Abstract
It is argued that Repetitive Strain Injuries (RSI) form a typically multi-factorial syndrome of complaints with muscular overuse, non-neutral and static postures together with enhanced muscular activation and cocontraction as the primary ingredients for a take-off of the pain and fatigue complaints. It is hypothesised that in a further stage of development of the syndrome it are hormonal and neural disturbances of the stress response system (HPA-axis) that are responsible for the continuation and the persistance of the complaints. In an experiment that focussed on the primary steps of our etiological model it was found that cognitive task load in the form of a memory load has significant impact on the overall level of muscular activation. Both agonist and antagonist muscles exhibited higher levels of EMG activity in a condition of stress. In addition to this finding it appeared that participants with high scores on Spielberger's test for trait and state anxiety manifested higher cocontraction scores. Literature findings on RSI and the results of the present experiment are discussed from the perspective of a recent theory on stress and human performance developed by the senior author and co-workers. This neuromotor noise theory predicts that physical as well as cognitive stressors both lead to higher levels of muscular activation and limb stiffness. The latter stiffness response is considered being a natural response to the impoverished signal-to-noise ratio in the neuromotor system as a result of neural dissemination of neuromotor noise.
