Daniel McCrobie

Effects of keyboard tray geometry on upper body posture and comfort

The effects of a downward-tilting (DT) keyboard tray on wrist posture, seated posture and self-assessed musculoskeletal discomfort were investigated in a field experiment. Thirty-eight professional office workers were studied. A pretest assessed how they typed using either a conventional keyboard on a desk or on an articulating keyboard tray, and with or without wrist rests. Workers were randomly allocated to a control (n = 15) or test group (n = 23) that used their existing keyboard in a DT system. A post-test was conducted 3 weeks later. Results showed no significant changes in wrist posture, seated posture or reports of musculoskeletal discomfort for the control group, and approximately 50% of typing wrist movements put the hand in a neutral zone. There were significant improvements in wrist posture, seated posture and upper body musculoskeletal discomfort for the test group using the DT system. Over 80% of typing wrist movements put the hand into a neutral zone with the DT arrangement. Reactions to using a conventional keyboard on a DT system were positive.

Healthy Keyboarding: Effects of Wrist Rests, Keyboard Trays, and a Preset Tiltdown System on Wrist Posture, Seated Posture, and Musculoskeletal Discomfort

A field experiment is described in which wrist posture, seated posture measured using the RULA method, and musculoskeletal discomfort, recorded by self-report questionnaires, was assessed for 38 office workers while they typed the same text. A pretest survey was conducted to assess the effects of typing with a conventional keyboard on a desk or on an articulating keyboard tray, and with or without wrist rests. Following this, workers were randomly allocated to either a control group (n=15), for whom nothing changed, or a test group (n=23) that used their existing keyboard in a preset tiltdown (PT) system. After some 3 weeks of using the PT system a posttest survey was conducted for both groups. Results showed no significant changes in wrist posture, seated posture, or reports of musculoskeletal discomfort for the control group. Significant improvements in wrist posture, seated posture, and upper body musculoskeletal discomfort were found for workers using the PT system. Workers expressed a strong preference for using a keyboard with the PT system.

Aiding Vertical Guidance Understanding

Abstract A study was conducted to evaluate training and displays for the vertical guidance system of a modern glass cockpit airliner. The experiment consisted of a complete flight performed in a fixed-base simulator with airline pilots. Three groups were used to evaluate a new flight mode annunciator display and vertical navigation training. Results showed improved pilot performance with training and significant improvements with the training and the Guidance-Flight Mode Annunciator. Using actual behavior of the avionics to design pilot training and FMA is feasible and yields better pilot performance.

Reactions to Use of a Computer Screen Glare Filter

Results from three surveys of almost 200 computer workers are described. An initial survey asked about office lighting and screen glare problems, and results served as a baseline. A second survey was conducted about one-month after two thirds of the workers received a grounded, glass screen glare filter, the rest served as a control group. The final survey was conducted about one month after the remaining control group workers received their screen glare filters. Measures of illuminance and screen luminance contrast were taken at 117 workstations. Results showed that various screen image attributes and visual health measures were substantially improved with the screen glare filter. The filter minimized electrostatic shocks to workers. Most workers liked the screen glare filter and reported improved productivity.