Member Blog Post / Gear / Technology

Ergonomic shoulder straps that reduce shoulder pain

by Nenta WAKO, Dr.Eng.

February 15, 2022

Two methods for reducing backpack shoulder load have been well known.
One is the load distribution to the lower back with hipbelt or lumbar pad. The other is the load distribution within the shoulder area.

Regarding the latter method, strap design in width, core material, and shape is effective. However, many of researchers and manufacturers tried only significant reduction of pressure hotspot or overall load. So, I investigated the shoulder loading condition that reduce the overall pain and tried to realize proper load distribution using differences of pain perception among shoulder parts.

And in the process, I designed the shoulder pad that avoids the clavicle load.
This pad reduced the clavicle load but increased the load directly under the clavicle region. And the medians of the overall pain intensity became smaller than that for the coventional flat pad. (Not signifficant difference was observed in statistical analysis in 8 subjects, though.)

With the result, I have a firm belief in a possibility to achieve the shoulder pain relief by proper shoulder loading even when carrying heavy stuff.

Thank you for reading this post.
I have released more details on my YouTube channel “Backpack Researcher.”
Please check it out.

【Backpack Engineering】What are the loading conditions that reduce shoulder pain?
https://www.youtube.com/watch?v=Ne8N39isxfo

Discussion

This topic has 12 replies, 6 voices, and was last updated 1 year, 11 months ago by Nenta WAKO, Dr.Eng..

Viewing 13 posts - 1 through 13 (of 13 total)

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Feb 15, 2022 at 12:53 am #3740407

Nenta WAKO, Dr.Eng.
BPL Member

@nentaw_backpackresearcher

Companion forum thread to: Ergonomic shoulder straps that reduce shoulder pain

Two methods for reducing backpack shoulder load have been well known.
One is the load distribution to the lower back with hipbelt or lumbar pad. The other is the load distribution within the shoulder area…

Feb 17, 2022 at 12:58 am #3740615

Rex Sanders
BPL Member

@rex

Interesting! If I understand your video correctly:

– Keeping heavy weight close to the back is very important for reducing pain.
Good to know that measurements confirmed conventional backpacking wisdom.

– Changing shoulder pad thickness can also reduce pain.
The diagram looks like pad thickness and pressure was less over the clavicle, transferring more pressure across the top of the shoulder, and just below the clavicle.

As you noted, with only 8 male subjects, hard to know if this design works for a wider range of people. Are you planning any more tests?

— Rex

Feb 19, 2022 at 8:09 am #3740790

Nenta WAKO, Dr.Eng.
BPL Member

@nentaw_backpackresearcher

Rex,
Thank you for your comment.

In the experiment, the strap didn’t have an buffering effect by itself as it was made of solid PVC sheet. And the pad for padded level was the same material. The purpose was to investigate the effect of load separation.

Regarding the small number of subjects, I couldn’t perform the experiment fully owing to Covid pandemic.
Now this research has closed, but when the product whose spec is applied is developed, I will confirm this effect, again.

For the loading on the clavicle, some adverse effects are reported. So, its load needs to be reduced. What I have to investigate is the adverse effect due to loading on the portion under the clavicle.

Feb 23, 2022 at 10:50 am #3741313

Russell Biser
BPL Member

@rbiser

Have you compared this to Klattermusen’s butterfly bridge / carry on bone system which seems to do the same thing?

Feb 23, 2022 at 1:03 pm #3741321

YoPrawn
Spectator

@johan-river
Locale: Cascadia

Interesting stuff. As someone who suffers from spinal birth defects and can’t hold much weight on my shoulders regardless of strap design, I have found that once a pack is beyond the 20lb mark, using a front pack eliminates all of my shoulder and back pain. It does require a more robust hip belt to then take the load, but the system works great. My front pack only adds 1 ounce of weight because I modified my bear bag to clip to my shoulder straps and hip belt.

I personally think not anywhere close to enough people are using chest/front packs that hook into either the shoulder straps or go around under the armpits and connect directly to the main pack. Beside shoulder pain, there is also a lot of energy loss in trying to keep one’s body balanced with a huge imbalance in the load.

Feb 23, 2022 at 8:49 pm #3741371

Nenta WAKO, Dr.Eng.
BPL Member

@nentaw_backpackresearcher

Russell,

Thank you for your comment.
I haven’t tried butterfly bridge.
It seems easy to establish the strap position onto the clavicle when users wear the backpack to place V-shaped frames over the clavicle.

And regarding the clavicle load, it would be designed for applying larger in lateral part than in medial part. It might be reasonable design for the clavicle to avoid moving downward that compress the brachial plexus and axillary artery, relatively.

But, on the whole, it is designed to support the load on the clavicle positively. So, I think it would be an opposite concept for my suggestion.

Feb 24, 2022 at 2:55 am #3741381

Nenta WAKO, Dr.Eng.
BPL Member

@nentaw_backpackresearcher

Johan,

Thank you for your comment!
Even if shoulder load is distributed within shoulder area, the compressive load of intervertebral discs can’t be reduced. So, in your case, I think that distributing to the lower back is necessary. Also, it is necessary for your lumbar spinal moment to be reduced by way of keeping load balance between front and back even.

Contrarily, the constraint due to hip belt generally brings compensation in walking motion.
It reduces the relative phase between thorax and pelvis in walking with backpack and hip belt, comparing to that in natural walking. And, to keep the same walking speed, it’s necessary for stride larger, regardless of less range of pelvic rotation.

Considering both aspects, users should choose a better way to reduce shoulder load depending on their situation.

Feb 24, 2022 at 8:49 am #3741388

Russell Biser
BPL Member

@rbiser

Nenta,

“But, on the whole, it is designed to support the load on the clavicle positively. So, I think it would be an opposite concept for my suggestion.” It doesn’t feel like it. Having used it myself it does seem to deload the clavicle itself if one side of the V is on each side of the clavicle, and the stiffening provided by each arm of the V accomplishes something like the thickened padding does in your straps.

“it would be designed for applying larger in lateral part than in medial part.” I have not noticed this in actual use.

Achieving this with differing padding thicknesses is more elegant, manufacturable, and ultralight though, so style points to you.

Feb 24, 2022 at 9:14 am #3741389

Nenta WAKO, Dr.Eng.
BPL Member

@nentaw_backpackresearcher

Russell,

Thank you for sharing user review!
Sorry, I haven’t actually try it.
Therefore, my comment was a design review only based on the description of official site. The actual performance seems to be different.

I want to try it, one day! Thanks.

Jun 1, 2022 at 4:25 pm #3750858

Eric Blumensaadt
BPL Member

@danepacker
Locale: Mojave Desert

Since I have L4 and L5 spinal dic problems my backpack shoulder straps only touch the front of my shoulders and merely keep the pack from falling backwards. All the weigh is on my hip belt and thus my pelvic girdle and legs, not my spine.

My Osprey day pack is always under 15 pounds so the design of those shoulder straps work well.

Jun 2, 2022 at 9:44 am #3750914

Ron Bell / MLD
BPL Member

@mountainlaureldesigns
Locale: USA

Six main factors of shoulder strap comfort in lightweight frameless packs.

1. Width – Total width of the padded strap over the shoulder area. Bound, non-padded binding at edges of the straps do no count, but are always listed in the specs and they are faster to make. Inverted and stuffed uses the whole width as padded area- PITA to stuff and build. Stuff 15 sets and your hands are numb all day.

2. Thickness : .5 ” EV50 foam + 1/8″ spacer mesh is pretty good. Maybe 25-40% nicer than only 3/8″ EV 75 (harder) foam. Harder the foam = faster to build.

3. Shape: Varies in comfort perception person to person. When we used to make J and S straps there was little correlation of preference, small to large, men to women. A slight curve seems to fit a very wide range of people.

4. Foam Type: Varies, EV 50 is pretty good and lasts a good long time. Some pack makers use .75″ slightly softer foam on light-ish framed packs and that also works well.

5: Strap spacing at neck. Varies person to person. 3″ seems about right for most. 2.75″ for Small. 2.5″ for smaller. Big neck people need custom.

6: Entry angle over shoulder. Varies. Everyones should slope is different. Somewhere between 8 and 12 degrees seems to fit a wide range of people well. A nicely padded wide strap also add a wider measure of perceived variance compatibility here.

Jun 2, 2022 at 10:15 am #3750920

Nenta WAKO, Dr.Eng.
BPL Member

@nentaw_backpackresearcher

Eric,

Hipbelt is the one method that I described the former one. In this topic, I introduced the latter method.

Jun 2, 2022 at 11:40 am #3750923

Nenta WAKO, Dr.Eng.
BPL Member

@nentaw_backpackresearcher

Ron,

Thank you for your comment.
What I want to say in this topic is the way of load distribution is important if pain is set to the evaluation function for comfort.

It is generally known that strap width, shape, and entry angle contribute contact area (physical fitness) that reduces the mean load if it increases. Also, it was demonstrated that the overall foam thickness and material combination of the strap contribute to reduce pressure hotspot. Those are the factors that you showed.

I showed that there is a design possibility to reduce the overall pain sensation more, depending on the way of load distribution even if the load is partially increased under the same pack weight conditions.

In my research, I investigated the relationship between mechanical stimuli and overall shoulder pain intensity, and made reglession model. If you want to know in detail, please watch my YouTube video on the link.
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