The Validity of Petzoldt’s Energy Mile Theory
In 1976, Paul Petzoldt, a mountaineer and founder of the National Outdoor Leadership School, proposed a theory to help backpackers plan trips and calculate their energy needs while on the trail in his book, Teton Trails. As defined by Petzoldt’s theory, one energy mile is equal to the energy required to walk one mile on flat terrain. He also said that you should add two energy miles for every 1000 feet of elevation gain. In other words, if you hiked 1 mile while climbing 1000 feet, you would’ve used the equivalent of three energy miles.

Petzoldt’s theory, however, had never been tested before – that is until recently, when a study was conducted at Western Carolina University’s Exercise Physiology Laboratory, by Maridy Troy, assistant professor in WCU’s health and physical education program, and Maurice Phipps, professor of parks and recreation management.

The study measured the energy cost and perceived exertion for walking on flat terrain, with and without a backpack, as well as an elevation gain of 1000 feet. Results from the data show an average of a 1.6-mile equivalent for a 1000 foot gain in elevation. Differences between females and males ranged from 1.32 to 2.02. Professor Phipps stated in an article for WCU news that the range revealed by the study was due to the “hikers” personal weight differences. The abstract from the study states that further research using heavier expedition packs at higher altitudes could also reveal changes in energy cost.

“It is remarkable that Petzoldt’s energy mile theory is so close to the actual energy cost measured during our study,” Phipps stated.

Phipps also said the energy required for hiking up steep mountain trails would vary for individuals and groups, and the variables of the trail would also factor in, but he recommends that backpackers stick with Petzoldt’s theory of adding two energy miles for every 1,000 feet in elevation gain.

I found this information to be extremely interesting. Petzoldt’s theory happens to be the same formula that I use to calculate difficulty ratings for trails in the Smokies. I discovered the formula while visiting a website for trails in Colorado several years ago. The website stated that the equation was developed by Dick Holley, and came from Rocky Mountain National Park Dayhiker’s Guide by Jerome Malitz. I guess we didn’t follow the tree all the way to its roots!

Although the formula may not be exact, what Paul Petzoldt was essentially trying to solve was how many calories a hiker or backpacker burns while hiking. With today’s internet technology that is much easier to do. The Hiking Dude has an excellent calorie calculator on his website. It takes into account your weight, plus the weight of you backpack, the distance you’ll be hiking, and how much elevation you’ll gain along the way. This can be useful in determining (roughly) how much food you’ll need to pack for a hike.

http://hikinginthesmokys.blogspot.com/2011/06/validity-of-petzoldts-energy-mile.html

There is additional interesting information in this research article:
https://advances.sciencemag.org/content/5/6/eaaw0341
Or straight to PDF:
https://advances.sciencemag.org/content/5/6/eaaw0341

It’s not about hiking but has some interesting insights on sustained maximal human energy expenditure.

“…we find evidence for an alimentary energy supply limit in humans of ~2.5× BMR; greater expenditure requires drawing down the body’s energy stores”.

So bringing more seems unnecessary / counter productive?

As an aside, with a BMR of 1600 this would amount to 4000.

But if you are suffering he whole time, why are you doing it?

I think Ryan suffers on his treks. He admits to sleeping cold…….improper amounts of food….I suspect so.

Take an additional days worth of light weight Mountan House meals ;)

Thanks Ryan. A good, easily understood calculation.

“More cheese!
More chocolate!
More salami!”
Ha, really good trail food!

pretty much all you can find in many alpine villages.
And fresh bread – real bread, not Wettex stuff.

I do remember descending one day to a village (Europe somewhere), when we passed a girl going upwards. She had 3 – 4 baguettes sticking out of her pack!

Cheers

stomping on the bread worked well to compress it
Heathen!
Did you clean up the crumbs?

Cheers

Geoff mentions bread and it reminds me of a 17 day trip I pulled in the mountains of TN inside Bald River wilderness—and I brought bread—

stomping on the bread worked well to compress it

I do that with potato crisps, chips?, in the big 350gm bags. I then eat them with a spoon. Surprisingly they taste just the same too. 1900 kcals.

You should have seen the look on the checkout girl’s face when I did it whilst trying to get the bag into my backpack. (She had lent me her scissors to cut an air hole).

John says “I am also adding a lot of coconut oil to hot drinks and meals to increase the calorie density. Could be tricky when it gets hot enough to melt the oil.”

I’m on a current Avocado oil kick and usually bring it in an empty water bottle like this (filled with olive oil in the pic)—Avo oil never has the throat burning like Olive oil.  On my last trip I used a 17oz Evian bottle of Avo oil—that’s just about right for 21 days.

Another trick is to buy several lbs of raw whole cashews and use a food processor to make Cashew Butter—and add this to my morning peppermint tea as a sort of non diary creamer.  Works great.

This rule seems like a good estimate but just a comment, I am wary of the equation that leaves the hiker with no food remaining on the last step of the walk.

On a multiday walk I always plan to arrive with at least one day’s worth of food left in my pack, to accommodate forced delays or emergencies.

I’ve had to have an enforced rest day in the mountains  a couple of times due to stormy weather.  I’d have hated to have had my food planned so closely as to have nothing left on the last day…. that last day might become the second or third last one.

In some very wet areas it is nothing to be mid-walk and have to wait two-three days for a swollen river to go down.  I have seen hikers in similar solutions have to mooch food of other hikers because they haven’t planned for predictable but unforeseen delays – which leaves everyone short.  Yep, ultralight – but ultra-annoying for everyone else as well.

My equation is usually: Calories of Food Packed  = Calories of Food predictably required + emergency allocation 

Addit: Energy production can vary enormously even in the one individual – altitude and ambient temperature and humidity will raise metabolism.   off track walking, altitude, sleep loss and cold humid weather (in an extreme case postholing through unexpected snow!), even when adequately prepared, raises metabolism significantly over walking on a graded track in fine weather.

Raised metabolism = raised energy input requirement=more food required.

The planning method described in the article is good for planning a minimal baseline of food (except i don’t concur with the planned underfeeding) but it does concern me that the casual reader will take this as gospel and not account for contingencies or other predictable variables..

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• This reply was modified 3 years ago by Matthew / BPL.

“Energy production can vary enormously even in the one individual – altitude and ambient temperature and humidity will raise metabolism.”

I think it is worth mentioning that the mix of one’s food should shift to an emphasis on carbohydrates when hiking at altitude, particularly while on the move.  This is due to the decreased availability of  oxygen required for aerobic metabolism.  Both fat and protein require more O2 to metabolize.  In my experience the majority of the fat and protein is best taken in the evening, when the demand for O2 for movement is minimal and is thus available for metabolizing fat and protein.

Edit:  I guess I should add that for extended trips, fat will inevitably be increasingly relied on.  But this will require a slower pace and/or a high degree of aerobic fitness.  Most people on this website will probably not have to worry about this, but it is worth mentioning nonetheless.

https://www.climbingnutrition.com/diet/why-you-need-oxygen-to-burn-fat/

• This reply was modified 3 years ago by Matthew / BPL.