Spend five minutes on any busy street corner and you'll spot people using tablets and smartphones in dangerous ways, whether it's texting behind the wheel or strolling with their eyes on the screen.
But distracted driving and walking aren't the only perils lurking behind touchscreen devices such as iPads, iPhones, BlackBerrys, Windows Phones, and Androids. Although not quite as dramatic, other touchscreen-oriented health hazards are even more insidious because most people aren't even aware that they exist. The potential for injury from using touchscreens will only go up as more people use smartphones and tablets, especially if Microsoft's Windows 8 effort succeeds in popularizing touchscreen PCs and laptops.
Ergonomic risks are not new to computer users. Laptops and netbooks, whose sales now outnumber desktop computers by more than two to one, pose their own health-related problems. But the rise of the touchscreen means both new kinds of health hazards and more usage in risky scenarios.
[ Watch the "Safer Computing" guide to preventing repetitive stress injuries in your workplace: as a video or as a slideshow. | Learn why touch capabilities in Windows 7 failed and what Microsoft has in store for Windows 8's touch plans. ]
After decades of research on machine-human interactions, medical experts have pinpointed three categories of computer-related illnesses, both in traditional PC use and in the new class of touchscreen devices:
Repeated motion injuries. Commonly known as RSIs, for repetitive stress injuries, these ailments result from recurrent large or small movements that affect joints, muscles, tendons, and nerves. For example, people who frequently use their thumbs to type text messages on cellphones sometimes develop de Quervain syndrome, a painful affliction that involves the tendons that move the thumb. Although the causal link isn't as well established as in patients who suffer from pain from prolonged desktop keyboard use, there's little doubt that overzealous texting can cause debilitating pain.
Diseases caused by unnatural postures and forces. Closely related to RSIs, these disorders occur when people use their bodies in ways that induce physical stress, such as tilting their hands too far inward or outward while tapping or putting force on their wrists while typing. Carpal tunnel syndrome, perhaps the best-known disease in this category, results from pressure on the median nerve in the wrist.
Eyestrain. Struggling to read computer monitors, either because the characters and images aren't clear or because the screen is obscured by glare or reflections, may cause problems that range from annoying to incapacitating. Termed "computer vision syndrome" by some ophthalmologists, symptoms include eye pain or redness, blurred or double vision, and headaches.
Many people are also concerned about the radiation emitted by old-style CRT monitors and the cellular radios in smartphones and some tablets, as well as the Wi-Fi radios in various devices. The research here has been contradictory, though the risk is probably low if you follow the manufacturers' guidelines for safe use.
Thanks to efforts by government agencies, trade associations, and professional groups such as the Human Factors and Ergonomics Society, people who use desktop computers are now more familiar with strategies to reduce risk by choosing equipment wisely and using it properly than they were 10 or 15 years ago. Vendors of computers, accessories, and office furniture routinely plug the ergonomic advantages of their products, and manuals often include advice about how to work with them safely.
Regrettably, awareness about risks hasn't trickled down to the world of touchscreen devices and notebooks. Here are some of the ways notebooks and mobile devices can hurt you and what you can do to prevent injury.
First up: Notebooks' health perils
For years, notebook users were forced to trade power for portability. No longer -- recent laptops rival desktop rigs in speed and storage. For many people, laptops pull double duty on the road and in offices and homes. Unfortunately, their design limits them ergonomically. Because the display and keyboard are attached to one another, you can't position them optimally at the same time.
For extended desktop use, an add-on monitor lets you place the keyboard at desktop height, with your elbows bent at a 90-degree angle and the top of the external display at about eye level, as the "Safer computing" video and "Safer computing" slideshow demonstrate. If that's too expensive, get a stand to elevate the laptop's built-in monitor, and buy a separate keyboard and pointing device.
Notebooks pose even more problems when you use them in casual settings or at an office's guest desk or a hotel room's desk, where it's harder to find positions that don't put too much stress on your neck, shoulders, arms, wrists, and hands. If you work on the road a lot, consider carrying a lightweight external keyboard and pointing device, then elevating the laptop with a phone book or other object.
If you insist on using your laptop in bed or while you're watching television on the couch, avoid the temptation to lie on your side with your head propped up on your arm: That puts stress on your neck and makes it nearly impossible to type or use a keyboard or trackpad in anything resembling a natural position. In bed, sit with your back upright, supported by a firm cushion, place a pillow beneath your knees, and angle the screen to minimize reflections from lights behind you. Even if you take these precautions, don't use the computer for more than, say, 5 or 10 minutes at a stretch without taking a break. If you have to work for more than a half-hour or so, move to a desk if you can.
Dealing with the new hazards of touchscreen devices
If notebooks tempt people to employ them in awkward ways that promote injury, tablets and smartphones almost guarantee such awkward use because they can be accessed almost anywhere and in any position -- most of which involve poor posture.
Your neck and the cervical spine that supports it are highly susceptible to poor posture, which can compress or stretch on the nerves that exit the spinal cord. Resist the temptation to bend your neck forward or backward, and especially avoid turning your head or tilting it to one side or another for prolonged periods. Take frequent breaks, and if you feel any pain, numbness, or tingling, stop what you're doing immediately and find a more comfortable position.
How to properly position the touchscreen. Unlike laptops, tablets like Apple's iPad and e-readers like Amazon.com's Kindle function vertically, horizontally, and anywhere in between. Horizontal use is typically less stressful, especially when the tablet is in a comfortable position for your arms and hands (similar to how you should use a keyboard on a laptop or desktop PC) -- though the fact the screen is positioned at or near lap level means you're likely to bend your neck, which is problematic for your posture.
Touchscreens positioned upright are ergonomically inferior. Like the futuristic computer screen that Tom Cruise's character used in the 2002 movie "Minority Report," vertical touchscreens such as in the new breed of Windows 8 PCs expected later this year (and in some current PCs) force you to use the large muscles in your shoulder and arms in ways that promote fatigue. Then-Apple CEO Steve Jobs put it aptly at a press conference in October 2010: "Touch surfaces don't want to be vertical." The more perpendicular the screen, the more you have to bend your wrist to type, a posture that anatomists call "dorsiflexion." That puts more pressure on the median nerve and the other structures in the carpal tunnel in the wrist.
Vertically oriented touchscreen monitors require you to reach forward and lift your arm against gravity, which tires your muscles rapidly. That also happens to some extent when you use a mouse or trackpad while sitting too far away from your desk, but the fix is easy: Move closer.
If both horizontal and vertical positions are problematic, what angle is acceptable? Unlike desktop computer setups, where there are well-established guidelines based on scientific research, recommendations for people who use touchscreens are scarce and sometimes contradictory because they depend on the task you're doing. For reading, it's best to place the device so that you can see the entire screen clearly. Generally, that means a steep angle close to perpendicular to your line of sight -- in other words, like that of a standard monitor. But for typing and tapping, shallow angles (about 30 degrees) are best.
Avoiding injuries from typing and tapping. The position of your wrist also affects the likelihood of injury from performing multitouch gestures on touchscreens. According to Alan Hedge, director of the Human Factors and Ergonomics Laboratory at Cornell University, the more you dorsiflex your wrist, the greater the chance of injury. But, he adds, most gestures don't require too much force, so you're usually safe as long as you don't bend your wrist excessively or repeat gestures too rapidly.
In theory, the onscreen keyboards on tablets and smartphones pose the same risks of RSIs and related injuries as physical keyboards. Currently, the main unique problem with touchscreen keyboards is their lack of tactile feedback. Unlike mechanical keys, which move and offer resistance, virtual keys don't react when they're pressed. As a work-around, manufacturers typically let you turn on audible key clicks, but that's not always effective, particularly in noisy surroundings. As a result, says Hedge, users strike virtual keys with as much as eight times the force as they tap real ones -- and all that force puts strain on your fingers, wrist, and forearm. If you have to type more than a few sentences at a time on a tablet or smartphone, consider using a Bluetooth or other external keyboard.
At the same time, onscreen keyboards confer unique advantages, not just risks, such as the ability to provide alternative layouts that place keys in less stress-inducing positions. Unfortunately, that's a benefit that vendors haven't embraced much yet.
Excessive force is sometimes an issue even if you're not moving your fingers. Holding them rigidly in anticipation of the next tap when you're taking notes on a tablet or zapping enemies in a game on your smartphone requires so-called isometric tension, which puts stress on muscles and tendons. To appreciate the effect, let your arm hang loosely at your side, with your fingers curved naturally. Now, force your finger to maintain the same position by tightening your muscles and joints. Feel the difference? As with larger muscles, the more relaxed you are, the better.
Avoiding eyestrain when using mobile devices. It seems intuitive that the more your eyes have to work to see what's on your touchscreen device, the more likely they'll suffer -- just like reading a book in dim light for hours can lead to headaches, eye pain, and other conditions. Although the physical mechanisms behind many of these conditions are surprisingly obscure, the symptoms are no less real.
In broad terms, the risk of eyestrain and similar problems from tablets and smartphones is directly related to three inherent attributes of the display: resolution (the sharpness of the image), contrast (how bright or dark characters and images are compared to the background), and brightness (how much light the display emits). Since the days of dim, low-resolution screens in early PDAs, technology has made substantial strides in all three areas, and sharp, bright displays like the one in Apple's iPhone and Samsung's Galaxy smartphones are thankfully commonplace nowadays.
But newer high-resolution screens pose problems of their own. Because they pack more pixels per square inch, they're capable of displaying ever-smaller fonts. Like the fine print on paper documents, tiny characters can be difficult to read and cause eyestrain, even if you adjust the brightness to a level that's comfortably balanced with the ambient lighting. Smartphones with touchscreens that support multitouch zooming usually let you selectively magnify text that's too small, though that gets tiresome when you're viewing a page on a handheld. Glasses tailored for reading tablet displays may help, especially if your vision has declined because of age (just as many people benefit from wearing "computer glasses" whose prescriptions are tweaked for sustained computer usage).
Environmental factors also play a role in aggravating some visual complaints. Unlike desktop workspaces, where it's usually not too difficult to find a monitor position that avoids glare from lights, mobile devices are often used in situations where the surroundings are constantly changing. As with laptops, the best you can do is to be aware of what's around you and avoid reflections. And because dryness contributes to some symptoms, avoid arid settings or ask an eye care professional to recommend lubricating drops.
Where we stand, where we're going
Health problems from laptops and mobile devices are probably underreported, in part because people don't know about the risks and may attribute symptoms to other causes. In the 1990s, heightened alertness to computer-related disorders led to a flood of complaints and spawned an industry devoted to helping suffering desktop computer users.
Although it's unlikely that we'll see a similar response to health problems caused by mobile devices, vendors are working on solutions like onscreen keyboards with tactile feedback. Eventually, we may even see smarter devices that alert us when we're using them unsafely. Until then, it pays to be aware of the hazards and take sensible precautions.