Date: Wed, 19 Oct 1994 05:40:02 GMT From: "Gary L. Karp" Subject: Thoughts on Keyboard Trays To: Multiple recipients of list SOREHAND Organization: Faludi Computing & Online Zone, SF USA X-To: SOREHAND@UCSFVM.UCSF.EDU Here is what I've been discovering about keyboard trays in my ergonomic evaluation work. First, and most obvious, if someone is a heavy mouse/trackball user, a tray that is only for the keyboard sets them up to reach and stretch to the mouse/trackball, unless they have a good corner layout that can put it in comfortable range. One recent client had the tray set very high up so she could cross her legs. Being in a corner unit, she could no longer pull out the mouse tray, so had the mouse ahead of the tray on the desk, which meant she leaned forward very awkwardly to use it, and the monitor had to stay too far away. She craned her neck a lot, and never sat back in her chair! And she wondered why her back and neck were sore. I've seen trays that have a slide out tray for the mouse yet are not stable enough for someone to rest the hands on it. That means muscular effort to suspend the hand and arm - which means overuse, especially for the shoulder. Some slide out trays have their edge far enough away from the front edge of the tray - necessary in order to slide underneath the keyboard to retract - which can mean needing to reach anyway. Some mouse extensions have a little lip around the edge which precludes the ability to add a mouse pad. It's not flat enough. Certain trays travel out from under the desk in an arc, rather than on a straight track. That means that you have to deal with height adjustment each time it is moved, and for some people that's quite often, as they need to get it out of their way. I see this happen in L- and U-shaped desk layouts. It also means that they don't tighten the height adjustment so they can move it easily, which means they can't rest the hands on it, and now we're back to the unnecessary muscular effort I mentioned earlier. In other words, I prefer a straight track where the height can be fixed and tightened down. Although one assumes that an articulating keyboard tray means the arms are relaxed because the keyboard is low enough, I find people still need a soft place to rest the hands. That means a proper wrist rest - soft, gentle, and wide enough but not too wide. One infamous product has a narrow, rounded, barely cushioned wrist pad that, in my opinion, only serves to direct pressure directly on the carpal tunnel and is anything but comfortable. I often find an articulating tray is not an appropriate solution for given desk layouts and for a given set of tasks in a job that require the need to comfortably reach other surfaces and objects. A tray can pull someone too far away, particularly from the monitor. That means you will not recline in your chair, and will overwork the back, neck, and shoulders, craning to see the screen, leaning forward on the elbows, leaning your chin on your palm, twisting the body, etc. When you use an articulating keyboard tray, make sure everything else is in proper relationship. When appropriate, I like a product from Ergonomic Design. It comes in lengths from 19 to 27 inches, includes a good quality wrist support, and installs on a straight track. The mechanism is not too obtrusive, and won't limit leg space or threaten hosiery. It adjusts vertically and rotates. Contact me by private email if you'd like more info. Breathe. Close your eyes. Stand up. Stretch. Drink a glass of water. Take care. Gary Karp Onsight Technology Education Services San Francisco