A Method to Measure Discomfort of Static, Submaximal Force Exertion

Abstract

The degree of discomfort during force exertion is little investigated in literature. In daily life, however, comfort is an important aspect when using or operating products. It would therefore be useful for designers to know about the subjective experience of (dis)comfort during the exertion of submaximal forces by users of products. No standard measurement methods were found in literature. Two experiments have been carried out, using different methods. The first experiment was combined with the measurement of endurance time at different force levels and in four different postures. Subjects were asked every half minute to rate the discomfort they experienced on a five-point scale. Alas, the results generated by this method were found to be not sufficiently reproducible. The second experiment was set up in such a manner as to prevent subjects thinking explicitly about their feelings. This time, only one posture was investigated (pushing with the arm) and a spontaneous change of posture was taken as an indication of discomfort. The time to the first change increased consistently with lower force levels and these results proved to be sufficiently reproducible. Therefore this measurement method is recommended to get an idea about the level of discomfort experienced by subjects. A formula is given to indicate the relation found between the force level and the median of the time to the first change of hand.