[pct-l] Backpack Packing strategies...

[Glen Hoshizaki]

I'm comfortable with the use of oxygen consumption as an indicator of energy
use by humans (and other living things). However, the investigators did not
define "energy cost" as simply oxygen consumption rate, but instead as
something more complex. Thus, "energy cost" using their definition was
indeed lower in their control (i.e., unloaded) condition. However, my guess
is that oxygen consumption (and therefore energy consumption, as opposed to
"energy cost") was actually higher with load (whether upper or lower back)
than unloaded. (I don't see how it could be otherwise.) However, the study
in question (Abe, et al) doesn't include that data.

Perhaps Abe et al's definition of "energy cost" is standard. I wouldn't
know. (I'm an anesthesiologist.)

Thanks for the information on the dynamic walking model. Another piece of
the puzzle to wrap my brain around.

Glen

-----Original Message-----
From: Yoshihiro Murakami [mailto:completewalker at gmail.com] 
Sent: Saturday, May 14, 2011 12:05 AM

Dear Glen

The oxygen consumption is widely used as an energy cost among
Ergonomics professionals, because it is valid and reliable index.

This article clearly indicated that the energy cost significantly
decreased during walking with load than without load, and the load on
the upper back condition was more energy saving than lower back
condition.

The contradictory result, that the with load condition was energy
saving,  may be perplexed you. But, these result may be well
interpreted by the recent dynamic walking model ( inverted pendulum
analogy). That is, if the pendulum movement  might be facilitated by
the pack weight, energy expenditure will decrease.

I have uploaded the excerpt from a recent Ergonomic article at my
site. http://bit.ly/iSnVzl

The very classic book "Complete Walker IV"(2002) page.34  stated that

The maximum for backpacking as an enjoyment is perhaps one-third of
body weight. A well-conditioned body can handle more weight, if
necessary, and training routines can help. A reasonable load would be
one-fourth or one-fifth of body weight. Unbearable Lightness would
kick in down around one-eighth.

I think many people can walk up to 20 % body weight without an
increase of energy by using  inverted pendulum movement. The
description of Complete Walker is easy to understand by the recent
dynamic walking model.

2011/5/13 Glen Hoshizaki <hoshizaki at ca.rr.com>:
> On page 37 of the paper the investigators defined energy cost as oxygen
consumption rate per walking speed, all normalized over total mass (body
mass plus mass carried). So for any given walking speed (at least within a
certain range) even though oxygen consumption increased with increasing
load, it did so less than proportionately.
>
> Or am I completely confused?
>
> -----Original Message-----
> From: pct-l-bounces at backcountry.net [mailto:pct-l-bounces at backcountry.net]
On Behalf Of CHUCK CHELIN
> Sent: Thursday, May 05, 2011 8:31 PM
>
> Good evening, Yoshihiro,
>
> I have a question about your Interesting Point No. 1:  If more force is
> necessary to move a large mass compared to a small mass; and if energy is
in
> terms of force applied over a distance, how can it be as you say that
moving
> a large mass over a distance requires less energy than moving than a small
> mass over that same distance?
>
> Steel-Eye