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Tech Tip 69 - Ergonomics of Computer Pointing Devices
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Being the dedicated geek that I am, I spend a lot of time with my face in the computer screen. Much of that time, I am driving a cursor around the screen using a pointing device of some kind. In this installment, I want to talk about the long-term physical effects of computer pointing, in other words, the ergonomics of riding a mouse. We will look closely at how to use a computer-pointing device for maximum comfort and minimum wear-and-tear on your arm and shoulder. This is not something to ignore unless you want to be too crippled in your geek old age. Don’t laugh, it really happens, as I will personally relate. |
1. Keyboard Injury
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While our topic here is pointing devices, it helps to quickly review how keyboards can hurt us. Most people have heard of a type of injury caused by the long-term effects of typing on a keyboard called RSI, or Repetitive Stress Injury. The damage is usually done to the carpal tunnel in your wrist where the nerve passes through the wrist joint. The wrist, when bent back to align with the keyboard, can squeeze the nerve that runs through the wrist joint. The nerve sheath becomes inflamed and swells, which further crushes the nerve. Once started, it is very difficult to stop this cycle and repair the damage completely. Often, you have to totally give up typing for several weeks, and then wear a wrist brace to hold your wrist straight for many months until the injury is healed.
The protection from keyboard injury is pretty straightforward. Use an 
My desk is arranged so that my arms are straight and wrists are not bent back while typing. The proper relationship between keyboard height and seat height can help here. One solution is a keyboard tray that fits under the desk and lowers the keyboard. Another alternative I like is to put your keyboard in your lap so your arms are completely relaxed. A 2. Ouch! My Elbow Hurts
Then, why does my right elbow have shooting pains and my shoulder killing me? Why can’t I straighten out my arm? I thought I did all the right ergonomic things, so why is working on my computer so painful? This is the real story of my experience, not some made-up example to illustrate a point. I had to learn this the hard way! |
So, I’m sitting here at my custom computer desk. I have the ergonomic keyboard and my desk was just right so my arms were completely relaxed. I should have no problem wailing away on my computer day and night, right?3. Mousing Around
At the time, I was doing a lot of engineering work and that involved a lot of drawings done on my computer. Drawings tend to need a lot of mouse work to get the lines in just the right spot. It doesn’t make a difference if you are designing a computer chip, updating the company organization chart, or laying out the plays for your Pop Warner football team, drawing on the computer comes into everyone’s life.
When the drawing on my computer was zoomed, it filled the screen and I could see the whole drawing where the lines had to be placed with extreme care to get them to line up. With a complex drawing, it was almost impossible to get exact alignment in the full-page view mode. It helped to zoom in to expand the parts where I was working. The line placement was easier not only because I could see it better blown up like that, but also because the mouse movement was not as critical to get the line where it belonged. Of course, I ended up going back and forth between the full-page view and the expanded view to figure out where I was and where to place the lines. That made for a lot of extra mousing around. |
4. Snap-to-Grid
When the Snap-to-Grid feature is turned on, a series of tiny dots in rows and columns are overlaid on the screen. This is the grid. When you place the end of a line, it will snap from the place you put it to the closest grid point. This makes laying out your drawing much easier, faster and neater. Use the widest grid spacing that allows placement of the lines where you need them. Wide grid spacing means you can be pretty sloppy with the placement and still get nice even alignment. You can accomplish your work so you don’t have to tighten up your grip on the mouse. You can relax and use more fluid movements that take the stress off your arm. Many computer graphics applications have a Snap-to-Grid feature or something close to it (no pun intended). Sometimes, a program will have a Snap-to-Object feature, which achieves a similar result. You might be placing boxes that represent people in an organization. The connection lines will automatically snap to the center of a side, top, or bottom of the box making it real easy to get the lines neatly spaced. |
One trick I learned was that I could use the Snap-to-Grid feature of my CAD program. Instead of tensing up while trying to hold the mouse just right to get the lines exactly where they belonged, I could relax a little and just get the end of the line close. The end of the line would then snap to the grid position.5. Say Goodbye to the Mouse
Even after using all my tricks, my elbow kept getting more and more painful. I couldn’t sleep at night and I ended up working left-handed on the computer. That wasn’t a solution because I could see that soon I would have two elbows that were crippled.
I noticed that after using the mouse extensively, my elbow hurt more than ever. I took a week off of the computer and my arm didn’t hurt as much. When I went back to work, the pain came right back the first day. Finally, I realized that as I held the mouse, I twisted my arm to an unnatural position. To make accurate mouse movements, I had to tense up my arm and shoulder muscles. This combination was the source of the pain. Unfortunately, to use a mouse I had to make these movements that are so painful. It became clear to me that I had to find an alternative to the mouse. |
6. Let’s Try Something Different.
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Being the gadget freak that I am, I had accumulated an assortment of computer pointing devices. One of these gadgets was a cheap trackball. I had discovered that the mouse is a more natural feeling pointing device so the trackball was relegated to my junk drawer. I bought a new 7. The Marble Mouse
This exposed ball concept is great. You can manipulate the ball with just the tips of your fingers while keeping your forearm in a natural position. You do not have to twist your arm as you have to do for a mouse or even an old style trackball. I use my forefinger to steer the cursor with the ball with occasional help from my middle finger if I’m scooting across the screen quickly. My thumb presses the left mouse button while my middle or ring finger can operate the right button. You can switch around if you feel comfortable in other configurations. It takes a little getting used to, but I find the Marble Mouse much more responsive than a standard mouse.
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The Marble Mouse is only one example of the modern trackball. There are many others by Logitech and other manufacturers. Of course, the trackball has not been left out of the wireless revolution. There is a 8. Works for Southpaws Too
If you are lucky enough to be left-handed, you probably despise all these computer pointing devices that are shaped for right hands. The Logitech Trackball Marble Mouse is exactly symmetrical so it is neither right nor left handed. The ball is exposed on both sides and the buttons are exactly the same. If you go into the Control Panel and to the mouse applet, you can switch the left and right mouse buttons. By doing so, left-handed people can have exactly the same comfortable pointing experience as right-handed people. |
9. Pen Tablets
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An input device that many people find more comfortable to use than standard or trackball mice is the pen tablet like those made by Final Words
This issue of computer pointing device ergonomics cannot be taken lightly. A senior member of the staff at work abused himself so badly that even with a brace on his hand, he could not use the mouse or the keyboard. We had to hire a typist for him while he suffered a long recovery. I consulted with the typist who has a strong IT background and discovered that he came to the same conclusion that I have. Get rid of the mouse and invest in a modern trackball. Following his advice, I just ordered three more Marble Mice, one for my mom, and one each for my wife at work and at home. They are a lot cheaper than wrist braces, physical therapy and stand-in typists. |
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