The Effect Of Task Complexity And Time Pressure On Trapezius Muscle Activity

Shoulder-neck pain is a kind of Work-related Musculoskeletal Disorders(WRMSD) .Most of previous research mainly investigated the risk factors aboutshoulder-neck pain from epidemiology , biomechanics or physiology. But recentresearch reveal there is a relation between psychosocial factors and shoulder-neck pain,for example, trapezius muscle activity is mainly influenced by psychosocial factors.Three experiments were included. The effects of task complexity on trapezius muscle activity were explored in Experiment One. The effects of time pressure on trapezius muscle activity were considered in Experiment Two. The effects of time pressure on trapezius muscle activity in keyboard typing were investigated in Experiment Three.Some major results were revealed:Firstly, task complexity influenced trapezius muscle activity. Averaged electromyography (AEMG)was significantly increased with task complexity, but Mean power frequency (MPF ) and Median frequency (MF) hardly changed in the experiment.Secondly, time pressure had a significant effect on trapezius muscle activity, but the load on left and right trapezius muscle wasn't equal in keyboard typing.Thirdly, there was consistency between heart rate and AEMG in reflecting the change of psychology load, but sensitivity of AEMG was better than heart rate's in low work load.Fourthly, subject discomfort and AEMG showed no consistency, subject discomfort couldn't completely reflect the change of trapezius muscle activity in low work load.It is concluded that in low work load, the effects of task complexity and time pressure on trapezius muscle activity are significant, which maybe is one of risk factors induced WRSMD.