatigue.

Possible Solutions

• Place rows of lights parallel to your line of sight (Figure 1).
• Provide light diffusers so that desk tasks (writing, reading papers) can be performed while limiting direct brightness on the computer screen.
• Remove the middle bulbs of 4-bulb fluorescent light fixtures to reduce the brightness of the light to levels more compatible with computer tasks if diffusers or alternative light sources are not available. NOTE: a standard florescent light fixture on a nine-foot ceiling with four, 40-watt bulbs will produce approximately 50 foot-candles of light at the desktop level.
• Provide supplemental task/desk lighting to adequately illuminate writing and reading tasks while limiting brightness around monitors.
  • Generally, for paper tasks and offices with CRT displays, office lighting should range between 20 to 50 foot-candles. If LCD monitors are in use, higher levels of light are usually needed for the same viewing tasks (up to 73 foot-candles).

Potential Hazard

Bright light sources behind the display screen can create contrast problems, making it difficult to clearly see your work (Figure 2).

Possible Solutions

• Use blinds or drapes on windows to eliminate bright light. Blinds and furniture placement should be adjusted to allow light into the room, but not directly into your field of view (Figure 1). NOTE: vertical blinds work best for East/West facing windows and horizontal blinds for North/South facing windows.
• Use indirect or shielded lighting where possible and avoid intense or uneven lighting in your field of vision. Ensure that lamps have glare shields or shades to direct light away from your line of sight.
• Reorient the workstation so bright lights from open windows are at right angles with the computer screen (Figure 1).

Potential Hazard

High contrast between light and dark areas of the computer screen, horizontal work surface, and surrounding areas can cause eye fatigue and headaches.

Possible Solutions

• For computer work, use well-distributed diffuse light. The advantage of diffuse lighting is that:
  • There are fewer hot spots (or glare surfaces) in the visual field.
  • The contrasts created by the shape of objects tend to be softer.
• Use light, matte colors and finishes on walls and ceilings to better reflect indirect lighting and reduce dark shadows and contrast.

Glare

Potential Hazard

Direct light sources (for example, windows, overhead lights) that cause reflected light to show up on the monitor (Figure 3) make images more difficult to see, resulting in eye strain and fatigue.

Possible Solutions

• Place the face of the display screen at right angles to windows and light sources. Position task lighting (for example, a desk lamp) so the light does not reflect on the screen (Figure 1).
• Clean the monitor frequently. A layer of dust can contribute to glare.
• Use blinds or drapes on windows to help reduce glare (Figure 1). NOTE: vertical blinds work best for East/West facing windows and horizontal blinds for North/South facing windows.
• Use glare filters that attach directly to the surface of the monitor to reduce glare (Figure 4). Glare filters, when used, should not significantly decrease screen visibility. Install louvers, or "egg crates", in overhead lights to re-direct lighting.
• Use barriers or light diffusers on fixtures to reduce glare from overhead lighting.

Potential Hazard

Reflected light from polished surfaces, such as a keyboards, may cause annoyance, discomfort, or loss in visual performance and visibility.

Possible Solutions

• To limit reflection from walls and work surfaces around the screen, paint them with a medium colored, non-reflective paint. Arrange workstations and lighting to avoid reflected glare on the display screen or surrounding surfaces.
• Tilt down the monitor slightly to prevent it from reflecting overhead light.
• Set the computer monitor for dark characters on a light background; they are less affected by reflections than are light characters on a dark background.

NOTE: Generally, a large number of low powered lamps rather than a small number of high powered lamps will result in less glare.

Ventilation

Potential Hazards

• Users may experience discomfort from poorly designed or malfunctioning ventilation systems, for example, air conditioners or heaters that directly "dump" air on users.
• Dry air can dry the eyes (especially if the user wears contact lenses).
• Poor air circulation can result in stuffy or stagnant conditions.
• Temperatures above or below standard comfort levels can affect comfort and productivity.

Possible Solutions

• Do not place desks, chairs, and other office furniture directly under air conditioning vents unless the vents are designed to redirect the air flow away from these areas.
• Use diffusers or blocks to redirect and mix air flows from ventilation systems (Figure 6).
  • Keep air flow rates within three and six inches per second (7.5 and 15 centimeters per second). These air flow rates are barely noticeable or not noticeable at all.
• Keep relative humidity of the air between 30% and 60%.
• The recommended ambient indoor temperatures range between 68° and 74° F (20° and 23.5° C) during heating season and between 73° and 78° F (23° and 26° C) during the cooling season.

Potential Hazard

Exposure to chemicals, volatile organic compounds (VOCs), ozone, and particles from computers and their peripherals (for example, laser printers) may cause discomfort or health problems.

Possible Solutions

• Enquire about the potential for a computer or its components to emit pollutants. Those that do should be placed in well-ventilated areas.
• Maintain proper ventilation to ensure that there is an adequate supply of fresh air.
• Allow new equipment to "air out" in a well-ventilated area prior to installing.