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Upper trapezius muscle activity patterns during repetitive manual material handling and work with with a computer
1Department of Research on Monotonous Repetitive Work, National Institute of Occupational Health, Copenhagen, Denmark. cj@ami.dk
Summary
This study found that computer mouse use in CAD operators leads to more continuous and repetitive upper trapezius muscle activity, increasing the risk of shoulder symptoms. Production work also showed repetitive EMG patterns, suggesting potential musculoskeletal risks.
Area of Science:
- Occupational Health
- Ergonomics
- Biomedical Engineering
Background:
- Repetitive tasks and static muscle load are risk factors for musculoskeletal disorders.
- Understanding upper trapezius muscle activity is crucial for assessing occupational risks.
Purpose of the Study:
- To investigate upper trapezius electromyography (EMG) activity differences between industrial production workers and computer-aided design (CAD) operators.
- To compare EMG patterns on the mouse-operating side versus the non-mouse side in CAD operators.
Main Methods:
- Recorded upper trapezius EMG activity in industrial workers and CAD operators during typical work tasks.
- Utilized Exposure Variation Analysis (EVA) to assess EMG pattern repetitiveness.
- Compared EMG data between mouse and non-mouse sides in CAD operators.
Main Results:
- EMG levels and gap frequencies were similar across different work tasks, suggesting load may be independent of movement frequency.
- CAD work showed more static muscle activity, while production work exhibited more repetitive EMG patterns.
- The mouse-operating side in CAD users displayed significantly lower EMG gaps and more repetitive activity compared to the non-mouse side.
Conclusions:
- Both production and CAD work present distinct EMG patterns that may contribute to musculoskeletal symptoms.
- Increased continuous and repetitive upper trapezius muscle activity on the mouse side of CAD operators likely explains the higher prevalence of shoulder symptoms.