The effect of shoulder strap width and load placement on shoulder-backpack interface pressure

Area of Science:

• Biomechanics
• Ergonomics
• Human Factors Engineering

Background:

• Backpack use can cause shoulder pain and injury due to pressure and poor design.
• Understanding pressure distribution is key to improving backpack ergonomics.

Purpose of the Study:

• To investigate how shoulder strap width and load position affect shoulder and axilla pressure.
• To identify optimal backpack configurations for minimizing user discomfort.

Main Methods:

• A 20kg backpack load was tested on a manikin with varying strap widths (5-8 cm).
• Load placement was varied (high vs. low), and interface pressure was measured at the shoulder and axilla.

Main Results:

• A significant interaction between strap width and load placement was found.
• Wider straps reduced shoulder pressure more effectively with high loads, and axilla pressure with low loads.
• Narrow straps showed a large pressure difference between high and low loads, which decreased with wider straps.

Conclusions:

• The optimal configuration for minimizing interface pressure involves 8 cm shoulder straps and high load placement.
• These results provide evidence-based recommendations for backpack design and user guidelines.