Calories Burned



rclouviere

Member
Apr 10, 2011
126
8
18
I use a garmin 705, and I consistently have readings of around 1,000 calories burned in an hour. I did a century yesterday and burned 6,000 calories! Could this be accurate? Another rider had a garmin 505, I believe, and his were about half of mine...
 
60c/mile? Yeah, sounds high.
How much do you weigh? How fast did you complete that 100 miles? Hilly, flat, rolling terrain?

FWIW, I'm 195lbs and at 220w I burn 18c/min - numbers obtained from lab tests, by the way. 220w gets me about 20mph on the flat, or 3min/mi. when there's no wind. So, according to the math I'd burn around 54c/mile at 20mph, which makes 5400c burned for the century. Hills will, of course, alter that speed number.

Unless you're as incredibly ineffecient as I am - need to thank my parents for my preponderance of type IIb muscle - I'd tend to doubt your Garmin numbers...
 
Yeah, I'm 170 lbs, and rode the century in 6 hours (pedal time) and the elevation was 2,300 feet. Yeah, seems really high for me. On all my rides, when I push hard, it says around 1,000 calories an hour. When I run hard, that's how many calories I burn, so I doubt cycling would burn the same amount?
 
rclouviere said:
Yeah, I'm 170 lbs, and rode the century in 6 hours (pedal time) and the elevation was 2,300 feet. Yeah, seems really high for me. On all my rides, when I push hard, it says around 1,000 calories an hour. When I run hard, that's how many calories I burn, so I doubt cycling would burn the same amount?
From what I understand the garmin edge isn't too good with tracking calories burned so I use my polar heartrate monitor for tracking heartrate instead...
 
Originally Posted by SpecializedMok .



Quote: Originally Posted by rclouviere .

Yeah, I'm 170 lbs, and rode the century in 6 hours (pedal time) and the elevation was 2,300 feet. Yeah, seems really high for me. On all my rides, when I push hard, it says around 1,000 calories an hour. When I run hard, that's how many calories I burn, so I doubt cycling would burn the same amount?

From what I understand the garmin edge isn't too good with tracking calories burned so I use my polar heartrate monitor for tracking heartrate instead...


The Polar CS600 (without the power module) that I had before my PowerTap was just as bad as the Garmin would seem to be. The Polar would always guestimate just under double what the PowerTap would measure.
 
^^^Polar CS600?! You?? Puleez! More unverified story-telling claims to having ridden a bike...this character apparently is fully capable of talking a good game with NOTHING to back it up...How credible is that, oh omniscient one?? LOL!

Can't put up, and definitely won't shut up - what a winner of credibility combination you got there pal...
 
I actually still have it - just don't use it. Put it up for sale on CL a while back but had a bunch of people enquire but noone prepared to party with the money they said they had...



... as you were Tony.
 
sounds right about 60 a minute but thats purely depended on lots of varibles: terrain, speed, your fitness/health.
Rule of thumb though is 60/min.
 
Swampy the PowerTap measures heart rate and is able to calculate calories spent based on those numbers? I don't have PowerTap so I'm not sure. I Polar RS800 heart rate monitor. I hope it isn't off...
Originally Posted by swampy1970 .





The Polar CS600 (without the power module) that I had before my PowerTap was just as bad as the Garmin would seem to be. The Polar would always guestimate just under double what the PowerTap would measure.
 
The PowerTap or any power meter measures watts and over the course of a ride measures average watts which is much more closely tied to Calories burned than any HR or speed based estimate. It breaks down like this:

kilojoules of energy = average power (watts) * seconds/1000

So in terms of hours:

kj = AP (watts)*3.6*hours (there's 3.6 kilo-seconds per hour)

Calories combusted by your metabolism = 4.184*kj

So far that's straight physics and unit conversions and does not vary between individuals. But individual riders each have their own Gross Metabolic Efficiency which isn't about how pretty a circle you spin while riding, it's a measure of how much of that combustion energy makes it down to the pedals in terms of useful power. Most of the remaining energy gets burned off as waste heat. The variation across riders is very small and in the range of 19-26% or and typically shown in the published research to be normally distributed with a mean near 22 or 23%. Interestingly GME statistics are the same for both trained and untrained populations so even though individuals vary there's little evidence that GME necessarily increases with increased training as even grand tour pro cyclists have GME distributions statistically similar to untrained populations.

So in terms of dietary calories burned during cycling it comes down to the average power you sustain in watts, the time you sustained it and a narrow range of variation based on your own GME that can be measured during a lab VO2 Max test if gas exchange measurements are taken which means the full breathing mask rig. Since most folks don't do gas exchange testing and haven't nailed down their GME it becomes simpler to assume their GME is ~23.9% or the reciprocal of 4.184 (the kj to Calorie conversion factor). When you do that you're basically estimating dietary Calories as straight kj burned in exercise which is what power meters measure. So you end up with:

Calories ~ AP (watts) * 3.6 * hours with a normally distributed error with a variance of ~ +/- 8%


So if you maintain an average power of 200 watts for an hour you'll burn approximately 720 Calories. Do that for a five hour century and you'll burn approximately 3,600 Calories. Sustain 300 watts for an hour and you'll burn approximately 1,080 Calories and so on.

Short of riding with a gas exchange mask that's the most accurate way of estimating dietary calories burned while cycling (or rowing on a power equipped rowing erg). Heart rate based estimates must make a similar GME assumption but they also are forced to estimate the power you sustain at a given HR. They try to do this by having you enter weight, perhaps tracking speed, perhaps taking into consideration an estimate of your HR at LT or HR max but they're forced to layer estimates on estimates which only increases error.

For instance take two riders who both have an LT HR of say 160 bpm and even assume their weight and aerodynamics and tire rolling resistances are the same but one is a new rider who barely sustains 150 watts at LT and the other a Cat 3 cyclist that sustains 300 watts at LT. They both go out and ride at LT for an hour and both come back with an average HR of 160 bpm for the ride. A HR based estimate of Calories burned is going to be way off in one or both cases as the Cat 3 rider will have burned roughly twice as many Calories per hour as the untrained rider.

Bottom Line, dietary Calories are a measurement of energy, power is defined as energy per unit time or IOW, energy is defined as power integrated over time. A PM directly measures both power and energy which is what we're after.

-Dave
 
Originally Posted by swampy1970 .

I actually still have it - just don't use it. Put it up for sale on CL a while back but had a bunch of people enquire but noone prepared to party with the money they said they had...



... as you were Tony.

Oh, posting a pic proves something? Well, okay, then I have a Polar CS600 too. LOL!

 
tonyzackery said:
 


Oh, posting a pic proves something?  Well, okay, then I have a Polar CS600 too.  LOL!
 

 
Take a look at the headunit dopey... Either I'm first class photoshop guy and managed to get my nickname on the screen and the reflections correct or I just have a cs600.
 
Originally Posted by swampy1970 .


Take a look at the headunit dopey... Either I'm first class photoshop guy and managed to get my nickname on the screen and the reflections correct or I just have a cs600.

LOL! You're neither, because if you actually owned/used the unit or was a photoshop guru you should've been able to erase that Michelin Man gut of yours in either case.../img/vbsmilies/smilies/ROTF.gif
 
Thanks daveryanwyoming! That was definitely food for thought! Thanks for the explanation!

Originally Posted by daveryanwyoming .

The PowerTap or any power meter measures watts and over the course of a ride measures average watts which is much more closely tied to Calories burned than any HR or speed based estimate. It breaks down like this:

kilojoules of energy = average power (watts) * seconds/1000

So in terms of hours:

kj = AP (watts)*3.6*hours (there's 3.6 kilo-seconds per hour)

Calories combusted by your metabolism = 4.184*kj

So far that's straight physics and unit conversions and does not vary between individuals. But individual riders each have their own Gross Metabolic Efficiency which isn't about how pretty a circle you spin while riding, it's a measure of how much of that combustion energy makes it down to the pedals in terms of useful power. Most of the remaining energy gets burned off as waste heat. The variation across riders is very small and in the range of 19-26% or and typically shown in the published research to be normally distributed with a mean near 22 or 23%. Interestingly GME statistics are the same for both trained and untrained populations so even though individuals vary there's little evidence that GME necessarily increases with increased training as even grand tour pro cyclists have GME distributions statistically similar to untrained populations.

So in terms of dietary calories burned during cycling it comes down to the average power you sustain in watts, the time you sustained it and a narrow range of variation based on your own GME that can be measured during a lab VO2 Max test if gas exchange measurements are taken which means the full breathing mask rig. Since most folks don't do gas exchange testing and haven't nailed down their GME it becomes simpler to assume their GME is ~23.9% or the reciprocal of 4.184 (the kj to Calorie conversion factor). When you do that you're basically estimating dietary Calories as straight kj burned in exercise which is what power meters measure. So you end up with:

Calories ~ AP (watts) * 3.6 * hours with a normally distributed error with a variance of ~ +/- 8%


So if you maintain an average power of 200 watts for an hour you'll burn approximately 720 Calories. Do that for a five hour century and you'll burn approximately 3,600 Calories. Sustain 300 watts for an hour and you'll burn approximately 1,080 Calories and so on.

Short of riding with a gas exchange mask that's the most accurate way of estimating dietary calories burned while cycling (or rowing on a power equipped rowing erg). Heart rate based estimates must make a similar GME assumption but they also are forced to estimate the power you sustain at a given HR. They try to do this by having you enter weight, perhaps tracking speed, perhaps taking into consideration an estimate of your HR at LT or HR max but they're forced to layer estimates on estimates which only increases error.

For instance take two riders who both have an LT HR of say 160 bpm and even assume their weight and aerodynamics and tire rolling resistances are the same but one is a new rider who barely sustains 150 watts at LT and the other a Cat 3 cyclist that sustains 300 watts at LT. They both go out and ride at LT for an hour and both come back with an average HR of 160 bpm for the ride. A HR based estimate of Calories burned is going to be way off in one or both cases as the Cat 3 rider will have burned roughly twice as many Calories per hour as the untrained rider.

Bottom Line, dietary Calories are a measurement of energy, power is defined as energy per unit time or IOW, energy is defined as power integrated over time. A PM directly measures both power and energy which is what we're after.

-Dave