Computer screen work: effects of working postures and pointing devices on energy expenditure, biomechanical stress on the upper-limb , task performance and user perception

Background and Objectives The most commonly observed working posture among computer-based employees is sitting on an office chair. If prolonged, this posture leads to sedentary behavior, which is harmful to health. In order to limit exposure to this occupational risk factor, several alternative working postures have emerged in recent years. However, these postures, often more dynamic, may affect the use of pointing devices. The standard mouse, placed next to the keyboard, is the most frequently used pointing device. Nevertheless, its intensive use is associated with risk factors for discomfort, pain, and even neck and upper-limb musculoskeletal disorders (MSDs). To reduce the biomechanical stresses associated with its use, new pointing devices have been developed. The objective of this laboratory study was to jointly analyze the effects of different working postures and several pointing device configurations, using multiple outcome measures related to sedentary behavior, discomfort, pain, or MSDs, work performance and users' perceptions. Methods Thirty-one right-handed women took part in this study. Twenty experimental conditions were analyzed: five pointing device configurations (standard and slanted mice placed next to or in front of the keyboard and a central pointing device) combined with four working postures (sitting on an office chair, sitting on an exercise ball, pedaling on an ergocycle and standing). After a training period, participants completed one experimental day during which they performed a pointing clicking dragging task lasting approximately 30 seconds, repeated five times in each of the 20 conditions. Energy expenditure, heart rate, biomechanical stresses (muscle activities and joint angles), task completion time and users perceptions were assessed. MAIN RESULTS Compared to sitting on an office chair, the three alternative postures induced increased energy expenditure and heart rate, with more pronounced effects observed for the cycling and standing postures. During this short experimental task, the standing posture appeared preferable with regard to lumbar muscle activity, whereas sitting on an office chair and standing postures appeared preferable with respect to trapezius muscle activity. The use of a central pointing device and the placement of the mouse in front of the keyboard reduced biomechanical stress on the dominant upper limb. However, regardless of the pointing device configuration, a risk of wrist extensor muscle fatigue was observed. Task completion time was shortest when sitting on an office chair and when using a standard mouse placed next to the keyboard. DISCUSSION No single working posture or pointing device configuration was found to be beneficial across all measured variables. However, with regard to biomechanical stress on the dominant upper limb, the central pointing device and mouse placement in front of the keyboard appear preferable. Furthermore, our results suggest that standing and cycling postures represent the most interesting alternatives for reducing sedentary behavior.