Potential applications of this study include ergonomic and human computer interface design strategies in reducing the exposure to risk factors that may lead to upper extremity musculoskeletal disorders.

OBJECTIVE: Tablets and other mobile devices can be tilted during use. This study examined the effect of tablet tilt angles on reading performance, target-tapping performance, wrist and forearm posture, user comfort and users' tilt angle preferences. METHOD: Ten participants used tablets alternating among four different tilt angles: 0 • , 30 • , 45 • , 60 • and a user selected angle. Head, neck, wrist and forearm postural data were collected, along with reading and target-tapping performance. Subjective, perceived impressions were gathered via Likert scale questions. RESULTS: Neck flexion decreased significantly as tilt angle increased. The extreme tilt angles, 0 • and 60 • , were least preferred while the self-chosen tilt angle, averaging about 34 • , was most preferred. Tapping performance was significantly better for the self-chosen tilt angle; however, this may be a practice effect. No effect of tilt was observed on reading performance or for forearm and wrist posture. CONCLUSIONS: Tablet tilt angles should include a range of 20 • to 50 • at minimum.

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Objective: Research has shown that fixed-split, ergonomic keyboards lessen the pain and functional status in symptomatic individuals as well as reduce the likelihood of developing musculoskeletal disorders in asymptomatic typists over extended use. The goal of this study was to evaluate design features to determine whether the current fixed-split ergonomic keyboard design could be improved. Participants: Thirty-nine, adult-aged, fixed-split ergonomic keyboard users were recruited to participate in one of three studies. Methods: First utilizing non-functional models and later a functional prototype, three studies evaluated keyboard design features including: 1) keyboard lateral inclination, 2) wrist rest height, 3) keyboard slope, and 4) curved "gull-wing" key layouts. Results: The findings indicated that keyboard lateral inclination could be increased from 8 • to 14 • ; wrist rest height could be increased up to 10 mm from current setting; positive, flat, and negative slope settings were equally preferred and facilitated greater postural variation; and participants preferred a new gull-wing key layout. The design changes reduced forearm pronation and wrist extension while not adversely affecting typing performance. Conclusions: This research demonstrated how iterative-evaluative, user-centered research methods can be utilized to improve a product's design such as a fixed-split ergonomic keyboard.