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Movement Table



On our posture page we have seen that we can eliminate the leverages caused by an offset load (and the extra forces acting on the body) by aligning the centers of gravity of the load and the body in the vertical axis. A head supported load does this perfectly. If you have ever seen African women carrying loads on their heads you will notice their upright posture and their beautiful graceful gait. If you have developed the spinal support muscles and balancing ability to do this as you grow up this is a highly energy efficient way to carry a load.

The biggest drawback of a head supported load is the inherent instability of the load, making this method of load carrying unsuitable for active movement, rough terrain or high winds. To achieve dynamic movement in all situations we need to lower the center of gravity of the load until it matches the height of the body's own center of gravity,while still keeping the load aligned on the vertical axis. The body's center of gravity is around the navel area. If we make the center of gravity of the load coincide with the body's own center of gravity, the center of mass of the load can move around your own center in a balanced and fluid way.

When we approach this ideal weight distribution both horizontally and vertically with an Aarn Bodypack, we also need to incorporate connections into the harness, hipbelt and Balance Pockets systems which allow free body movement (rather than restrict movement like a backpack does).

Imagine a pack where the shoulder straps and hipbelt move freely with body movement while the pack remains glued to your back.

The buildup of fatigue will be reduced and your performance under load will approach the pack-less state. Our patented U Flow systems achieve this by linking the shoulder harness and hipbelt parts on each side of the pack to each other via cord or web which passes through a U shaped tube and by a central pivoting hipbelt connection to the pack.

Aarn pioneered the development of high stability free movement systems in the late 80s. Since that time the systems have been extended and refined to allow all needed arm, shoulder, hip and torso movements, shown by the arrows in the picture below. Some major brands are now beginning to follow our lead.

The drawings below show how each U Flow system works and the body movement it facilitates.

The shoulder and hip U Flow systems are combined differently for small and large packs to achieve the optimum load stability. Twisting of the shoulders relative to your hips is achieved at shoulder level on the daypacks (linked stabilisers) and at hip level on the larger packs (linked side connectors). See diagram below.

Our U Flow systems give you an amazing ability to twist, rock, stretch and bend forward under load - to move your body freely and naturally. You can dance with a pack on!

Yet you don’t have to be doing extreme moves to experience the benefits and freedom that U Flow brings. Even when walking, you will feel the shoulder straps and hipbelt move with each step, reducing the build-up of fatigue.

Research verifies that our U Flow systems enhance balance and make your pack more stable than fixed harness designs. With a naturally balanced load, your safety is maximum in difficult & dangerous country.


 Linked bottom tensioners

The lower ends of the shoulder straps are linked together by a low-friction web that slides freely through a slot in the bottom of the pack when the shoulders move up and down (all models).

 Sliding Stabilisers

The top stabilisers are attached freely to each vertical frame stay so they slide up and down with shoulder movement and automatically adjust to your back length (large packs).

 Linked stabilisers

The top stabiliser straps are linked together by a web or cord which slides freely through a U shaped channel in the top of the pack. The slide freely when your shoulders twist relative to your hips (large daypacks).

 X linked chest straps

The chest straps link the shoulder pads across the chest in a movement facilitated X configuration, spreading the load over a larger area of the chest and increasing stability.

 Forward pivoting hipbelt

Daypacks The bottom of the backpanel flexes as you bend forward.

Larger packs The bottoms of the hipbelt are linked by an elastic connector which allows the bottom of the hip belt and the pack to move further apart when you bend forward.

 Linked side connectors

The sides of the hipbelt are connected to each other by a cord which runs through a U shaped low friction tube the bottom of the back panel. The cord runs freely through the tube when the hips rock or rotate. (large packs).

"I have cervical a slipped vertebrae and suffer way less problems with my neck using your packs due to the Flow Motion systems. I really dread having to resort to another kind that locks my shoulders stiff since these often has caused my traps to go into spasm. Can I also just say how massively I appreciate your invention and very grateful to for making it possible for me to hike and carry again with my neck the way it is. I would never have been able to experience the incredible mountains of the French Alps and Norway last year in the way I did without your pack, and it was a really unforgettable and sublime experience."
Alison Moore, Sydney, NSW, Australia

"The Flow Motion systems work! The pack hugs the back closely and moves with the body without the feelings of restriction and discomfort. Stability is much better than with an ordinary pack on. I was skiing down from Cairngorm in a high wind; conditions were icy and darkness was falling – the pack was like a limpet, not swaying or moving at all, yet I had complete freedom of arm and shoulder movement."
Chris Townsend, Equipment Editor TGO Magazine and Author “The Advanced Backpacker”