Research Related to Pack Wieght

Mark:

I used to have a hard copy of a translation of an article along those lines. The research described in the article I had was done by the Swiss army, and the article was originally published in a German-language medical journal. The translation was published in a biomedical engineering newsletter I found in the University of Iowa engineering library.

After six house moves in just under 20 years, I can’t find that almost unreadable, bad library photocopy anywhere.

But what I recall is this: The report proposed that everyone has a backpack weight threshold at which they become significantly more encumbered. They defined this weight as the point where a person’s balance-time degrades by 20%. They determined this point by measuring the time that one could stand on one foot without a pack, and the compare that to the time they could do so with a pack on. They found that for the age range of men in the Swiss military, their balance degraded by 20% carrying a pack weight between 8% and 10% of their lean body weight.

I had hoped that more papers being digitized / put online, and more extensive search tools would help me find this paper… but no such luck.  Anyone have a paper similar to the one I mentioned above, in particular, the break point where carrying a pack increase fatigue noticeably / measurability compared to performing the same all day activity carrying nothing.

Also interested in any studies about other points where things notability change.  Looking for a copy of https://academic.oup.com/milmed/article-abstract/174/12/1308/4339313 whose abstract suggestions 30% body weight has a measurable (though I don’t know if it is significant) impact to balance and situational awareness.

Hi Mark,

Saw your cross post on reddit.  Here’s what I responded with, hope it sparks more discussion here.

I researched this when coming up with a better estimate of my calorie needs. Caloric needs are a good proxy for effort, and by extension, an estimate for fatigue.

While not directly applicable to an ultralight context, “The Validity of Petzoldt’s Energy Mile Theory” https://js.sagamorepub.com/index.php/jorel/article/view/6629 found that a 44.5lb pack required ~ 29% more calories in the subjects they tested.

The US military refined the Pandolf equation which estimates calorie needs based on your weight, pack weight, speed, incline and terrain type by testing numerous subjects and fitting the data to a formula.

Details here https://www.outsideonline.com/outdoor-adventure/hiking-and-backpacking/ultimate-backpacking-calorie-estimator/ .

While the extra calories needed to carry a pack depend on your weight, its not quite a linear relationship.

The Australian army refined this formula in 2017. Here’s a good overview of their results:

https://www.goruck.eu/pages/rucking-calorie-calculator

That site has a great graphic that reinforces the ultralight mindset by quantifying in hard terms 3 important factors:

– 10 lb pack and no pack are similar in caloric need

– caloric expenditure starts to grow quickly after as pack weight grows beyond 20lbs

– the benefit of the lighter pack is much more modest at slower hiking speeds but grows quickly as the rate of travel increases

I ran studies on myself over a few years estimating my calorie burns on longer harder trips. This isn’t an exact science because its hard to estimate calorie burn from weight loss, but in general I found the Australian formula to be a pretty accurate estimate of my calorie needs.

I also compared it with my own model derived from Japanese BMR/PAL research here and Ryan’s caloric estimator.  Pandolf equation (from Goruck/Oz army) predicts slightly fewer calories than I do but Ryan’s method from field data predicts many more calories than either my model or Pandolf.