Overuse of tablets may also interfere with getting a good night's sleep, says Dr. Mariana Figueiro, director of the Light and Health Program of the Lighting Research Center at the Rensselaer Polytechnic Institute in Troy, N.Y. Exposure to bright light in the evening will suppress the body's production of the sleep-aid chemical melatonin, making it harder to go to sleep.
The use of an iPad at full brightness for two hours is enough to trigger melatonin suppression, she has found. (She also tried the experiment with TVs and CRT computer screens, but did not find any suppression, presumably because they are less bright and used at greater distances from the eye.)
Some old-school ergonomics still apply
You've probably heard them since the fourth grade, but the admonitions about posture in relation to office ergonomics still hold true.
"As a rule of thumb, you should be able to touch the screen with your fingertips," says Dr. Magdy Akladios, associate professor at the University of Houston-Clear Lake. "The knees, hips and elbows should be at a 90-degree angle. But it's also okay to, for instance, cross your legs — as long as you don't do it for eight hours straight."
The keyboard should also be flat on the desk. "There is no functional reason for the feet on the back of the keyboard," adds Linda Weitzel, senior ergonomist for Xerox in Rochester, N.Y. (One keyboard maker says the feet serve only to improve visibility for those who can't touch-type.)
Ignoring the rules is as risky as ever. "The complaints have not changed that much since the 1990s," says Weitzel. "The number one problem is back complaints, since they are sitting all day long. Part of it is how effective the computer is today. Whereas five years ago office workers still printed out documents, today they don't even have to get up and go to the printer because they are forwarding documents electronically, or sending links."
In the face of discomfort, act immediately. "The best fix is to stay away from the cause," says Akladios. "You need to prevent the problem motion and introduce a new set of motions, or take frequent breaks. Rather than do any one specific thing, you need to do something different from what you have been doing."
Extensive typing on a tablet opens another can of worms, Hedge warns. "We've done a lot of work on this," he says. First, it slows people down compared to typing on a regular keyboard since it provides no feedback, the varying resistance of a key as it's pressed.
Second, "the fingers tend to get sore since there is no give on that surface. It's like drumming your fingers all day on your desk," Hedge says. "For the convenience of technology we have moved people away from typing and back to poking and prodding, dramatically reducing their productivity. It's ludicrous."
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