Ergonomics 101 : Working Painlesslyby Tom Revelle, Vice President of Marketing for Humanscale,
(article from Interiors & Sources, June 2000)
Technology has had a profound effect on the way we live and work. As a result, we are spending more time sitting and using computers, which has greatly increased the occurrence of related musculoskeletal disorders. This article reviews a number of techniques for avoiding work-related, repetitive stress injuries and enhancing both the comfort and productivity levels of the workers who adopt them.
Technology. The ultimate buzzword of the past decade, it touches nearly every corner of our lives, from medicine to entertainment to the way we buy groceries. A quick retrospective reveals it's also had a profound impact on the way most of us work.
Only 10 years ago, if you wanted to send or retrieve a fax, you got up from your desk and walked to the fax machine. Today, with online faxing, a couple of keystrokes is all it takes. In days of yore, if you wanted to ask your coworker a question, you'd probably get up and walk to their desk or office.
Today, however, there are several less taxing ways to communicate. E-mail and on-line messaging, in addition to sophisticated phone paging and voice mail systems, have taken the place of the leisurely stroll down the hall brandishing coffee and (only two decades ago) a cigarette.
The result of all these changes is that we're spending more time at our desks, and more time on our computers - a lot more time. While 90 percent of all U.S. office workers now use computers, 40 percent work on their computers at least four hours a day. But Dr. Alan Hedge warns that the risk of musculoskeletal discomfort increases by using the computer as little as one hour a day. Even worse, the risk of musculoskeletal injury is nine times greater when you spend four hours a day at the computer than it is for a one hour-per-day user. These statistics shed some light on the growing number of work-related office injuries, and the increasing importance of ergonomics in the workplace.
So what exactly is ergonomics? In a broad sense, office ergonomics applies science to workplace design to maximize productivity while reducing operator fatigue and discomfort. While the concept is fairly straightforward, its application is often open to debate. This is why it's important to articulate the real issues facing workers in today's office, and to debunk the misconceptions that typically surround discussions of ergonomics.
SOME ERGONOMIC MISCONCEPTIONS
Most of us learn early that if something is good for us, it may not be pleasant. Unfortunately, the same logic has trickled into our ideas about healthy workplace posture and behavior.
Despite what your mother said sitting up straight is not good for you. And despite what the old ergonomic theories proposed, sitting with your body at 90-degree angles is not the healthiest way to spend a workday. In terms of workplace ergonomics, the startling truth is that comfort and health are synonymous. If you're not comfortable at your desk, it's because you're probably sitting and working wrong.
More adjustability doesn't necessarily mean more ergonomic. While the ability to adjust is a critical component of most ergonomic products, workers may unwittingly adjust themselves into bad postures and positions. Products should be adjustable within a safe operating range to keep un trained users from putting themselves at risk. Since most people know precious little about ergonomics, when workers set up their own work stations, the position of the keyboard, mouse, monitor and copy holder is typically determined by available desk space, in which case the likelihood of an ergonomic workspace is next to nil. Not all products labeled 'ergonomic' are actually good for you. There are currently no laws or governing bodies overseeing the use of the 'ergonomic' label. This means anyone can call any product 'ergonomic'-from toasters to baby pins to steam-proof mirrors. As a result, the term has been overused and watered down. Bottom line, ergonomics in the workplace is serious business, and product claims and functions must be backed up by serious research and testing.
Not all products labeled 'ergonomic' are actually good for you. There are currently no laws or governing bodies overseeing the use of the 'ergonomic' label. This means anyone can call any product 'ergonomic'-from toasters to baby pins to steam-proof mirrors. As a result, the term has been overused and watered down. Bottom line, ergonomics in the workplace is serious business, and product claims and functions must be backed up by serious research and testing.
EMPLOYERS PAYING THE PRICE
While workers suffer from task-related injuries, employers are footing the staggering costs. Musculoskeletal disorders (MSDs) now account for one-third of all occupational illnesses and injuries. They constitute the largest job-related illness and injury problem in the U.S. today. In 1997, employers reported a total of 626,000 lost workdays due to work-related MSDs. They pay approximately $20 billion annually in direct worker's compensation costs and another $60 billion in indirect costs.
THINGS TO REMEMBER ABOUT ERGONOMICS
So much for the bad news. The good news is that most work-related, repetitive stress injuries are avoid able. By attending to a few basic principles, employers can enhance their employees' comfort and productivity and reduce their risk of MSDs and other costly injuries. Remember these words: 'Ergonomic principles are most effectively applied on a preventive basis. Good design with ergonomics provides the greatest economic benefit for industry.'
Environment affects behavior. Proper placement of the workspace components (i.e., an ergonomically-designed workspace) will naturally encourage users to assume safe, low-risk postures. The top of the Empire State Building is not fenced in to keep sightseers from leaping to their doom, but to avoid the likelihood that accidents will happen. So too, the office work environment must be designed to minimize the risk for workers. In factories, industrial engineers spend hours analyzing the tasks performed by each worker to determine the most efficient and risk-free work station layout for that worker. Why not the same concern for the office worker?
Movement is critical. Despite the old school of thought on the desirability of fixed postures, the overwhelming evidence today shows that fixed postures are inherently dangerous. 'Any fixed posture, no matter how closely it approaches the optimal, will generate muscle fatigue; therefore, it is important to build in flexibility to allow operators to shift positions easily.' Our bodies were designed to move. In fact movement, more than anything else, provides nourishment for the spine, keeps the joints lubricated and flexible, improves circulation and removes waste products from the muscles. Conversely, when we don't move, the elasticity of our spine and joints is reduced and waste products build up in the muscles, causing fatigue. While constant motion is obviously not the goal, frequent positional changes are vitally important to good health.
Minimize extreme postures. While movement is important, so are the postures you assume while performing your daily tasks. Neutral postures, meaning those that require minimal muscle activity to maintain, are synonymous with health and comfort. Extreme postures like abducted shoulders and extended wrists must always be avoided. Maintaining body symmetry is equally important, particularly with respect to the spine. Don't sit for extended periods in bent or twisted postures.
Avoid contact stress. Focused pressures are extremely dangerous, causing circulation problems and nerve damage in more severe cases. 'Contact stress affects the soft tissue on the fingers, palms, forearms, thighs, shins and feet. This contact may inhibit blood flow, tendon and muscle movement and nerve function.' Stress like this can be transmitted to arms and wrists by extended contact with the hard, sharp edges of desks and hard armrests on chairs. Likewise, the undersides of thighs are at risk from hard seat edges or simply seats that are too high.
Take breaks. Breaks could include actual work breaks, short exercise or stretch breaks, or simply switching gears and performing a different task for a few minutes. 'Appropriate rest breaks, combined with stretching exercises, allow computer workers to sustain work at an appropriate pace, while minimizing postural injury risks,' says Dr. Hedge.
Education, education, education. When all is said and done, a worker educated on ergonomics in the workplace is more likely to remain healthy. Such an employee will be aware of critical risk factors, healthy working postures, and more importantly, the warning signs of injuries.
DESIGNING THE PERFECTLY ERGONOMIC WORKSTATION
Let's say you're about to design a user-friendly work station. It's important to remember that a well-designed office work environment is made up of several critical components:
1. The Chair.
Ergonomically, the most important piece of office equipment is the chair. 'Low back pain remains the most prevalent and costly work-related musculoskeletal disorder,' says a leading health insurer. Low back pain can be the direct result of sitting for days, months and years in poorly adjusted chairs. The typical office worker will spend more time sitting in an office chair than anywhere else, with the possible exception of bed. With all this time spent together, it's critical that task chairs meet these human criteria.
Task chairs should encourage movement. Frequent movement and position changes are critical to health and comfort. However, in order to get people moving, they must first know how to operate their chairs. And this is easier said than done. According to a 1995 study, less than two percent of the subjects were able to identify the purpose of the back tension adjustment knob--the most basic of chair controls--on a variety of chairs. The problem is that if the tension spring is set too firm, the chair won't recline and the user will be forced to sit in an upright posture. If the spring is set too loose, the chair will fall back to its most reclined position, where the user may sit for hours at a time. Even if set properly, the tension spring will only provide optimal support in the middle of the recline range.
To accommodate for these inherent failings of the tension spring, many chairs are equipped with recline locks. But locks can also be dangerous exactly because they're designed to keep the chair in a fixed position. The solution? Adjust the spring tension to best support the user. Also, use locks with caution and conscientiously unlock them on a frequent basis to change recline positions.
Recline is healthy. Nowadays, researchers everywhere agree that reclining is healthy. The renowned industrial designer once said, 'The more you recline, the more comfortable you get. Ergo, the best chair is a bed.' Essentially, the more work you can perform while reclining, the more of your body weight will be distributed to the backrest of your chair, and the less pressure your spine will have to endure. However, extended recline can put additional stress on your neck and shoulders while they work to maintain the upright position of your head. Therefore, it's wise to consider a chair with a headrest if you expect to perform extensive work in a reclining position.
Disc pressure in the spine varies with the different seated postures assumed during a typical work day. As shown, the spine sustains far less pressure when reclined, which translates into more comfort and less risk of injury.
Task chairs should fit the user. In addition to proper support, it's important that a task chair provide good body fit. No one would consider wearing a pair of shoes that didn't fit. Yet millions of office workers sit in chairs that are maladjusted to their body size and shape. Not surprisingly, such workers are at high risk of injury. Since office workers come in all shapes and sizes, it's vital that each worker's chair be sized to fit. The most common size adjustment is seat height. Ideally, the seat height should be set so the user's feet rest comfortably on the floor while the upper body is high enough to work comfortably at the desk. But because the height of most desks is fixed, petite users may need to raise the chair to a point where their feet are lifted off the floor. This. puts undue stress on the undersides of the thighs, often causing circulation problems and potential nerve damage. Placing a height-adjustable footrest under the desk solves the problem by giving petite workers proper support for their feet and legs.
Seat depth. Here the primary concern is to provide maximum surface area on which to distribute the body weight, while keeping the delicate area inside the knee clear of potential contact stress from the front of the seat. When sitting with your back properly supported, there should be approximately two to four inches of space between the front of the seat cushion and the inside of your knee.
Backrest height. As with seat depth, the idea of adjustable backrests is to maximize surface contact and minimize pressure points. While the curvature of the spine varies somewhat from person to person, it is the position of the curvature that matters. Thus, a contoured and height-adjustable backrest provides lumbar support while maximizing surface contact and weight distribution.
Armrests should be adjustable and kept level. Armrests should be quickly and easily adjustable. That's important because different tasks and different sized users require different armrest positions. In addition, users should be encouraged to keep their armrests level. Otherwise, they will sit, possibly for years, with one arm lower than the other and their spine therefore in a lateral curve. And that's a high risk posture for injury.
Ultimately, when it comes to seating, it's critical that users be trained to fully understand the features and operational controls on their chairs in order to gain the most benefit from this extremely important work tool.
2. The Keyboard and Mouse.
The thought of carpal tunnel syndrome (CTS) strikes fear into the hearts of most office workers, and for good reason. The statistics surrounding CTS are astonishing. In 1996, CTS cases resulted in the highest median number of days away from work for any injury or illnesses--25, compared to five days for all other injuries and illnesses combined. CTS is a painful and debilitating disorder that can take months and even years to heal. However, it can be avoided in most cases with some basic preventative measures.
Get the keyboard off the desk. Recent research shows that the keyboard should be angled away from the user and placed below desk level, so the user's wrists remain straight and the elbows open up to a greater-than-90-degree angle. The best way to achieve this position is with the use of an articulating keyboard holder with negative tilt adjustability. A 1995 Cornell study found that using a lowered keyboard holder on a preset tilt away from the user can help prevent carpal tunnel syndrome. This keyboard position also encourages a healthier seated posture. In addition, the palm support should only be used as a resting place for the palms between periods of typing. It should never, ever support the wrists during periods of typing.
Typical seated posture while keying; abducted shoulders, forward head, extended wrists, maximum disc pressure on spine.
A negative slope keyboard in a lowered position keeps wrists straight (neutral posture), opens up elbow angles and hip angles, keeps shoulders neutral and encourages recline, which reduces stress on the spine.
Movement is critical-II. As with seated postures, the ability to change positions frequently and easily is the foundation upon which a good ergonomics program is based. A keyboard platform should allow the user to easily change keyboard height and depth as different tasks necessitate.
Keep the mouse within the Neutral Reach Zone. With the phenomenal increase in graphics applications and Internet use, mousing has become a major cause of CTS. To combat these dangers, it is important to always mouse within the Neutral Reach Zone. Avoiding extreme postures minimizes the possibility of shoulder abduction and wrist flexion/extension.
Beware the bite of the mouse. In addition to position, the mouse itself also can be a major risk factor. Cornell University research suggests that a larger mouse can reduce wrist extension and CTS risks. Users should monitor their mousing hand and immediately begin mousing with their other hand at the first sign of any pain or tingling. Ideally, the mouse should be symmetrical so it can be used easily in both hands. Likewise, the keyboard platform should allow for mousing on both sides of the keyboard.
3. Monitor Placement.
Researchers overwhelmingly agree that the top line of text on the monitor should be at or slightly below eye level. That's because any portion of the monitor above eye level contributes to neck and shoulder strain. If your monitor is too high because it rests on top of the CPU, invest in a below-the-desk CPU holder. Placing the CPU below the desk not only allows for better positioning of the monitor, but also creates additional desk space. Alternatively, if the monitor is positioned too low, consider spacers or adjustable monitor arms to lift it off the desk.
The monitor also should be placed directly in line with the keyboard to minimize twisting of the neck and/or body. Again, maintaining body symmetry is a critical component of healthy work habits.
4. Document Placement.
Considering the importance of body symmetry, all reference documents should be positioned in line with the keyboard and monitor to avoid asymmetrical neck motion. If you do not have an in-line document holder and instead place input documents to one side of the monitor, alternate the placement of such documents from one side of the monitor to the other to avoid long-term one-directional injuries.
5. Lighting and Glare Issues.
Another major issue facing office workers today is computer vision syndrome (CVS), which can cause headaches, eyestrain, neck and back pain, and light sensitivity. According to OSHA, some studies estimate that 90 percent of the seventy million U.S. workers using computers for more than three hours per day experience CVS in some form.
There are several ways to reduce the risks of CVS. The most effective is to reduce or remove screen glare, which primarily affects vision but can also cause awkward postures as people move to avoid the glare. The first line of defense against screen glare is to position monitors away from windows and other light sources. Beyond that, says Dr. Hedge, 'Optical glass glare filters on computer monitors can dramatically reduce health and vision problems related to computer glare and help boost productivity in full-time computer users.' While there are many screen filters on the market, some low-cost products can actually impair vision, so choosing a quality eye protection filter is critical.
Installing task lighting at each work station is another way to combat CVS. Office lighting is generally not bright enough for most desk work, particularly for the growing population of older office workers who require more light. Task lighting solves the problem by offering a direct source of light where it is needed most--on the task at hand. Good task lights provide a wide range of adjustability to avoid glare on the monitor, work surface and documents. The best ones also have an asymmetrical design, which reduces the glare by diffusing the light.
Implementing an ergonomics program using some or all of the above-mentioned guidelines will produce recordable, trackable results. In 1997, the city of Tucson, AZ, realized a 77 percent decrease in injury hours and a 16 percent decrease in injury occurrence after standardizing on an ergonomics program. Likewise, betWeen 1992 and 1996 the New York Times reported an 84 percent decrease in MSDs, a 75 percent decrease in lost-time cases and a 91 percent decrease in total lost days as a direct result of creating ergonomic workspaces for their employees. In these instances, and countless others, the investment in ergonomics paid for itself in a relatively short amount of time, not to mention huge gains in productivity and overall employee satisfaction. When all is said and done, though employee health and comfort are the primary objectives of a well-designed ergonomics program, employers can be sure that such a program will make their bottom-line feel good too.
|Slouching, slumping or bending forward at the waist in a chair can lead to discomfort, fatigue and backache. Follow these guidelines to help prevent problems from occurring when sitting at your workstation.|
||Top one-third of the screen at or below eye level; distance from operator a minimum of 18 inches, typically at arm's length.
||Wrists should be a natural extension of the forearm, not angled up or down. Elbow relaxed. Lower arm open at least 100° to upper arm.|
||Elbow relaxed. Lower arm open at least 100° to upper arm.|
||Adjustable back rest to accommodate the normal curve of the lower spine.|
||Keyboard flat at elbow level with palm rest to support hands during rest.|
||Thighs approximately parallel to the floor.|
||Easily adjustable seat height. Seat pan short enough (front to back) for knee clearance and with a waterfall front edge.|
||Swivel chair with 5-point base and casters.|
||Feet resting firmly on the floor; footrest needed if feet are not supported by the floor.|
||Document holder in line with front of monitor. Height and angle adjusted for the comfort of the user.|
The preceeding information taken from: