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Heartrate and caloric burn relationship - How much does HR actually influence it?
andrektan
Posts: 196 Member
So I'm having trouble pinning down a somewhat informed/scientific answer to this question -
Given two identical people (same body composition, etc.) who are performing the same *light* activity (e.g., Office work, a hundred steps here and there, and NOT exercise), how big of a difference (in very, very rough percentage terms) would there be between their caloric burns if one was at a HR of 70 bpm and the other had one of 90 bpm?
I know that in the real world, this would ultimately be dependent on a number of factors, but what if HR was the only variable?
Given two identical people (same body composition, etc.) who are performing the same *light* activity (e.g., Office work, a hundred steps here and there, and NOT exercise), how big of a difference (in very, very rough percentage terms) would there be between their caloric burns if one was at a HR of 70 bpm and the other had one of 90 bpm?
I know that in the real world, this would ultimately be dependent on a number of factors, but what if HR was the only variable?
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Heart rate is highly individual. Take two people of the same age and fitness and you're likely to find wildly different max and lactate threshold heart rates. Then it's also influenced by things like heat, mood, hydration, caffeine intake, etc. During exercise, your heart rate will rise while you maintain a specific amount of effort, and it's really the effort that's responsible for burning energy. Heart rate is your body's reaction to that effort.
The best calories from HR formulas use HRV not pulse rate to tell things like whether you're working above or below your threshold, how much energy you're using from aerobic vs anaerobic pathways, etc.0 -
The calorie burn in your case (In nearly all scenarios) is simply weight moved x distance. The extra calories, if any, from the heart rate increase is negligible.0
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Let me put that another way: on a bike, you need maintain an average output of ~135 watts to burn 500 kCal per hour. That's true no matter what your heart rate is while you're doing it.0
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Wouldn't that vary to individual based on weight? Also, that is measured at the pedals, correct?NorthCascades wrote: »Let me put that another way: on a bike, you need maintain an average output of ~135 watts to burn 500 kCal per hour. That's true no matter what your heart rate is while you're doing it.
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Thanks for the replies so far, everyone.
Some background - I recently upgraded from a Fitbit Flex (no HR monitor) to a Fitbit Blaze (with HR) and I'm seeing caloric adjustments twice as much (or more) as I had before. I have a resting (according to the Blaze) HR of ~65, but during the day at work (Sitting at a desk much of the time) my HR fluctuates between 75 bpm up to the low-90s depending on stress/caffeine intake/etc.).
While I was using the Flex and targeting a 250/500 calorie deficit based on its numbers, I lost weight at a rate that was generally in line what would be expected (and was consistent with my hypothetical TDEE). But with these new values (at a similar activity level), I would have theoretically been at a 500-1000+ calorie deficit which seems absolutely crazy to me.
It makes sense to me that the only difference in the scenario I posed above would effectively be the amount of energy it would take for a heart to pump faster (plus whatever else that physiologically needs to happen), which as Waffle mentioned would be negligible.
However, Fitbit is clearly considering HR in their algorithms. I'm just wondering *why* they're doing that, and if there's any scientific validity to it. I'm guessing they assume that if the user has an elevated HR, they're more heavily active at a given moment?2 -
Garmin gives me just under 100 fewer calories for a 6 mile run with a HRM than without. They do factor your pulse into that apparently but I wouldn't hold that to be a major difference considering that's a full hour's worth of work. We're talking about potentially 1.6 calories per minute difference max.
There is a difference no doubt. Just not a vast difference or much worth worrying about unless you're trying to squeeze in an extra beer at the end of the day.
ETA: To beat the system I added on 0.2 miles so I always get over 1k calories. This difference is easy to overcome.
2nd ETA: Simply walking around? Not sure what the difference would be. Seems like it would be tiny.1 -
Wouldn't that vary to individual based on weight? Also, that is measured at the pedals, correct?NorthCascades wrote: »Let me put that another way: on a bike, you need maintain an average output of ~135 watts to burn 500 kCal per hour. That's true no matter what your heart rate is while you're doing it.
It would not depend on the individual's weight. But a heavier cyclist is going to require more watts than a lighter one ride up a hill, so they'll usually burn more calories than a light rider because they're putting out more effort to go the same speed. But it's the effort not the HR that burns the calories. It'll differ by up to about 5 % on the individual's metabolic efficiency, but that's a pretty small amount.
You can measure power output on a bike at:
* the pedals (I do, it's easy to move pedals to another bike)
* the crank arms
* the chainrings
* the chain itself
* the rear wheel
* I'm probably leaving something out.
I hope that wasn't too convoluted an explanation.
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However, Fitbit is clearly considering HR in their algorithms. I'm just wondering *why* they're doing that, and if there's any scientific validity to it. I'm guessing they assume that if the user has an elevated HR, they're more heavily active at a given moment?
In general it's scientifically valid to say that if you're heart is doing 180 bpm you're using more energy than if it's going 80 bpm. The question is how much more energy?
When you exercise you use your muscles to do some kind of work, maybe your legs to run. As your exercise gets more intense, your leg muscles need more and more energy. They get a lot of it by using oxygen to release the energy stored in fat. That's why you breathe harder at higher intensity, to get more oxygen in, and it's why your heart rate increases, to pump oxygenated blood to your muscles. You can get to the point where this just doesn't supply enough energy so you keep doing it but also use glycogen which does not require oxygen. Most of the time you're using some aerobic and some anaerobic energy to exercise, but mostly aerobic until the intensity gets very high. Really clever HRM systems can figure out where that point is for you but this can't really be measured at the wrist.
A lot of things (Fitbits, Garmins, phone apps) factor HR in their calorie algorithms. Generally people consider a calorie estimate more accurate if HR was part of calculating it. But some algorithms are a lot better than others. And even then, sometimes a good algorithm gets put into a system that has some other bug and you wind up with gibberish anyway.
Since you know your weight loss agrees with the numbers before you upgraded, I'd say the old one was more accurate for you.2 -
NorthCascades wrote: »
Wouldn't that vary to individual based on weight? Also, that is measured at the pedals, correct?NorthCascades wrote: »Let me put that another way: on a bike, you need maintain an average output of ~135 watts to burn 500 kCal per hour. That's true no matter what your heart rate is while you're doing it.
It would not depend on the individual's weight. But a heavier cyclist is going to require more watts than a lighter one ride up a hill, so they'll usually burn more calories than a light rider because they're putting out more effort to go the same speed. But it's the effort not the HR that burns the calories. It'll differ by up to about 5 % on the individual's metabolic efficiency, but that's a pretty small amount.
You can measure power output on a bike at:
* the pedals (I do, it's easy to move pedals to another bike)
* the crank arms
* the chainrings
* the chain itself
* the rear wheel
* I'm probably leaving something out.
I hope that wasn't too convoluted an explanation.
Makes sense. It is a measure of work.0 -
I'm pretty sure fitbits with HR monitors are designed to only take your HR into account when it comes to calorie burn when you're in "workout mode" or when its software recognizes that you're working out. That's why it tracks your resting heart rate as a separate category. That's the idea anyways. I'd think if you're just sitting around or doing light housework it wouldn't make much of a difference.0
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Fascinating info here. Thanks to all adding their knowledge as this is an area I know nothing about.1
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extra_medium wrote: »I'm pretty sure fitbits with HR monitors are designed to only take your HR into account when it comes to calorie burn when you're in "workout mode" or when its software recognizes that you're working out. [1] That's why it tracks your resting heart rate as a separate category. That's the idea anyways. [2] I'd think if you're just sitting around or doing light housework it wouldn't make much of a difference.
I'm gonna take these points in reverse order.
2 - You're right. Heart rate monitors are made for tracking cardio exercise and the formulas they use for calories don't really apply to washing the dishes. (Or to lifting weights or maybe to HIIT.)
1 - That's actually not what resting heart rate is, though. You'd think so based on the name. But it's kind of like BMR, the calories you burn just existing without doing anything else. Your RHR is the lowest heart rate you can do, or the one right after you wake up, or after you lay down for 10 minutes, or however you prefer to measure it. There are two reasons this can be useful: it'll go up when you're getting sick or if you've exercised too much and you need a break. Also some zone systems (%HRR) take your resting heart rate into account.0 -
NorthCascades wrote: »However, Fitbit is clearly considering HR in their algorithms. I'm just wondering *why* they're doing that, and if there's any scientific validity to it. I'm guessing they assume that if the user has an elevated HR, they're more heavily active at a given moment?
A lot of things (Fitbits, Garmins, phone apps) factor HR in their calorie algorithms. Generally people consider a calorie estimate more accurate if HR was part of calculating it. But some algorithms are a lot better than others. And even then, sometimes a good algorithm gets put into a system that has some other bug and you wind up with gibberish anyway.
Since you know your weight loss agrees with the numbers before you upgraded, I'd say the old one was more accurate for you.
I agree, but this is why I'm annoyed with Fitbit. It just shouldn't be the case.
I accept that in the end it's all an estimation game, but it's just ridiculous that in my case we're probably looking at a >100% margin of error when HRM functionality is thrown into the mix. It's not like my stats and behavior are some kind of weird edge case.0 -
The calorie burn in your case (In nearly all scenarios) is simply weight moved x distance. The extra calories, if any, from the heart rate increase is negligible.
I'm gonna agree here. I've done my own little experiences where I've run (attempting as much exactness of each ) the same distance, pace & conditions ) two different runs but one with the HR strap and one without. There's such little difference in the calorie burns it gives me.0 -
NorthCascades wrote: »However, Fitbit is clearly considering HR in their algorithms. I'm just wondering *why* they're doing that, and if there's any scientific validity to it. I'm guessing they assume that if the user has an elevated HR, they're more heavily active at a given moment?
A lot of things (Fitbits, Garmins, phone apps) factor HR in their calorie algorithms. Generally people consider a calorie estimate more accurate if HR was part of calculating it. But some algorithms are a lot better than others. And even then, sometimes a good algorithm gets put into a system that has some other bug and you wind up with gibberish anyway.
Since you know your weight loss agrees with the numbers before you upgraded, I'd say the old one was more accurate for you.
I agree, but this is why I'm annoyed with Fitbit. It just shouldn't be the case.
I accept that in the end it's all an estimation game, but it's just ridiculous that in my case we're probably looking at a >100% margin of error when HRM functionality is thrown into the mix. It's not like my stats and behavior are some kind of weird edge case.
I have a solution for you, but you won't like it .0 -
mommarnurse wrote: »NorthCascades wrote: »However, Fitbit is clearly considering HR in their algorithms. I'm just wondering *why* they're doing that, and if there's any scientific validity to it. I'm guessing they assume that if the user has an elevated HR, they're more heavily active at a given moment?
A lot of things (Fitbits, Garmins, phone apps) factor HR in their calorie algorithms. Generally people consider a calorie estimate more accurate if HR was part of calculating it. But some algorithms are a lot better than others. And even then, sometimes a good algorithm gets put into a system that has some other bug and you wind up with gibberish anyway.
Since you know your weight loss agrees with the numbers before you upgraded, I'd say the old one was more accurate for you.
I agree, but this is why I'm annoyed with Fitbit. It just shouldn't be the case.
I accept that in the end it's all an estimation game, but it's just ridiculous that in my case we're probably looking at a >100% margin of error when HRM functionality is thrown into the mix. It's not like my stats and behavior are some kind of weird edge case.
I have a solution for you, but you won't like it .
Shut the HRM off?
It's an option I've considered, but there wouldn't be any reason for me to keep the Blaze at that point.
Or do you have a different idea?0 -
I had tachycardia, resting heart rate over 100, when I started now it's in the 60s. I don't burn any less calories now.
It's valid for the monitor to consider the number. Valid in if the same person uses it and their heartrate is the only change that person is likely burning more calories. Where the logic may not make sense is attempting to compare person A with person B.0 -
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NorthCascades wrote: »However, Fitbit is clearly considering HR in their algorithms. I'm just wondering *why* they're doing that, and if there's any scientific validity to it. I'm guessing they assume that if the user has an elevated HR, they're more heavily active at a given moment?
A lot of things (Fitbits, Garmins, phone apps) factor HR in their calorie algorithms. Generally people consider a calorie estimate more accurate if HR was part of calculating it. But some algorithms are a lot better than others. And even then, sometimes a good algorithm gets put into a system that has some other bug and you wind up with gibberish anyway.
Since you know your weight loss agrees with the numbers before you upgraded, I'd say the old one was more accurate for you.
I agree, but this is why I'm annoyed with Fitbit. It just shouldn't be the case.
I accept that in the end it's all an estimation game, but it's just ridiculous that in my case we're probably looking at a >100% margin of error when HRM functionality is thrown into the mix. It's not like my stats and behavior are some kind of weird edge case.
Does the Blaze actually tell you you're burning X amount more calories? Or are you just extrapolating that based on its HR readouts? I honestly feel like all the newer apps and wearables keep increasing the overestimation of calories. Its like vanity sizing, but for calories. A marketing thing.
As to your original question, you're looking at it a bit backwards:
Caloric burn is NOT dependent on HR. HR happens to be an indirect indicator of oxygen usage, so we're able to use it to estimate calories during steady state cardio. It's not even a good measure during intervals or strength training. Definitely not during everyday activities.Heartrate and caloric burn relationship - How much does HR actually influence it?0 -
With all the fitness devices these days, as well as all of us who like the data from many sources, it's really surprising that nobody has made some type of real "meter" of HR vs absolute power output and thus calorie burn. I know some devices test VO2max and such, but it seems that if you could also meter power on a Velotron or bike with good meters, then you could more accurately define calorie burn vs HR and differing levels.0
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The fitbit is a more accurate measure of how much you are burning than whatever mfp is telling you, if that is what you are eventually trying to get at here.
If you walk up a flight of stairs and your heart rate goes up to, say, 100, it is because your body had to work to a certain level to walk up that flight of stairs, fast enough to cause your heart to go up to a rate of 100. If it goes up to 120, that is because your body had to work harder, and therefore you burned more. If you are a very efficient person maybe it only went up to 80. It could be that it only went up to 80 because you are smaller - or it could be that you are more fit in spite of being larger. In either case, the heart rate is, overall, the best measure of how many calories you are burning during your exercise regimen for this reason.
So two people who weigh 150 and walk three miles at the same rate may not burn off the same amount of calories. If one walks the same distance daily, they will burn off less because their body has adapted to walking it and does so at maximum efficiency. The unfit person will actually burn MORE (but might feel worse afterward).0 -
@robertw486robertw486 wrote: »With all the fitness devices these days, as well as all of us who like the data from many sources, it's really surprising that nobody has made some type of real "meter" of HR vs absolute power output and thus calorie burn. I know some devices test VO2max and such, but it seems that if you could also meter power on a Velotron or bike with good meters, then you could more accurately define calorie burn vs HR and differing levels.
Regarding the bolded....
I use a Polar FT60 with the fitness test/VO2 test functionality.
But it's not actually really a test as it's just using your resting HR and a formula to estimate VO2 max. To really test VO2 max you need to measure oxygen uptake. A bit impractical for home or on the road!
So my apparent VO2 max score (typically between 50 and 54) is really just tracking my RHR and making assumptions.
I had a spell of over training / under recovering recently which increased my RHR by 10% - my fitness level didn't actually change but my Polar would have thought it had.1 -
seekingdaintiness wrote: »The fitbit is a more accurate measure of how much you are burning than whatever mfp is telling you, if that is what you are eventually trying to get at here.
If you walk up a flight of stairs and your heart rate goes up to, say, 100, it is because your body had to work to a certain level to walk up that flight of stairs, fast enough to cause your heart to go up to a rate of 100. If it goes up to 120, that is because your body had to work harder, and therefore you burned more. If you are a very efficient person maybe it only went up to 80. It could be that it only went up to 80 because you are smaller - or it could be that you are more fit in spite of being larger. In either case, the heart rate is, overall, the best measure of how many calories you are burning during your exercise regimen for this reason.
So two people who weigh 150 and walk three miles at the same rate may not burn off the same amount of calories. If one walks the same distance daily, they will burn off less because their body has adapted to walking it and does so at maximum efficiency. The unfit person will actually burn MORE (but might feel worse afterward).
Sorry, but no. Two people with the same weight walking the same distance at the same rate will burn essentially the same number of calories. Differences in efficiency exist but are negligible. Differences in HR between people for the same work may not be.
Heart rate is not a very good measure of calorie burn except under certain circumstances, as many have already posted and explained.0 -
mommarnurse wrote: »1
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robertw486 wrote: »With all the fitness devices these days, as well as all of us who like the data from many sources, it's really surprising that nobody has made some type of real "meter" of HR vs absolute power output and thus calorie burn. I know some devices test VO2max and such, but it seems that if you could also meter power on a Velotron or bike with good meters, then you could more accurately define calorie burn vs HR and differing levels.
There are power meters available for bikes. The cheapest one you can buy (new) costs $400 and they go up to $3,500 or so.0 -
@robertw486robertw486 wrote: »With all the fitness devices these days, as well as all of us who like the data from many sources, it's really surprising that nobody has made some type of real "meter" of HR vs absolute power output and thus calorie burn. I know some devices test VO2max and such, but it seems that if you could also meter power on a Velotron or bike with good meters, then you could more accurately define calorie burn vs HR and differing levels.
Regarding the bolded....
I use a Polar FT60 with the fitness test/VO2 test functionality.
But it's not actually really a test as it's just using your resting HR and a formula to estimate VO2 max. To really test VO2 max you need to measure oxygen uptake. A bit impractical for home or on the road!
So my apparent VO2 max score (typically between 50 and 54) is really just tracking my RHR and making assumptions.
I had a spell of over training / under recovering recently which increased my RHR by 10% - my fitness level didn't actually change but my Polar would have thought it had.
Completely agree, and poor use of wording on my part. Of the ones I'm aware of all devices estimate VO2max through varied types of fitness tests, but the true measure is in a la@robertw486NorthCascades wrote: »robertw486 wrote: »With all the fitness devices these days, as well as all of us who like the data from many sources, it's really surprising that nobody has made some type of real "meter" of HR vs absolute power output and thus calorie burn. I know some devices test VO2max and such, but it seems that if you could also meter power on a Velotron or bike with good meters, then you could more accurately define calorie burn vs HR and differing levels.
There are power meters available for bikes. The cheapest one you can buy (new) costs $400 and they go up to $3,500 or so.
I'm aware of the true meters for bikes, as well as some machines h@robertw486
But that's my point. If instead of a device type of estimate such as the Polar or other tests, an absolute power measure was included, we could calculate actual calorie burn. Sure it would still leave the variable of efficiency, but it would kill the measure of power as another estimate in the equation.
Combined with logging, I'd think a person could find a fairly strong relationship between HR and calorie burn if the power measure was in the picture. X watts steady state = Y calories per minute absolute and HR = Z +/- a percentage for drift/workout time/fueling/cadence variables. Naturally that would change as training levels change, but VO2max already changes in the same way.
I've actually found that to some extent, the resistance of the movement impacts HR beyond just wattage. If I crank the same wattage at higher resistance and lower cadence my HR rise is often greater than if I crank that same wattage at lower resistance and higher cadence. I'm fairly certain I could impact my RER if I did testing on my elliptical, even staying at the same output wattage.0 -
There may be a case for looking at the differential of HR over resting HR to tease out the differences.
The heart is a calorie consumer and it may itself be using more energy at faster beat rate. Above that it usually reflects extra O2 demand from extra calorie burn.0 -
robertw486 wrote: »But that's my point. If instead of a device type of estimate such as the Polar or other tests, an absolute power measure was included, we could calculate actual calorie burn. Sure it would still leave the variable of efficiency, but it would kill the measure of power as another estimate in the equation.
Those areas where power metering is a viable option, are areas where HR is a reasonable proxy for power consumption anyway; cycling, running, rowing.
For the kinds of activities where many ask for advice around HRMs on this board, the ability to measure power output is very limited; circuit training, bodyweight, prancing around in front of a DVD etc
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@robertw486
It's not difficult to disturb the relationship between power and HR.
I was planning a one hour "time trial" on a power meter equipped cycle trainer the other day, keeping to the maximum HR I can sustain for an hour.
After a while I've settled into a nice cadence, HR steady around 155bpm and producing c. 200 watts of power.
Stays pretty consistent for about 20 minutes and then I overheat, the gym really needs some fans for the Wattbike section!
I keep my HR steady at 155bpm but power produced is steadily declining as my body is working hard to regulate my temperature as well as power my legs. By 30 minute mark my power at the same HR is down to 170 watts (-15%).
Power measuring is probably the gold standard but you are still estimating the efficiency ratio and really can't estimate the metabolic cost or impact of other factors outside of a lab environment.
Just as well it's really not desperately important to be that accurate with exercise calories..... Reasonable accuracy is fine.
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The circulation provided by the heart serves many purposes and does not necessary implies a direct related to the oxygen utilization in the body which is a major component of energy expenditure (as it cannot account for energy expenditure derived from anaerobic pathways and the pathways are concurrent not one or the other). The HR and energy algorithm assumes a direct corollary minus some noise and the fit is generally derived from trained individuals. Furthermore, HR is highly individual and easily influence by environmental factors and fatigue.
It may be possible to establish your own power to HR fit but don't expect it to fit anyone else. (For example pro cyclist can push out 6 w/kg under 80% of maximal aerobic power where as a novice is lucky to be just under 3 w/kg.) To get the most out of your training with a power meter, one needs to monitor not just performance but also fatigue (see Banister's impulse response model). To establish that trend, one typically needs a month or more data. During this transition, the most effective way of maintaining status quo is to continue with one's current measure/gauge of performance and fatigue with an eye on the power output.
The bottom line is we want to know the economy (miles per gallon to use the car analogy). HRM does not gives you how much fuel (O2, CHO, etc) are being pushed to the entire system (body) or to the primary engine (muscles). Under IDEAL conditions, a reasonable fit can be establish. It's not gospel.
A power meter also does not fill that void but gives you a very precise measurement of the work done. To fully account for the energy expenditure, one needs to know one's metabolic efficiency. However, in the absence of that information, a power meter still provides much better estimate than what a HRM can hope to (especially over the entire metabolic spectrum).1
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