Now that tablet devices like the Apple iPad, Samsung Galaxy Tab, and Amazon Kindle Fire are becoming commonplace in everyday society, researchers have started examining some of the possible ergonomic impacts of these devices. After all, almost every other technological gizmo and device that has become ubiquitous in society seems to have an impact on our bodies, from desktop computer users suffering carpal tunnel syndrome and circulation problems to gamers and “Generation Text” experiencing thumb and wrist injuries. Before then, centuries of people wore down their bodies on telephone and telegraph gear, industrial machinery, looms, and countless other devices. Why should tablets be any different?
According to researchers at the Harvard School of Public Health, they aren’t. A new study (PDF) published this month in Work: A Journal of Prevention, Assessment, and Rehabilitation is among the first to look at the possible ergonomic impacts of tablet use, and there’s good news and bad news. The good news is that tablet users seem to shift position and move around more than folks locked in to traditional desktop and notebook computers. The bad news is that most common ways of holding and using tablets seem to put considerable strain on users neck muscles — especially compared to typical desktop computing setups.
What did the Harvard team find, and what can tablet users do to protect themselves?
The Harvard study is among the first to look at the ergonomics of using a tablet, and its scope is necessarily limited: It only examines the effects of tablet use on the head, neck, and shoulders while seated in a relatively deep lounge-style chair, with a slightly reclined back and no arm rests. A myriad of other parts of the body (like the hands, arms, and the back) weren’t considered, nor were a number of other postures and ways people use tablets, such as standing, walking, lying flat, perched on a stool, crammed into an airplane or bus seat, and many more.
To look at the effects of tablet use, researchers wired up subjects with a infrared three-dimensional motion analysis system (think of it as something akin to the motion capture systems used in movies), and asked subjects to perform a range of tasks with tablets in four different positions:
- Lap Hand: User holds the tablet in their lap without a case, supported (or not) by their hand
- Lap Case: Tablet sits on the lap with its case set to its lowest angle
- Lap Table: Tablet rests on a table with its case set to its lowest angle
- Table-Movie: Tablet rests on a table with its case set to its highest angle (for media viewing)
The researchers came up with four basic tasks—Internet browsing and reading, playing a game (solitaire), composing short replies to email messages, and watching short videos. Not all tasks were performed in all positions. The video-watching task, for instance, was exclusive to the Table-Movie position. Subjects didn’t watch videos in the other positions, nor did they have to surf the Web, play a game, or write email in the Table-Movie position.
So what tablets were used? The researchers picked two: an Apple iPad 2 with a Smart Case running iOS 4.3 and a Motorola Xoom tablet with Motorola’s Portfolio Case running Android 3.0.
The tilt angles offered by the cases are quite a bit different: the iPad Smart Cover can handle tilt angles of 15° and 74°, while the Motorola Portfolio case does angles of 45° and 63°. As we’ll see, that might make a big difference.
Overall, the researchers found that subjects came closest to generally-accepted neutral ranges of head and neck flexion in the Table-Movie posture, with the neck being well within neutral values and the head falling just inside it. However, for the three other postures, subjects’ head and neck flexion fell some 15 to 25 degrees outside the neutral range. Users tend to hold their heads out and look downward when using a tablet on their laps or on a tabletop. That, in turn, puts stress on the neck muscles, far more strain than someone using a traditional computer, who can maintain a more-or-less neutral position where the weight of their head is supported by the bones of the neck and spine, rather than muscles.
Generally speaking, using a tablet on a tabletop (the Table-Case posture) rather than a lap resulted in a lower cranio-cervical angle — meaning their heads tended to be more aligned vertically with their spines.
However, there were significant variations between the iPad and its Smart Cover and the Motorola Xoom and its Portfolio Case, and they don’t bode that well for iPad users. Angles of neck and head flexion were significant higher for the iPad 2 with Smart Cover in both the Lap-Case and Table-Case postures when compared with the Xoom and its case. Presumably, the Smart Cover’s lower angle (25° compared with 45°) meant users held their heads and necks at at more of an angle. Similarly, the researchers found iPad users had a significantly lower gaze angle in the Lap-Case and Table-Case postures. Researchers also found that iPad users put the iPad significantly lower and closer to them than they put the Xoom in the Lap-Case and Table-Case postures — again, probably influenced by the Smart Case’s flatter orientation. Researchers found that subjects consistently positioned the Xoom so their viewing angle of the tablet was nearly perpendicular for all four postures, meaning their view of the tablet’s screen was more-or-less flat. However, in the Lap-Case and Table-Case postures, iPad users tended to have a more oblique view of the screen.
Just in case
Although the study only examines a few ergonomic factors associated with tablet use, one result that jumps out is that cases make a big difference if you’re going to use a tablet on a table or on your lap. Although Apple’s Smart Cover offers two significantly different viewing angles, its shallow 25° tilt intended for typing seems to make users more prone to hunching over their tablet, putting strain on their neck. (That’s not to knock Apple’s Smart Cover exclusively; the same thing likely applies to other tablet cases that offer shallow use angles.) However, that doesn’t necessarily mean a steep tilt is better. It doesn’t take much more than a glance at someone using a tablet at a 45° angle on a tabletop to realize trying to use an onscreen keyboard at such a tilt is difficult— and likely hard on the wrists over time.
Another interesting finding is that the only posture in the study where subjects exhibited neutral values for their neck and head angles was the highly-angled, passive Table-Movie posture. Put another way, the least stressful way to interact with a tablet is not to interact with it at all: Just prop it up and look at it.
As more people rely on tablets for everyday communications and tasks — and are using them to replace things like netbooks, notebooks, and even traditional desktop computers — they’re spending more and more time with the devices, increasing their risk of stress and injury from prolonged use. So, the best advice for using a tablet over the long term likely derives from all the ergonomics lessons we’ve learned from PCs, gaming, and other tasks:
- Try to keep your upper body posture neutral and well supported. Keep your neck straight, your shoulders relaxed, and your arms positioned near your sides.
- Part of the “tablet hunch” comes from placing them them well below the field of vision when we’re in a neutral posture. If you’re using a tablet for a long time, consider adjusting your seating or the position of the tablet so it’s at or just below your field of vision when you hold your head and back at a neutral angle. That may mean positioning the tablet well above a table or desk surface, just like many people do with notebooks (with or without desktop docking stations).
- It may look silly, but for long periods of use, using a separate keyboard rather than on on-screen keyboard is probably a good idea to help maintain good ergonomics. You don’t have to take it with you everywhere you go like some 21st century version of a pocket protector, but if you find yourself doing long writing or messaging sessions on a tablet, a keyboard might be a good idea.
- Move around. Tablets are inherently portable devices, and people take them everywhere they go, so that means tablet users are more likely to shift position, get up, walk around, and change their posture than a typical desktop PC user who might stay in a chair for hours at a time. Whether using a desktop, notebook, gaming console, or tablet, frequent breaks to stretch, move around, and get blood flowing are critical. Use it or lose it.
Reports have the Harvard team next looking to examine the effects of tablet use on the arms and wrists, which could be even more interesting. And, just in case folks were wondering, the study was partially funded by Microsoft, which is looking to make a big splash in the tablet market with Windows 8 later this year. (Although two Microsoft researchers helped design the study, they didn’t participate in data collection or analysis.)
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