A recent thesis from Laurea University of Applied Sciences presents an insightful pilot study on low back extensor muscle activity in various lifting, transfer, and carrying tasks. Using electromyography (EMG) with the innovative MBelt system, researchers measured muscle activity in eight participants (four women and four men) as they handled loads ranging from 8–16 kg for women and 12–20 kg for men.
Fig. 1. Low back EMG in load transfer and static load among men (n=4).
The EMG data was analyzed using Ergolink software, which synchronized EMG and motion sensor data with video footage to provide a comprehensive overview of muscle activity during the tasks.
Key Findings of MBelt Study
Increased Muscle Activity with Heavier Loads:
For men, EMG activity in the left-side extensors was consistently higher than in the right-side extensors.
For women, the opposite trend was observed, with higher EMG activity in the right-side extensors.
Dynamic vs. Static Tasks:
During dynamic tasks, such as load transfer at table level, significant differences in EMG activity were observed between the left and right extensors.
In static tasks, like holding a load, EMG activity was symmetric between the left and right extensors.
Carrying Tasks:
When carrying loads, EMG activity was higher on the same side as the carrying arm.
In symmetric carrying tasks with both hands, the right lower back muscles showed greater activity than the left side, particularly among women.
Fig 2. Muscle load in carrying among women.
Lifting Techniques:
Interestingly, EMG levels were similar for both ergonomic lifting and non-recommended straight leg lifting, especially for the heaviest load (16kg). This suggests a need for further investigation into muscle recruitment strategies and the true muscle load in different lifting techniques.
Fig. 3. Muscle load in lifting among women.
MBelt Implications
The MBelt study reveals systematic trends in lower back muscle activity during lifting, carrying, and load transfer tasks. These findings highlight the importance of ergonomic practices to reduce physical strain, which can prevent work-related musculoskeletal symptoms, improve workplace productivity, and accommodate employees with disabilities.
Future MBelt and Lower Back Load Research
The study suggests the need for further investigation into the observed gender differences in muscle load activity and the potential equal muscle load in recommended versus non-recommended lifting techniques.
Overall, MBelt proves to be a fast and accurate tool for evaluating physical load in the workplace, offering valuable insights for improving occupational health and safety.
Link to the thesis (in Finnish)
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