women's center of gravity
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dan mchale
(wildlife) - MLife

Locale: Cascadia
women's center of gravity on 11/24/2005 14:55:13 MST Print View

The subject keeps coming up at my shop. Women tell me they are told to carry the heavy things lower in their packs in general compared to guys. This is not for climbing but in general. I have read this is because the female body has a lower center of gravity. I understand why any climber might benefit from a lower center of gravity while climbing but women are being told they should carry weight low in general. I disagree with this very much. I think it is a bit of misinformation that has infiltrated the industry. It pretty much goes against what Dick Kelty and others established years ago regarding carrying loads higher where they end up straight over the center of gravity of the lower body because; the higher you go up the slightly forward leaning walking back, the greater is the volumetric area that is directly over the center of gravity of the lower body.

I have worked with several women recently and they agreed their packs carry better when they actually get the load close to the back AND higher. I thought it would be a good idea to bring this up for discussion - this being a more technical site. The misinformation has been with us for a number of years now - let's clear it up!

Edited by wildlife on 11/30/2005 21:44:11 MST.

Ken Helwig
(kennyhel77) - MLife

Locale: Scotts Valley CA via San Jose, CA
center of gravity on 11/24/2005 17:52:30 MST Print View

Nice post Dan. I think my wife would agree with you. Food for thought for us out there. Now is this on a shop to shop basis? I feel that there are so many out there that are working in retail that they have no clue on what they are trying to sell you as well as how you are supposed to move in the backcountry.

Edited by kennyhel77 on 11/24/2005 17:53:07 MST.

Mark Larson
(mlarson) - MLife

Locale: Southeast USA
Re: women's center of gravity on 11/24/2005 18:18:17 MST Print View

I definitely agree, from both the physics of the situation and what I've heard from fellow female hikers.
-Mark

Vick Hines
(vickrhines) - F

Locale: Central Texas
Re: women's center of gravity on 11/24/2005 18:24:33 MST Print View

Dan,
How would you suggest going about clearing ignorance about women's C of G in an industry rife with misinformation - much of it intentional?

WARNING: The rest of this is a rant. In summary, a) the industry promulgates misinformation and ignorance and has done so for years because that is how it makes money (with some notable exceptions); b) women in particular are the victims of the lack of information, research, general butt ignorance in the business; c) don't believe any of the BS about how scientific the manufacturers are.

Now:
Industry leaders stopped research to establish a standard for sleeping bag comfort ranges. Accurate information is bad. Large companies base sales on marketing (product differentiation), not product performance. This is true of all gear - not just sleeping bags.

Manufacturers dominate the literature. Have you read Backpacker lately? And their job is selling stuff to ignorant folks. Notice that Backpacker maps are now all GPS dependent. Navigate without knowing anything. How responsible is that?

Separate gear for women is what the marketing department likes to call 'a new and lucrative nitch.' (I'm not saying some specialized changes are not needed. Just let women say what they really need.) So of course there is going to be misinformation about women's packs. That despite the glaring fact that if you have a low C of G, you can carry a load even higher than someone who is already top heavy. Duh.

Take a look at women's shoes. In my experience, women get more bad advice about their feet than anything else. I once hiked with a woman who was told she had to stop hiking. Then the salesman talked her into a SMALLER size of the same model shoe (probably because that was all he had in stock). Her problem was her shoes were too small to start with and an inappropriate model for her feet. Finally I convinced her to get light runners and she sailed up the AT.

Women are told they are cold natured and need more insulation -- although they carry more insulation than men to begin with and have a WIDER comfort range. Notice the drill team the next time you are at a football game on an icy Friday night. And don't talk to a mother about handling discomfort.

Enough. You bet, we could have a special threads just for women's specialized needs - good idea. And maybe one for exploding industry-promulgated myths. That would be a good BPL function. The users could say things that BPL can't for fear of being banned from the trade shows. Heh, Heh.

Edited by vickrhines on 11/24/2005 18:26:46 MST.

David Lewis
(davidlewis) - MLife

Locale: Nova Scotia, Canada
Re: center of gravity on 11/24/2005 18:25:03 MST Print View

Well... I guess you could say that about all retail in general... no clue what they are selling... unless it's a small local shop.

And as far as outfitters go, they are all selling 5 pound packs anyway. It pains me when I see a newbie in a store getting a sales pitch about the latest 6 pound North Face pack... and all the guy wants to do is start doing a few weekend overnight trips. The suspension system alone on that pack probably weighs more than my heaviest peice of gear.

As for Dan's original post, I'm not a woman... so I don't know :) But it probably is a myth. With a 5 pound base weight though, it's probably not quite as crucial how you pack... no? I put my food on top personally. Not only is it easier to get to, but with UL backpacking, it's also, often, your heaviest item.

Sarah Kirkconnell
(sarbar) - F

Locale: In the shadow of Mt. Rainier
Re: women's center of gravity on 11/24/2005 22:33:59 MST Print View

My 2 cents as a lady....well, I pack my pack in how it is comfortable-I don't pay attention to where stuff is inside-just in how I know it will ride.
REI is a huge spreader of the low G theory....
Now granted, some women's only products do work well and are well designed-for instance, my current pack is a ladies Kelty Shadow-and it works great-cut for a woman's body. Same with my Thermarest Prolite ladies pad-short but long enough ;-) Can't imagine wearing unisex boots! Or unisex pants....
But yes, there is some overkill out there.
Though most women DO have cold feet and hands at night and the temp ature theory for a warm bag at night do pay out for quite a few ladies. Most of my female hiking partners are ALWAYS cold on trips after the sun goes down.

paul johnson
(pj) - F

Locale: LazyBoy in my Den - miss the forest
CG on 11/25/2005 04:12:42 MST Print View

i believe merely considering CG as being longitudinal (i.e. fore-and-aft, or front-to-back) in nature is a mistake.

CG is three-dimensional and lateral and vertical components should also be taken into account together with the longitudinal component.

i think when this is done, that, for all practical purposes (based upon the general shape of packs and where we wear/carry them), the vertical component will be seen to be more critical to balance when wearing/loading a pack than the longitudinal component. it also provides a greater range for adjusting. the goal should be, when wearing a fully loaded pack, to minimize in all three directions the movement of our CG from our body's normal, unladen CG.

as such, keeping as much wt. down low, for both men and women, is preferable to keeping it up high as is traditionally recommended.

Edited by pj on 11/25/2005 13:57:47 MST.

Sunny Waller
(dancer) - M

Locale: Southeast USA
Re: women's center of gravity on 11/25/2005 11:27:26 MST Print View

I took church groups on backpacking trips for 15 years. I provided all the gear. I quickly learned that most women sleep cloder then men. I would issue the women a North Face Cats Meow Polarguard sleeping bag. The men got the Jansport synthetic fill bags. Both of those bags were rated 20 degree bags but the North Face bag had twice the loft (at twice the price) and were much warmer. I had a mixture of internal frame and external frame backpacks. Most of the men were more comfortable with the heaviest item (usually the tent) packed up high on the pack. Women did better with the heavier stuff packed lower. That setup worked well with the way packs were designed then..packs that had to carry the heavier-less packable gear you had back then. I think the "lower-higher" rule of thumb is leftover from that era. BUT my how things have changed. Gear is different..it's lighter..it packs up smaller (now you can actually fit your tent and your pad INSIDE your pack). Packs have different suspension systems that all ride differently on peoples backs. AND peoples backs are different-espically women's backs. Many women work out now. Some of them have very developed neck and back muscles..this effects how a backpack rides. Granma Gatewood could shoulder that duffel bag because she was a farm girl..she didn't need no backpack :)
The best advice that I give anybody now is to pack your gear different ways until you find what feels the best for you. As for the theory that women sleep colder than men don't ask me. Go to the experts. Ask the men who go backpacking with their wives because they are definitly gonna know the answer to that :)

dan mchale
(wildlife) - MLife

Locale: Cascadia
Re: Re: women's center of gravity on 11/25/2005 12:56:05 MST Print View

I don't think the misinformation is intentional or intentional for marketing purposes although that is what happens. These rural myths get started and through laziness from company to company they get duplicated. This happens in the general media. This site is a perfect place to do a study complete with illustration. A picture is worth a thousand words. I suppose if you had to have a rule for beginning packers it would not be carrying heavy things high. If you look at the way women carry water on the top of their heads in Africa you have to ask what that's all about! THEY aren't stumbling to and fro.

Years ago in my teens ( 30+ years ago ) I worked in a shop where the owner always mentioned that womens center of gravity was lower because of the reproductive function of pregnancy. Shorter legs in general prevented accidents. Less upper body mass helped too I guess. Look at the way womens' arms have evolved to clear the hip area. Anyway, he made the point that the hip area was the strongest part of a womens body and was a good place to carry the weight via the hipbelt. This did not mean the weight of the pack had to be low. Most women have strong enough upper bodies to control lateral shift of packs provided they know how to operate the harness. THAT is what the harness is mostly for. This thing about women needing to carry the weight low because their body mass is low is something I did not hear in the past. It is something new. The rule should be to keep the load as close to the back as possible and this usually means spreading it out over as much of the back as possible. With today's loads getting so much lighter there's not much to worry about it getting too high.

Edited by wildlife on 12/01/2005 09:44:09 MST.

dan mchale
(wildlife) - MLife

Locale: Cascadia
cg on 11/25/2005 13:13:46 MST Print View

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Edited by wildlife on 11/28/2005 13:21:31 MST.

paul johnson
(pj) - F

Locale: LazyBoy in my Den - miss the forest
Re: Re: CG on 11/25/2005 13:18:43 MST Print View

let me reiterate the rule mentioned in my prev. post that i use in loading my pack:

"the goal should be, when wearing a fully loaded pack, to minimize in all three directions the movement of our CG from our body's normal, unladen CG."

when i load my G5 and G6 packs, i place food or any other heavy items as close to the bottom AND as close to my back as possible. i use stuff sacks containing lighter gear placed rearward of the items that i'm trying to keep closer to the small of my back and lower thoracic region. generally, if i can't fit all of my heavier items below my shoulder blades, then i'll use a slightly larger pack, that way the heavier items are all low AND close - being mostly or totally in the area of the small of my back. this also means that i generally don't use the extension collar of a pack as i feel that this, even with lighter objects can affect vertically the body's laden CG - this can more readily unbalance the body laterally. with some packs these heavier items can also, if desired, be evenly distributed, down low, between the outer side pockets of some packs (e.g., G5) - though i rarely do this, preferring to also keep these heavier items closer to my lateral CG. this arrangement works for me. unless i am mistaken, i believe that a prev. poster is also recommending a somewhat similar loading configuration, but is stressing just one benefit of doing so, viz attempting to eliminate "backwards pulling"..

the basis of my personal rule is that our balance is better without a pack than with a pack. however, since we must carry a pack, how do we do this and least affect our balance and stability. this is where minimizing the deviation in ALL THREE directions (viz, laterally, longitudinally, and vertically) from our body's normal, unladen CG comes into play.

as long as you do this, however you accomplish this, i believe you have acheived (from a balance and stability standpoint) the optimal pack loading configuration. also, purely from a balance and stability standpoint, given a choice of moving my CG a certain small distance slightly further back versus the same distance slightly higher, it is, to my way of thinking, generally preferable to keep it lower rather than more forward. my reasoning is that when traversing, in particular, uneven terrain, it is, in my experience, other than toe-kicking a root or stone, easier to loose my balance laterally, than it is to loose it longitudinally. having a lower CG is also beneficial to lateral stability. this is especially true if trekking poles are not used.

if one still feels a "backwards pulling", then i think that the pack is probably NOT loaded according to my personal rule.

the "trick" referenced in another post, to my mind, neglects the lateral and vertical components of CG and especially how they come into play with the structure of the human body, particularly while walking. the "trick" is only addressing the longitudinal component of CG, and as such misses, in most situations, the most important aspects of balance and stability. however, given the clarification in that Post of L/UL packs smaller capacity, this "trick" may in actuality be exactly the way i load my packs - i'm not sure though. i'm not sure precisely how to understand it and what are the vertical limits chosen in that Post when loading gear as close to the back as possible.

Edited by pj on 11/25/2005 16:22:48 MST.

dan mchale
(wildlife) - MLife

Locale: Cascadia
Re: Re: Re: CG on 11/25/2005 15:57:28 MST Print View

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Edited by wildlife on 11/30/2005 20:31:42 MST.

paul johnson
(pj) - F

Locale: LazyBoy in my Den - miss the forest
Re: Re: Re: Re: CG on 11/25/2005 16:31:48 MST Print View

Mr. McHale,

>>"Im outta here"

0. not sure if the statement is "time constraint related". if it wasn't, then...

1. if i have offended you in anyway, i am truly sorry and would like to apologize to you.

2. i hope you will continue to participate in these Forums. i very much appreciated the insightful reply you gave me in another Thread, englightening me as to my confusion.

3. if my presence here would mean that you wouldn't return to the Forums, i will very gladly bow out of the Forums as i feel that overall your contributions, given your excellent credentials, will be far more useful to other Forum participants than any contribution that i may be able to make.

4. please understand that my 2 or 3 uses of "you" in my prev. post were NOT addressed to you personally, but were more general in nature, i.e. of anyone who does a certain thing. my refs to you, personally, were always in the 3rd person as in "a prev. poster".

5. please know that i have a peculiar way of learning by drawing out info from an individual by stating what i truly believe to be true and the reason for it. once that person understands my reasoning, if i am right, they will then agree with me. if i am wrong, then they can correct me by showing me how my reasoning is flawed. that's all i was attempting to do.

again, if i have offended you in anyway, please forgive me.

sincerely,
paul johnson

Edited by pj on 11/25/2005 16:49:17 MST.

dan mchale
(wildlife) - MLife

Locale: Cascadia
Re: Re: Re: Re: Re: CG on 11/25/2005 17:27:04 MST Print View

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Edited by wildlife on 12/01/2005 11:00:14 MST.

S H
(huijing) - F
Re: Re: Re: Re: Re: Re: CG on 11/26/2005 01:21:19 MST Print View

I felt he was rude to my h. That's why I post. I want to apologize to him.

Edited by huijing on 11/30/2005 02:18:07 MST.

dan mchale
(wildlife) - MLife

Locale: Cascadia
re: --------- on 11/26/2005 16:48:24 MST Print View

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Edited by wildlife on 11/28/2005 13:27:40 MST.

Robert Ebel
(poop) - F

Locale: Earth Orbit
Re: Re: Re: CG on 11/30/2005 17:12:49 MST Print View

Dear P J: If the weight you are putting down low can be put close to the back this would improve lateral stability as oposed to just putting it low. Simply putting it low can increase the lever arm length backward. I disagree with you also on the point that the longitudenal aspect is the least important. They are all important and all become less important equally as the overall pack load becomes less - as in going from heavier pre-historic loads to lighter loads. You gave examples of losing your balance in the longitudenal sense. Can you please give an example of how you lose balance in a lateral sense?

Your basic premise and rule that a pack should imitate what it is like without having a pack on at all seems to ignor having a pack on at all.

Edited by poop on 11/30/2005 19:01:52 MST.

dan mchale
(wildlife) - MLife

Locale: Cascadia
Re: Re: Re: Re: CG on 11/30/2005 19:43:07 MST Print View

Quote from PJ: "i believe merely considering CG as being longitudinal (i.e. fore-and-aft, or front-to-back) in nature is a mistake."

What I said in my original post is inclusive - it takes in the lateral component: Keeping things close to the back automatically address lateral rotational forces - and they usually are rotational lateral forces rather than merely lateral. Keeping things close to the back minimizes what R Ebel is probably noting with his lever arm. The less the load, or the less the main mass of the load sticks out to the rear, at any level, the easier it will be to recover from a lateral mishap. A lateral mishap can occur even without a pack so let's not get carried away with 'pack caused' lateral mishaps. If a mishap occurs, a load that sticks out more to the rear will want to keep the body rotating and is more difficult to stop than one that is close in.

WE ALL KNOW that tall top heavy packs can be unstable. Carrying weight moderately high does not, however, doom somebody to certain chaos. It depends on experience, both experience with varying topography, and experience in adjusting packs and loading packs. Much instability comes from ignorance of correct harness adjustment. Some people 'trade' the potential instability of a high load for long term comfort. For people carrying heaving weights long distances, the main goal is pack comfort all day long, and NOT so much worrying about falling over with every step. People that are clumsy and do not do well with heavy loads of any kind tend to not carry heavy loads so I was not really addressing those people in my original post.

If I was to make a general rule it would be to keep heavy things as close to the back as possible. This immulates the body simply being a heavier body as much as possible without putting weight in front of the body. This hides them within the bodies center of mass as much as possible. Whether you put them high or low is less important than close in but there is a point where going higher is better as long as the pack has a good functional harness and the wearer knows how to use it. Since most people carry their sleeping bags low this does not lead to many options. If weight is concentrated low, and there is enough of it that it starts to gain a dimension front to back that is more than if it was spread out across the back, then it adversely affects center of gravity. It becomes a force of it's own and works on displacing the bodies mass at what ever level the load is at. If the load is right behind the lower back and sacrum then it wants to push the sacrum forward so that the 2 masses have a common center.

Anyone that has had the experience of not being able to escape the weight of the load, no matter how far they lean forward, is a victim of a load with a center of gravity that is too low and prutrudes too far back. If that same load was higher up the back, then at least the forward lean would bring it over the body at some point, and the the weight can rest more on the plane of the back and relieve the shoulders somewhat. The load can set on the back more as the back becomes an inclined plane. The cohesive forces that make the pack want to stick, or cling to the back increase. It is easy to see in this picture that the higher the load is carried the more quickly it comes into balance. It also comes into balance more quickly if it is kept flat or spread out. To carry big loads comfortably some of these rules must be adhered to. Hipbelts, and whether a pack has a frame or not complicate things but the basic forces remain the same. Just because a pack has a hipbelt does not mean the load does not have to be packed close to the back for instance. Ignorance of the rules is one of the things among many others that is fueling the UL movement - not that there's anything wrong with the movement. For me it is nothing NEW and there will always be people that have to carry heavier packs, or will find a good reason to.

Edited by wildlife on 11/30/2005 22:07:09 MST.

ivo zlatinov
(ivaylo) - F
a couple of ideas on 11/30/2005 22:15:27 MST Print View

first, i think the advice to keep heavy things lower for women is based on female physiology. Women have relatively more strength around their hips, and men - up in the core / shoulders. I have sen this numerous times swimming: most men swim utilizing more the upper body, and the women - driving w/ strong kicks from the hips. SO, it may be that the advice just tell women to keep heavy things closer to the part of the body, which is (generally, and relatively) stronger.

the comment that a forward lean should balance the load under the C of G: i believe such an unnatural position and load are going to hurt your body. not an optimal position for the human spine. good thing this is forum is about (U)LW

just saying... this is what I think, not trying to start an argument or something.

cheers
ivo

dan mchale
(wildlife) - MLife

Locale: Cascadia
Re: a couple of ideas on 11/30/2005 23:19:22 MST Print View

I'm not advocating a forward lean of any kind. Above, I tried to point out that when a pack is loaded poorly, a forward lean does not even help. In my first post I say the body leans slightly forward while walking, even without a pack, and if a pack is loaded properly, the body does not have to lean any more forward than it already does. Above, I try to point out the consequences of a load that is too low and far back. I also made comments about womens physiology in other posts and made comments about women that carry large water jugs on their heads even though their hips are larger and stronger. It's not so much where you carry it vertically on the body but how close to the center of gravity you can get it. Womens hips are strong and I made the point that does not mean they are limited to having the mass at their hips. The mass of the load can be in a number of places and still be carried by the hips.

It's funny; some people I suppose think that this means that men would carry the weight high in a pack because their upper bodies are more massive or stronger. That has nothing to do with where the mass is placed in a pack. If a big strong guy carries all the weight with his shoulder straps and does not even use a hip belt you still don't know where the 'mass' is located in the pack. It can be high or low. If he carries all of the weight with a hipbelt you still don't know where the mass is in the pack unless you are told. External frames where designed to keep the load close to the back - you could hardly miss. With most you could shift the bag and carry the sleeping bag high or low. Years ago when Dick Kelty advocated carrying weight high he was not being sexest and leaving women out of the equation, but that would be the assumption today, leaving room for the silly rule I posted about. The silly rule that women need to carry the weight low leaves out the important point that it should still be kept as close to the back as possible. I made my first post in response to the damage this rule was doing to women that have to carry unusual amounts of weight as in climbing. When this is the case the weight needs to be spread as much as possible over the entire back for the most effecient carry. I maintain that women are not built so differently than men that they need a different loading technique. I say the same about hip belts. What they need in packs are packs that work. Just when the industry in general is providing some choices to women with internal frames, women are being ushered into frameless packs that are not giving them what they need. Nothing could be more damaging.

That does not mean that some women or men cannot benefit from simply carrying less, but you have to carry exponentially less for a frameless pack to work well for most people. I don't think Dick Kelty advocated carrying heavy packs any more than Collin Fletcher. I believe he left the scene before the whole thing became yuppified and people had more gear than they knew what to do with.

I forgot to say also that this is not just a packing issue. Many women are ending up with very short fat high volume packs. If these are not packed correctly they are a bear to carry.

Edited by wildlife on 12/02/2005 12:42:20 MST.