Upper limb repetitive movement risk assessment by means of semg parameters

The aim of the study was to provide a biomechanical risk assessment in a mechanical engineering industry using sEMG fatigue parameters. Two experienced right-handed workers were enrolled for the study. sEMG signals were recorded bilaterally from the following upper limb muscles: middle Trapezius, anterior Deltoid, lateral Deltoid and long head of Biceps Brachii. The envelopes of the activity of each muscle were computed as a percentage of the Maximal Voluntary Contraction (%MVC). We also computed Root Mean Square (RMS) and Median Frequency (MDF) to investigate localized muscle fatigue. For the studied workstations, right muscles were more involved than left ones and consequently by means of JASA fatigue plot we observed more fatigue events in the right than in the left upper limb in both workers. Results showed different muscular behavior for each workstation and specific motor patterns. Despite the fact that the mean cycle activity failed to exceed 10% of MVC, activity peaks frequently reached up to 30% of MCV. These short-term peak values could be the cause of increased biomechanical risk. By studying sEMG fatigue parameters, it is possible to obtain a more detailed risk assessment and to provide insight towards workstation improvements.