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Heartrate and caloric burn relationship - How much does HR actually influence it?
Replies
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MeanderingMammal 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.
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.0 -
NorthCascades wrote: »MeanderingMammal 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.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.0 -
NorthCascades wrote: »MeanderingMammal 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.
Oh indeed. But I can think of other things to spend a grand, Sterling, on that support my objectives.
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NorthCascades wrote: »MeanderingMammal 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.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.0 -
MeanderingMammal wrote: »NorthCascades wrote: »MeanderingMammal 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.
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. 0 -
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.NorthCascades wrote: »NorthCascades wrote: »MeanderingMammal 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.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.
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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-reading0 -
work = energy expended x efficiency or kcal = (kj / 4.184) / efficiency0
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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.0
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NorthCascades wrote: »NorthCascades wrote: »MeanderingMammal 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.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.0
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