Effect of armrest positioning and workspace constraints on muscle activity for touchless gestural controls

The recent development of affordable technologies now allow touchless gestural controls to be integrated in common computing environments, however, ergonomic issues (user fatigue, in particular) have not been solved. This experiment investigates shoulder muscle activity for different traditional supported or user-preferred touchless gesture interaction scenarios and quantifies the location that touchless gestural control users would like to position armrests in different gestural workspaces. A custom hand/finger-based gestural control system was developed using a motion tracking system. Users browed an online shopping website while a prototype office chair allowed them to positon armrests easily in a wide space in front of themselves. Results show that median muscle activity of the upper trapezius, medial deltoid, and anterior deltoid are significantly affected by armrest configuration. User-preferred armrest positions generally reduced muscle activity compared to traditional positions, but this reduction was greatest when the gesture space is constrained over the desktop. In those conditions, average user preferred positioning of the armrest was higher and closer to the sternum of the user.