Demystifying Ergonomic Correctness

May 10, 2002
What makes an office chair or other product "ergonomic"? A human-centered approach to selecting ergonomic products can help clear up the confusion.

How many times have you heard a product, whether it is a mouse, a chair or a keyboard, referred to as "ergonomically correct?" I consider that term, at the risk of sounding pretty harsh, to be too easily applied, too frequently used by people who don't know what they're talking about and all too misleading. The problem with calling something "ergonomically correct" from a design and application standpoint is that it makes it all too easy to purchase something that just won't work for employees from an ergonomic perspective. Just look on the back shelves of your office storeroom at all of the "ergonomically correct" office products that just weren't ergonomic, nor correct.

Every workplace has its own collection of "ergo stuff" that just didn't work. The real problem with this is that there is always someone around who remembers how much was spent on that "stuff" employees no longer use. Office ergonomics can really have a bad reputation in some organizations because of this. Like the ghost of Jacob Marley in Dickens' "A Christmas Carol," well-meaning ergonomic professionals seem to drag every poor choice in office ergonomics around for all of the organization to see as if chained to them. So the questions remain, what constitutes good ergonomic design, what should you look for in selecting good office ergonomic products, and how do you avoid the "ergonomically correct product" trap?

The old adage "form follows function" should be the key in evaluating and selecting ergonomic products. The "function" in this case is the human body's natural design and the work that is expected to be performed. Given this function, the "form" or design of the ergonomic product should be totally supportive. This type of product design concept is "human-centered" in that tasks performed using this type of product are not hazardous and make the job physically and mentally easier to perform.

Ergonomic and medical experts have identified four key physical risk factors associated with complaints of discomfort in the work environment: awkward postures, biomechanical stresses, repetition and force. Given these risk factors as they relate to office workers who use computers, the key is to eliminate the risk by providing a well-designed environment.

Awkward Postures

The first risk factor, awkward postures, has to do with how the human body is positioned throughout the day. Awkward postures are probably the most significant risks in an office environment. Often, a rigid, strained image comes to mind, such as holding a book on the head. Instead, try thinking of posture as the most efficient way for a body to be or to move depending on the demands of the situation. The human body is well-designed for a large variety of movements and postures. Each joint (like the knee) or series of joints (like the spine), however, has a so-called "neutral" position or posture. In this position, the surfaces of the joint and the tissues around it are neither overstretched nor overcompressed.

Ergonomic products should support the body's natural postures. A chair, for example, that forces the spine to change out of its natural "S" shape is not ergonomically designed. Most office seating now has a molded shape that supports the curvature of most spines. Additionally, many manufacturers offer "lumbar rolls" and "back cushions" that retrofit to poorly designed (usually older) chairs to achieve this support. Good office ergonomics with regard to posture, however, doesn't only mean seating.

The head is heavy; it weighs between 10 and 15 pounds. It is balanced on the neck, which consists of bones (the vertebrate of the spine), numerous muscles, ligaments, blood vessels and nerves. Think of the head as a bowling ball balancing on a stick. If it is perfectly straight, gravity helps to support its weight. If the head is tilted to the side, forward or backward, however, the neck and shoulder muscles must work to hold it there. These muscles are well-designed for this job and contract without conscious effort, but if the head is held off center for any length of time, the muscles can get tired and, after awhile, may begin to hurt.

One postural risk factor is excessive or prolonged positioning of the head away from its "neutral" position. While working at the keyboard and anytime while sitting in one position for a long time (on the phone, reading, writing, watching TV, driving, etc.), an employee should keep the head as straight as possible with the ears lined up over the shoulders. Sometimes, the desk surface on which the monitor sits provides for height adjustments of the monitor. If not, a monitor stand, ranging from a simple, stable surface on which to place the monitor at a better height to an adjustable arm, can be used. To determine monitor height, reams of photocopy paper or phone books work well as temporary monitor risers.

As a variety of monitor risers are available, know what range of adjustability is needed and the size of the monitor. Many movable arms and lift mechanisms have a maximum weight that may easily be exceeded by the larger (21 inches or more) monitors. Besides, lifting the large monitors very far off the workstation may create a safety hazard. Ensure that employees understand the need for a monitor lift or riser.

Awkward posture can also affect the upper torso. The shoulder and upper back are "at rest," or in a neutral posture, when the shoulders are in line with the body and the arms are by one's sides. Employees should take a deep breath and sigh, letting the body relax. This is a neutral position. If the shoulders are held in a rounded or slumped position, or if the arms are held away from the body in any direction for a length of time, the upper back and shoulder muscles may fatigue and eventually get sore. To assist in preventing discomfort, employees should change positions frequently throughout the day and return to the "straight shoulder position," with arms by one's sides, as much as possible.

Research has shown that the muscles around the elbow function best when the elbow is bent to about 90 degrees (give or take about 10 degrees), depending on the activity. Holding the elbows too bent or too straight can cause fatigue in these muscles. That's why adjustable, soft armrests on office seating and adjustable-height, articulating keyboard trays are a good idea.

Most of the muscles that move the wrist and the fingers are located in the forearm, with their long tendons (connective tissue that connects muscles to bone) crossing the wrist area. On the palm side, nine finger tendons and a major nerve (the median nerve) go through a passageway called the carpal tunnel. The back of the tunnel is made up of wrist bones, and the front of the tunnel is comprised of a thick band of connective tissue. The carpal tunnel is largest when the wrist is straight; this is the "neutral" position for the wrist. When the wrist is bent too far, whether forward or backward, the tissues in the tunnel may be compressed or pinched. Imagine them as a garden hose, which can't function well when bent at an angle or squished. Therefore, it is important to keep the wrists fairly straight when using the hands.

The primary cause of poor wrist postures in an office environment is the use of a keyboard or other input device such as a mouse, a trackball or a touch pad. It is important to select input devices based on the needs of employees, the tasks that they perform and the configuration of their workstation. For example, the best keyboard for most people is the "standard" QWERTY keyboard that comes with most computers. The keyboard layout allows most users to key without deviating the wrists to one side or the other.

The wrist should be straight as if you drew an imaginary line through the center of the elbow, extending it through the wrist and the fingertips. This imaginary line should be parallel to the floor. The keyboard tray should clear the legs and should be at a height to keep the forearms parallel to the floor. Wrist rests can be helpful, but they are not essential for all individuals. Occasionally, the use of a wrist rest can create problems. Explain the purpose and use of a wrist rest, then let the individual experiment and decide. Wrist rests come in a variety of materials (foam and gel), with no major difference other than personal preference for feel. Individuals who are reporting mild symptoms of discomfort and fatigue in their arms or hands should probably try using a wrist rest and observe any changes. (Any questions about the causes or treatments of such symptoms should be referred to a health professional.)

The thicker the keyboard, probably the more important the use of a wrist rest. Wrist rests should be approximately the same thickness as the bottom edge of the keyboard and should fit on the work surface. Broad-shouldered, large or obese employees may have difficulty using the standard QWERTY keyboard. Because this body type tends to force the elbows out, this changes the neutral position of the wrists. For employees with this type of body shape, alternative keyboards such as a "split" keyboard may be appropriate. Before changing keyboards, ensure that the alternative will reduce the wrist deviation.

Nonkeyboard input devices should be selected based on task and if they provide a comfortable, neutral posture. Again, imagine a line drawn through the center of the wrist. This line should be parallel to the floor. The input device should be located immediately to the right or left of the keyboard, at the same height as the keyboard and within a near reach like the keyboard.

The spinal column is not straight. In its neutral position, it has three curves balanced over one another; one going in at the neck, out at the shoulders and ribs, and in again at the low back behind your stomach. An exaggeration of these curves in either direction can cause problems, especially if the posture is maintained for a long period of time. In particular, when employees slouch forward and round the back, the muscles can no longer support them and they are "hanging" on their ligaments. This may feel fine for brief periods of time, but prolonged slouching puts strain on the back ligaments, which can overstretch them and lead to fatigue and back ache. Slouching also compresses the internal organs and could interfere with their function. In the long term, it is much better for the back if pressure is taken off the ligaments by sitting up straight in the chair.

Ideally, support for the lumbar spine should come from the chair itself. All newer, more "ergonomically designed" chairs have varying degrees of such support built into the chair. It is appropriate to first check the fit and adjustments of the chair if an individual has questions about lumbar support. Ensure that any chair you evaluate allows the height of the backrest to be adjusted for desired support. Specifying a chair with seat pan tilt (forward/backward) can affect the amount of support for the individual.

If additional support is still desired, be very cautious with the use of most lumbar rolls or pillows. These items may be "too much of a good thing" if used with an ergonomic chair. An individual should first experiment with a flat baby pillow or a towel folded to the appropriate thickness.

Employees should keep their weight evenly distributed on the buttocks, with the hips and knees at about a 90-degree, or "L," angle. Good sitting posture is obtained when the ears, shoulders and hips are aligned. This keeps the natural back curves safely balanced.

Now that we have reviewed some basic anatomy, you should understand why certain postures are recommended and others are not. Let's go over how to apply these principles to the employee's work areas with regards to ergonomic products.

One of the easiest ways to adjust the furniture is to sit in the chair while bending the elbows to the "L," or 90-degree, position with the arms directly at one's sides and the wrists straight. Then slide up to the keyboard. All of the fingers should touch the keys without having to change position, and the feet should touch the floor. Then the keyboard is at a good height. If not, adjust the seat height and try again. If the keyboard height is adjustable, adjust it to reach the hands without changing the arm position.

Next, check the position of the legs and feet. The legs should be supported and the thighs approximately parallel to the floor. This helps keep the hips and knees at a 90-degree angle. If the employee has raised the chair and the feet no longer touch the floor, a footrest can be used to "bring the floor up to you." Other individuals may simply like a footrest for variety. Use a footrest with a nonskid surface, and one that is heavy enough to remain stationary and is large enough to accommodate both feet.

The chair should assist in maintaining good posture. When performing typical office tasks, an employee should be able to sit back into the chair and allow it to provide support. Office task seating comes in different sizes for a diverse work force and has different features that can be adjusted to meet an individual's needs. You would be surprised at how many people do not know how to adjust their chair properly. Demonstrate their chairs' adjustments. (Refer to manufacturer literature whenever possible).

One final important note on posture: no one can, nor should, sit in one position, even a "correct" one, for the entire day. It is critical to change positions frequently to allow blood flow and nutrients to the muscles. Postural adjustments don't have to be drastic.

Employees should return to the recommended posture as much as possible throughout the day. In the short term, it might feel hard to avoid slouching. Keep in mind that this may be due to weak muscles. If that is the case, they should sit in the recommended posture at the beginning of the work shift for as long as they can, and then return to it often throughout the day. Gradually, they will be able to maintain better posture for longer periods as they get stronger.

For people who work in offices, the features and functions of a task chair should not be discussed in isolation, but considered along with the functions of the job and the rest of the immediate work area (desk, computer, telephone, etc.). The most important purpose of the chair is to provide stability for the body at work and to assist in the maintenance of neutral body postures. For the all-day user, the chair also might provide options for mobility or alternative positions. "Comfort" in a chair is an individual and relative state. The chair should feel reasonably comfortable given its purpose of support. Keep in mind, for example, that a soft slipper might feel comfortable on the feet but would not give the user appropriate support for all-day wear.

An employee should be able to view the screen without bending the neck forward or to the side. If the neck is being bent, try raising or lowering the monitor to find a better position. In some cases, raising or lowering the chair may help in this process. A good "rule of thumb" for a starting point is to line up the menu bar on the screen with the eyes. Also, if the screen tilts, try tilting it very slightly downward, as the normal visual gaze is slightly downward. This can help to prevent the screen from reflecting overhead light. Keep in mind, however, that these recommendations often can vary with individual visual needs (for example, the use of bifocals), as well as the type of job being done. The primary goal is to maintain a healthy posture for the head and neck. Some experimentation may be necessary.

While keying, an employee should try to avoid constantly bending the neck and head down to look at the keys or at documents. If looking down is necessary, try to look down with the eyes while keeping the neck fairly straight. To avoid turning the head to one side for long periods of time, evaluate the placement of any documents and bring them as close to the monitor as possible.

A document holder can assist in the proper placement of materials. Objects and materials used frequently should be kept within a comfortable reaching distance. Show the employee a document holder and how it can help by placing materials in position for better vision and posture. Ask for feedback about the use of document holders and what type may be appropriate for that employee's tasks and needs. If writing tasks are required, a heavier, fixed document platform may be necessary.

Because we are all individuals, it is important that employees take the time to adjust their workstation to fit them. If they have questions after trying this, have them ask for assistance.

Workstation Component Design and Mechanical Stresses

The next factor for discomfort has to do with problems that can occur where the work equipment contacts the human body. For video display terminal (VDT) users, the first main area of potential contact is at the wrist. When keying, if the wrists rest on a table edge, there may be a prolonged mechanical stress on that area. The lips on pullout keyboard drawers are usually rounded and generally give adequate wrist support, but some people may prefer to also use a soft, contoured wrist rest for additional padding and support.

The same mechanical stresses found on the sharp edge of a workstation can increase pressure on another nerve in the forearm or elbow area if an employee pushes back the keyboard and leans on the table. Because this nerve is close to the elbow (this is what reacts when you hit your "funny bone"), it is wise to avoid prolonged resting of the elbows on any hard surface, be it an arm rest, table top, etc.

The last potential area of mechanical stress is the front edge of the chair seat. If the feet dangle or are hooked around the chair supports, circulation may decrease to the legs and feet. More and more chairs now have a "waterfall" front edge, which helps to decrease their pressure. For short employees whose chair will not get low enough so the feet rest flat on the floor, a footstool may be a temporary solution to remove pressure off the back of the thighs.

Reducing Force and Repetition

How employees key is as important as where they key. The last two risk factors, force and repetition, primarily have to do with keying techniques in an office environment. Force should not be a problem for VDT users, as the force required for a keystroke is quite small. Some individuals, however, consistently hit the keys with unnecessary force as they work. This can put excessive strain on the small finger muscles and tendons, so they should remember to key lightly. They can select keyboards and other input devices based on "feel." This may be appropriate when specifying a keyboard for someone who already has an injury.

The other risk factor is repetition. Keyboard use by its very nature requires repetitive use of the hands. Some people, however, habitually bend their wrists away from the neutral position while keying. This is strongly discouraged because it can unnecessarily fatigue the wrist muscles and tendons. They should try to keep their wrists straight and still while keying, and move their arms slightly to reach the keys, if necessary, instead of their wrists.

Voice recognition is an emerging technology that may solve some of these keyboarding issues. The ability to "talk" to the computer not only may remove classic risk factors from the office, but increase efficiency and productivity for a work force that does not have the typing skills of a generation ago. Voice recognition software, however, still is not perfect. It can make mistakes, requires "training" of the software and user, and is limited with regards to interface with some software and operating systems.

How to Find the Good Stuff

When selecting and specifying ergonomic office products, how should you proceed? First, if it's a large order or an expensive item such as a chair, ask to see and evaluate sample products. For example, you wouldn't buy a new car sight unseen without taking it for a test drive. Why would you buy a chair that people would spend the majority of their work week in without testing it for durability, quality, looks and ergonomic design? If it's smaller items, ask the vendor for technical literature or a sample. Second, ask questions. If vendors are competent and understand ergonomics, they will be able to discuss products and their intended applications. This will help you quickly find out if vendors really know what they are talking about. Finally, seek alternatives. In many cases, different manufacturers offer alternatives for the same needs. Only in a few cases is the product you need manufactured or offered by only one source.


Visual Comfort: The Insidious Risk Factor

One other common problem for video display terminal (VDT) users is eyestrain. Every day, our eyes are constantly responding to the demands we place upon them; focusing and refocusing through the action of very small muscles within the eyes. As the eyes age, their ability to focus decreases slowly over time, and a person's comfortable focus point moves farther away. This change usually begins in the mid-20s, so at each age, there might be a different comfortable viewing distance for an individual. In addition, a large percentage of the "normal" adult population has uncorrected vision conditions. The intensity of any visually demanding job or lifestyle, including VDT usage, can certainly bring such conditions to our attention. For all of these reasons, employees should have regular visual checkups. As part of this, it is important for them to tell the doctor that they work at a VDT, how much time they spend at it daily, what the light source is, what type of light they are exposed to and the approximate distance from the screen that they tend to sit.

Glare, or what more appropriately should be called nuisance lighting, on the monitor screen also can be a problem if it causes the eyes to make unconscious adjustments from the reflections. Minimizing or eliminating glare is important and can be done in several ways. First, just raising, lowering or turning a monitor slightly can do a lot to decrease glare. Next, check for items that cause reflective glare in the field of vision (such as task lighting, glass picture frames, large pieces of jewelry, etc.) and move such objects. Window coverings (blinds, curtains, etc.) may need to be adjusted throughout the day as the light changes. Finally, the employee may have to reposition the monitor screen so it does not face a nuisance light source.

If glare or reflected light on a screen is a problem, the first step should be the identification of the source(s) of the glare, followed by dealing with these sources as possible. Glare screens should be a last method of dealing with sources of reflected light, because they tend to decrease the clarity and visibility of the images on the screen. Glare hoods may be an effective accessory as they "shield" the screen from some overhead light and are cost-effective solutions.

A Word About Bifocals

Many people in an office environment wear glasses. It is important to ask employees whether they wear glasses and, if so, ask them what type of glasses they wear. Bifocal or multiple-lens glasses present unique issues for monitor and document placement. If someone wears bifocals, ask them if they view the monitor and documents out of the top or bottom of their glasses (usually, they will check right then).

Start with the monitor at the normal height (eyes level with the menu bar on the screen) and normal distance (16 to 28 inches). If the employee views the screen from the bottom of his or her glasses, lower the monitor 4 to 6 inches below the normal height. This will prevent them from bending their head back to view the monitor through the bottom of the lenses. If they view the monitor screen through the top pf their lenses, raise the monitor approximately 4 to 6 inches. Bring the monitor in as close as necessary for the employee to view it comfortably. Monitor risers and lifts can be used to achieve monitor height adjustment to accommodate progressive or bifocal-lens eyeglass users. Monitor slides and some of the monitor lift arms allow the user to adjust the distance of the monitor. A major advantage of flat screen monitors is that they are easily adjusted for distance from the user.

About the author: James M. Stewart, M.S., M.P.H., CPE, CIE, CHES (e-mail: [email protected]) is director of research and development/senior ergonomist for Essential Safety Products (ESP)/OfficeSafe in Denver. OfficeSafe, the ergonomic division of ESP, offers ergonomic products and consultative services to corporate customers through a combination of Web-based e-commerce sites and a traditional "bricks-and-mortar" approach.

About the Author

EHS Today Staff

EHS Today's editorial staff includes:

Dave Blanchard, Editor-in-Chief: During his career Dave has led the editorial management of many of Endeavor Business Media's best-known brands, including IndustryWeekEHS Today, Material Handling & LogisticsLogistics Today, Supply Chain Technology News, and Business Finance. In addition, he serves as senior content director of the annual Safety Leadership Conference. With over 30 years of B2B media experience, Dave literally wrote the book on supply chain management, Supply Chain Management Best Practices (John Wiley & Sons, 2021), which has been translated into several languages and is currently in its third edition. He is a frequent speaker and moderator at major trade shows and conferences, and has won numerous awards for writing and editing. He is a voting member of the jury of the Logistics Hall of Fame, and is a graduate of Northern Illinois University.

Adrienne Selko, Senior Editor: In addition to her roles with EHS Today and the Safety Leadership Conference, Adrienne is also a senior editor at IndustryWeek and has written about many topics, with her current focus on workforce development strategies. She is also a senior editor at Material Handling & Logistics. Previously she was in corporate communications at a medical manufacturing company as well as a large regional bank. She is the author of Do I Have to Wear Garlic Around My Neck?, which made the Cleveland Plain Dealer's best sellers list.

Nicole Stempak, Managing Editor:  Nicole Stempak is managing editor of EHS Today and conference content manager of the Safety Leadership Conference.

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