In Part 2 of our 4-part series we talked about the fact that “nearly all desks in North America are already too high for most of us.”Doctors, researchers and ergonomists tell us that proper positioning is so important when using our computers. When keying, we need to keep our shoulders relaxed and our arms comfortably at our sides. Our elbows should be bent at a 900 to 1200 angle and our wrists should be at a neutral position. Attaching a height adjustable keyboard and mouse tray to the underside of a work surface seems to be a natural solution for getting the keyboard and mouse down to a comfortable position. So why are so many keyboard trays not being used once they are installed?
PROS of Keyboard Trays
People get height adjustable keyboard trays because their desk top is too high to be comfortable when keying, and the height adjustable tray allows them to get the keyboard down to a comfortable level, alleviating “elevated shoulders and other awkward postures, which increases the risk for discomfort, fatigue and injury”.1
Your keyboard should provide optimal support for keying. This can be accomplished with an articulating keyboard, other ergonomic equipment or adjusting desk/chair height.
- Move your chair close to the keyboard.
- Position the keyboard in front of you.
- Adjust the keyboard to center with the area that you use frequently.
Adjust the keyboard height with your shoulders and arms relaxed.
The recommendation for the elbows is 100°-110° with your wrists and hands straight.
- Adjust the tilt of your keyboard. If you sit upright, the angle should be in a slightly negative position. Tilt the keyboard by slightly tilting the keyboard forward (away from you). If you are in sitting in a reclining position, a slight positive tilt (towards you) by using the “feet” will help you with keeping your wrists straight.
- Wrist rests may be necessary if the keyboard does not have a wrist rest. These act as a cushion for the palms of the hands to avoid stress to the nerves and capillaries. Avoid wrist rests that are too wide or higher than the space bar.
- The mouse should be close to you such as on the keyboard, on mouse extension of the keyboard or on a bridge over the numeric keypad.
- You may need additional adjustments such as raising the desk or chair or using a footrest if alignment is not supportive or you are uncomfortable.2
- “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.”3
But then they don’t use height adjustable keyboard trays because it’s difficult to reach everything else on their desk when the keyboard tray is pulled out.
What about “Reach Zones”?
“”Human reach envelopes” only give feedback concerning whether a point is reachable. This is not enough for the designers. The more important information the designers need to know is the zones with different discomfort levels”.1
Although this statement actually applies to designing the interior of a cockpit of an airplane or automobile, the principal applies to office furniture equally well. All too often our North American mindset is focused on basic function and esthetics without taking into consideration the merits of “comfort” or the negative ramifications of “discomfort”.
Too often height adjustable keyboard trays are simply attached to work surfaces without understanding the consequences of ignoring human reach envelopes or “reach zones”. By pulling the keyboard out from under a straight front desk top, we are forced to move away from the work surface which, in turn, forces us to bend and reach for articles other than our keyboard and mouse. In helping to solve one problem, keyboard trays can contribute to another.
Work Organization with a Keyboard Tray
- Divide your workstation into sections as shown above into 3 sections: Primary, Secondary and Reference.
- Place your keyboard and mouse in the Primary section.
- Place your monitor, document holder, telephone, calculator, printer and other equipment that you use frequently in the Secondary section or within arm’s length of you. Documents/document holders should be in front of you between the keyboard and monitor such as an in-line document stand. If workspace is limited, position the document holder next to the monitor. If you use the telephone frequently, consider using a headset or speakerphone to avoid cradling the handset.
- Place other equipment and books infrequently used in the Reference section.2
The Importance of Training
Why are few height adjustable keyboard trays used in Europe and Scandinavia? The reason is that, for many years, computer users have had access to height adjustable desks that allow them to adjust their work surface to their personal, comfortable working height which includes keying height. Equally important, early on they understood the “why” as well as the “how”. They are taught, not only how to use the various levers and buttons of their chair, desk, monitor arm, etc., they learn and understand why it is so important to maintain a good fit between them (the user) and the equipment they are using.
Height Adjustable Keyboard Trays and Sit-Stand Requirements
Although keyboard trays are height adjustable, they seldom meet the range needed to accommodate sit stand requirements. Those that do leave the work surface and all the support items (documents, phone, etc) behind/below.
Designing a workstation that is ergonomic can help reduce musculoskeletal disorders and discomfort. Keeping objects within a closer range of motion where the user’s joints do not have to deviate far from neutral posture is a great way to improve ergonomics.
Electric Height Adjustable Work Surfaces (EHAWS) or sit stand desks provide the ability to easily transition from a sitting to standing posture and, in addition, enable the user to lower the entire surface to a comfortable keying height while keeping everything else close at hand.
Have any questions or comments about this article? We’d love to hear them, leave a comment below!
1 Human Factors and Ergonomics in Manufacturing & Service Industries, Volume 19, Issue 1 http://onlinelibrary.wiley.com/doi/10.1002/hfm.20135/pdf
2 https://cfo.asu.edu/ergonomics-office-workstation 3https://www.osha.gov/SLTC/etools/computerworkstations/components_monitors.html