Abstract
In order to analyse writing work which was considered to be continuous burdens of the hand-arm-shoulder system, the electromyogram (EMG) of the shoulder and the arm on the writing hand side using surface electrodes and the writing pressure were observed during writing performance. Factors associated with writing such as writing tools (a ball-point pen and a pencil of hardness of HB) diameters of pen-holder (7 mm and 11 mm), number of sheets of paper (1 and 3) and sex difference were analysed quantitatively with the experimental design method. Above all, the muscular tension and the writing pressure during a 20 min writing were examined. The subjects were asked to write, through hearing from a loud-speaker, one Japanese "kana" leter per 1 sec under the usual writing pressure or the writing pressure above the given minimum value of 0.13 kg.
It can be concluded that the burden of muscles of the arm and the shoulder caused by the pencil is lighter than that by the ball-point pen and the burden of shoulder muscles indicates spectrum change in the low frequency components of EMG below 20 Hz even in 20 min continuous writing. The larger diameter pen-holder and the thicker sheets of paper promote increase of muscular tension which may induce muscular fatigue. The writing pressure which shows spectrum of 1-7 Hz also endorses these findings.
