Shoulder Strap Education
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Chris W
(simplespirit) - MLife

Locale: .
Re: interesting on 09/05/2011 10:48:39 MDT Print View

Jennifer

Here's one article referencing a study of it.

http://www.faa.gov/library/reports/medical/oamtechreports/1960s/media/AM65-14.pdf

That was done in 1965, but I had my PT wife check mine with one of her fancy tools, and it's almost identical to what they came up with. I measured the slope of her shoulders as well, and it's slightly different. I'd have to check again to verify the exact angle.

Diana Vann
(DianaV) - MLife

Locale: Wandering
Which pack? on 09/05/2011 10:56:56 MDT Print View

Daryl,

Can you give a make and model for the pack you are wearing in the photos?

Thanks

Jennifer McFarlane
(JennyMcFarlane) - MLife

Locale: Southern California
Another question for Chris on 09/05/2011 11:05:59 MDT Print View

What is the name of the fancy tool your wife used so I can get one of the PTs at work to measure me? :)

This whole topic is interesting to me because I end up with numb arms.hands/fingers from most packs, but not the Osprey Hornet, which attaches the same way the Mutant does. My only problem is the Hornet's hip belt does not work for me.

Chris W
(simplespirit) - MLife

Locale: .
Re: Another question for Chris on 09/05/2011 11:15:50 MDT Print View

Orthopedic Goniometer


It looks pretty close to this one.

Depending on how they measure they should either get something in the 60-70ish range or something in the 110-115ish range. If it's the latter, just subtract from 180.

Edited by simplespirit on 09/05/2011 11:18:51 MDT.

Jennifer McFarlane
(JennyMcFarlane) - MLife

Locale: Southern California
Shoulder straps on 09/05/2011 11:20:03 MDT Print View

Thanks Chris!

Chris W
(simplespirit) - MLife

Locale: .
Re: Shoulder straps on 09/05/2011 11:25:02 MDT Print View

Also, make sure they measure the slope along the upper trap or where you'd want the shoulder strap to lay. The angle along the outer shoulder is a little different and most people don't wear packs that far out anyway.

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Re: Shoulder straps on 09/05/2011 13:49:47 MDT Print View

Another way to accomplish this is to have more of a point connection between shoulder strap and pack, then the straps would just naturally rotate to be flat against your shoulder.

Like, I had a shoulder strap with a grommet connection to the pack. Or you could narrow down to a 3/4 inch webbing or something.

Daryl Daryl
(lyrad1) - MLife

Locale: Pacific Northwest, USA, Earth
Re: Which pack? on 09/05/2011 19:33:34 MDT Print View

Diana,

The pack is one I made for myself.

Daryl

Chris Peichel
(momo)

Locale: Eureka
RE: Shoulder Strap Education? on 09/06/2011 10:05:35 MDT Print View

@ Chris
I Agree the shoulder strap needs to conform to ones shoulder, from where it starts to make contact with ones back all the way to the armpit.

I disagree with the statement that the strap has to be sewn on at an angle to match the top of the shoulder. The shaping of the strap and the angle at which it comes off the pack (wether or not is is sewn on at 90deg or not) will determine if the strap lays properly on the body.

One of your examples, the osprey mutant, has a yoke attaching the straps to the back panel of the pack. The yoke is sewn on at fairly close to 90deg to the pack, the yoke then angles outward giving proper fit over the shoulders. I did own a mutant 38. The trouble with using a yoke attachment is then you also need to employ load lifter straps to keep the pack snug against the upper part of your back. I don't feel load lifter straps are necessary in a properly fit and loaded pack with weights under 35lbs.

The same thing ( and proper fit ) CAN be accomplished with properly shaped shoulder straps sewn on to a pack at 90deg to the pack body yet angled out in a V-shape. This will help keep the load snug against the back and eliminate the need for extra pieces. AND if the strap is shaped properly, it will match the shape of ones shoulder and be comfortable.

I have worn many many packs, not being able to find the idea pack for me caused to to start making my own. Shoulder strap fit is the first thing I notice when I put on a pack. I have made over 40 variations of shoulder straps, slowly refining the shape and the fit. I will also add that I prefer to not use a hipbelt with loads under 20lbs. Carrying all the weight on the shoulders lets you know pretty quickly if the fit is right or not.

I have seen some great packs made recently on this forum, I would say the people making these packs know as soon as they load them up and try them on wether or not the pack fits.

TO the pack makers out there. Keep up the great work, you know what works for you. It is either comfortable or it isn't. If it isn't, you can change it. Thats the beauty of myog.

Chris W
(simplespirit) - MLife

Locale: .
RE: Shoulder Strap Education? on 09/06/2011 10:10:16 MDT Print View

I'll let the science do any arguing for me at this point. It's been studied and the results posted.

David Drake
(DavidDrake) - F - M

Locale: North Idaho
Re: Shoulder Strap Education on 09/06/2011 11:22:57 MDT Print View

Timely discussion for me, as I'm just starting to design a pack. I've been looking at the small pack I currently use, which has s-curved straps sewn in at 90 degrees, but angled out (similar to Jerry's first drawing). As Jerry points out, when the straps are in wearing position, this does make an angle where they cross the shoulder. But I've noticed I need to use the sternum strap to hold them in that position.

I'm wondering if a combination of s-curved straps and an angled seam (as Chris Wallace is recommending) would result in a good fit with no need for sternum strap. Maybe a wider spacing between straps at the seam would help as well.

There's been a lot of BPL articles and forum posts on how to make packs following particular patterns. Maybe one of the experienced pack makers could do an article on how to custom fit a MYOG pack (designing for shoulder angle and width, torso length, difference between men's and women's packs, etc).

Michael Duke
(mpd1690) - F
My thoughts on 09/06/2011 11:32:38 MDT Print View

I think it is not too big of a deal to be honest.

From the article provided: "Shoulder Straps of relatively inflexible or coarse material, will tend to concentrate the load toward one edge"

The main thing to take from this is relatively inflexible or coarse.

I know that the materials I use have the ability to flex in the center of the pack between the straps. The straps also have a significant amount of flex to them. I feel this is the case with most MYOG packs, as the general materials used are not "relatively inflexible or coarse".

Daryl Daryl
(lyrad1) - MLife

Locale: Pacific Northwest, USA, Earth
Re: Re: interesting on 09/06/2011 11:32:49 MDT Print View

Chris,

I read and enjoyed the study. Straight forward and easy to understand. Good place to start when designing any pack.

The importance of shoulder strap shape was made clear to me when I started designing my current backpack about 15 years ago. I started out by purchasing a canvas paper delivery sack (with front and back bags) to experiment with. It had a small neck hole and very little slope, if any, to the straps. It felt horrible! The side of the straps dug into my neck and traps so badly I couldn't wear it more than a couple of minutes without pain.

Thanks for the post and the info. It helped me clarify my thinking on the subject.

Daryl

Chris W
(simplespirit) - MLife

Locale: .
Re: My thoughts on 09/06/2011 13:31:59 MDT Print View

In reference to the "inflexible or coarse material" tidbit, I've experienced the load being concentrated to one edge as described in the study with a lot of packs. This includes everything from those that use a layer of spacer mesh combined with a layer of Dyneema-X as on the HMG packs to those that use foam padding (Evazote) like the current GoLite Jam. Both of those have fairly flexible and curved straps mounted at 80-90 degrees, yet suffer from the problems described in the study. The best straps I've tried personally were on a ULA Ohm, which, not surprisingly, are mounted at a decent angle.

Edited by simplespirit on 09/06/2011 13:32:28 MDT.

Chris Peichel
(momo)

Locale: Eureka
Re: Shoulder Strap Education? on 09/06/2011 13:40:29 MDT Print View

@ Chris Wallace

What pack do you use?

I am not arguing the science that peoples shoulders are not square. You are making a firm statement that a pack shoulder strap will not fit properly if it is attached at a 90deg angle to the pack body, irregardless to the shape of the strap.

I will let the FACT that I have shoulder straps attached at a 90deg angle to the pack body, but angled out and contoured to fit the shoulder properly (even matching the angle of the shoulder) do the arguing for me at this point.

Chris W
(simplespirit) - MLife

Locale: .
Re: Re: Shoulder Strap Education? on 09/06/2011 14:10:50 MDT Print View

Right now I'm using a Jam. The straps are curved and attached at a measured 80 degrees. They're more padded than the typical spacer mesh people are using but still relatively flexible and will support a real load. Unfortunately, they suffer from the load being concentrated to one side as mentioned in the article. Chris Townsend noticed the same thing with a Jam on his PNT thru, although he describes it a bit differently.

I'm also testing packs for some other companies and working on my own design (thus the research).

I suspect the reason you aren't experiencing it with your straps is because you let the pack ride fairly low on your back. That works ok with a very light load and no transfer to the hips, but not so much on an expedition where you might carry 25-30 lbs due to food and water with no resupply.

Yes, some people claim to be able to carry that much weight on their shoulders and be comfortable. That too has been studied medically, though, and the results can be long-term damage to the nervous system, muscle weakness and atrophy, and scapular winging amongst other things. It's known as Pack Palsy. That's also a very good reason to go out as light as we reasonably can. We aren't designed to carry heavy weight, even on our hips.

Edited by simplespirit on 09/06/2011 14:15:04 MDT.

Michael Duke
(mpd1690) - F
Pack Specific on 09/06/2011 14:21:23 MDT Print View

I am curious, do you have a scientific study that is pack specific? The article linked seems to be related to aviation harnesses. I just don't see any true problem with a 90 degree attachment. It seems that a ability to of the material to flex pretty much mitigates the need for angled attachments

Chris Peichel
(momo)

Locale: Eureka
re: Shoulder Strap Education? on 09/06/2011 22:13:58 MDT Print View

Chris,
My pack rides high on my back, tight and close. I haven't carried more then 25lbs, nor do I want to. Usually I only have 15lbs total.

I am interested to see what you come up with. Good luck in your design.

Hendrik Morkel
(skullmonkey) - MLife

Locale: Finland
Some photos on 09/07/2011 03:23:22 MDT Print View

Snapped some photos of packs I own. I found two cottage packs are at the 90° angle, and I don't find them comfy. The ULA Epic, while having a slight angle, has the straps too close to each other, which is uncomfortable as well. All other packs are fine - it seems the big players know how to do the straps, while some cottages go with the fast and easy solution of 90° angles to the backpanel.

Scott Littlefield
(sclittlefield) - F

Locale: Northern Woods of Maine
Shoulder Straps Images on 09/08/2011 13:54:13 MDT Print View

Here's roughly the design I've been using and like a lot.
Backpanel Shoulder Straps

A real life image:
Pack BackPanel Straps