Load Bearing and the Human Body

I know nothing about the mechanics of load bearing or proper ergonomic balance. I don’t even know what ergonomics is. Never really cared. But such topics have been showing up in my research into the best way of carrying loads long distances using only the human body.

I’m considering taking an epic walk, perhaps up the Pacific coast, and I’ve been trying to think outside the envelope, box, and backpack. An envelope, of course, could not contain all I would need to carry; though I do intend to travel light, that is too campinglight even for me. A box would be too awkward. And a backpack — well, for those of us not used to carrying loads on our backs, a back pack can contribute to back and neck problems, gait issues, muscular pain, foot problems, bad posture, and wasted energy.

In my case, even light loads in a backpack are a problem. I recently lost a few pounds, so I figured my body would be able to handle a five-pound backpack load with no difficulty, but that wasn’t the case. After a mere three miles, I ended up with pain on the tops of my feet and in my lower back. Someone suggested that I get orthotics, but why would I need them when I’d been used to carrying more weight without even a hint of discomfort?

I have a short back, and according to Aarne Packs, “With a backpack, the center of gravity of the load is behind the body. The load acts like a lever on your back, increasing the forces acting on the body well above the force of the weight alone. When this lever acts over a shorter distance on a small torso, the forces are magnified. Therefore the reason women with short torsos may not be able to carry such heavy loads is not because they are weaker but because of these increased forces.”

When you carry extra body weight (as opposed to carrying some kind of pack), the weight is distributed all through the body, so no single muscle group or tissue has to deal with the load, which cuts down energy expenditure as well as muscle fatigue, and there is no change in the center of gravity. Ideally, then, an external load-bearing system would need to take those matters into consideration.

Traditionally, humans have used various means of transporting loads on their bodies: a simple hobo pack with a bandanna tied on the end of a stick, a pole balanced on the shoulders with a basket hanging from each end, a trumpline around the head tied to the load hanging down the back (supposedly this allows a person to carry greater loads longer distances than shoulder straps, but . . . ouch; my neck is squealing in pain just thinking about it), and the ever popular balancing the load on top of the head.

Balancing loads on the head, if done right, is supposed to be the best way since there is zero increase in metabolism. It has to do with one’s gait. According to Biomechanics of Locomotion, when we walk, our bodies go “up and down, and faster and slower, within each step. The energy changes associated with these fluctuations in height and speed are out of phase and therefore tend to cancel each other, minimizing the energy required to keep the movements going, much like in a pendulum. But in walking the energy fluctuations are not completely cancelled (as would occur in a perfect pendulum); at most about 65% of the energy fluctuations are cancelled, leaving at least 35% of the energy fluctuations which must be supported by the muscles each step, requiring metabolic energy input. When the African women carry loads on their heads, they are able to increase the amount of energy that is cancelled, reducing the muscular energy required to maintain the walking gait and compensating for any increase in muscular energy required to support the additional load.”

Carrying loads on one’s head might be fine for those who are used to it or even for those trying to improve their posture, but I cannot see me balancing anything on my head (except perhaps a hat) for hundreds, maybe thousands of miles.

I’ve been considering making two shoulder tote bags, one for each side, thinking that might help balance the weight in a more natural way, or perhaps a combination of a light backpack, belly bag, and maybe side bags. Apparently, these are good ideas. In fact, I don’t even have to make these load-bearing packs. Someone already did. One company I found makes a pack with the load balanced on either side of the body, and another company makes a pack with front pockets to balance the weight of the backpack, though the pack itself is much heavier than I would like.

It’s amazing to me all the things one has to consider when going for a simple (well, perhaps not so simple) walk, especially if one doesn’t want to look like the survivor of a wilderness romp.

***

Pat Bertram is the author of the suspense novels Light Bringer, More Deaths Than One, A Spark of Heavenly Fire, and Daughter Am I. Bertram is also the author of Grief: The Great Yearning, “an exquisite book, wrenching to read, and at the same time full of profound truths.” Connect with Pat on Google+. Like Pat on Facebook.

One Response to “Load Bearing and the Human Body”

  1. Planning Epic Transcendental and Mystical Journeys | Bertram's Blog Says:

    […] can ward off a bear, the spray could ward off any human predator, too). I am also researching the best way of carrying things, and no, it isn’t on the back, it’s on the head, but that I won’t even consider. I want to […]


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