Medium and large-sized backpacks usually consist of a carrier system centered on a backpack frame, which can be divided into two types: external frame and internal frame.

External Frame Backpack

• Characteristics: The pack is fixed to a rigid frame, commonly made from aluminum alloy. It includes nylon shoulder straps and a hip belt.

• Advantages:
  • Easy to load and access items.
  • Weight is distributed between shoulders and hips.
  • Good ventilation for the back.
• Disadvantages:
  • Can get snagged in dense forests or bamboo thickets.
  • May lose balance during climbing or skiing due to sudden shifts in the center of gravity.
• Suitable Scenarios: Ideal for long-distance trekking on flat terrain.

Internal Frame Backpack

• Characteristics: No visible frame, slim and tall design, internal aluminum frame, includes a hip belt.

• Advantages:
  • Fits closely to the back, distributing weight evenly across shoulders, back, and hips.
  • More stable, less prone to sudden shifts in the center of gravity.
  • Slim design is less likely to get snagged in dense vegetation.
• Disadvantages:
  • Less convenient for loading and accessing items, though this can be mitigated with good packing techniques.
• Suitable Scenarios: Ideal for climbing, walking through dense forests, and bamboo thickets.

Comparison of Internal and External Frame Backpacks

• Center of Gravity:
  • External Frame Backpack: Higher center of gravity, around shoulder level or above.
  • Internal Frame Backpack: Lower center of gravity, adjustable between shoulders and hips.
• Carrying Comfort and Balance:
  • Higher center of gravity is more comfortable on flat terrain.
  • Lower center of gravity is better for balancing in climbing situations, preventing swaying at shoulder height.

In summary, external frame backpacks are suitable for long-distance trekking on flat terrain, while internal frame backpacks are better for activities requiring balance, such as climbing or navigating dense environments.