Electromyographic analysis of shoulder muscle load

Area of Science:

• Occupational health
• Biomechanics
• Ergonomics

Background:

• Occupational shoulder disorders are a significant concern in industry.
• Workplace design can influence the risk of these disorders.
• Understanding muscle load is key to prevention.

Purpose of the Study:

• To investigate the influence of hand tool weight and arm position on shoulder muscle load.
• To provide recommendations for workplace design to reduce occupational shoulder disorders.
• To identify key factors contributing to shoulder muscle strain.

Main Methods:

• Electromyography (EMG) was used to record myoelectric activity in six shoulder muscles.
• Nine volunteers held 21 different arm positions with loads of 0, 1, and 2 kg.
• EMG data was automatically analyzed for amplitude variations.

Main Results:

• The degree of upper arm elevation was the primary factor affecting shoulder muscle load.
• Shoulder stabilizing rotator muscles showed higher dependency on hand load compared to the deltoid muscle.
• Increased arm elevation and hand weight led to greater shoulder muscle activation.

Conclusions:

• Workplace design should prioritize keeping the arm close to the body to minimize shoulder load.
• Minimizing the weight of hand-held tools is crucial for reducing the risk of shoulder disorders.
• Ergonomic interventions should focus on reducing upper arm elevation and applied hand loads.