Office Ergonomics... what is the essence of it? We all have our own concepts and philosophies when it comes to the optimal office setup. Yet over the years, the notion of office ergonomics has conjured up a mental image of a graphic outlining a perfectly positioned, faceless individual. Each joint of the body has been precisely measured and labeled. You are familiar with the graphic: a perfectly proportioned individual sitting with knees and hips bent at 90 degrees, an impeccably erect spine, elbows positioned at an exact right-angle and finally, the keyboard and the monitor placed without flaw.
This ideal picture or so it would seem is the visual aide that has been used countless times by educators and consultants to outline and communicate the ideal position that end-users should aspire to. However, a problem does exist. Regardless of how ideal this picture may be, this standard-bearer has seldom, if ever, been observed in the workplace male/female, East Coast/West Coast, first floor or the penthouse.
It is time we get practical. Our teaching approach and message need to match up with the realities of a call center and the rigors of the data-processing suite. Believe it or not, people move, shift, reposition and redistribute their weight throughout each and every day. I do it. You do it. It is done with great frequency and consistency. The paradigm of the statically positioned, faceless individual needs to be transformed to a message that encourages freedom of movement within the context of three simple strategies: Stability, Clearance and Support.
Stability
Stability is a key piece to the overall equation. By definition, stability refers to the state or quality of being stable, or resistant to change or deterioration. When present, it forms the basis upon which we move. When it is absent, the equilibrium of the equation is lost and efficient movement, movement with purpose, is compromised.
In the office environment, stability starts at the foundation. That foundation is the basis upon which the seated posture is positioned. If for some reason the foundation is altered or compromised, the resultant posture will deteriorate. The underpinning of an upright, neutral posture begins with the feet positioned squarely/firmly on the floor itself or on an adequate footrest.
If the feet are not adequately positioned in relation to the ground, a fundamental deterioration of the postural infrastructure will take place. In the case of the seated posture, as our feet dangle, gravity will begin to pull us downward as we seek a measure of stability from the floor. As this process continues, our pelvis will eventually rotate backwards. This rotation of the pelvis directly affects the normal curve of the lower back (lumbar spine). As the lower back moves backwards, the remainder of our spinal column the thoracic and cervical regions of the spine moves forward. The net result is a rounded, slumped posture with a corresponding forward head.
As you can see, the equation for the collapse of one's posture is rather complex but it remains consistent across gender, age and body make-up. In the final analysis, we all seek stability when performing tasks.
Clearance
Clearance is a critical factor as we seek to acquire an upright, neutral seated posture. When a barrier(s) exists within a work environment, an individual worker will inherently seek solutions and/or accommodations to minimize the effect of the barrier. Fundamentally, they are substituting an efficient movement pattern with a less efficient, altered movement pattern. Sometimes, these accommodations or altered movement patterns are appropriate, resulting in minimal or no effect on the body's musculoskeletal system (muscle, joint, tendons, etc). However, more often than not, the accommodation or altered movement patterns will lead to a compromise of neutral posture, thus placing an increased stress/strain on the musculoskeletal system. The net result is that this places the individual worker at risk for injury.
Let's exam two very specific issues of clearance as it relates to setup of a neutral, seated posture in the office:
Seat Seat depth is an important factor for fit. If the "seat-pan" of the chair is too long for the user, the potential for problems exists. Let's consider the three potential accommodations that could take place:
1. The user will appropriately modify the chair's seat depth adjustment to accommodate the "buttock to knee" distance, thereby providing the appropriate 2- to 3-inch clearance between the back of the knee and the front of the chair
2. The user does not adjust or modify the seat depth. Hence as he/she sits, the potential exists for compression of the fleshy tissues behind the knee. This region of the knee houses the primary blood and nerve supply to the lower extremity. Compromise of these structures can lead to pain, numbness and/or swelling of the lower leg. Such positioning should be avoided.
3. Finally, the user may choose to scoot outward, away from the back support of the chair. This will provide the need clearance for the structures behind the knee. However, it will take the user away from the critical support of the backrest. Over time, the posture will collapse and the user will end up in a slouched, rounded posture, as described above.
Work Surface Height Positioning the user to the work surface is critical if we are to maintain neutral positioning of the hands and wrists. An ideal position would place the elbows slightly above the level of the keying/mousing surface. This will allow a slight "waterfall" position from the elbows to the wrists and hands. In all situations, it is important to have both the keyboard and the mouse placed on the work surface. Variable heights between these work tools will lead to problems.
Conversely, if the work surface is too high (the elbows are positioned below the level of the work surface), the edge of the work surface will become a barrier around which the user has to adapt as he/she interacts with the keyboard and mouse. To adapt, the employee will typically move into a position of wrist flexion. This posture can lead to compression and over-use injuries, including tendonitis and carpal tunnel syndrome.
Be very cautious of barriers and pinch-points. Work station setup should allow for appropriate clearance, regardless of the body part involved. If appropriate clearance is built into the equation, the end-user's need to move into adapted postures will be minimized.
Support
Support is the final and perhaps most important variable to consider. Inherent to the word is the capacity to bear weight or distribute forces, thus withstanding any aspect of slippage or collapse. To maintain a neutral seated posture it is essential that the user support the normal curve of the lower back (lumbar lordosis). By doing so, the user will unload the forces of the spine, thus minimizing the potential for collapse. As we have seen above, if the normal curve is lost or compromised, the spine collapses and the head moves forward. This forward-head posture places significant stress on the musculoskeletal system, particularly the head, neck and shoulders. Our data on office workers indicates that over two-thirds of the users report head, neck and shoulder regions as their primary work-related discomfort. Conversely, when the forward-head postures are appropriately addressed via support of the lumbar spine, these complaints essentially disappear.
Support can be generated in one of two fashions: actively or passively. Active support of the lumbar spine is generated through our muscles holding us upright, much as was the case when your mother told you to sit up straight. This is a great short-term solution. However, it will consistently fail with time given the demands on the musculoskeletal system to hold this position. A passive support is a much better choice. By utilizing a passive constraint to support the lumbar spine, our musculoskeletal system can be at rest. Hence, our lumbar spine is supported and our head, neck and shoulders are placed in a neutral posture.
Passive support for the lumbar spine is provided by the adjustable backrest featured on the majority of ergonomically designed chairs used today. When correctly positioned, the curve of the backrest will match the contour of the curve of the lumbar spine.
Will an armrest help support the upper extremities while employees perform computing tasks? A bit of a debate lingers on this issue, but the scientific evidence clearly indicates that seated work with arms supported will reduce the strain to the body. Seated work with proper arm support reduces muscular loads on:
- Neck/shoulder region (Karlqvist et al., 1998)
- Upper limbs (Well et al.,1997)
- Forearms (Hasegawa & Kumashiro, 1998)
- Spine (Occhipinti & Columbini, 1985)
- Hips and knees while rising and sitting (Arborelius et al.,1992).
Seated work with proper arm support also reduces:
- Keying forces during typing (Rose, 1991)
- Discomfort and perceived exertion (Fernandez et al., 1999)
- Muscle activity of one-handed keyboard operations (numerical data entry) (Hasegawa & Kumashiro, 1998).
Finally, seated work with arm support significantly increased comfort, decreased effort and decreased the rating of perceived exertion (Garcia, 1998).
Movement
Movement, as we noted earlier, is the final consideration. Since the dawn of time, our bodies have been tailored for movement. Be it running from danger or jumping for joy, movement is part of the human experience. Regardless of race, gender, age, size or origin, people choose to vary their posture. People do it to aide the circulatory, nervous and musculoskeletal systems of our bodies. Plain and simple, we perform better when we move. Hence, the notion of static, fixed posture is misguided and problematic.
Freedom of movement along with stress-free movement patterns should be encouraged, but not at the expense of the prerequisites of stability, clearance and support. Frankly, it is important that these worlds live together, for together they can provide a healthier and more comfortable environment for work activities.
Drew G. Bossen, PT, MBA, is with Atlas Ergonomics LLC. He has a strong clinical background rooted in the assessment and evaluation of the injured worker. He developed a fully integrated ergonomic program throughout the Rockwell Collins organization and continues to direct those efforts today. Contact him at [email protected] or visit www.atlasergo.com.