The standardized SMS message task (B) was performed by all 56 subjects and 24 of the 56 subjects performed all tasks (A–E).
The subjects were instructed to sit and stand using the same positions and working techniques that matched how they used their mobile phones in real life. The chair used in sitting tasks had a backrest, and armrests and no wheels. The subjects‘ hand size (width and length) was measured according to Pheasant (Pheasant, 1986) and a video documentation was made of the subjects’ posture during every task.
The muscular load in six muscles in the right forearm/hand and both shoulders were registered by electromyography (EMG) and thumb position and movements in the right thumb were registered by an electrogoniometer during each task.