EMG Study on the Effect of a New Armrest on Neck, Shoulders and Arms

We have developed a new armrest (NA) with adequate width supporting forearms, inclining upper surface, an area for mouse, and fixers at the edge of a shallow desk. We compared the cervicobrachial load among NA, NA with a mouse-pad (NAM) and a conventional palmrest with a mouse-pad (PRM) during word processing work. Seventeen healthy subjects operated a word processor for 1-h, alternately using 3 devices. EMG and subjective pain scores (PS) were recorded mainly from the right-side upper limb. EMG of the trapezius in PRM was significantly lower than in NAM; EMG of the anterior deltoideus (DELTa) in NA lower than in NAM; EMG of the medial deltoideus (DELTm) in NA lower than in PRM. The shoulder PS in NA/NAM was significantly lower than in PRM; the upper arm PS in NAM lower than in PRM; the forearm PS in NA/NAM lower than in PRM. These results suggest that NA reduces the cervicobrachial load than PRM.