Operation of controls on consumer products by physically impaired users

The self-reliance of the physically impaired can be seriously jeopardized by their inability to operate everyday products, especially if both upper extremities are impaired. To determine the difficulties impaired users encounter in operating consumer product controls, on-site video recordings were made of subjects suffering from arthritis or a muscular disease. Subjects' force exertion was compared with that of a group of nonimpaired users. The resulting inventory allowed the analysis of the manipulation problems faced by impaired subjects and the development of design recommendations. In this study the force exerted by the subjects and that required to operate the controls were measured. A comparison of the results of these force measurements led to a number of conclusions. This study led to the following design recommendations: the amount of force required to operate controls should be kept as low as possible; the user should not be required to make two manipulations at the same time, such as simultaneously pushing and rotating a control device; pushing is preferable to rotating; and there should be a great degree of freedom to manipulate controls.