Abstract
Pulling is one of the manual material handling activities that could lead to work-related musculoskeletal disorders. The objectives of this study were to explore the development of muscular fatigue when performing intermittent pulling tasks and to establish models to predict the pull strength decrease due to performing the tasks. A simulated truck pulling experiment was conducted. Eleven healthy male adults participated. The participants pulled a handle with a load of 40 kg, which resulted in a pulling force of approximately 123 N. The pulling tasks lasted for 9 or 12 min with one, two, or three pauses embedded. The total time period of the embedded pauses was 3 min. The pull strength after each pull and rest was measured. Ratings of the perceived exertion on body parts after each pull were also recorded. The results showed insignificant differences regarding the development of muscular fatigue related to rest frequency. We found that the development of muscular fatigue for pulling tasks with embedded pauses was significantly slower than that for continuous pulls. The forearm had a higher CR-10 score than the other body parts indicating that the forearm was the body part suffering early muscle fatigue. An exponential model was developed to predict the pull strength of the pulling tasks with embedded pauses. This model may be used to assess the developing of muscular fatigue for pulling tasks.
Highlights
Musculoskeletal disorders (MSDs) have been a significant burden for both workers and industries worldwide
The ANOVA results indicated that total time periods (TT) had a significant effect on the strength decrease (p < 0.01), but the number of breaks was insignificant
The results showed that TT had significant effects on the CR-10 score of the upper arm (p < 0.05)
Summary
Musculoskeletal disorders (MSDs) have been a significant burden for both workers and industries worldwide. In 2017, there were 1.3 billion MSD cases and 138.7 million disabilityadjusted life years, a measure of lifetime with disability and the time lost due to premature mortality, in the world [1]. These numbers highlight the significance of MSD problems. MSDs occur primarily because the repetitive and/or forceful loading on the joints and body tissues while performing physical demanding tasks, such as lifting, lowering, pushing, pulling, carrying, and so on [3,4,5]. Shoulder, and wrist are the primary body parts that suffer from MSDs [6,7,8,9]
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