Selection of Convenient Locations for the Placement of Push- and Rotary-Type Controls

The purpose of this study was to describe the most convenient areas for operating push- and rotary-type controls that are commonly used in various electric appliances. The participants were ten males (Mean age = 21.7 years, SD = 0.5 years) with no history of trauma and no medical history of abnormal motor function. The push- and rotary-type controls were set on the intersections of a specified grid with six conditions in the anterior direction (40%, 60%, 80%, 100%, 120%, and 140%) and nine conditions in the left–right directions (−75%, −50%, −25%, 0% [median sagittal plane], 25%, 50%, 75%, 100%, and 125%) based on the ratio of the maximum reaching distances of the participants. The participants pushed and rotated the controls to adjust the height of a red bar to a white target line displayed on a monitor. The participants reported the subjective ease of operation of the controls as follows: push control from 0% to 25% in the left–right direction from 60% to 80% in the anterior direction, rotary control of 25% in the left–right direction, and 80% in the anterior direction, regardless of whether they used the dominant or the non-dominant limbs. Our results indicate that the most convenient locations for the push- and rotary-type controls could be calculated by the maximum reach distance of the upper limbs using the above ratios.