Cognitive performance and muscle activation in workers with chronic shoulder myalgia

The present study determined whether workers with chronic shoulder myalgia exhibit impaired cognitive performance and elevated muscle activation. Ten workers with and 10 without shoulder myalgia performed three sessions, each consisting of three different cognitive tasks. Subjective pain was reporte d on visual analogue scales (VAS). Surface electromyography was recorded bi laterally from the trapezius and forearm extensor muscles. Speed and error rates of the cognitive work were almost the same in the two groups, but the myalgia subjects reported more stress during the work. In two of the cogni tive tasks, both groups increased their speed of performance to the same ex tent from the first to the third session, despite pain increase in the myal gia subjects. In the biomechanically demanding task, the speed fell from th e first to the third session in both groups. Muscle activation was equal in the two groups and constant throughout the protocol despite changes in spe ed of performance and pain. It is concluded that localized chronic muscle p ain does not significantly alter cognitive performance, or muscle activatio n level during cognitive work. However, the perceived burden of work is lar ger, as indicated by the higher stress reported during cognitive work in th e myalgia subjects compared with their pain-free controls.