Why BackTpack Works

Unlike backpacks or messenger bags, BackTpack bags and tumpline products apply the load to the body’s vertical axis, thereby eliminating posture distortion and decreasing the effort required to carry the load, in obedience to the laws of physics. The load feels lighter and you stand straighter.

The Center of Gravity

When we support a weight, we have a new center of gravity -- the combination of our body's center of gravity plus the center of gravity of the weight we are supporting. When what we carry is balanced side-to-side or front-to-back, or is on top of our head, its center of gravity aligns vertically with ours.

However, if what we carry is off-axis (in front, to the side, or behind our vertical axis), we must lean away from the load to keep the shifted center of gravity over our feet so that we don't fall. Posture must change to accommodate the load we carry. The heavier the off-axis load, the more we must lean.

Backpack and BackTpack comparison showing why BackTpack works

Line of Force

The force applied to support a load must go through the center of gravity of the load. So again, when the load is aligned and balanced through our vertical axis, the supporting force is simply equal to the weight we carry and in the opposite direction: Straight up!

If we must support a load that is off-axis, we must pull in a direction such that the direction of the pull goes through the center of gravity of the load, rather than through our own body's vertical axis. This introduces a horizontal component to the force which is added to the weight, meaning that more force is required. For example, a heavy backpack requires you to lean forward and pull forward with your shoulders. This is why we see hunched shoulders and forward heads with backpack use. With the same weight packed into the balanced side-bags of a BackTpack, the forward pull is eliminated. This is the reason that people say, "The load feels lighter!" when they carry the contents of their conventional backpack in a BackTpack.

Line Drawing of Posture