Upper limb muscular assessment in a workshop of welding workers - case study

Welding has one of the highest prevalence of musculoskeletal disorders (MDS) and clinical diagnosis. According to some studies, the disorders related to the activity are in the shoulders, neck, and low back, primarily by work in static load in postures above the shoulders. This study is focused on welding in joints and prefabs workshops in real working conditions. After an ergonomic diagnosis, and according to the literature, a muscle evaluation was performed using surface electromyography (sEMG) in a sample of three subjects without any upper limb diagnosis. The muscles evaluated were trapezius, deltoids, extensor carpi ulnaris and radialis, flexor carpi ulnaris and radialis in the dominant arm. The measures were 30-60 minutes, depending on the welding piece. The equipment used was the Biometrics DataLOG (MWX8) and six EMG sensors (SX230). The data processing was following the SENIAM standardized norm. As a result of the assessment, the trapezius and the flexor carpi radialis presented the highest mean muscular activity, 20.92% and 24.43%, respectively, according to the maximum voluntary contraction (MVC) evaluation. The static load should not exceed 15% of the muscular activity; if it is exceeded, it could lead to the development of musculoskeletal disorders. It was found that the muscular activity associated with welding is risky, especially in the cervical region. To improve the working conditions in a workshop for muscular activity and the postural condition, it is recommended to implement a hydraulic press to adjust the working height.