Relationship between weight, fitness, HR & cals burned?

numinousnymph

So, i was under the impression that the higher one's heart rate got doing a physical activity (if the heart rate increase is purely or mostly from the exertion and not any other factor, such as hydration level, ambient temperature, anxiety levels), the amount of calories the body uses to do such activity will increase. However, specifically on topics concerning HRMs and their calorie burn calculations, i've seen some people on here say that if, say, a 130lb, more fit person or a 430lb, less fit person walks up a hill at 3mph for 15 minutes, they will both burn the same amount of calories. Now, because of the difference in weights and fitness levels, i figure that there will be a difference between the heart rates of the two people, because it will take less energy for the more fit, less heavy person's body to move itself. Wouldn't that mean that the less fit, heavier person would burn more calories, because their body is working harder to do the same job? What if both people were 130lbs but one person hadn't exercised in a few years and was very out of shape and so their heart rate went up higher than the more fit person -- wouldn't that also mean that their body is working harder, and thus burning more calories? I'm confused, because to me it doesn't make sense that no matter the weight or fitness level that the same amount of calories would be burned. Anyone with more knowledge on physiology have any input?

Hornsby

I'm not sure of the answer, but would love to hear what others have to say.

annabeladcock

I think you're right - the lighter, fitter person would have a lower HR than the heavier, unfit person, so would burn less calories, or at least that's how I understand it!! I think it's wrong that people say they would burn the same amount of calories because whilst they are doing the same task, one of them is working much harder than the other!

cwolfman13

I would disagree that they would burn exactly the same calories...a 430 Lb person has to move that mass and that is going to burn more calories than moving 130 lbs of mass. That said, in RE to the HR thing, your HR is not in anyway directly responsible for your calorie burn...if it were then I'd just have someone come give me a good scare every 5 minutes or so and I'd be burning up the calories like crazy.

One's HR is simply used in an algorithm to estimate to what level of VO2 max an individual is working at; in this RE, a steady state aerobic event is also a necessary factor to arrive at anything remotely accurate for calorie burn from a HRM. Most basic HRMs work off of statistical averages (with fancy ones you can adjust VO2 max, etc for more accuracy) so someone who is out of shape is going to have a higher HR than the average person for the same aerobic event...this is going to skew the results and artificially inflate calorie burn because the HRM is going to assume the individual is working at a higher level of VO2 max than they really are.

numinousnymph

But, even if people were the same weight but had a differing fitness level, wouldn't the less fit person's body still be working harder, and at a higher VO2 max level, and thus burning more calories?

numinousnymph

basically i'm just wondering -- if i did a new kind of cardio routine that my body was not used to, and even though it may not be deemed a very difficult activity (say, walking briskly on an incline), my heart rate (and i guess VO2 max level too) would go up higher than a person of the same weight whose body is used to that activity. my body would be working harder, would it not? doesn't this translate to more calories burned?

Soobies

You're right, the less fit person will burn (slightly, not a significant amount) more calories during the same type exercise because the trained individual has gone through adaptation and gained "fitness" meaning their body has become more efficient at doing the same stimulus.

Edited to add, that whatever new exercise you're adding to your regime will also require new adaptations and will stress/condition the body differently, the new stimulus will burn slightly more calories for the trainee but a trained individual who is already fit shouldn't expect it to be a big difference.

Unknown

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CoolDad67

I'm by no means an expert, but here's what I understand.

Calories burned is a factor of several things including: Age, Gender, Weight, Duration, and Average Heart Rate.

I believe this is the mechanism that many use.

I don't believe that fitness level would come into play except that a less fit person would probably have a higher average heart rate than a less fit person.

I am not sure of the why's on the male vs female difference; but I've read that it is because of average muscle makeup of men vs women.

TeaBea

By no means an expert, but I've never heard the similar calorie burns argument.

Anyway, things I've heard or read points to this....

Bigger people generally burn more than smaller people because it takes more effort to move....everything.

Men generally burn more than women because men have more muscle mass. Fat burns nothing.

Younger people burn more than older people.....I think this is related to muscle mass (above). Muscle is a use it or lose kind of thing. Lots of older folks....lose muscle and become less active in general. There are other factors too.....hormones for one.

Heart rate monitors compare (a users) resting heart rate against heart rate while working out....some people naturally have higher heart rates. As you become more fit, the difference in heart rates will decrease, unless you step up the effort. As you become more fit, your heart rate returns to normal fairly quickly. But, there are many forms of exercise that aren't based on heart rate....strength training, it's about fatiguing the muscle which is good for an after burn.

SoLongAndThanksForAllTheFish

So, i was under the impression that the higher one's heart rate got doing a physical activity (if the heart rate increase is purely or mostly from the exertion and not any other factor, such as hydration level, ambient temperature, anxiety levels), the amount of calories the body uses to do such activity will increase. However, specifically on topics concerning HRMs and their calorie burn calculations, i've seen some people on here say that if, say, a 130lb, more fit person or a 430lb, less fit person walks up a hill at 3mph for 15 minutes, they will both burn the same amount of calories. Now, because of the difference in weights and fitness levels, i figure that there will be a difference between the heart rates of the two people, because it will take less energy for the more fit, less heavy person's body to move itself. Wouldn't that mean that the less fit, heavier person would burn more calories, because their body is working harder to do the same job? What if both people were 130lbs but one person hadn't exercised in a few years and was very out of shape and so their heart rate went up higher than the more fit person -- wouldn't that also mean that their body is working harder, and thus burning more calories? I'm confused, because to me it doesn't make sense that no matter the weight or fitness level that the same amount of calories would be burned. Anyone with more knowledge on physiology have any input?

No, the 430lb person will burn many times more the calories going up the same hill, it depends on the mass moved over the distance. Heart rate does not = calories burnt, this is one reason HRMs are innacurate. HRMs calculate based on an estimate of calories burned in a certain control group studied. So, they are easily off. Basically: "our group of 130lb people burned about x calories at this heart rate, so we are going to say thats what you are burning".

In the case of the unfit person same weight as a fit person they will both burn about the same calories, but the HRM will erroneously record more calories burnt for the unfit person OR under report for the fit person, depending on the study used to set the tables.

parkscs

Your body is not 100% efficient when it comes to performing movements. As such, your body burns more calories when performing a movement than the energy required by the movement itself. At a basic level, there's more going on when your body performs a given movement than the movement itself (e.g., your lungs are bringing in and absorbing oxygen, your heart is pumping blood throughout your body, and so on). If your body is more efficient at performing a given movement (i.e., if you're more fit), you'll consume fewer calories in addition to the base energy involved in performing the movement itself, and inefficient people (i.e., less fit people) will burn more calories in addition to the base calories.

Now in your hypo, the people are actually different weights and so the base energy involved in the movement is not the same. As such, when it comes to walking up a given hill, the base energy required to move 400 pounds of human up a hill is more than the energy required to move 130 pounds up a hill, and so just considering the base energy alone we're talking more calories for the 400+ pounder. A more interesting hypo is when you have 2 people at the same weight walking up the hill for 15 minutes, yet one person is incredibly fit and the other is incredibly unfit. In that hypo, the less fit person is still going to burn more calories than the more fit person, even though the base energy required to move 150 pounds up that hill is identical. That said, the delta is perhaps less than you might think and the more fit person can easily make-up for this efficiency by walking up the hill at a faster rate.

Lyle McDonald's written a pretty interesting article on the subject if you want to read more about it:http://www.bodyrecomposition.com/fat-loss/an-explanation-of-exercise-efficiency.html

Soobies

Good post, Iove Lyle's stuff.

SoLongAndThanksForAllTheFish

basically i'm just wondering -- if i did a new kind of cardio routine that my body was not used to, and even though it may not be deemed a very difficult activity (say, walking briskly on an incline), my heart rate (and i guess VO2 max level too) would go up higher than a person of the same weight whose body is used to that activity. my body would be working harder, would it not? doesn't this translate to more calories burned?

For your body trained vs performing a new activity but doing the same work, yes you will burn slightly more at the new activity. But, the accuracy of the burn depends on the similarity of the exercise to those exercising in the control group. HRMs are based on steady state cardio. If you go weightlift, generally the HRM will be wayyy off. This is complicated by the variation in effort lifting and baseline HR of the lifter, which means someone not working very hard lifting weights, or someone with a low heart rate may actually get a reasonable approximation of calories burnt weight lifting, and then come on the boards saying how accurate theirs is all the time for weight training. While someone whos working very hard using a lot of oxygen pushing very heavy weights or HR spikes may get a gross over estimate. Thus the continual confusion on here on this topic.

As you become more fit, your baseline heart rate drops, and according to the HRM you "burn less" according to it, but you may not burn much less at all, just your heart got more efficient, however your muscles could still be doing the same work and now you are compared to a "less fit" baseline person from the study...it depends on how closely your weight/height/activity/fitness and heart rate match the control group's. These are a few of the many reasons I don't use them: for my weight and height I'm out of the "normal average" range, and my heart rate is also probably not matched closely by those in the study baseline test.

3dogsrunning

So, i was under the impression that the higher one's heart rate got doing a physical activity (if the heart rate increase is purely or mostly from the exertion and not any other factor, such as hydration level, ambient temperature, anxiety levels), the amount of calories the body uses to do such activity will increase. However, specifically on topics concerning HRMs and their calorie burn calculations, i've seen some people on here say that if, say, a 130lb, more fit person or a 430lb, less fit person walks up a hill at 3mph for 15 minutes, they will both burn the same amount of calories. Now, because of the difference in weights and fitness levels, i figure that there will be a difference between the heart rates of the two people, because it will take less energy for the more fit, less heavy person's body to move itself. Wouldn't that mean that the less fit, heavier person would burn more calories, because their body is working harder to do the same job? What if both people were 130lbs but one person hadn't exercised in a few years and was very out of shape and so their heart rate went up higher than the more fit person -- wouldn't that also mean that their body is working harder, and thus burning more calories? I'm confused, because to me it doesn't make sense that no matter the weight or fitness level that the same amount of calories would be burned. Anyone with more knowledge on physiology have any input?

You may want to check out this link and maybe a few other of his blogs
http://www.myfitnesspal.com/blog/Azdak/view/the-real-facts-about-hrms-and-calories-what-you-need-to-know-before-purchasing-an-hrm-or-using-one-21472

Heybales is another user that has a really good grasp on this. (this link doesn't apply but if you want to search other posts by him).
http://www.myfitnesspal.com/topics/show/773451-is-my-hrm-giving-me-incorrect-calorie-burn
http://www.myfitnesspal.com/topics/show/774337-how-to-test-hrm-for-how-accurate-calorie-burn-is

Essentially, calories burned is determined by weight and intensity. If two people of the same weight are working at the same intensity, they burn the same calories, regardless of fitness level. There will be a difference in perceived exertion. There are activities that efficiency plays a larger role, but for things like walking and running, for most people, there isn't a huge difference.

Someone who is 430lbs is going to burn more calories because they are moving more weight.

ETA - a good HR monitor will give you an option to adjust the VO2 max for a more accurate reading. HRMs are more inaccurate for individuals with a better than average fitness level unles you can adjust the VO2 max.

bwogilvie

Essentially, calories burned is determined by weight and intensity. If two people of the same weight are working at the same intensity, they burn the same calories, regardless of fitness level. There will be a difference in perceived exertion. There are activities that efficiency plays a larger role, but for things like walking and running, for most people, there isn't a huge difference.

3dogsrunning has it right. For many activities, there is almost no difference in calorie burn from fitness and very little from efficiency. For some activities, such as cycling, form matters because of aerodynamics.

The fitter person can expend more energy, though—often a lot more. Put me and Lance Armstrong on identical bikes in identical positions, and we'll both burn more or less the same number of calories bicycling at 20 mph - about 700 calories/hour. The difference is that 20 mph is close to my top speed on flat terrain, while Lance could do over 33 in a time trial, which would burn calories at more than twice the rate.

Now, 5 years ago I couldn't ride 20 mph on flat ground; 15-16 was pushing it. I've also lost nearly 60 lb., though, so while I've increased my ability to burn calories cycling, I haven't increased it that much, especially when climbing hills.

It's true that Lance and I in our hypothetical 20-mph ride would have different heart rates. Mine would probably be around 165, his a lot lower. But that simply means that if we used HRMs to estimate energy output, we'd need to calibrate them differently. My Garmin Edge 800, which uses Firstbeat's technology for energy expenditure, asks me to rate how often and how intensely I exercise; my entry there determines how it interprets the data. Its estimates are a lot lower than my other HRMs, which probably use the Keytel et al. formula (http://www.ncbi.nlm.nih.gov/pubmed/15966347).

Azdak

The general use of HRMs has skewed, and continues to skew, this discussion. Essentially, it makes it *kitten*-backwards.

Heart rate is a RELATIVE measure of intensity. It is only valuable when it can be associated with a scale of ABSOLUTE intensities, i.e. oxygen uptake. Heart rate DOES NOT drive calorie expenditure independent of oxygen uptake (which is why HRM calorie estimates are only somewhat accurate under limited conditions).

Steady-state cardio activities have a relatively fixed energy cost. I often use the workload of running 6.0 mph (10:00 mile) because it simplifies the numbers. The energy cost of running 6.0 mph is about 10 METs (METs are a shorthand version of expressing oxygen uptake). The cost is relatively fixed--that means that whoever is doing the activity is working at 10 METs--regardless of age, gender, height, fitness level, etc. (With a few exceptions, like someone who is morbidly obese, and, obviously does not hold true for individuals with some medical conditions).

When heart rate decreases for a given exercise workload, it is because the person's max fitness level has increased, not because they are doing less work and burning fewer calories. The HRM shows fewer calories, but that's because the HRM has not changed its "reference scale". It doesn't know that max fitness level has increased, so it just assumes you reduced the workload. Some HRMs--like the Polar FT40 and FT60--allow you to manually change your VO2max setting so that you can "recalibrate" the HRM when this occurs. I have no idea how or even the lower-level Polar models adjust themselves to your increased fitness. Maybe there is something in the mystical Finnish algorithms that detect those changes--or maybe you are just SOL.

Then there is the question of "mechanical efficiency". That means that one physically becomes more efficient at performing a movement, so it requires less energy. In general, for standard steady-state cardio activities (running, walking, etc), "mechanical efficiency"--while it may occur over time, is insignificant.

To quote Lyle McDonald:

But here’s the next question, how much training does it take for me to go from a 20% efficiency to a 25% efficiency? Or even to increase my efficiency by 1%?

The short answer is: essentially forever.

The longer answer is: ok, not exactly forever but it’s a time frame that is utterly irrelevant to the general population.

So, let's just take the whole "efficiency" thing off the table. For all intents and purposes, calorie expenditure for activities such as running or walking are not affected by fitness level. A fit and unfit person who weigh the same and do the exact same workload will burn roughly the same number of calories per minute.

For more unstructured activities--e.g. a group exercise class--there are different dynamics at work. Because the movements often require a higher skill level, mechanical efficiency plays a larger role. However, the effect is the opposite of what most people think.

In this case, increased efficiency often leads to INCREASED calorie burn, not less. Why?

A person who is not trained in performing the movements will be limited as to how hard they can push themselves. Their movements will be slower, less forceful, more tentative, etc. As they become more efficient, they will be able to move faster, exert more force, jump higher, maintain vigorous movements longer, etc. In short, they can push themselves to a higher level of oxygen uptake, and thus burn more calories.

But why doesn't the inefficient person have a lower heart rate? Why do heart rates "explode" sometimes when doing a new activity. Surely that means more calories burned, right?

No. What that means is that your body is so overwhelmed by the demands of the new activity, that it just goes a little crazy for a while. The relationship between heart rate and oxygen uptake is completely disrupted. In this instance, the HRM calories estimates are absolutely useless--they are a complete fantasy.

When starting a new exercise activity, there is always a period of acclimation and adaptation. During the time, the usual rules don't apply. In research studies, when they are testing the response to new exercises, subjects always go through a process of habituation before the study begins, in order to make sure the physiologic responses are stable and meaningful.

So if you are using HRM readings from the first workouts as a comparison, then it is a false baseline.

Unfortunately, as I said in the opening, the increased use of HRMs has introduced numerous inaccuracies and misconceptions about exercise intensity and calorie expenditure--to the point where even people who should know better repeat the inaccuracies.

parkscs

A person who is not trained in performing the movements will be limited as to how hard they can push themselves. Their movements will be slower, less forceful, more tentative, etc. As they become more efficient, they will be able to move faster, exert more force, jump higher, maintain vigorous movements longer, etc. In short, they can push themselves to a higher level of oxygen uptake, and thus burn more calories.

But why doesn't the inefficient person have a lower heart rate? Why do heart rates "explode" sometimes when doing a new activity. Surely that means more calories burned, right?

Yes and no... if the more efficient person is doing the same activity, he still burns less. If the more efficient person is pushing himself as you say he can do (and should do), he may burn more but then again his heart rate will be just as elevated due to doing more work (e.g., pushing himself by going faster, etc.). The point remains that for a given activity, you will burn less calories if you're more efficient at doing that activity. Is it significantly more? Probably not, but it depends on how you define significant. In any event, that point is probably academic because the more efficient person will almost certainly be doing a higher intensity exercise than the less efficient person (you don't get more efficient by half-assing it :laugh:).

At the end of the day, a lot of this debate is academic - but interesting (at least to me) nonetheless.

numinousnymph

Wow, thanks for all the answers. So many different arguments here. I guess it seems more people are saying that calorie burn is not changed for the same activity even if fitness level is different but body weight is the same (which is kind of the question I was more curious about getting an answer to). Even after reading people's explanations, I'm still not sure exactly how that works, because to me it still makes sense that a body working harder to do the same activity would burn more calories. Maybe there's just something I'm just not able to wrap my head around. But that seems kind of a bummer, too! I'd like to think that, say, hiking a medium-high difficulty trail, which I don't do often, would burn more calories for me than someone of the same weight who has hiked the same trail every day.

cwolfman13

I'd like to think that, say, hiking a medium-high difficulty trail, which I don't do often, would burn more calories for me than someone of the same weight who has hiked the same trail every day.

Yup...unfortunately doesn't really work that way. An unfit person would burn more...but it would not be that much more.

And actually, as you gain more fitness you'll be quite glad that it works this way...otherwise you'd have to do a crazy and unsustainable amount of work as a fit individual to keep burning the calories.

Azdak

Wow, thanks for all the answers. So many different arguments here. I guess it seems more people are saying that calorie burn is not changed for the same activity even if fitness level is different but body weight is the same (which is kind of the question I was more curious about getting an answer to). Even after reading people's explanations, I'm still not sure exactly how that works, because to me it still makes sense that a body working harder to do the same activity would burn more calories. Maybe there's just something I'm just not able to wrap my head around. But that seems kind of a bummer, too! I'd like to think that, say, hiking a medium-high difficulty trail, which I don't do often, would burn more calories for me than someone of the same weight who has hiked the same trail every day.

The error is that you are mistaking individual effort for the actual energy cost of an activity. An unfit person must work harder because the workload/energy cost represents a higher percentage of their maximum. A fit person doing the same activity incurs the same energy cost-- however it is a lower percentage of their maximum, so their effort is less.

The comparison would be two people lifting the same weight, say 50lbs. The weaker person would work much harder to lift the weight than the stronger person---but the weight is still 50lbs for each person.

Azdak

I'd like to think that, say, hiking a medium-high difficulty trail, which I don't do often, would burn more calories for me than someone of the same weight who has hiked the same trail every day.

Yup...unfortunately doesn't really work that way. An unfit person would burn more...but it would not be that much more.

And actually, as you gain more fitness you'll be quite glad that it works this way...otherwise you'd have to do a crazy and unsustainable amount of work as a fit individual to keep burning the calories.

Or you would eventually become so efficient that you would cease to burn any calories whatsoever and just implode.

And in the the previous example of the hiking trail, no, the unfit person would not burn more calories simply because of lack of fitness. Hypothetically, someone who is UNTRAINED at walking up an irregular trail (but still fit) might burn insignificantly more calories due to being less efficient at stepping up on rocks, negotiating rougher terrain, etc. However, it is almost certain that the decreased efficiency would result in a slowing down of pace, resulting in a lower absolute rate of effort.

In this case, you can measure the calories two ways: if you measure by rate of burn (cals/min), then the unfit/inefficient person will burn less because they are moving more slowly. If you measure by total distance, then calorie burn will be roughly the same, because, even though rate is lower, the unfit person will take longer to complete the distance. Either way, the unfit/untrained person will not burn more calories than the fit person.

VelveteenArabian

Play with your profile and see it for yourself.

The heavier person would burn more calories. The heavier person also requires more calories for their BMR than a lighter person. The heavier person needs more calories per day to maintain.

If you try changing some settings in your profile you'll see that you are allotted different amounts of calories.

cwolfman13

However, it is almost certain that the decreased efficiency would result in a slowing down of pace, resulting in a lower absolute rate of effort.

good point..