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Special Interest Magazine: Tablet Computer Injuries

avoiding repetitive strain injuries when using an electronic stylus

Magazine feature originally written for the Repetitive Strain and Overuse Injury Society.

Hand-held tablet computers are increasingly popular forms of technology that enable easy access to all the benefits of the Internet and on some devices even telephone contacts. However, tablets currently do not conform to any standard of ergonomics. A tablet can be designed to look sleek and operate smoothly, but not be functionally shaped for easy use in your hands. The finger tapping required for touch screens can add an additional level of stress to your body.

The research study “Holding a tablet computer with one hand” published in the Proceedings of the Human Factors and Ergonomics Society Annual Meeting reports that smaller tablets and styluses tapered from thick tops to smaller tips are considered most comfortable to hold and use.

Desktop computers and keyboards have undergone ergonomic review and adjustment over time, but newer technologies have not yet undergone the same scrutiny. The 1995 regulations from the United States Department of Defense advised that hand-held equipment should weigh less than 2.3kg and be smaller than 100mm high by 255mm deep by 125mm wide.

These weights and dimensions seem irrelevant to the increasingly thin, modern style of devices we are accustomed to using, and make no statement about the most ergonomic shape of the device. Although our modern tablet computers are small and lightweight, their shape and the way we hold them make ergonomic assessment essential.

Tablet computers are often held in the user’s non-dominant hand while the user operates the device with their dominant hand. Shoulders, necks, and thumbs are most often the sites of pain associated with cellphone texting, which requires similar biomechanics to using tablet computers. Additionally, users flex their necks and slouch their backs more when using a tablet than when using a desktop computer. Over time, the poor posture and shorter viewing distance can create back pain and vision problems.

The shape, size, and weight of different tablets were evaluated for ease of use in the research study, conducted as a collaboration between researchers at University of California Berkeley, Microsoft, and Synaptics, an American company that designs laptop mouse pad and touch-screen interfaces.

For users with decreased dexterity in their fingers, a stylus can be more comfortable and accurate than finger- tapping the screen. Gripping the stylus with the hand for extended times can create its own problems, though. Therefore the diameter and shape of different styles of stylus were also included in the study.

The research team designed non-functional models of some popular tablets, like the iPad (large tablet), Kindle (medium tablet), and Samsung Galaxy Note (small tablet). In addition to size, the researchers added differently shaped backs to the models to test if adding a handle to the standard flat back of the tablet affects a user’s comfort. Three different models of styluses were also included to evaluate which size and shape is most comfortable to use: thick like a large marker, thin like a pencil, or tapered from thick at the top to thin at the tip. The researchers observed thirty different study participants complete a variety of typing tasks using the tablets and then asked the users to complete surveys about their comfort or discomfort after using the device. The study participants also wore sensors to measure the activity of five different muscles in their forearms.

The small model tablet received better rankings for all parameters in the study than the medium and large model tablets, including requiring less muscle activity and creating less discomfort for the user. Adding a handle to the back of the large tablet did make holding the large tablet more comfortable, but the small tablet was just as comfortable to hold with or without a handle.

Holding a tablet in the portrait or landscape orientations did not change the study participants’ typing efficiency, but the portrait orientation required less wrist extension and was more comfortable for the shoulder and forearm. The research also revealed that when study participants felt more confident and secure that they would not accidentally drop the device, their comfort ratings improved. Indeed, the psychology of how users hold their tablets is as important as the mechanics.

The tapered stylus received better rankings than the thick (second best) and thin (worst) stylus models. The researchers attribute the popularity of the tapered stylus to it not requiring as much of a pinch grip as the thin stylus and being lighter than the thick stylus. Although not mentioned in the research article, the popularity of the tapered stylus suggests that perhaps the shape of pen or pencil we write with when not using our electronic devices is something to consider.

Older individuals are considered at higher risk for the types of repetitive strain injuries related to tablet use because of their greater propensity to injury, but the small joints of the hand and wrist make it susceptible to injury at any age. Taking breaks while using a tablet, or any device, for long periods can give the entire body – back, shoulders, arms, and hands – a chance to return to more natural or comfortable positions and reduce the risk of developing overuse injuries.

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