Design of a horizontally dynamic armrest for joystick controlled mobile equipment

BACKGROUND: Joystick operators often experience constant low level muscle loading in the upper limb when using joysticks, which can lead to repetitive strain injuries. It has been hypothesized that the strain on the muscles may be reduced by supporting the arm during joystick manipulation. OBJECTIVE: To design a horizontally dynamic armrest which appropriately supports the motion of the forearm during sideto-side joystick movements. METHODS: The paper describes the process used to design a dynamic armrest which appropriately supports an operator’s arm throughout the range of side-to-side joystick movements. RESULTS: The trajectory of the elbow and wrist during these joystick movements was determined, and a new horizontally dynamic armrest designed and built. CONCLUSIONS: Most heavy mobile equipment seat armrests fail to provide appropriate support throughout the range of joystick motion resulting in constant upper body muscle loading. Our paper describes the development of a dynamic armrest which is designed to provide appropriate support throughout side-to-side joystick movements.