Abstract:

Objective In order to promote the musculoskeletal health of the workers and understand the situation of work-related musculoskeletal disorders（WMSDs） in a certain biopharmaceutical factory in Tianjin，this study intends to conduct on-site surface electromyography（sEMG） measurement on the workers，focus on analyzing the key points and measures of quality control，put forward suggestions for prevention and control measures，and explore the measurement and evaluation methods. Methods From October to December 2024，all 5 workers（S1-S5） in the parts assembly and finished product packaging position were selected to measure the left extensor carpi ulnaris（L-ECU），right extensor carpi ulnaris（R-ECU），left flexor digitorum superficialis（L-FDS），and right flexor digitorum superficialis（R-FDS） with fatigue symptoms under the normal working conditions at the workplace. The measurement process covered a complete operation process，MegaWin（3.b-10） software was used to calculate the root mean square（RMS） for time-domain analysis，and the median frequency（MF） and mean power frequency（MPF） were calculated for frequency-domain analysis. Results The RMS of all four muscles of S1，S4，and S5 increased significantly（all P<0.05），with an increase range of 13-48 μV and an average increase of 24.5 μV. The MF and MPF of all four muscles of S1 and S4 shifted significantly towards the low-frequency direction（all P<0.05），with a decrease range of 2-5 Hz. MF decreased by an average of 4 Hz，while MPF decreased by an average of 3 Hz. It was determined that the muscles of S1，S4，and S5 did not show fatigue sign with significant strength decline，but they were already in the initial stage of fatigue. The 4 muscles of other workers did not show significant fatigue. Conclusion The sEMG signals of all workers were successfully measured and analyzed. The muscle fatigue of S1，S4，and S5 was early warned. The variation of RMS，MF，and MPF may be related to the contraction of individual muscle fibers，the recruitment and firing frequency of motor units，and the process of muscle fatigue. The quality control measures for sEMG measurement in the workplace were proposed，primary/secondary/tertiary prevention suggestions were put forward for the fatigued workers and the practical significance of on-site sEMG measurement in the workplace and the future development of fatigue measurement were discussed.

Key words: Work-related musculoskeletal disorders, Surface electromyography, Fatigue, Prevention, Workplace, Quality control