Future Of Backpacks

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Tom_H
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Re: Future Of Backpacks

Post by Tom_H » Thu May 17, 2018 12:44 am

maverick wrote:Outside Magazine:...when you strap a pack on, the actual cost of supporting the pack against gravity isn’t a big deal. Instead, it’s decelerating and then reaccelerating it with each step that costs energy...
If you were to do one of those computer graphic video images of someone carrying a pack, you would see the pack itself surging forward, slowing down, surging again, etc. After learning the rest step many years ago, I tried to develop a rhythm whereby I let my leg land, but both feet stayed on the ground for a brief moment while my torso continued its forward momentum at about the same speed before the rear leg came off the ground and swung forward. I did find that that it's not only that brief moment when both feet on the ground that saves energy, but keeping the torso and pack moving forward in as smooth of a motion (as little surging and slowing) as possible also saved energy.

I saw a video this week of a bipedal robot running very smoothly at about 7-8 mph. Rather than one of those as my sherpa, I wouldn't mind one of those exoskeleton things the military is experimenting with for infantrymen. It could carry my pack and help me move my own body as well!

Image

Running robot:
https://www.cnn.com/videos/cnnmoney/201 ... g.cnnmoney








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Re: Future Of Backpacks

Post by Wandering Daisy » Thu May 17, 2018 9:04 am

That military photo shows everything wrong with distribution of weight and the pack itself. Center of gravity of the pack is well behind the person's center. The pack is too deep vs wide or tall and does not vary front-to-back depth based on position relative to the body. The pack is stiff and does not contour to the body. In my opinion, if carrying heavy weights, the old external frames with an extender bar carry the weight the best. The top duffle in the photo below is full of heavy climbing gear.
105-0556_IMG.JPG
Tom is exactly right, that when you walk with a pack, you need to do so such that the pack's movement is as forward and smooth as possible. When I walk behind people, I often find that they sway right and left (sort of waddle). Getting the pack moving again is also a reason that a slow and steady pace is much more energy efficient than stop-and-go.
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Re: Future Of Backpacks

Post by mrphil » Thu May 17, 2018 9:41 am

Wandering Daisy wrote:When I walk behind people, I often find that they sway right and left (sort of waddle).
You're right, walking behind someone is very enlightening in terms of seeing how efficient (or not) movement can be. I've actually found myself becoming annoyed by watching it, and I've not only commented on it for the sake of their awareness, I've been known to grab the sides of their pack for a few strides as they walk in order to make them feel the difference, in some cases, even going so far as to shove them forward when they keep doing it and I can't take it anymore. That side-to-side waddling ( I prefer to call it lumbering) just kills me. So much energy wasted, with so much weight and bulk going everywhere but forward.

With my lower back the way it is, if I don't stay squared up and moving as efficiently as possible, I'm hurting badly by the end of the day. Big loads aren't a problem with compression at all, but move it sideways long enough, and it's ibuprofen and Vicodin for dinner.

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Re: Future Of Backpacks

Post by longri » Thu May 17, 2018 11:04 am

[b]Alex Hutchinson of [i]Outside Magazine[/i]:[/b] wrote:...when you strap a pack on, the actual cost of supporting the pack against gravity isn’t a big deal. Instead, it’s decelerating and then reaccelerating it with each step that costs energy...
I question this premise. I think the opposite is obvious to anyone standing around for a length of time with a heavy pack on. Even though you aren't doing mechanical work on the load your muscles are still moving in subtle ways that require energy. I often walk faster in order to arrive at my destination sooner because it is my perception that there is a time cost associated with carrying a load.

The authors of the paper Hutchinson referenced in his article in Outside don't make the claim quoted above. That's something Hutchinson tacked on by himself. In the referenced paper the authors state:
Donelan et al. wrote:There are other costs of walking that are not explicitly represented in our models, as indicated by the y-intercept of the mechanical and metabolic power curves (Fig. 5).... It is also probable that there are additional metabolic costs not attributable to step-to-step transitions or external mechanical work, such as for supporting body weight, moving the legs, moving other limbs, or controlling stability.
The y-intercept they write about, the zero-speed component of the net metabolic power, is larger than that attributed to walking (without additional load) at one's normal pace. And that's after they had already subtracted the metabolic rate measured when the test subjects stood still.

What they do show is that taking longer steps at the same rate (hence, walking faster) requires greater energy expenditure. And they attribute this to fact that the center of mass has to be accelerated and decelerated. But nowhere do they say that standing still comes for free.

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Re: Future Of Backpacks

Post by Wandering Daisy » Thu May 17, 2018 12:54 pm

Gravity is not insignificant! Add weight and it squishes joints, pains your body, especially downhill. Standing still with a pack on may not be a big "energy" expenditure, but it sure adds to the day's total "pain". Me too on walking fast to get to camp earlier because the pack gets painful if on too long. Now, if I were UL and had a 15 pound pack, then maybe.

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Re: Future Of Backpacks

Post by longri » Thu May 17, 2018 1:39 pm

Even with a really light pack it matters because you still have your own weight to support.

When I do a dayhike with my wife my pack is usually well under 10lbs. We might do a loop that takes 8 hours. Sometimes I'll go back by myself and walk the same loop in a shorter time, like say 6 hours, and I won't be as tired afterward. That's just subjective of course, but I think there's something real behind it.

There's a significant difference in metabolic rate between sitting and standing without a load. It's something like 10-15%. It seems self-evident that adding weight would increase that difference. Just going by the old Pandolf equation you can make some very rough estimates. According to that, a 165lb person standing still with a 50lb pack burns as much energy as when walking without a pack on flat, even terrain at 1MPH.

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Re: Future Of Backpacks

Post by wildhiker » Thu May 17, 2018 2:01 pm

I agree with Wandering Daisy that an external frame pack is best for carrying large/heavy loads. I used my Kelty external frame pack exclusively for backpacking for over 40 years. I then bought an Osprey internal frame (about 60 liters) to use for trekking in Patagonia, just because it is easier to take on the airplane.

Here is a picture of my homemade "balance pack" from 1984. The front "load" is my 6 month old son. Total weight front and back was about 65 pounds on my then-140 pound frame. It was doable, but I never wanted to carry that much weight again! We also had our 5 year old and 4 year old daughters with us. They were good walkers, but my wife and I had to carry all the food and equipment for everyone for a 3 night trip.
84-09f05.tif
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Re: Future Of Backpacks

Post by longri » Thu May 17, 2018 2:45 pm

That's a great photo!

When I first started backpacking I weighed about 145lbs and thought nothing of carrying a pack that weighed over 60lbs. My base pack weight for summer was nearly 40lbs and my typical rations weighed about 3lbs per day. It was just normal for me to have a big pack. I liked it.

I won't argue about the the balance idea. I think it has merit. It just looks awkward to me. A baby I'd carry that way in the front for reasons other than load distribution. But a sleeping bag or bear canister? Not me. I want that space open.

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Re: Future Of Backpacks

Post by Tom_H » Thu May 17, 2018 4:35 pm

Wandering Daisy wrote:That military photo shows everything wrong with distribution of weight and the pack itself. Center of gravity of the pack is well behind the person's center. The pack is too deep vs wide or tall and does not vary front-to-back depth based on position relative to the body. The pack is stiff and does not contour to the body. In my opinion, if carrying heavy weights, the old external frames with an extender bar carry the weight the best. The top duffle in the photo below is full of heavy climbing gear.
If that pack was being carried by the human alone, I would be in complete agreement. My understanding of these things, however, is that all the weight is being carried by the exoskeleton alone and none of it by the person. These things are designed by mechanical and electrical engineers with expertise in robotics. I have not seen the detailed plans showing force vectors and so on, but I would think that center of gravity is the starting point for everything. It is possible that they don't want it to contour to one particular body, but to be able to fit a variety of bodies. If the mechanicals are carrying all of the weight, perhaps all these things that are so important in fitting a normal pack do not matter so much when the exoskeleton is doing all the work and supporting the loads. I really have no idea.

You are so right about people who sway side to side. I have known of people doing it for numerous reasons: locking knees and swaying side to side in order to avoid use of quadriceps and knee tendons, shifting of weight between left and right hip or left and right shoulder in order to get momentary relief on pressure points, etc. If much weight is being carried, proper fitting of the pack is critical, equal to or more important than what pack has been chosen. These Super-Ultra-Lite modern packs made of Cuben fiber, filled with 10 lb. or so of SUL gear make this issue far less important.

Fewer and fewer people have to carry the 90+ lb packs NOLS instructors (like WD) and CHA instructors (like me) had to carry. We had heavier basic gear back in the 60s and 70s, food and fuel for several weeks, full rack of climbing hardware, helmet, ropes, ice axe, crampons, snowshoes, repair kits, and first aid kits for sizable groups. We often had to carry weight for our participants when they were unable to carry all their own weight. Modern backpackers don't hike like that. The military is a different story, however. I have heard of soldiers and Marines in mountain warfare units who have to be able to make sustained runs with over a hundred pounds on their backs. These are some serious athletes, but that takes a huge toll on the human body, no matter how strong one is. I think the military will begin using robotic warriors as well as soldiers outfitted with these integrated exoskeleton/packs. Whether that technology transfers (in the same OR modified form) to civilian backpackers remains to be seen. IDK if it will be prohibited in NPs and wilderness areas or not. With the right boot soles, I'd think that exoskeletons would do less damage to the soil than pack animals. OTOH, would rich people with no athletic ability nor understanding of wilderness survival start buying them and flood the trails? I would not want to be a ranger or SAR personnel getting calls when those mechanisms break down in the middle of nowhere. Imagine getting rescue calls and when you reach the site, the person is fine-they just needed a AAA robotics repair!

So I don't know about the future, Mav. With SUL packs already around 1 lb. further weight reduction is almost irrelevant. Using mechanical technology to help carry the weight would have seemed a pipe dream years ago, but the reality is on our doorstep. It will be interesting to see how it all plays out.

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Re: Future Of Backpacks

Post by Wandering Daisy » Thu May 17, 2018 5:29 pm

Tom, you flatter too much! I never carried a 90 pound pack. Only time I ever did that was hauling an elk out during hunting. Our packs at NOLS were regularly 65-70 pounds starting. In a large group, we only carried enough climbing gear for part of the group to climb at one time. That still is heavy compared to today. But I agree that technology to carry heavy packs are somewhat a moot point now that so much gear is all going UL. What I see is adapting that technology to make light packs carry even better. Although it may be used to allow the disabled to participate in backpacking.

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