Objective This study aimed to investigate the correlation between typical muscle load levels and muscle fatigue of tunnel-construction workers during tunnel waterproofing operations using surface electromyography (sEMG). The findings will provide a methodological foundation for the objective assessment of muscle fatigue.
Methods Using the field experiment method, nine nail-gun operators were selected from the tunnel waterproofing operations site in April 2023. The surface electromyography signaling of their brachioradialis, biceps, and triceps in the whole process of the tunnel waterproofing operations was gathered using sEMG, and their rating of perceived exertion (RPE) was surveyed with the questionnaire. An analysis was conducted to determine the relationship between time-domain and frequency-domain indicators of the target muscles and the RPE scores. The JASA method was employed to analyze the local muscle fatigue of the workers.
Results The electromyographic data of nine workers under the same fatigue degree (calculated by RPE score) were in the normal distribution (P > 0.05). With the gradual increase of the RPE score, the percentage of maximal voluntary electrical activation (MVE) of the brachioradialis showed a trend of initially rising, subsequently falling, and then rapidly increasing;the MVE of the biceps showed a fluctuating upward trajectory;and the MVE of the triceps showed a trend of first decreasing, then rapidly rising, and then decreasing. With the gradual increase in RPE score, the corresponding media frequency (MF) of both the brachioradialis and biceps showed a trend of initially increasing and then decreasing, while the MF of the triceps showed a fluctuating downward trend. There were statistically significant differences in both MVE and MF of the brachioradialis, biceps, and triceps among different groups with varied RPE scores (P < 0.01). Fatigue occurred in the brachioradialis at RPE scores of 10, 15, and 17; fatigue in the biceps at RPE scores of 13, 14, 16, and 17; and fatigue in the triceps at RPE scores of 11, 12, 13, 14, and 15.
Conclusions The time-domain and frequency-domain signals of surface electromyography were consistent with the subjective RPE score survey in judging the current muscle fatigue state of the workers by the JASA method. Nevertheless, challenges still remained in applying sEMG technology to real-world operational settings, necessitating further research.
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