The effects of stiffness and speed on upper limb electromyography during joystick use

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Northey, Greg Warren

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University of Guelph


The manipulation of joysticks to control heavy machinery requires a wide range of repetitive wrist and upper limb positions and motions, all of which can increase the operator's susceptibility to repetitive strain injuries. The purpose of this study was to analyse muscle activation using surface electromyography (EMG) on eight muscles of the upper limb during joystick manipulation. Eight subjects performed a series of motions at two different speeds on three joysticks with varying stiffness. Two EMG activation variables (integrated EMG (iEMG) and average peak EMG) were statistically analyzed to assess the effects of speed, stiffness and motion on EMG activation. Results indicate that every joystick motion requires at least a constant low level (between 2-5% MVC) muscle activation for all muscles. In addition, wrist postures at the extremes of joystick motion and shoulder strain due to armrest design appear to contribute potentially to the development of long term muscular pain and injury.



joystick use, uper limb, electromyography, stiffness, speed