Any users of Aarn universal balance bags?

[Roger Caffin]

Packs that use the spine and back muscles and shoulders as part of the frame system are…crazy.
It’s a bit like the difference between the rigid suspension of a farm cart and the suspension of a modern passenger car. Putting the load directly on the hips is the rigid suspension, while the muscles of the back and shoulders are the springs and shock absorbers of a modern car.

Cheers

[jscott]

Actually, I wonder if a well designed lightweight external frame pack might not carry modern light loads remarkably well. remember, when externals were all there were, people were carrying 40 plus pound loads for a three day jaunt. even today folks think of “resorting” to an external frame to carry heavy loads.

Well, how would one feel with an ultralight load?

[Geoff Caplan]

Roger – sometimes you have brilliant insights, and sometimes you simply lose me. If the wearer’s back is vertical, I can’t see how there can be enough friction between the hiker’s back and the back of the pack to take much of the load? Nor can I understand why transferring most of the load to the hips is in some way a negative.

Packs that use the spine and back muscles and shoulders as part of the frame system are…crazy.

Absolutely my own experience, and I’ve carried frameless sacks for thousands of days over the years.

Here’s one way to think of it. To my shame, in the fairly recent past I slipped into a situation where I had 50lbs of flab distributed around my gut. Yet I was still able to walk for hours in reasonable comfort, despite suffering from a fatigue disease.

Hang the same 50 lbs off my shoulders in an unframed pack and I would hardly have lasted 20 minutes – a different experience entirely.

Really big people manage to walk around with north of 200lbs of flab, when they couldn’t lift a 200lb pack off the ground.

The weight of a big gut is taken entirely by the legs, and (within reason) the center of balance isn’t much affected. So it has FAR less impact on your comfort than the same weight hanging off your shoulders, causing strain in the shoulders, neck and back and throwing out your natural gait.

The ergonomics of how we carry the weight can make a very significant difference.

The bodypack concept is the closest you are ever going to get the the sensation of carrying the weight on your gut rather than your shoulders. A good fitting framed pack is the next best option for walkers – or the best if you’re mountaineering. And the frameless sack seems to offer the worst of all worlds. I’m genuinely baffled by the resurgence in their popularity – a triumph of fashion over functionality, IMHO….

[Roger Caffin]

Hi Geoff

If the wearer’s back is vertical, I can’t see how there can be enough friction between the hiker’s back and the back of the pack to take much of the load?
You would be quite right – if my whole body was vertical.
But as I have repeatedly said, I lean forward from the ankles. My WHOLE body is tilted, just not my upper spine.

Have a look at how your body is tilted when you are climbing a steep path. Leaning forward from the waist rarely helps at all: you have to lean forwards from your ankles to get up the hill. But you do it without noticing.

I had 50lbs of flab distributed around my gut. Yet I was still able to walk for hours in reasonable comfort,
Three thoughts to consider here.
The first is that you were probably walking slower with that extra 50 lb weight. Well, I would be.
The second is that the weight was not hanging from your shoulders. It was, as you said, ‘distributed around my gut’. That makes carrying it easier as it is spread over many different bones and muscles.
The third is the huge difference between slowly, over (say) six months, adding 50 lb to your body in a balanced manner against suddenly just picking up a 50 lb weight at the end of your arm. In the former case your body adjusts over time – and you learn to walk more slowly.

The old A-frame packs were terrible: you did have to bend at the waist with them. But they were copied from northern European packs designed for ski touring, where you had to have your shoulders free to flex independent of your hips. We had them in Oz for a while.

The internal frame pack was designed for mountaineering, where an external frame was for ever catching on the rocks. A smooth exterior was needed to slide over the rock. Their transition into walking use was due to marketing spin which persuaded people that it was more cool to carry a pack designed for mountains rather than an old load hauler like a Kelty. Coolth prevailed over sense.

The frameless pack evolved from a little day pack designed to carry your lunch. Apart from the loss of the weight of the frame, it has no redeeming merits at all, but many serious inconveniences. The SUL preoccupation with weight above everything else has glamorised it, to the discomfort of many. The two major problems with it are, to my mind, the awful unergonomic round shape against your back and the complete collapse of the torso length. They end up shaped like a pretzel.

Cheers

[James Marco]

*Any users of Aarn universal balance bags?*

To me, this is simply against any logic.  Let’s see…the balance design is to prevent weight on your back and hips from being too much on the front or back. It does indeed do that.
1) As simply stated by Roger, you can bend at the ankles for any balance needed.

2) Any weight to “balance” the pack will mean more stress in the downward on your shoulders. This is crazy! Weight on your shoulders is the LAST thing you want. All this weight is transfered down your backbone to your hips, meaning it is inefficient when compared to a regular framed (or unframed) pack using a full hip belt.

3) All weight transferred down your back bone means: More muscles involved in keeping your back straight compared to the vast majority of weight (60-90%) simply being put on your hips/legs/feet. (Even a 20pound pack benefits from a good hip belt.)

4) Your leg/hip muscles are the largest muscles in your body. They can take the extra load. Your back has a LOT of small muscles all using energy maintaining your balance. They cannot handle larger movements, soo, all pressure goes on your vertebrae and cartilage. This is a recipe for damage.

5) Even iff you lean forward to hike, this means a LOT less weight on your backbone because the lean is simply used for balance. Weight is on your hips, soo it doesn’t matter if you bend a little…there is little weight to contend with on your backbone…it sits on your hips.

There is more but I gotta run…

[PaulW]

Having recently purchased a set of Aarn balance pockets which I modified for several of my non-Aarn packs, I can say that there is NO weight on my shoulders, if I adjust things properly. This is one of the stated benefits of the Aarn system. Since I don’t own a full Aarn pack kit, I can’t comment too much further other than to say that when the balance pockets are loaded and adjusted properly, I can stand straight up, with no leaning whatsoever, maintain a neutral pelvic tilt, and have no weight on my spine. This is a biggie for me since I have lumbar issues. I’ve never felt as comfortable wearing a backpack as I do now.

[Stumphges]

James,

As Paul mentioned, the Aarn packs are expressly designed to transfer all of the pack mass to the hipbelt.

I’ve gotta call BS on the claim that one can compensate for backpack load posturally by simply dorsiflexing the ankles more and keeping the alignment of the rest of the body the same as always. It does not work like that. The calves would be severely overloaded. Biomechanical (kinematic) studies of gait with backpack carriage do not show that pattern. The body will flex at the hips, not the ankles.

[Roger Caffin]

The calves would be severely overloaded.
Why?
Any published research to support that claim?
What actually happens is that your calf muscles adapt, and the tilt is not great anyhow.

Biomechanical (kinematic) studies of gait with backpack carriage do not show that pattern.
URLs to published research?
As opposed to my watching my wife walking in the mountains with a pack on her back?

Cheers

[Geoff Caplan]

Roger

I’m afraid I’m with Stumphges on being sceptical about the leaning at the ankles thing. It’s not what egonomists have found when they examine load carrying or what I experience myself and see in the hills. And even if it was true, it would still disturb your gait and cause unnatural stresses over a long day.

In a way it’s an academic issue, because if you’re happy with your pack what’s the problem? But I wouldn’t want to release a commercial pack based on that theory.

Personally, I’d much rather have a pack that didn’t involve any lean at all – and the only practical way to achieve that is a bodypack with a counterbalance at the front.

Now I’m a bit like the canary in the coalmine – a lifetime of bodywork and a chronic fatigue disease have made me very sensitive to any inefficiency in my setup. Younger and/or fitter people will be more tolerant to less-than-ideal setups. And as a yoga teacher, I have practical experience that many people have surprisingly little body awareness, which may also contribute at times to acceptance of inefficient packs (present company excepted!). Just look at all the fanboys for frameless potato-sack thingies – what are they thinking??

As for the move from externals to internals for hiking, I can see additional arguments for the internal. First, they are likely going to be lighter. Second, if they’re well done they are probably less rigid and flex better as the body moves. Thirdly, that should make them better for scrambling and difficult ground. And lastly, they are likely simpler and more fail-safe.

On the other side, you could argue that there’s been far less development effort put into lightweight externals, so I guess there may be more room for improvement.

The only real contender I know of is the Vargo range. Some people seem to like them a lot, but they’re about as niche as the Aarns from what I can gather.

https://vargooutdoors.com/backpacks.html

[Doug Coe]

Geoff—I’m also working on a myog backpack. I take most of my suspension (shoulder strap and hipbelt) cues from Paul McLaughlin here on BPL.

For lightness and simplicity I’m thinking of sewing the shoulder straps directly to the bag. For this level of load I suspect that would be good enough, though I’d welcome feedback.

The main decision is how to handle the hip-belt suspension.

Take a look at his comments and photos on hipbelts on the bottom of the first page of this thread. Also, notice he sews the shoulder straps directly onto the pack (with reinforcing fabric on the inside).

He often makes a full-wrap hipbelt and sews it to the pack (through the 1/4″ foam) (again with reinforcing fabric).

Paul says (elsewhere) that one time he made a hipbelt that was freely hinged at two attachments points at the bottom—similar concept to Seek Outside—but considered it too heavy and harder to make. I’m going that route on my pack though.

[Sean P]

Perhaps to end the argument,  Roger, you could load some footage onto youtube of you or your wife walking on the flat and carrying a loaded backpack whilst flexing solely at the ankles and not flexing the torso at the hip.

I’d be happy to run this past my physio colleagues at the university where  I work.

If you are concerned about privacy the clip could be unlisted and deleted after sharing the link.

[Roger Caffin]

I don’t do YouTube.

Anyhow, I think I have worked out why the difference. If you look at the frame on my pack here

you will see that it has a long straight external frame and mesh across the back from top to bottom. I have always made my packs with long straight frames like this (since I was about 18). I tried wearing my current pack and bending forward at the waist: it was most unsatisfactory. It felt all wrong. It may well be that the straight frame has ‘trained’ my back to always be straight?

The hip belt is very light: it is just for anti-sway, and the pack carries more or less the same without it.

Cheers

[Murali C]

Interesting how folks have strong opinions of what kind of backpack is the best backpack for all:-)

I used a frameless pack for my recent CT thru hike. 485 miles, 90K feet of climbing. Obviously I wouldn’t have done it if I was hating it or suffering. I don’t do it because of weight savings. I use a frameless because of the joy I get from hiking with it. The simplicity and the freedom of movement. No load lifters. No hip belt. Just put in on and start hiking.  I don’t pack it any differently than a framed backpack. No virtual frames in the form of pads etc. I do have a hip belt which I will employ occasionally – especially when I had to carry 4L of water for a dry camp for 3 miles of a 21 mile dry section. Even when I use a framed backpack, the moment I dis-engage the hip belt, I feel a sense of joy that is hard to explain! I do not see myself going back to a framed backpack anytime soon.

The most important factor is to enjoy the activity of backpacking without worrying about the backpack and a frameless does it for me.

I have looked at Aarn backpacks a while back – but it seemed like a steep learning curve on the various aspects of the design. Simplicity always wins. Simple is elegant!

[Craig B]

It’s really interesting what different people deem ‘comfortable’.  Clearly, there is a huge range.  The forces that exist in worn backpacks and how they are distributed over the body are quite complicated and can vary widely based on design.  Everyone’s own personal experiences with this are absolutely valid, but certain things are not subject to ones opinion, no matter how much they wish it to be so (this is a big problem in the US at the moment).  I hate to see that dynamic showing up here.

Roger, I’m a bit disappointed with your responses on this thread.  Normally you’re spot on with physics/engineering principles, and you’re gear designs are very good.  However, YOU were the one that offered the picture of your wife with a loaded backpack as evidence that it’s possible to NOT lean forward, where clearly she IS leaning forward in that picture.  I also disagree with your analogy:

It’s a bit like the difference between the rigid suspension of a farm cart and the suspension of a modern passenger car. Putting the load directly on the hips is the rigid suspension, while the muscles of the back and shoulders are the springs and shock absorbers of a modern car.

I would say that putting the load directly on the hips and standing with legs straight is the rigid suspension of a farm cart (or lack of suspension entirely) while bending the legs at the knees are the springs and shock absorbers of a modern car.

So let’s please all agree that when you wear a backpack, your center of gravity changes and your body has to adjust in some manner.  We humans are very good at adjusting for this and do it without thinking.  What IS up for debate is the amount this adjustment affects us while carrying the backpack.  For some it’s a lot, for others it’s barely noticeable.  Additionally some people don’t mind using their back and shoulder muscles to transmit some (or all in packs without hip belts) of the weight to the legs, while others find this very taxing.

I’m definitely in the later camp.  I want all my carried weight to be on my hips and I also dislike the ‘hunch’ I adopt while wearing a backpack.  For me this is true even with a relatively small weight of 17 or 18 lbs.  I only weigh 130 though, so that’s a decent percentage of my weight.

I like the Aarn concept, and developed my own version of it a couple of years ago.  There were very few details of the design on their site however, so I assumed that the front bags were merely hung off the shoulder straps, which would just put more weight on the shoulders.  I also tried to look up their patents but couldn’t find anything either.  Thanks Geoff for sharing some of the details and showing that the front bags are supported from below by the hip belt.  I thought I had come up with the unique idea of supporting the main backpack bag at a single point in the center bottom of the bag, but it appears that Aarn has done that as well!  (I’ve realized over the years that good ideas are rarely if ever unique)  This definitely allows your hips to rotate about that point so that the iliac crests can move up toward the shoulders or down towards the ground on each stride (think of the stereotypical sexy woman walk).  A typical backpack with hip belt is NOT designed to move in this manner so resists your hips moving naturally like this.

I’ve worn my front/back setup for 2 years now and will never go back to a traditional setup.  At a hair under 24 Oz, it’s only slightly heavier than my zpacks arc blast was (which I did not find comfortable at all) and way more comfortable than any pack I’ve ever had.  In it’s current configuration it’s good for carrying up to about 26 Lbs, which I use for training.  On trips I have about 20 Lbs in it.

Having a bag in the front takes a bit of getting used to, and my design is a little tricky to get on and off (think of putting on an old-school paper-rout bag or a weight vest), but to me the trade offs are worth it.  Especially since I could design it exactly with all the features I wanted in it.

OK, that’s the end of my book….

[Doug Coe]

Craig / @kurogane says:

I’ve worn my front/back setup for 2 years now and will never go back to a traditional setup. At a hair under 24 Oz,…

You can’t just leave us hanging! Would you mind showing some photos of your pack? Here or in a new thread if that makes more sense. I’m working on my own myog pack and love to see new ideas.

[Roger Caffin]

Hi Craig

HYOH.
Whatever suits you.

Cheers

[PaulW]

Craig, +1 to what Doug said. Any info you’d care to provide would be very much appreciated.

[Geoff Caplan]

Craig – another vote here – please let us see what you’ve been up to!

I agree 100% with the logic of your post – pretty much what I’ve been trying to say too. To me it seems beyond reasonable argument – but I guess we’re not going to carry the day with everyone here.

I think you make a critical point about weight on the hips. We don’t need any kind of suspension above the hip belt to absorb impact, because that’s what the human gait is designed to do. We absorb the impact with our knees and the other complex elements of the human stride.

[Craig B]

Fair enough.  I’ve been debating whether to post about this design or not, toying with the idea of pursuing a patent.  Especially after seeing the patent that zpacks has on the arc blast;  It’s for the tensioned back panel that can hold the body of the pack away from your back for ventilation.  Not for anything about carrying the load better or a good suspension, just ventilation!  Although I might have forgotten about some other claim, it’s been a couple years since I looked at it.  I like the idea of open-source stuff, and I’ve made use of such things many times in the past, but it’s hard for me to get past the idea keeping patentable ideas to yourself, which I was raised on.  Well now that I see the Aarn design is fairly similar to what I came up with, maybe it’s time to share it.  Based on the responses to this thread, it seems like it will be a very niche style anyway!

I’ll make a proper MYOG entry at some point in the near future, but here’s a couple of pictures in the mean time:

First, an REI Flash 62 (old model from like 10 year ago) 50 Oz, loaded with 22.7 Lbs for total of 25.8 Lbs.  I tried to stand with my core muscles neutral to show the slight lean forward I have to adopt to stand naturally, although I have to put some energy into keeping my hips from rotating under due to the weight of the pack.

OK, that same weight in my pack but I added some extra water bottles for a total of 26.25 Lbs (24 Oz pack, 396 Oz stuff):

Here I tried to capture the rotational ability of the hip belt vs the back pack.  It’s kind of like it’s on a rotational bearing, but it only needs to roll maybe 10° in either direction:

It’s a bit hard to see from that angle, but I tried to keep the rotation point at the center of where my hips rotate.

Anyway, more to come in a dedicated MYOG thread….

[Roger Caffin]

Hi Craig

I dare say a Patent Attorney will be happy to take your money, but any patent on a ‘tensioned back panel that can hold the body of the pack away from your back for ventilation’ will have pretty much zero value. There are too many older packs on the market with the same idea – Osprey comes to mind, as do the packs which I have sold.

Cheers

[Doug Coe]

Craig—Cool pack! It looks like you’ve brought the frame for the main pack around the sides of the hipbelt, and the frame for the front pack towards the sides too.

Unlike Aarn, it looks like you have one front pack vs their two tall, thin “balance pockets.

rotational ability of the hip belt vs the back pack

What is the purpose of that aspect? To feel less locked into the pack as you walk, I guess?

[jscott]

It ‘looks’ like you’re carrying a fair amount of weight on your shoulders with the front pack. But I think the value of single shots is minimal–you need to watch someone walking for a while to get a sense of how a pack is functioning, I believe.

[Stumphges]

Craig, does your hipbelt rotate around all three cardinal axes? How does it pivot? I’d love to see how the joint/articulation functions.

[Stumphges]

Roger,

There are quite a few good studies on the effects of backpacks on posture and gait biomechanics. Since the topic of this thread is Aarn stuff, you may as well start with this paper, which compares an Aarn Bodypack with a conventional pack design: https://www.researchgate.net/profile/Alicja_Rutkowska-Kucharska/publication/271052654_Choosing_the_Right_Body_Position_for_Assessing_Trunk_Flexors_and_Extensors_Torque_Output/links/5669542008ae7dc22ad4e537.pdf#page=65

The references section has a lot of other good reading materials to help you get up to speed on the basics of this topic.

This page summarizes some of the results of the linked-to study, including a graph of Forward Lean (defined as the angle from hip to shoulder, compared to vertical) just a little way down:

https://www.aarnpacks.com/pages/pioneering

You can see that a backpack results in very significant forward lean at the hips. Other studies show additional flexion (forward bend) of the spine. This should not surprise, as the photo you posted of Sue shows her flexed at both the hips and spine, as was pointed out upthread.

[Nick Gatel]

Roger – sometimes you have brilliant insights, and sometimes you simply lose me.

Over the past week, we were camping. I spent a lot of time watching people hike. It does seem that most do lean slightly (very slightly) forward. Not at the back, but “from the ankles” as Roger states. When walking we are pushing our bodies forward, keeping the hips somewhere behind the strides of our two legs. I noticed people who were “strolling” were most upright. Those hiking fast (around 3 mph) had a minor lean. Those using trekking poles, had the most lean, which makes sense, since they are helping to propel their bodies with the arms and shoulders.

However, I can’t agree with the back and shoulder muscles being the springs. If the shoulders and back muscles are carrying weight, that weight has to be transferred to the hips via the spine, which is not designed to carry much weight.

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