If you work in an office, chances are the desk height is too high for most employees because furniture industry guidelines have suggested furniture manufacturer design must accommodate a seated elbow height and leg-height clearance for the 95 percentile male. This height, in most office applications, is about 29 inches. If adjusting desk height is not an option, you may want to choose a keyboard tray as an alternative solution to help you sit more comfortably at work.
A recent article on Ergoweb.com written by Janet Peterson, an ergonomic consulting business owner, discussed when a keyboard tray is appropriate, what type of keyboard tray to choose depending on workstation configuration, and considerations for a “sit/stand” keyboard tray. Keyboard trays are an option for seated work when there is a mismatch between comfortable elbow height and desk height.
“This can be checked by having the worker adjust their chair away from the desk so that their feet are comfortably on the floor, shoulders are relaxed, upper arms are resting against their torso, elbows are bent to around 90 degrees and wrists and fingers are straight. If the desk is above fingertip level, that’s an indication that a keyboard tray might be helpful,” wrote Peterson.
If a worker’s tasks require frequent use of desktop equipment, a keyboard tray might not be the best option because it could result in excessive reaching postures. Also, Peterson advises that you should be sure that there is sufficient clearance behind the worker’s chair to use a keyboard tray, since the tray will position the worker eight to 12 inches away from the edge of the desk.
Important features to look for in a pullout keyboard tray, according to Peterson are:
- Adjustable in height by at least 4 inches
- Adjustable in tilt by at least 15 degrees
- Sturdy enough to not “drift” in height or shake with normal keying and mousing pressures
- Low profile
- Free thigh/knee clearance
- Able to raise/lower the height without using a knob
- Sufficient width to accommodate a keyboard and a mouse at the same height
Keyboard trays can be purchased as two separate pieces or as one combined unit. Since there is less space in a corner, you will most likely need the longest “arm” available so that the worker can pull the keyboard tray out far enough to clear the sides of the desktop, according to Peterson. You will most likely need a keyboard tray that has a sliding, under-mounted mousing surface or else an attached mousing surface. If you choose a model of tray with a sliding mouse surface, the mouse platform will sit below the rest of the tray. In that case, you may need to build up the mouse platform with multiple mouse pads, a book to bring the mouse surface height up to the level of the keyboard.
Using anthropometric tables for seated and standing elbow height for the five percentile female and the 95 percentile male, the difference between seated and standing height is at least 15 inches.
“That means that a sit/stand keyboard tray will need to adjust approximately 15 in. in height to work effectively as a sit/stand device, no matter how tall the individual is,” said Peterson.
Many keyboard trays that are advertised as sit/stand only offer nine or 10 inches of height change, which is not sufficient for most workers. Other models of keyboard trays do allow for 14 inches or more of height excursion, but the movement is split from below and above the desk height. Some keyboard trays can be adjusted by adding a riser piece under the tray piece of the tray mechanism or by adding a scissor platform in order to provide additional height in a standing position.
These days, many vendors are promoting sit/stand keyboard trays that are advertised to be able to allow the worker to easily change from a seated position to a standing position. Most of these keyboard trays do not adequately adjust to both a seated and a standing position, however, so Peterson advises that you research and consider what the worker’s needs are for a sit/stand configuration.
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Edited by Jamie Epstein