Ergonomically Designed Computer Products: Are All Beneficial?
There are many computer-related "ergonomic" products, the most common ones being:
- "Ergonomic" keyboards - most of these are keyboards where the alphanumeric keys are split at an angle. For a non-touch typist this design can be a disaster! The split design only addresses issues of hand ulnar deviation, and research studies show that vertical hand posture (wrist extension) is more important. There is no consistent research evidence that most of the split-keyboard designs currently available really produce any substantial postural benefits. For most people a regular keyboard design works just fine if it's put in the proper neutral position.
- "Ergonomic" mouses (yes it's 'mouses' not 'mice') - many of these mouse designs or alternative input device designs can work well to improve your hand/wrist posture. However, it's important to check that you can use these with your upper arm relaxed and as close to your body as possible. Overreaching to an "ergonomic mouse" defeats any benefits of this design. Check out the 10 tips for using a computer mouse.
- Wrist rests - these were very popular a few years ago, but research studies haven't demonstrated any substantial benefits for wrist rests. In fact, a wrist rest can actually increase pressure inside the carpal tunnel by compressing the undersurface of the wrist (take a look at your wrist and you'll probably see blood vessels that shouldn't be compressed!). Studies by Dr. David Rempel at the University of Berkeley, California, show that pressure applied to the underside of the carpal tunnel is transferred into the tunnel itself via the transverse carpal ligament and that intracarpal pressure doubles with a wrist rest compared with floating the hands over a keyboard. If you choose to use a wrist rest, using one with a broad, flat, firm surface design works best, and rest the heel of your palm on this NOT your wrist. Try not to rest while you're actually typing, but rest in between bursts of typing movements. Avoid soft and squishy wrist rests because these will contour to your wrist, restrict the freedom of movement of your hands, and encourage more lateral deviation during typing. Look at the surface of a typical wrist rest that's been used and you'll see that it gets eroded away, which means that the user has been sliding their wrists over the surface which also compresses the blood vessels often visible at the wrist. Remember, your hands should be able to glide above the surface of a wrist rest during typing, don't lock them in place on the rest while you type.
- Support braces/gloves - there is no consistent research evidence that wearing wrist supports during computer use actually helps reduce the risk of injury. If you do like wearing a wrist support make sure that it keeps your hand flat and straight, not bent upwards. There is some evidence that wearing wrist supports at night in bed can help relieve symptoms for those with carpal tunnel syndrome.
- Sit-stand Workstations - the use of a height adjustable worksurface for sitting and standing work is becoming fashionable. However, there is scant evidence that sit-stand furniture has cost effective benefits. The evidence suggests that there may be a reduction in back discomfort, but the research for this has not used adequate comparison groups (e.g. testing people who stand for the same time at the same frequency without doing keyboard/mouse work). There is no evidence that sit-stand improves wrist posture when keying or mousing. Logically, the real benefit of sit-stand is just that, changing between sitting and standing. But standing in a static posture is even more tiring than sitting in a static posture, so movement is important. We recommend that the most cost effective way to obtain the benefits from sitting and standing is for people to sit in a neutral work posture and then intermittently to stand and move around doing other things, like filing papers, making phone calls, getting coffee, making photocopies etc.) rather than trying to keyboard or use a mouse while standing.
- Height adjustable, split worksurfaces - with respect to wrist posture, the issues are the same for height adjustable, split worksurfaces and sit-stand worksurfaces:
2. If the surface is too high the elbow will be in sustained flexion
3. If it's a flat surface then it's just the same argument as is used above for a negative-slope keyboard tray arrangement.
You can't set a flat worksurface at an appropriate height for the 5 main tasks of office work - keyboarding, mousing, writing, viewing documents and viewing the screen- these all require different heights for an optimal arrangement. A negative-slope keyboard tray system serves as the height and angle adjustment mechanism for the keyboard, and the mouse platform serves as the height and angle adjustment for the mouse when attached to a worksurface that is set for writing height. Monitor height is best adjusted by a separate monitor pedestal rather than trying to move a whole worksurface.
These and the previous steps give a brief summary of good ergonomic design practice for computer workstations, but there's lots more to consider. You can read about ergonomics in many books, you can browse other materials on the CUErgo web site, you can get information from the Human Factors and Ergonomics Society.