While I've always been interested in measuring this in the "field", I have yet to take out the proper equipment (a good heart rate monitor). Still, I feel one can get a decent estimate and feel for calories burned on a certain hike with indoor studies, and so I did someinterpretation of a research paper and consequently made a '1st generation' caloric expenditure hiking calculator.

Now there is still a lot of work to improve the estimates, but generally they will be decent. At least to give a sense of relative magnitude of different hikes in terms of energy demands (sorry climbers, I have no idea what to do with climbing )

Sorry if you're not interested, but I figure some people will be.

Ze, this is quite interesting, thanks for posting it. I just played around with it a little bit. Does the absolute altitude have an influence on the calories consumed as well? For example would you use more calories if you had 3000ft of elevation gain from 11,000 to 14,000ft compared to let's say seal level to 3000ft with everything else (distance, trail condition etc.) being equal? I guess you would.

Cool!

mstender wrote:Ze, this is quite interesting, thanks for posting it. I just played around with it a little bit. Does the absolute altitude have an influence on the calories consumed as well? For example would you use more calories if you had 3000ft of elevation gain from 11,000 to 14,000ft compared to let's say seal level to 3000ft with everything else (distance, trail condition etc.) being equal? I guess you would.

yeah people say it can, I've haven't looked for studies that verify this. It will definitely changed the 'type' of calorie being burned (more carbohydrates --> more fatigue). if I find something I'll try to implement that, would be cool to see the effect.

It doesn't factor in altitude, or whether you are using trekking poles or no--which are said to increase calorie expenditure by 4-6%t? Neither do heart rate monitors

mstender wrote:altitude

jeep1212 wrote:altitude

I don't see why altitude would be a factor. The amount of work necessary to move your legs, arms, and body in a given pattern does not vary with altitude. If you're hiking level or ascending 1000 feet or descending 1000 feet, there are certain motions in which your body moves for each of those three situations. But the motions do not change with altitude, so why would the body's energy use change?

At higher elevation, your maximum power is reduced, so you won't be able to maintain the same ascent rate as you could lower down. But even if you go slower up high, you're still doing the same movements in order to do a given hike at a given profile, regardless of absolute elevation and how long it took. If one of the two hikes took a bit longer, you could expect a slight increase in the total energy used, but only because of the longer included time of base metabolic functions. The energy put into the hike itself should be identical, although it seems there would be no way to verify this with measurement.

But two hikes with identical distance and identical elevation profile, hiked at identical speed, should take the same energy. So ascending 1000 feet on a 15% grade in 30 minutes takes a certain amount of energy, regardless of whether it's from 0 to 1000 feet or from 10000 to 11000 feet.

seems like individual physiology would play a role as well. individuals with "high metabolism" would burn more calories than individuals with "low metabolism".

Neat stuff. Of course there are going to be variables (obviously a 180-pound person with 10% body fat isn't going to have to work as much as one with 30%, for instance) but this is a great base estimate.

...on the downside, it's very sad to see that hiking the mountain behind my house - which I do quite a bit - only burns about as many calories as drinking 7 beers puts in me.

Day Hiker wrote:

mstender wrote:altitude

jeep1212 wrote:altitude

I don't see why altitude would be a factor. The amount of work necessary to move your legs, arms, and body in a given pattern does not vary with altitude. If you're hiking level or ascending 1000 feet or descending 1000 feet, there are certain motions in which your body moves for each of those three situations. But the motions do not change with altitude, so why would the body's energy use change?

I think that's the point. One goes into anaerobic respiration a bit more quickly at altitude. The output calories are the same (in terms of work done), but the potential caloric value (from the same food supply) differs.

Day Hiker wrote:

mstender wrote:altitude

jeep1212 wrote:altitude

I don't see why altitude would be a factor. The amount of work necessary to move your legs, arms, and body in a given pattern does not vary with altitude. If you're hiking level or ascending 1000 feet or descending 1000 feet, there are certain motions in which your body moves for each of those three situations. But the motions do not change with altitude, so why would the body's energy use change?

At higher elevation, your maximum power is reduced, so you won't be able to maintain the same ascent rate as you could lower down. But even if you go slower up high, you're still doing the same movements in order to do a given hike at a given profile, regardless of absolute elevation and how long it took. If one of the two hikes took a bit longer, you could expect a slight increase in the total energy used, but only because of the longer included time of base metabolic functions. The energy put into the hike itself should be identical, although it seems there would be no way to verify this with measurement.

But two hikes with identical distance and identical elevation profile, hiked at identical speed, should take the same energy. So ascending 1000 feet on a 15% grade in 30 minutes takes a certain amount of energy, regardless of whether it's from 0 to 1000 feet or from 10000 to 11000 feet.

The amount of energy used for breathing and keeping your heart beating at the higher rate needed at higher elevations changes a lot with altitude. I doubt that this is an insignificant difference (although I don't have any proof of that).

This is the way I thought of it….So I would burn the same amount of calories if I walked a flat mile at sea level vs. 8,000 meters? Even though my heart rate walking at sea level would be 80 vs. 180? Even though 1 mile at sea level would take around 15 minutes and a mile at 8,000 meters would take hours? Your HR is higher for a longer period of time….

A lot of good points. I agree with Day Hiker essentially...I don't know the research, so if someone can point to specific articles explaining why you would burn MORE calories at altitude, then I'd love to see it.

We all agree that work at altitude appears harder.

Yes, heart rate will be higher, but a lot of that increase is because the blood is not 100% oxygenated anymore. The total oxygen delivered (~ calories burned) may still be the same.

However, it is key that the TYPE of calorie burned changes. Use of energy from fatty acids will decrease and use of energy from glycogen will increase (RER increases). Use of glycogen anaerobically will increase. These things will make you fatigue (lose glycogen stores) MUCH more rapidly. At some point I'll make a post on what I've read about how quickly you loose glycogen anaerobically vs aerobic, it's huge!

Still these things do not make total energy used higher. However, I would still think there would be some increase, as the body is working harder overall to deliver the oxygen (higher ventilation and respiratory muscle usage).

jeep1212 wrote:This is the way I thought of it….So I would burn the same amount of calories if I walked a flat mile at sea level vs. 8,000 meters? Even though my heart rate walking at sea level would be 80 vs. 180? Even though 1 mile at sea level would take around 15 minutes and a mile at 8,000 meters would take hours? Your HR is higher for a longer period of time….

I agree that at 8000 meters your higher respiratory and heart rates would consume more energy, although the comment about taking longer is a little off because I was specifically talking about "two hikes with identical distance and identical elevation profile, hiked at identical speed." And I didn't understand the "flat mile" thing because you won't find that anywhere on this planet at 8000 meters.

I was actually thinking of more moderate elevations, like the 10000 and 11000 feet mentioned. Respiratory rate would need to increase with elevation, even at low elevations, I suppose. But heart rate should only be affected by elevation if the elevation is high enough to cause the percent oxygenation to drop below 100.

So at what elevation does a person's percent ox generally deviate from 100? Maybe at 10000 feet it is generally below 100%; I don't know. I am sure the "magic elevation" is not sea level because people have pulse ox readings of 100 here in Vegas (1500 to 3000 feet), and they probably do in Denver too. But also if I remember correctly (over 3 years now), my pulse ox reading was only in the low 90s at 14400 feet, even after days spent at that elevation or above. I wish I had checked it upon return, after the 22850-foot summit and 90 hours above 18300.

Ze wrote:A lot of good points. I agree with Day Hiker essentially...I don't know the research, so if someone can point to specific articles explaining why you would burn MORE calories at altitude, then I'd love to see it.

We all agree that work at altitude appears harder.

Yes, heart rate will be higher, but a lot of that increase is because the blood is not 100% oxygenated anymore. The total oxygen delivered (~ calories burned) may still be the same.

However, it is key that the TYPE of calorie burned changes. Use of energy from fatty acids will decrease and use of energy from glycogen will increase (RER increases). Use of glycogen anaerobically will increase. These things will make you fatigue (lose glycogen stores) MUCH more rapidly. At some point I'll make a post on what I've read about how quickly you loose glycogen anaerobically vs aerobic, it's huge!

Still these things do not make total energy used higher. However, I would still think there would be some increase, as the body is working harder overall to deliver the oxygen (higher ventilation and respiratory muscle usage).

+1....


You burn more calories at altitude because the human body isn't built for maximal efficiency at altitude. A physiological corollary is what happens to the human body in zero G, even at 100% O2 saturation: all kinds of weird things. At higher altitudes, even the body's renal processes make food processing less efficient.... you can eat all you want and all that nutrition gets pissed away.

It's also true that energy source changes as a function of altitude; a very large amount of muscle is lost at altitude, even from just sitting around. As for total work done, the statement is irrelevant: the work required in lifting a 1Kg mass at sea level isn't (largely) different at 8,000m. However, it's the efficiency of the machinery that changes. That's probably where future research will go. Not biomechanical (hardware) but hormonal (software).

Physiologists can barely understand why hormones play such a huge role in metabolic efficiency, at sea level. Who knows how hormones will play out in regulating efficiency at altitude.

basal metabolic rate affects how many calories a person would burn for a given activity. i'm not sure, but i think bmr increases slightly when at high altitudes. would it not then play a factor in calories burned?