Reliability of myoelectric trapezius muscle activity in repetitive light work.

The aim of this study was to evaluate the reliability of selected electromyographic (EMG) parameters describing the muscle activity in repetitive light work. EMG from the trapezius muscle of twelve female workers were recorded during a 20-min work session, morning and afternoon; Monday, Wednesday, Friday and the following Monday. The estimated reliability coefficient was 0.59 for static muscle activity and 0.85 for short interruptions in muscle activity (EMG gaps) during work. The reliability coefficient was 0.94 for the EMG signal's average median frequency of test contractions associated with the work session. The median frequency declined significantly during the work session. No time trend was found during the day or the week for these parameters. Consequently, it is possible to get representative measurements of the mentioned EMG parameters during repetitive light work by a recording taken at any time of the day or week.