"It doesn't even feel like I am wearing a pack!"


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Balance - U Flow

U Flow:
  • A pack which flows with your body motion.
Balance Pack:
  • A pack which wraps around your body so that you can balance the weight in front and behind so that your posture and balance are unaltered by the load.
  • A pack where all body-contact parts can be customized to your torso size and shape for a perfect fit.
Aarn Packs use Sports Science to verify in the lab the energy savings and strain reduction of our packs. An extensive body of outstanding testimonials verifies how beautifully they work in the field. Our covers most activities where you need to carry a load on your body. Choose this link to see the designer, Aarn Tate, explaining the principles and benefits of our Balance Packs.


The key part that Balance plays in load carrying efficiency is little understood in the outdoor industry - yet it has been extensively explored by biomechanics - the study of the muscular, joint and skeletal actions of the body when load carrying. It is therefore essential to use biomechanics to optimise performance, minimise effort & strain and to prevent injury. It's the key to designing a load carrying system with minimum impact on the body.

In addition, Sports science research needs to be used to verify the success of the load carrying system. Research comparing different shapes, harnesses and frame systems of various backpacks and different backpack brands has found no
significant differences in energy consumption. This is why you do not see any backpack manufacturers quoting Sports Science benefits in advertising their products.

There is research comparing backpacks with traditional load carrying systems such as trump-lines and head supported loads. This research has found that the traditional methods often require significantly less energy to carry the same amount of weight! The urgent need for a superior method of load carrying is highlighted by the disturbing growth of backpack related back problems in school children (subject to world wide research). Clearly something is wrong with the backpack system of load carrying.


Aarn Tate has spent 30 years perfecting a new concept in load carrying - the U Flow Balance Pack. The key is counter-balancing the load in front and behind and harness systems that facilitate full body movement. The back portion of Aarn Balance Packs optimize slim side profiles, low pack weight and full torso length backpanels to keep the load as close to the back as possible. The front portion of the Balance Pack is either a pair of Balance Pockets or a single Balance Bag. Packed with your heaviest items, these remove all leverages on your back from your pack and bring your posture as close to upright as possible. Patented Flow systems allow natural body movement under load. By splitting the load into front and rear compartments, we reduce the height of the backpack above the shoulders for big loads, and we bring the center of gravity of the load forward and downwards to match that of the body (horizontally and vertically). Most of the load can now be taken off your shoulders and spine and transferred evenly around your pelvis -
the most suitable bone structure in the body for load carrying. The load on the front is carried in pockets with a gap in between so that you can see your feet as you walk. The resulting U Flow Balance Pack is the first practical, high-efficiency load carrying system that maintains the natural curve of the spine. As well as overcoming the disadvantages of backpacks, Aarn Balance Packs also overcome the disadvantages of traditional load carrying systems: the instability and balancing problems of head supported loads, and the forward lean and the need for strong neck and back musculature when using trumplines.
Generally the front compartments of our Balance Packs are a smaller volume than the back compartment to maintain good forward visibility. Pack your heaviest and most compact items in front and your light bulky items behind to achieve the upright posture. Pack your lightest gear at the top of the pack to lower the center of gravity for the greatest fluidity of movement.


Before our Balance Packs became available it was hard to choose between different backpack brands and models. When you go into an outdoor and see a multitude of packs on the wall, how do you evaluate which is going to be the most comfortable? Using the following principles, heres how to evaluate the energy differences and pull back force on the shoulders of different backpacks at a glance.

The greater the leverages from the offset load, the more you have to bend forward to counteract these leverages to prevent falling backwards. Research shows that the greater the forward lean and the more restricted the torso movement, the greater the strain on the body and the greater the energy needed to carry a given weight.

To reduce forward lean in a backpack:
  • The side profile should be as slim as possible.
  • The pack length should be at least as long as your back, taller if practical.
  • Heavy items should be packed close to your back.
  • The weight should be minimum.
  • Add Aarn Balance Bags to counter-balance your load.
To reduce the movement restrictions of a backpack:
  • The shoulder straps should be interlinked to allow free shoulder movement.
  • The hipbelt should pivot to allow rocking of the hips and forward bending.
  • The harness should allow twisting between the shoulders and hips.

To see at a glance which backpacks in the store cause the least strain, check the width (front to back) of the pack sides. Choose packs with the slimmest side profile. Avoid all backpacks with a deep side profile and very short backs! These cause the greatest back strain. Next check whether the harness parts are interlinked and whether the hipbelt moves to facilitate free body movement. Avoid packs that strap you in like a straight jacket when you put them on and tighten the shoulder straps and hipbelt.

With a backpack, the center of gravity of the load is behind the body. The load acts like a lever on your back, increasing the forces acting on the body well above the force of the weight alone. When this lever acts over a shorter distance on a small torso, the forces are magnified. Therefore the reason women
with short torsos may not be able to carry such heavy loads is not because they are weaker but because of these increased forces. In addition, the loads smaller women carry often represent a higher percentage of their body weight than the loads of men on the same trip. Therefore it is unreasonable to expect shorter or smaller women to carry the same loads in their backpacks as men!