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Heartrate and caloric burn relationship - How much does HR actually influence it?

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  • seekingdaintinessseekingdaintiness Posts: 136Member Member Posts: 136Member Member
    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).
  • sijomialsijomial Posts: 15,981Member Member Posts: 15,981Member Member
    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.
    @robertw486
    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.
  • stealthqstealthq Posts: 4,307Member Member Posts: 4,307Member Member
    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.
  • mommarnursemommarnurse Posts: 515Member, Premium Member Posts: 515Member, Premium Member
    andrektan wrote: »
    andrektan wrote: »
    andrektan wrote: »
    However, Fitbit is clea
    edited June 2016
  • NorthCascadesNorthCascades Posts: 9,535Member Member Posts: 9,535Member Member
    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.
  • robertw486robertw486 Posts: 2,080Member, Greeter Member Posts: 2,080Member, Greeter Member
    sijomial 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.
    @robertw486
    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 [email protected]

    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 [email protected]


    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.
  • yarwellyarwell Posts: 10,573Member Member Posts: 10,573Member Member
    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.
  • MeanderingMammalMeanderingMammal Posts: 7,870Member Member Posts: 7,870Member Member
    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
  • sijomialsijomial Posts: 15,981Member Member Posts: 15,981Member Member
    @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.





  • kcjchangkcjchang Posts: 663Member Member Posts: 663Member Member
    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).
  • NorthCascadesNorthCascades Posts: 9,535Member Member Posts: 9,535Member Member
    Those areas where power metering is a viable option, are areas where HR is a reasonable proxy for power consumption anyway; cycling, running, rowing.

    It really depends what you're after. For short interval training, like punchy hill repeats, I have a power target, driving that sort of workout by HR just doesn't work because of the way heart rate lags power output (by up to 30 seconds). For a time trial, you can pace yourself pretty well by heart rate.

    I live in a hilly city so all of my rides have a high variability index and that makes the immediacy of power measurement a valuable thing for me. :smile:
    sijomial wrote: »
    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.

    Yes but the efficiency of humans on road bikes doesn't really vary that much. Everybody spends most of their time sitting in a similar position turning circles with their legs (most with a radius of around 165 to 175 mm), mostly at around 80 to 90 rpm, etc. Running economy changes with stride length, vertical bounce, etc, but the constrained nature of a bike eliminates a lot of the variables for cycling.
  • sijomialsijomial Posts: 15,981Member Member Posts: 15,981Member Member
    Those areas where power metering is a viable option, are areas where HR is a reasonable proxy for power consumption anyway; cycling, running, rowing.

    It really depends what you're after. For short interval training, like punchy hill repeats, I have a power target, driving that sort of workout by HR just doesn't work because of the way heart rate lags power output (by up to 30 seconds). For a time trial, you can pace yourself pretty well by heart rate.

    I live in a hilly city so all of my rides have a high variability index and that makes the immediacy of power measurement a valuable thing for me. :smile:
    sijomial wrote: »
    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.

    Yes but the efficiency of humans on road bikes doesn't really vary that much. Everybody spends most of their time sitting in a similar position turning circles with their legs (most with a radius of around 165 to 175 mm), mostly at around 80 to 90 rpm, etc. Running economy changes with stride length, vertical bounce, etc, but the constrained nature of a bike eliminates a lot of the variables for cycling.

    The efficiency ratio is only one component and I've seen a range of 20 - 25% given for that so still significant variations from person to person. Obviously experienced cyclists are going to be in a narrower band than that.

    The point I was making is that there are many variables that affect HR and/or have a calorie burn outside of just the power produced.

    I know you love your power meter and it's certainly a valuable training aid but it's an accurate measuring tool for power produced only - the rest is a series of assumptions, estimations and immeasurable variables.
  • MeanderingMammalMeanderingMammal Posts: 7,870Member Member Posts: 7,870Member Member
    Those areas where power metering is a viable option, are areas where HR is a reasonable proxy for power consumption anyway; cycling, running, rowing.

    It really depends what you're after. For short interval training, like punchy hill repeats, I have a power target, driving that sort of workout by HR just doesn't work because of the way heart rate lags power output (by up to 30 seconds). For a time trial, you can pace yourself pretty well by heart rate.

    Oh indeed. But I can think of other things to spend a grand, Sterling, on that support my objectives.

  • NorthCascadesNorthCascades Posts: 9,535Member Member Posts: 9,535Member Member
    sijomial wrote: »
    Those areas where power metering is a viable option, are areas where HR is a reasonable proxy for power consumption anyway; cycling, running, rowing.

    It really depends what you're after. For short interval training, like punchy hill repeats, I have a power target, driving that sort of workout by HR just doesn't work because of the way heart rate lags power output (by up to 30 seconds). For a time trial, you can pace yourself pretty well by heart rate.

    I live in a hilly city so all of my rides have a high variability index and that makes the immediacy of power measurement a valuable thing for me. :smile:
    sijomial wrote: »
    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.

    Yes but the efficiency of humans on road bikes doesn't really vary that much. Everybody spends most of their time sitting in a similar position turning circles with their legs (most with a radius of around 165 to 175 mm), mostly at around 80 to 90 rpm, etc. Running economy changes with stride length, vertical bounce, etc, but the constrained nature of a bike eliminates a lot of the variables for cycling.

    The efficiency ratio is only one component and I've seen a range of 20 - 25% given for that so still significant variations from person to person. Obviously experienced cyclists are going to be in a narrower band than that.

    The point I was making is that there are many variables that affect HR and/or have a calorie burn outside of just the power produced.

    I know you love your power meter and it's certainly a valuable training aid but it's an accurate measuring tool for power produced only - the rest is a series of assumptions, estimations and immeasurable variables.

    That's only a difference of 5% variation from one person to the next. So if you rode 50 miles and burned about 1,000 calories, we're talking an uncertainty of 50 of them. Maybe you burned 975, maybe you burned 1,025. I don't think that's significant at all.

    For sure a power meter can't "see" all the calories you put into a bike. A lot of the time I'll push harder going up a hill and then recover while I coast down, the PM reports zero the whole way down, and without a doubt I'm burning more calories balancing the bike and recovering from the effort than I would be if I stayed home and watched a movie. But it measures the work you do very accurately, and it happens that that gets you closer to the truth about calories than a heart monitor can.
  • NorthCascadesNorthCascades Posts: 9,535Member Member Posts: 9,535Member Member
    Those areas where power metering is a viable option, are areas where HR is a reasonable proxy for power consumption anyway; cycling, running, rowing.

    It really depends what you're after. For short interval training, like punchy hill repeats, I have a power target, driving that sort of workout by HR just doesn't work because of the way heart rate lags power output (by up to 30 seconds). For a time trial, you can pace yourself pretty well by heart rate.

    Oh indeed. But I can think of other things to spend a grand, Sterling, on that support my objectives.

    Yeah, a power meter is expensive, it necessarily adds weight to a bike, and it's somewhat limited in what it can do. I love mine, as sijomial noticed, but they're absolutely not for everyone. Most people would be better off saving the money or spending on a vacation and riding or running in new scenery. But it's fun to talk about what is and isn't possible and the science of how the body reacts to different kinds of exercise. :smile:
  • The_EnginerdThe_Enginerd Posts: 3,933Member Member Posts: 3,933Member Member
    sijomial wrote: »
    Those areas where power metering is a viable option, are areas where HR is a reasonable proxy for power consumption anyway; cycling, running, rowing.

    It really depends what you're after. For short interval training, like punchy hill repeats, I have a power target, driving that sort of workout by HR just doesn't work because of the way heart rate lags power output (by up to 30 seconds). For a time trial, you can pace yourself pretty well by heart rate.

    I live in a hilly city so all of my rides have a high variability index and that makes the immediacy of power measurement a valuable thing for me. :smile:
    sijomial wrote: »
    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.

    Yes but the efficiency of humans on road bikes doesn't really vary that much. Everybody spends most of their time sitting in a similar position turning circles with their legs (most with a radius of around 165 to 175 mm), mostly at around 80 to 90 rpm, etc. Running economy changes with stride length, vertical bounce, etc, but the constrained nature of a bike eliminates a lot of the variables for cycling.

    The efficiency ratio is only one component and I've seen a range of 20 - 25% given for that so still significant variations from person to person. Obviously experienced cyclists are going to be in a narrower band than that.

    The point I was making is that there are many variables that affect HR and/or have a calorie burn outside of just the power produced.

    I know you love your power meter and it's certainly a valuable training aid but it's an accurate measuring tool for power produced only - the rest is a series of assumptions, estimations and immeasurable variables.

    That's only a difference of 5% variation from one person to the next. So if you rode 50 miles and burned about 1,000 calories, we're talking an uncertainty of 50 of them. Maybe you burned 975, maybe you burned 1,025. I don't think that's significant at all.
    No, that's a 20% possible variation in calorie counts. If you output 200 Calories through the pedals (232 Watts for one hour), that would represent 800-1000 Calories burned. Still, if you have enough long term data to determine your personal efficiency, it's going to be more accurate than HR based calorie calculations. In hot weather, my calorie count from my HRM can be 30% higher than the exact same run in cool conditions.
    edited June 2016
  • NorthCascadesNorthCascades Posts: 9,535Member Member Posts: 9,535Member Member
    Your efficiency at turning energy stored in fats and carbs into mechanical work is anywhere from about 20 to 25 %. How is that a 20 % possible variation?

    Now it would seem, after reading above that 1 Calorie = 4.186 kJs, that the total kiloJoules reported from your power meter divided by 4.186 would produce your energy expenditure, right? Actually no! Here’s why: the human body isn’t 100% efficient at converting chemical energy stored within food to actual work completed (mechanical energy) on the bike. Unfortunately 75-80% of the Calories (food) are converted into heat energy that’s lost to the external environment as “waste”, while only 20-25% is actually applied to the pedals. Or I guess that could be fortunate if you are trying to burn Calories to lean up or lose excess body weight. So essentially factoring back in efficiency after dividing the Calorie to kilojoule conversion cancels out one another. Just a note, there may be a small difference based on any given rider’s efficiency, but the only way to know this is with laboratory testing, so generally 1 kilojoule equating to 1 Calorie is widely accepted in cycling.

    http://home.trainingpeaks.com/blog/article/how-accurate-is-that-calorie-reading
    edited June 2016
  • kcjchangkcjchang Posts: 663Member Member Posts: 663Member Member
    work = energy expended x efficiency or kcal = (kj / 4.184) / efficiency
  • yarwellyarwell Posts: 10,573Member Member Posts: 10,573Member Member
    25% efficiency compared to 20% can be a 20% difference. 100W out from either 400 or 500W input - 20% less or 25% more input depending which way you go.
  • sijomialsijomial Posts: 15,981Member Member Posts: 15,981Member Member
    sijomial wrote: »
    Those areas where power metering is a viable option, are areas where HR is a reasonable proxy for power consumption anyway; cycling, running, rowing.

    It really depends what you're after. For short interval training, like punchy hill repeats, I have a power target, driving that sort of workout by HR just doesn't work because of the way heart rate lags power output (by up to 30 seconds). For a time trial, you can pace yourself pretty well by heart rate.

    I live in a hilly city so all of my rides have a high variability index and that makes the immediacy of power measurement a valuable thing for me. :smile:
    sijomial wrote: »
    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.

    Yes but the efficiency of humans on road bikes doesn't really vary that much. Everybody spends most of their time sitting in a similar position turning circles with their legs (most with a radius of around 165 to 175 mm), mostly at around 80 to 90 rpm, etc. Running economy changes with stride length, vertical bounce, etc, but the constrained nature of a bike eliminates a lot of the variables for cycling.

    The efficiency ratio is only one component and I've seen a range of 20 - 25% given for that so still significant variations from person to person. Obviously experienced cyclists are going to be in a narrower band than that.

    The point I was making is that there are many variables that affect HR and/or have a calorie burn outside of just the power produced.

    I know you love your power meter and it's certainly a valuable training aid but it's an accurate measuring tool for power produced only - the rest is a series of assumptions, estimations and immeasurable variables.

    That's only a difference of 5% variation from one person to the next. So if you rode 50 miles and burned about 1,000 calories, we're talking an uncertainty of 50 of them. Maybe you burned 975, maybe you burned 1,025. I don't think that's significant at all.

    For sure a power meter can't "see" all the calories you put into a bike. A lot of the time I'll push harder going up a hill and then recover while I coast down, the PM reports zero the whole way down, and without a doubt I'm burning more calories balancing the bike and recovering from the effort than I would be if I stayed home and watched a movie. But it measures the work you do very accurately, and it happens that that gets you closer to the truth about calories than a heart monitor can.

    You're still not really getting my point - your body isn't just producing power (hence the efficiency ratio), the immeasurable parts aren't just what you put into the bike but the everything else that adds to the 20-25% power produced to give the 100% calorie burn, the true overall metabolic cost. What I'm saying is neither a HRM or a power meter give the whole picture, just different perspectives and data - one gives HR and one measures power produced, neither can count complete calorie burn.

    Example: Producing 200watts at 20mph in very cold conditions, your body will burn a huge amount of calories just to keep warm when there's a high level of wind chill. Producing the same 200watts in warm weather would be a very different total burn.
    Ditto very hot conditions where your body is working hard to cool down as per my Wattbike Pro example up thread, a 15% variance under extremely tightly controlled conditions.

    I do agree a PM is closer to the "truth" and I enjoy using one indoors as it gives a different training perspective.
    Personally a wheel upgrade is next on my shopping list though. I'm perfectly happy using pretty crappy calorie burn estimates outdoors (Strava or Garmin) and regulating my body weight by the trend over time.
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