View Full Version : Limit to Human Endurance
TexasBob
06-06-2019, 08:40
Here is an interesting article about how the ultimate limit on long term endurance activities is how many calories your body can process and use over the long term. It also gives some insight into the answer to the perennial question "How many calories do you burn per day on the AT?"
https://interestingengineering.com/scientists-finally-answer-whether-there-is-a-limit-to-human-endurance
Tipi Walter
06-06-2019, 08:51
Cool subject. It concerns me of course due to how much decent food (calories and protein) a backpacker can carry long term.
Google up "Ranger School" and you'll find an interesting article on Wikipedia with this wonderful quote---
Physical effects
Following the completion of Ranger School, a student will usually find himself "in the worst shape of his life".
Military folk wisdom has it that Ranger School's physical toll is like years of natural aging; high levels of fight or flight stress hormones . . . . , along with standard sleep deprivation and continual physical strain, inhibit full physical and mental recovery throughout the course.
https://en.wikipedia.org/wiki/Ranger_School
gpburdelljr
06-06-2019, 09:26
Here is a calculator that will estimate your BMR, and calories burned for various exercise levels, based on gender, age, height, and weight.
https://www.thecalculatorsite.com/health/bmr-calculator.php
Just in case anyone was wondering if the above article applies to extreme hiking (the FKT hikers is what I am referring to here).
I had noted that their prime example was the race across America and that the runners averaged about a marathon a day. Then you compare that to Stringbean's average of about 48 miles a day on the AT and you wonder if they missed something. Extreme hikers are clearly out on the edge of what is humanly possible.
So I contacted the lead author Dr. Pontzer at Duke and asked him.
It turns out the extreme hikers match the data exactly and Stringbean is in their database.
So the gauntlet has been thrown down. It's up to you speedsters to prove them wrong.
TexasBob
06-06-2019, 10:41
I was thinking that you might be able to work backwards and figure out how many miles you could hike per day over 6 months without wrecking yourself. If 2.5 times your BMR is an upper limit then for me that would be about 4000 cal/day (1585 cal BMR x 2.5). Using this calculator ( https://caloriesburnedhq.com/calories-burned-hiking/#calculator ) to figure out how many calories you burn hiking, about 12 miles per day assuming a pack weight of 25 lbs walking 6 hours per day (2 mph) uphill and downhill with a 5-10% grade would require about 4000 cal. The article did not make clear whether the 2.5 x BMR is the total amount of calories you can expend or if that is on top of your BMR which would make quite a difference.
Feral Bill
06-06-2019, 12:04
Anish discusses her physical changes on the PCT is some detail in her book Thirst. She is certainly out on the ragged edge of what's possible.
Starchild
06-06-2019, 12:54
IIRC the NAZI's gave their troops some sort of drugs that allowed them to ruck something like over 100km per day. Yes drug assisted, but it is within the limits of the human body.
The article addresses very short term extreme efforts and the numbers generated. And goes on to describe how the numbers change as the duration of the event increases. Short term limits are very different than long term ones. And using drugs to enhance short term will carry an extra physical penalty which must be paid...but if you are likely going to be dead in a few days due to the Soviet army it does not make much difference.
Another interesting article on this subject: The limits of human endurance: what is the greatest endurance performance of all time?
https://www.ncbi.nlm.nih.gov/pubmed/18269203/?ncbi_mmode=std
Hmm. I learned there was a limit to human endurance when a 3 yr old standing too close for too long next to the fireplace. No scientists were around to tell me there was a limit either. :D
IIRC the NAZI's gave their troops some sort of drugs that allowed them to ruck something like over 100km per day. Yes drug assisted, but it is within the limits of the human body.
Yeah, methamphetamine. It was synthesized by a Japanese chemist working in Germany and later given to not only German troops but Allied and other Axis troops in WW II including, as a dirty little U.S. military and U.S. gov't approved secret, U.S. troops to avoid sleep and fatigue and increase endurance.
Japanese, U.S., British and German military (http://www.history.com/news/inside-the-drug-use-that-fueled-nazi-germany) personnel are reported to have used the stimulant to enhance endurance and ward off fatigue on long campaigns.
https://www.history.com/topics/crime/history-of-meth (https://www.history.com/topics/crime/history-of-meth)
It's become convenient and customary to isolate Nazis as only engaging in questionable behavior.
flemdawg1
06-06-2019, 15:09
Yeah, meth. Luckily it's readily available in the AT corridor. :-D
IIRC the NAZI's gave their troops some sort of drugs that allowed them to ruck something like over 100km per day. Yes drug assisted, but it is within the limits of the human body.
flemdawg1
06-06-2019, 15:10
Jinx! buy me a coke.
Starchild
06-06-2019, 16:23
Yeah, methamphetamine.
That was a later one, the earlier one was cocaine, oxycodon and something else.
Coca cola, - COKE and KOLA, - originally containing cocaine and kola nuts(for it's caffeine content), was a patented legalized "energizing", "invigorating" and "health promoting" medicine. Those exact words were use to sell Coca Cola not only by the manufacturer but scientists and medical doctors. Coca cola was truthfully advertised as such - a medicine. Cocaine was a patented medicine in different medicines - real medicine as defined at that time prescribed by medical doctors. It makes me ponder what currently are listed as patented pharmaceutical and OTC medicines - DRUGS - that in the future we'll find out have negative side affects that are not frankly discussed in context as they could. Medical and scientific quackery abounds as these industrial, business, and "educational" sectors garner enormous "educational" and economic influence.
That was a later one, the earlier one was cocaine, oxycodon and something else.
To the best of my knowledge, the Wehrmacht used Pervitin, which is basically Meth in low doses, as tablets and injections.
Even famous Alpinists like Hermann Buhl on his famous solo first ascent of Nanga Parbat, carried and used Pervitin, which he admitted later to have saved his life.
Starchild
06-07-2019, 06:37
Pharmacologist Gerhard Orzechowski (https://en.wikipedia.org/w/index.php?title=Gerhard_Orzechowski&action=edit&redlink=1) and a group of other researchers were commissioned in Kiel (https://en.wikipedia.org/wiki/Kiel) to develop this drug, and by later in the year developed a formula which contained in each tablet (https://en.wikipedia.org/wiki/Tablet_(pharmacy)): 5 mg of oxycodone (https://en.wikipedia.org/wiki/Oxycodone) (brand name Eukodal (https://en.wikipedia.org/wiki/Eukodal)), 5 mg of cocaine (https://en.wikipedia.org/wiki/Cocaine), and 3 mg of methamphetamine (https://en.wikipedia.org/wiki/Methamphetamine)(then called Pervitin (https://en.wikipedia.org/wiki/Pervitin), now available under the brand name Desoxyn (https://en.wikipedia.org/wiki/Desoxyn)).[4] (https://en.wikipedia.org/wiki/D-IX#cite_note-Paterson,_Lawrence_2006_p._16-4)
From https://en.wikipedia.org/wiki/D-IX
OMG oxy, cola, and speed in one drug.
Feral Bill
06-07-2019, 11:35
Our Air Force pilots still use Dexedrine on long missions. Probably other military do too.
In the grand scheme of human powered long distance races, the person who spends the least amount of time sleeping usually wins.
Wayne
Cool subject. It concerns me of course due to how much decent food (calories and protein) a backpacker can carry long term.
Google up "Ranger School" and you'll find an interesting article on Wikipedia with this wonderful quote---
Physical effects
Following the completion of Ranger School, a student will usually find himself "in the worst shape of his life".
Military folk wisdom has it that Ranger School's physical toll is like years of natural aging; high levels of fight or flight stress hormones . . . . , along with standard sleep deprivation and continual physical strain, inhibit full physical and mental recovery throughout the course.
https://en.wikipedia.org/wiki/Ranger_School
This is was certainly true for me. I could not have passed the Ranger PT test if they gave it prior to graduation. RLTW
Maineiac64
06-07-2019, 21:57
Cool subject. It concerns me of course due to how much decent food (calories and protein) a backpacker can carry long term.
Google up "Ranger School" and you'll find an interesting article on Wikipedia with this wonderful quote---
Physical effects
Following the completion of Ranger School, a student will usually find himself "in the worst shape of his life".
Military folk wisdom has it that Ranger School's physical toll is like years of natural aging; high levels of fight or flight stress hormones . . . . , along with standard sleep deprivation and continual physical strain, inhibit full physical and mental recovery throughout the course.
https://en.wikipedia.org/wiki/Ranger_School
I just read david goggins’ book and he went through both navy seal and ranger school and he found the ranger school toughest due to calorie restrictions.
4eyedbuzzard
06-07-2019, 22:18
Athletes sometimes use IV therapy for recovery and even for performance enhancement. So I would imagine that IV nutrients like those (vitamins, minerals, amino acids, hormones) plus some IV glucose and breathing supplemental oxygen would likely raise the caloric digestive and respiratory limits of the human machine - to some degree. But at what expense? What would the negative effects be of increase workload on heart, kidneys, liver, etc. As a species we physiologically evolved to be able to perform at levels that provided some advantage of being able to survive long enough to procreate and raise the next generation. Athletic endurance was only part of the equation of those that are our biological ancestors. We are a compromise of the physiological and all the other traits of the most successful breeders. Athletic endurance at some of the extreme levels people are taking it to is a pretty recent phenomena in human history.
I just read david goggins’ book and he went through both navy seal and ranger school and he found the ranger school toughest due to calorie restrictions.
When I asked my son how Ranger School compared to our Sierra High Route hike, his answer surprised me. He said it was about the same physically but the difference was they could eat something like 2400 calories.
I just read david goggins’ book and he went through both navy seal and ranger school and he found the ranger school toughest due to calorie restrictions.
When I asked my son how Ranger School compared to our Sierra High Route hike, his answer surprised me. He said it was about the same physically but the difference was they could eat something like 2400 calories.
I've been restricting daily caloric load for more than 20 yrs as pre hike prep for similar motivations as SEAL and Ranger schooling. You learn to operate mentally and physically at a high level without the over consumption U.S. civies are accustomed. Same with sleep. This approach to backpacking assumes a decent level of fitness pre hike. It's not a hike yourself into LD hiking shape(psychologically, physically, emotionally, spiritually) approach. It fits into UL backpacking. Operating on a restricted daily caloric load correlates with less food wt. Consider this approach uses the restricted caloric load technique on soldiers already fit with little body fat to make up for energy making them fitter and able to withstand extremes of combat.
TexasBob
06-08-2019, 17:23
....... Consider this approach uses the restricted caloric load technique on soldiers already fit with little body fat to make up for energy making them fitter and able to withstand extremes of combat.
Here is a link to the research article itself. https://advances.sciencemag.org/content/5/6/eaaw0341
As I read it, what the scientists found basically is that if you expend energy in excess of 2.5 times your Rest Metabolic Rate then the deficit can't be made up from eating more food instead you lose body fat and muscle mass. So for soldiers undergoing intense training, restricting calories below 2.5 times their RMR really doesn't make them fitter. It just increases loss of body fat and muscle mass. It may psychologically prepare them for the hardships they may encounter.