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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 Balance Pack, 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 hipbelt side connectors). See diagrams 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 while the load stays limpet like on your back. 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 building-up of fatigue.

Research vertifies that our U Flow systems enhance balance and make your pack more stable that 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 or cord that slides freely through a slot in the bottom of the pack when the shoulders move up and down.

 Linked shoulder & chest

Our optional butterfly harness links shoulder & chest strap through a loop at the bottom of the pack allowing shoulders to twist relative to the hips

 Forward pivoting hipbelt

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

Large packs : The bottom 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 Stabilisers

The top stabiliser straps are linked together by a web which slides freely through rings at the top of the pack when your shoulders twist relative to your hips (daypacks).

 Linked chest straps

Our optional X Flow straps link the shoulder pads across the chest in a slot on the connecting clip buckle allowing shoulders to twist relative to hips.

 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 bach 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”