Calories

Khannie

I'm pretty sure that the only way to get any kind of real idea of calories burned is to use a power meter. Any online calculators I've seen estimate that my 32K commute covers about 1000 calories. I think this is way, way too high for a road bike / no wind. Possibly to the tune of 50%. I currently allow 600 calories for it.

I cover the 32K in about 75 minutes these days and I'm currently walking around at about 70KG.

Could someone who owns a power meter tell me what a reasonable calorie burn for that kind of distance with that kind of time is?

(even if you can say for example, "I'm 85KG and my power meter tells me that for 50K @ blah average speed I use X calories" that would be somewhat useful because I can compare it to the online calculator)

Lumen

For me (68kg), 30kph = 200W = 720 kJ/hr = ~ 800 kcal/hr @1.1 efficiency.

On a road bike, with 40cm bars and an unexceptional position.

Rough estimates.

CardinalJ

Khannie wrote: »

I'm pretty sure that the only way to get any kind of real idea of calories burned is to use a power meter. Any online calculators I've seen estimate that my 32K commute covers about 1000 calories. I think this is way, way too high for a road bike / no wind. Possibly to the tune of 50%. I currently allow 600 calories for it.

I cover the 32K in about 75 minutes these days and I'm currently walking around at about 70KG.

Could someone who owns a power meter tell me what a reasonable calorie burn for that kind of distance with that kind of time is?

(even if you can say for example, "I'm 85KG and my power meter tells me that for 50K @ blah average speed I use X calories" that would be somewhat useful because I can compare it to the online calculator)

I often wonder the same. I use a heart monitor polar watch while mountain biking and it usually tells me I'm burning around 1000kcal/hr.

I'm 104kg and 6'4, so having my heart up at 145 average for an hour would be burning a lot, but the watch wouldn't be taking into account when I'm on a flat section or going down hill and my heart is still high from going up a path/trail.

I'd say I'm actually burning around 60-70% of what it claims.

Would be interested though to see what anyone else thinks.

Khannie

Lumen wrote: »

For me (68kg), 30kph = 200W = 720 kJ/hr = ~ 800 kcal/hr @1.1 efficiency.

On a road bike, with 40cm bars and an unexceptional position.

Rough estimates.

Perfect. Thanks.

markcroninbsc

to get an accurate value for calories burned you have to take too many variables into account to get an accurate result. All of the devices you can bring on your bike that gives you a calorie readin are just an estimate.

I'd say for an average person out for a 2 hour spin workin at about 70% your talkin around 600 calories per hour so 1200

Khannie

markcroninbsc wrote: »

All of the devices you can bring on your bike that gives you a calorie readin are just an estimate.

A power meter would be a particularly accurate estimate though.

Lumen

markcroninbsc wrote: »

to get an accurate value for calories burned you have to take too many variables into account to get an accurate result. All of the devices you can bring on your bike that gives you a calorie readin are just an estimate.

A power meter is very accurate at measuring output, and the gross efficiency calculations used to turn those numbers into calories burned are fairly well researched.

markcroninbsc

Khannie wrote: »

A power meter would be a particularly accurate estimate though.

Power without the other variables isnt very accurate tho. Lance could put out 500 watts for an hour and burn 600 calories but i could probably burn 600 doin 180. Then you have other things like temperature and altitude that will effect calories burned, not by that much but but a couple of percent.

then again if i was on what lance was on i could probably put out 500 watts too, so i suppose the biggest factor is how much epo you have in your system?

Khannie

markcroninbsc wrote: »

Power without the other variables isnt very accurate tho.

That's not true. Once the power estimate is accurate the other variables are going to have a much smaller impact.

markcroninbsc wrote: »

Lance could put out 500 watts for an hour and burn 600 calories but i could probably burn 600 doin 180.

This assumption is not correct. Total calories burned by both of you would be the same if you each expended 600W for one hour. He would just be less dead than you.

markcroninbsc

Khannie wrote: »

That's not true. Once the power estimate is accurate the other variables are going to have a much smaller impact.

Most power meters are only acurate to about 5%. You expend other effort while on the bike that the power meter doesnt count, e.g when climbing out of the saddle your expending more energy than whats going into your power meter

Khannie wrote: »

This assumption is not correct. Total calories burned by both of you would be the same if you each expended 600W for one hour. He would just be less dead than you.

if im cycling in the alps at 2000meters and its -2 degrees and hes cycling in texas at 2meters and its 38 degrees, that has a massive effect on calories burned thats not going to be directly captured by a power meter

niceonetom

markcroninbsc wrote: »

Lance could put out 500 watts for an hour and burn 600 calories but i could probably burn 600 doin 180.

Does that bsc represent a science degree? Because that's an alarming misunderstanding of both thermodynamics and physiology.

Lumen

markcroninbsc wrote: »

if im cycling in the alps at 2000meters and its -2 degrees and hes cycling in texas at 2meters and its 38 degrees, that has a massive effect on calories burned thats not going to be directly captured by a power meter

Meanwhile, back in the real world, for the purposes of "can I has another cake", the standard rules of thumb are perfectly sufficient.

Aside from anything else, if you're trying to balance calories with Lance-like scientific precision for your Grand Tour preparation, you'll need to work out BMR and other energy expenditure in the rest of the day that you spend not-cycling.

Cookie_Monster

markcroninbsc wrote: »

if im cycling in the alps at 2000meters and its -2 degrees and hes cycling in texas at 2meters and its 38 degrees, that has a massive effect on calories burned thats not going to be directly captured by a power meter

but the software of the GPS attached to the power metre will allow for that surely Do power metres plug into GPS like cadence and HRM?

I've only got a garmin 500 and a heart rate monitor. but it does air pressure, temp, gradient, speed, heart rate and you can programme in height, weight and activity class all which are taken into account to give a number. Seems comprehensive enough to me...

I think that's fairly accurate, I average about 8-900kcal an hour depending on effort, before the HRM was gotten it was estimating well over 1000kcal.

markcroninbsc

Cookie_Monster wrote: »

but the software of the GPS attached to the power metre will allow for that surely Do power metres plug into GPS like cadence and HRM?

I've only got a garmin 500 and a heart rate monitor. but it does air pressure, temp, gradient, speed, heart rate and you can programme in height, weight and activity class all which are taken into account to give a number. Seems comprehensive enough to me...

I think that's fairly accurate, I average about 8-900kcal an hour depending on effort, before the HRM was gotten it was estimating well over 1000kcal.

yea thats exactly what im saying. you cant just get your power number and change the watts to calories. you need to take the other variables into account. and most of the devices will have alot of the other variables, but most of the values they get wont be all that accurate and after all the calculations they do end up only being accurate to about +-30% out on the road compared to a test that would be done in a lab situation. Thats why i think your better off just sayin 600 cal per hour. and anyway its all useless unless your actually training for something and your not just a boards.ie fred

Lumen

markcroninbsc wrote: »

you cant just get your power number and change the watts to calories. you need to take the other variables into account. and most of the devices will have alot of the other variables, but most of the values they get wont be all that accurate and after all the calculations they do end up only being accurate to about +-30% out on the road compared to a test that would be done in a lab situation.

Do you have any references for this +-30% variability?

Khannie

markcroninbsc wrote: »

yea thats exactly what im saying. you cant just get your power number and change the watts to calories.

Ah you can yeah. Those other variables are not going to really affect things in my world. Mostly I'm going to be cycling at low altitude in temperatures between 10 and 20 degreesC. It's fair to say that for my purposes, those other variables don't mean squat compared to power when averaged over the 75 minutes of my commute.

markcroninbsc wrote: »

and anyway its all useless unless your actually training for something and your not just a boards.ie fred

I'm training for a fight in September. I have a very specific weight to make so getting a reasonable number for calories burned is important for me. 1000 calories seemed like nonsense (except to my stomach, which so badly wanted it to be true ). 600 was a guess on my part. I'd be happier (to the tune of a twix a day) if it was 700 each way.

seamus

Cookie_Monster wrote: »

I've only got a garmin 500 and a heart rate monitor. but it does air pressure, temp, gradient, speed, heart rate and you can programme in height, weight and activity class all which are taken into account to give a number. Seems comprehensive enough to me...

I think that's fairly accurate, I average about 8-900kcal an hour depending on effort, before the HRM was gotten it was estimating well over 1000kcal.

Sounds about right, in terms of estimate anyway.
I've been perplexed about my commute for a long time. It's more-or-less the same distance each way, but there's an elevation difference of about 120m. So on the way in, I hit decent speeds. On the way out it's 20% slower, because of the elevation difference but also because of traffic lights and such.

Every calculation punched into a website, every computer I've had, would tell me that such lightning speeds on the way into work were worth about 1200 kcals/hour, but the slower speeds on the way back only about 900kcals/hours.

With roughly an hour's commute, they were all telling me that I was burning over 1,000 kcals per day getting in and out of work. Assuming that I ate normally, that kind of rate was predicting that I should be losing half a stone every month. Or that I could pretty much eat whatever the hell I liked without gaining weight. Neither of which are true.

The Garmin has flipped all that on its head. It looks at the various pieces of data and tells me that the way in burns about 250kcal and the way out burns about 400 kcal. Which gives me a much more disappointing but eminently more sensible reading of roughly 600kcal per day.

I can't see a power meter making a particularly big difference to this calculation. For the purposes of weight loss (or gain), an accuracy improvement of 10% (or even 20%) isn't that much.

Khannie

seamus wrote: »

The Garmin has flipped all that on its head. It looks at the various pieces of data and tells me that the way in burns about 250kcal and the way out burns about 400 kcal. Which gives me a much more disappointing but eminently more sensible reading of roughly 600kcal per day.

That's for around an hour on the bike?

seamus

Khannie wrote: »

That's for around an hour on the bike?

About an hour on the bike, but 45-50 mins actually doing any work. Also note that I have about 20kg on you, so your estimates may be smaller again.

langdang

If the gps gizmos take elevation into account then they have a good stab at the "work done" which gives them an advantage for these calculations

markcroninbsc

niceonetom wrote: »

Does that bsc represent a science degree? Because that's an alarming misunderstanding of both thermodynamics and physiology.

I think that shows an alarming misunderstanding of what a science degree is.... I got mine in computing.

Ok I might have exaggerated the figures a little. but muscle efficiency alone could account for upto 10% or more between two different people, then you have bike position and pedaling technique to take into account aswell where a further 10% or more power to the pedals could be lost. Power meters measure the power that goto the pedals (or hub) so directly measuring calories from power only measures the calories that went thru the pedals. Air temperature and altitude also have an effect on calorie consumption that wont be measured thru the power meter, fairly slight i suppose but still.

I wouldnt claim to be an expert in all of this tho and i will admit that a power meter is probably the most accurate measure for calories burned, i was just trying to say that none of the devices you can use outside of the lab on the road can claim to estimate calories burned to within a couple of percent accuracy so your aswell off just taking a figure like 600 calories per hour for 70% effort and multiplying/dividing that by your time spent.

Dubba

Link to a bike calculator to add in some extra variables:

http://www.bikecalculator.com/veloUS.html

Lumen

markcroninbsc wrote: »

Ok I might have exaggerated the figures a little. but muscle efficiency alone could account for upto 10% or more between two different people, then you have bike position and pedaling technique to take into account aswell where a further 10% or more power to the pedals could be lost. Power meters measure the power that goto the pedals (or hub) so directly measuring calories from power only measures the calories that went thru the pedals. Air temperature and altitude also have an effect on calorie consumption that wont be measured thru the power meter, fairly slight i suppose but still.

What has bike position got to do with deriving calorie expenditure from forces at the crank? Do you have any sources for these 10% numbers?

morana

I am 92kg and on a normal training spin with the power meter I average about 800 per hour. The power meter is calibrated every few months by me so I think its fairly accurate..

lads relax you are out on a bumpy road, wind, extra breakfast, sunny 1 min rain next etc etc. he just wanted a guesstimate

markcroninbsc

Lumen wrote: »

What has bike position got to do with deriving calorie expenditure from forces at the crank? Do you have any sources for these 10% numbers?

bike positioning and pedaling technique has everything to do with how much power goes into the cranks no?

Lumen

markcroninbsc wrote: »

bike positioning and pedaling technique has everything to do with how much power goes into the cranks no?

Sure, but you're asserting that those things have an effect on gross energy efficiency, not effectiveness.

markcroninbsc

Lumen wrote: »

Sure, but you're asserting that those things have an effect on gross energy efficiency, not effectiveness.

well what im saying is that potentially alot of effort made isnt actually transfered to the pedals. And your calories burned should be a calculation of power transfered to the pedals(measured by your power meter) + power wasted.

markcroninbsc

Lumen wrote: »

Sure, but you're asserting that those things have an effect on gross energy efficiency, not effectiveness.

if you want to get really silly about it heres a test for you.

would you agree that you burn upto 80 calories an hour sittin on your arse doing only talkin on boards.ie

then this evenin go home set up your bike on the turbo trainer with your powertap wheel and stick your laptop on the handlebars and type away for an hour. i bet your powertap registers 0. calculate the 80 calories from that.

Lumen

markcroninbsc wrote: »

well what im saying is that potentially alot of effort made isnt actually transfered to the pedals. And your calories burned should be a calculation of power transfered to the pedals(measured by your power meter) + power wasted.

Saris say:

Saris wrote:

In the Applied Exercise Science Laboratory we actually measure mechanically efficiency and calculate personal conversion factors that allow athletes to convert mechanical Kjoules to metabolic Kcals. This conversion ranges from about 1.05 Kcals per Kjoule for the most efficient athletes to about 1.15 for our least efficient athletes. It's important to note, that a number of factors like training status, temperature, and biomechanics may change a person’s efficiency.

Now they don't say what the effects of these real world variables are, and they are in the business of selling power meters, but 1.05-1.15 is within +/-5%, so unless you can provide some vaguely authoritative references for your +/-30% it seems like you're pulling that out of thin air.

Lumen

markcroninbsc wrote: »

would you agree that you burn upto 80 calories an hour sittin on your arse doing only talkin on boards.ie

then this evenin go home set up your bike on the turbo trainer with your powertap wheel and stick your laptop on the handlebars and type away for an hour. i bet your powertap registers 0. calculate the 80 calories from that.

The 80 calories is BMR. I don't understand how that relates to cycling efficiency and calorie estimation.

markcroninbsc

Lumen wrote: »

The 80 calories is BMR. I don't understand how that relates to cycling efficiency and calorie estimation.

the original question wasnt about cycling efficiency it was about calories burned over 75? minutes, and it was a question around calories to weignt loss so i would say that the 80 calories should be included there. i dont have any documentation around that 30% number i was just saying that calculating calorie from power measured from a power meter could be upto 30% inaccurate. most manufacturers themselves only rate their power meters to be 98% accurate. i think your quote above only took into account mechanical efficiency not muscle efficiency. or air temperature or anything else. i was saying everything put together could amount to 30% of a difference in calories burned. altho i think i did give a figure of about 10% for mechanical efficiency so i might be out on that one but you are basing your argument of the 5% difference on one study, im sure if you googled enough youd get one that said 10%.

markcroninbsc

Lumen wrote: »

The 80 calories is BMR. I don't understand how that relates to cycling efficiency and calorie estimation.

and like i said that was only if you wanted to get silly about it... which you obviously are

blue chuzzle

markcroninbsc wrote: »

i dont have any documentation around that 30% number i was just saying that calculating calorie from power measured from a power meter could be upto 30% inaccurate. i was saying everything put together could amount to 30% of a difference in calories burned.

saying something could be something with no figures to back it up at all is meaningless.

the sun could be mostly cold. most elephants could be microscopic. getting annoyed at the internet could be a waste of time

what you should say(if you have to say anything about it) is "my guess would be that its not very accurate" and leave it at that.

you have no facts or figures to start with so ending with one is crazy.

markcroninbsc

blue chuzzle wrote: »

saying something could be something with no figures to back it up at all is meaningless.

the sun could be mostly cold. most elephants could be microscopic. getting annoyed at the internet could be a waste of time

what you should say(if you have to say anything about it) is "my guess would be that its not very accurate" and leave it at that.

you have no facts or figures to start with so ending with one is crazy.

thats just stupid!!

i was saying that the calories calculated from a power meter are from the power that passes thru the power meter and that there are alot of other places where power is wasted before it gets to the power meter. If you could back it up with an exact figure then there wouldnt be an inaccuracy you could just add that on at the end.

The figure i was talking about was a sum of all power lost before it gets to the power meter, and the 2% inaccuracy of the power meter itself.

Muscle efficiency varies between people by about 10% or so. if you've got an inefficient riding/pedaling style you could be burning an extra 5-10% calories rocking the sholders, pulling on the handle bars, not pushing properly on the pedals etc(that figure might be high im not sure on that one). Altitude and temperature will only effect things by a couple of percent too. if you want the exact figures for every variable then google it. i did kind of imply that i didnt know the exact figures the 30% is just a guess and that at the most extreme, using power is probably reasonably accurate for the average joe, but its still going to be only accurate to 5 or 10% which i think is alot. The thing about using power is that its more consistent than the heart rate calculations.

The only really accurate way to test the amount of calories being burned is in the lab monitoring the amount of oxygen being consumed.

Khannie

So it turns out my cycle in is worth about 800 odd calories. I'm delighted. I got offered a loan of a power meter and a garmin by a kind boardsie (thank you sir) which I jumped at. Averaged 205W for just over 70 minutes. Taking average efficiency of 25% that works out at 860 odd calories, give or take. Joules to calories roughly cancels out the human inefficiency element so the simplified calories formula becomes:

(Average power in Watts x Seconds) / 1000

Good to know anyway.