Shoulder-arm muscular activity and reproducibility in carpenters' work

Area of Science:

• Occupational health
• Ergonomics
• Biomechanics

Background:

• Carpenters perform physically demanding tasks.
• Understanding muscle activity is crucial for preventing injuries.

Purpose of the Study:

• Analyze arm-shoulder muscle activity in experienced carpenters during familiar tasks.
• Investigate intra- and inter-individual similarities in muscle activity.

Main Methods:

• Ten healthy carpenters participated in the study.
• Tasks included manual screwdriving, sawing, and upward nailing.
• Normalized electromyography (EMG) was used to measure muscle activity.
• Experiments were repeated within the same day and two weeks later.

Main Results:

• Median muscle activity levels did not exceed 15% of maximum EMG for any muscle group.
• Wide ranges in median activity levels were observed for certain muscles and tasks.
• The trapezius pars descendens, infraspinatus, and anterior deltoid were the most activated muscles across all tasks.
• Strong intra-individual similarity in median muscle activity values was found between trials.

Conclusions:

• Experienced carpenters exhibit relatively low muscle activation during common tasks.
• Muscle activity patterns show consistency within individuals, suggesting task familiarity.
• Further research can inform ergonomic interventions to optimize safety and efficiency.