We’re used to staring at computer and laptop screens, so it’s easy to think that using the iPad and other touch-screen devices is a no-brainer. But according to a team of researchers from Harvard School of Public Health, Microsoft and Brigham and Women’s Hospital, the use of media tablet computers is associated with high head and neck flexion postures, leading to muscular stress and pain.
People who use tablets tend to use them in positions that could mean “more of a concern for the development of neck and shoulder discomfort,” said Jack T. Dennerlein of Harvard and the study’s lead investigator. The study is “Touch-Screen Tablet User Configurations and Case-Supported Tilt Affect Head and Neck Flexion Angles.”
One significant difference between tablet and desktop or notebook computers is that a tablet’s touch screen integrates display and user input. Instead of just looking at the screen, the user touches it, and generally does so from varied positions—and the sudden popularity of the device means no one has really assessed the best ways to use it ergonomically, the researchers noted.
The inherently flexible, portable nature of the touch-screen tablet makes it easy to use in ways that can cause neck and shoulder pain. Lying on the couch, sitting propped up in bed, at a table—using a tablet in nearly any position can be at the whim of the user.
Because computer work has been and continues to be associated with neck and shoulder pain, many studies have examined how the positioning of the display or monitor affects neck and shoulder posture and muscle activity. Studies have shown that the higher the display, the lower the incidence of head and neck flexion. When a device’s display is lower down, the vantage point led to a higher degree of flexed postures, and an associated increase in neck and shoulder activity and pain. As a result, using a monitor in a very low position could be a factor in neck and shoulder pain.
The purpose of the study was to investigate head and neck posture for various positions common in typical tablet computer use, and how head and neck posture varies with different tablets and their case designs, with different tilt angle settings.
Fifteen experienced tablet users completed a set of simulated tasks with two media tablets, an Apple iPad2 and a Motorola XOOM. Each tablet had a proprietary case that could be adjusted to prop up or tilt the tablet computer. The Apple Smart Cover allows for tilt angles of 15° and 73°, and the Motorola Portfolio Case allows for tilt angles of 45° and 63°. Four user configurations were tested: Lap-Hand, where the tablet was placed on the lap; Lap-Case, with the tablet placed on the lap in its case set at the lower angle setting; Table-Case, with the tablet placed on a table with its case at the lower angle; and Table-Movie, with the tablet placed on a table with its case at the higher angle.
During the experiment, users completed simple computer tasks such as Internet browsing and reading, game playing, e-mail reading and responding and movie watching. Head and neck postures and gaze angle and distance were measured using an infrared three-dimensional motion analysis system.
Head and neck flexion varied significantly across the four configurations and across the two tablets tested. The iPad2 was associated with more flexed postures when it was placed in its case. This appeared to be driven by differences in case design, which drastically altered the tablet tilt angle and the corresponding viewing angle. For both tablets, the gaze angle changed in a similar fashion to the head flexion across all configurations, with nonperpendicular viewing angles causing increased head and neck flexion. Head and neck flexion angles were greater, in general, than reported for desktop or notebook computing.
Only when the tablets were used in the Table-Movie configuration, where devices were set at their steepest case angle and at the greatest horizontal and vertical position, did user’s posture approach neutral. This suggests that tablet users should place the tablet higher, on a table rather than a lap, to avoid low gaze angles, and use a case that provides steeper viewing angles. But the suggestion comes with a caveat: Steeper angles may be detrimental for continuous input with the hands.
Further studies on the effects of tablet and configuration on arm and wrist postures are needed, Dennerlein said. He noted that the results will be useful in updating ergonomic computing standards and guidelines for tablet computers, which “are urgently needed as companies and health care providers weigh options to implement wide-scale adoption of tablet computers for business operations."
The study is available here.