Office Ergonomics

Workstation Analysis

Workstations should be ergonomically designed to accommodate the full range of required movements among employees.  Moreover, they should be designed so that they accommodate the employees who are actually using them to perform the job, not just for the “average” or “typical” employee. 

Neutral Body Positioning

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 or bent slightly forward, 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 floor or footrest.
• Back is fully supported with appropriate lumbar support when sitting vertical or leaning back slightly.
• Thighs and hips are supported by a well-padded seat 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.

Workstation Components

Chairs

Chairs can be a crucial factor in preventing back pain as well as in improving employee performance in office work.  As the majority of office workers spend most of their time sitting, a properly designed and adjustable chair for comfort, efficiency, and for the task being preformed is critical.  All adjustments should easily be made from the seated position.  A good chair provides necessary support to the back, legs, buttocks, and arms, while reducing exposures to awkward postures, contact stress, and forceful exertions.

Chair Height

When an employee spends six to eight hours in the chair, the height of the chair and the work surface are critical.  The chair height is correct when the entire sole of the foot can rest on the floor or a 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. 

Backrests

Poor back support and inappropriate postures may result from inadequate backrest size, material, positioning, or use. Working in these postures may lead to back pain and fatigue.  Backrests should support the entire back including the lower region and conform to the natural curvature of the spine.

Seat

Using a chair with a seat that is too high may force the user to work with the feet unsupported or encourage the user to move forward in the chair to a point where the back is unsupported making it more difficult to maintain the S-shape of the spine.  These awkward postures can lead to fatigue, restricted circulation, swelling, numbness, and pain.

An inappropriately sized seat pan can be uncomfortable, provide inadequate support to the legs, and restrict movement. One that is too short can place excess pressure on the buttocks of taller users; one that is too long can place excess pressure on the knee area of shorter users and minimize back support. A seat pan that is too small can restrict movement and provide inadequate support. Prolonged use can restrict blood flow to the legs and create irritation and pain.

Armrests

Armrests that are not adjustable, or those that have not been properly adjusted, may expose you to awkward postures or fail to provide adequate support.

Armrests that are too low may cause the user to lean over to the side to rest one forearm. This can result in uneven and awkward postures, fatiguing the neck, shoulders, and back.

Armrests that are too high may cause the user to maintain raised shoulders which can result in muscle tension and fatigue in the neck and shoulders.

When the armrests are too wide the users is likely to reach with the elbow and bend forward for support. Reaching pulls the arm from the body and can result in muscle fatigue in the shoulders and neck.

Armrests that are too close to the body can restrict movement in and out of the chair.

Large or inappropriately placed armrests may interfere with the positioning of the chair. If the chair cannot be placed close enough to the keyboard, the user may need to reach and lean forward in the chair. This can fatigue and strain the lower back, arm, and shoulder.

Armrests that are made of hard materials or that have sharp corners can irritate the nerves and blood vessels located in the forearm. This irritation can create pain or tingling in the fingers, hand, and arm.

Armrests, if provided, should be soft and allow the user’s shoulders to relax and elbows to stay close to the body.   They should be adjusted to they just make contact with the lower arms when the lower arms are positioned comfortably at the users sides.

Possible solutions for chairs include;

If the seat cannot be lowered (for example, it would make the keyboard or monitor too high), use a footrest to provide stable support for the feet.

Provide a chair with a seat pan that is adjustable and large enough to provide support in a variety of seated postures. It is recommended that the seat should be

• Height adjustable, especially when shared by a number of users. The chair height is appropriate when the entire sole of the foot can rest on the floor with the back of the knee slightly higher than the seat of the chair.
• Padded and have a rounded, "waterfall" edge.
• Wide enough to accommodate the majority of hip sizes. Chairs with oversize seat pans should be provided for larger users.

Keyboards

Proper selection and arrangement of the computer keyboard helps reduce exposure to awkward postures, repetition, and contact stress.  The keyboard should sit directly in front of the users.  Shoulders should be relaxed and elbows close to the body.  Wrists should be straight and in-line with the forearms.

 

Keyboard Height

Keyboards, pointing devices (mouse), 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 include;

• 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.
• 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, and
• Have adequate space for the keyboard and pointer/mouse.
• Reduce awkward wrist angles by lowering or raising the keyboard or chair to achieve a neutral wrist posture.
• Adjust the keyboard tray tilt to achieve a neutral wrist posture.

Distance

A keyboard or pointer/mouse that is too close or too far away may cause you to assume awkward postures.  If the keyboard is too far away employees will have to reach with the arms and lean forward with the torso.  If the keyboard is too close to the users the elbows will be at extreme angles.  These awkward postures may lead to musculoskeletal disorders of the elbows, shoulders, hands, and wrists. 

 

Pointer/Mouse

The pointer/mouse should be positioned next to the keyboard.  Improper placement of the mouse can lead to awkward postures, contact stress, or forceful hand exertions while using the device.

Possible Solutions include;

• 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 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.

Monitors

Employees may spend considerable amount of time looking at the monitors.  Screens should have user controls for character brightness.  Screens that swivel horizontally and tilt or elevate vertically enable the operator to select the optimum-viewing angle.

Distance

Monitors placed too close or too far away may cause you to assume awkward body positions that can lead to eyestrain.

• Viewing distances that are too long can cause you to lean forward and strain to see small text. This can fatigue the eyes and place stress on the torso because the backrest is no longer providing support.
• Viewing distances that are too short may cause your eyes to work harder to focus (convergence problems) and may require you to sit in awkward postures. For instance, you may tilt your head backward or push your chair away from the screen, causing you to type with outstretched arms.

The preferred viewing distance from the front surface of the monitor to the user’s eyes is 20 to 40 inches.

Viewing Angle-Height and Side-to-Side

Working with your head and neck turned to the side for a prolonged period loads neck muscles unevenly and increases fatigue and pain.

• Position your computer monitor directly in front of you, so your head, neck and torso face forward when viewing the screen.  Monitors should not be farther than 35 degrees to the left or right.
• If you work primarily from printed material, place the monitor slightly to the side and keep the printed material directly in front. Keep printed materials and monitors as close as possible to each other.  The screen and document holder should be the same distance from the eye to avoid constant changes in focus and close enough together so the operator can look from one to the other without excessive movement of the neck or back.

Viewing Time

Viewing the monitor for long periods of time can cause eye fatigue and dryness. Users often blink less while viewing the monitor.

• Rest your eyes periodically by focusing on objects that are farther away (for example, a clock on a wall 20 feet away).
• Stop, look away, and blink at regular intervals to moisten the eyes.
• Alternate duties with other non-computer tasks such as filing, phone work, or customer interaction to provide periods of rest for the eyes.

Viewing Clarity

Monitors that are tilted significantly either toward or away from the operator may distort objects on the screen, making them difficult to read. Also, when the monitor is tilted back, overhead lights may create glare on the screen. This can result in eyestrain and sitting in awkward postures to avoid eye glare.  Dust accumulation associated with computer monitors and can reduce contrast and degrade viewing conditions.

• Tilt the monitor so it is perpendicular to your line of sight, usually by tilting the screen no more than 10 to 20 degrees. This is most easily done if the monitor has a riser/swivel stand. A temporary solution involves tilting the monitor back slightly by placing a book under the front edge. Note: Tilting the monitor back may create glare on the screen from ceiling lighting and a glare screen may be needed.

• Computer monitors should be periodically dusted and cleaned.

Telephones

A telephone that is placed too far away from the user and/or prolonged conversations on the phone can result in strain on the shoulder, arm, and neck. 

Possible solutions for telephone use include;

• Placing the telephone close to you to minimize repeated reaching;
• Use a “hands-free” heat set if your job requires you to spend a lot of time on the phone.

Desktops

The location of frequently-used devices (keyboard, phone, and mouse) should remain within the repetitive access (primary work zone).  Those items that are used occasionally should remain in the secondary work zone.          

Office Environmental Factors

Lighting and Glare

Direct light sources such as windows or overhead lights can cause reflected light to show up on the computer monitor make images more difficult to see, resulting in eye strain and fatigue. Light should be directed so that it does not shine into the operator’s eyes when the operator is looking at the display screen.  Further, lighting should be adequate for the operator to see the text and the screen, but not so bright as to cause glare or discomfort.

Bright light sources behind the display screen can create contrast problems, making it difficult to clearly see the work.  By using blinds or drapes the user can eliminate bright light. Blinds and furniture placement should be adjusted to allow light into the room, but not directly into the field of view.  Vertical blinds work best for East/West facing windows and horizontal blinds for North/South facing windows.

If necessary, the workstation can be reoriented so that bright lights from open windows are at right angles with the computer screen.  Glare screens can also be used to reduce the amount of glare on a monitor.

Eyestrain

Our eyes have three sets of muscles: one set controls motion (looking up, down and side to side), the second set controls focusing the lens and the third set controls the size of the pupil which controls light intake.  When viewing a computer monitor for long periods of time, you utilize all these muscles in a fixed position leading to fatigue. 

Eyestrain is the single largest category of complaints among users.  Eyestrain is often worse for employees doing “intensive” work (e.g., looking at an “interactive” terminal all day or continuously looking back and forth between hard copy and the screen).  Also, excessive overhead illumination that causes glare on the monitor screen can result in eye irritation, eye fatigue, headaches and blurred vision.