Calories Burned

[MKat]

Online calculators can only provide estimates - if you really want to know how many calories you might have burned, get a heart rate monitor. That will at least measure your level of exertion (which varies greatly according to fitness level). Tesco do a decent but cheap (£25) Kelly Holmes branded HRM with chest strap which does pretty much all you'd need it to do. Even that will only provide estimates, but still better than online calculators (which are very much based on the 'average' person).

If you are trying to lose weight through exercise, it's not an exact science because we're meatbags full of hormones rather than efficient machines. 3,500 calories burned off on the bike won't mean 1lb of fat melts off your tum overnight (sadly).

 

[Mr Haematocrit]

Explain.

My lightest bike is 5.85kg while my Dahon Folder weighs in at 12.5 kg.. I can ride both these bikes at 15 MPH.
The effort required to ride the Dahon at that speed is vastly higher that that to ride my other bikes at the same speed.
Equally when climbing a hill on any bike, my speed drops and the effort required increases.
As such redcard is correct that speed has very little to do with effort.

 

[Mr Haematocrit]

You can not accurately determine the amount of calories burnt from Heart Rate monitors, Online calculators, or most other means.
The only way to accurately measure calorie burn is through VO2 Testing.. to turn the fuel you receive from food into energy you require oxygen, Because of the direct relationship between how much oxygen you use and how much energy you burn, by measuring the carbon dioxide exchange through VO2 testing you will get a pretty accurate measurement of how many calories your burning.

Anything else is just a guess.

 

[amaferanga]

Online calculators can only provide estimates - if you really want to know how many calories you might have burned, get a heart rate monitor. That will at least measure your level of exertion (which varies greatly according to fitness level). Tesco do a decent but cheap (£25) Kelly Holmes branded HRM with chest strap which does pretty much all you'd need it to do. Even that will only provide estimates, but still better than online calculators (which are very much based on the 'average' person).

I don't know why a HR monitor that uses an unknown algorithm to guesstimate calories burned would be any better than a website using a similar guesstimate. An HR monitor doesn't tell you how hard you're working, only how fast your heart is beating.

 

[ColinJ]

I don't know why a HR monitor that uses an unknown algorithm to guesstimate calories burned would be any better than a website using a similar guesstimate. An HR monitor doesn't tell you how hard you're working, only how fast your heart is beating.

I agree. can categorically state that heart rate does not give a reliable indication of calories burned! My heart has been doing crazy things for 7 months, off and on, due to illness and I have had very little exercise in that time. I can be sat down reading a magazine with my heart doing 60 bpm and then, suddenly, for no apparent reason it starts to do 150 bpm.

A similar thing used to happen when I had a stressful job. I could get my heart going at 150 bpm just by thinking about work!

 

[MKat]

How fast your heart beats during exercise is a reasonable indicator of how hard you're working (unless you find exercise terrifying and there's some strange adrenaline rush going on). HRM aren't much good for estimating calories burned at rest or through static strength exercise. There are no doubt far more complex variables to consider, such as resting HR and how quickly you return the resting rate after exercising, as well as your body mass composition and efficiency rate. Unfortunately most of us can't always measure such things, but you can still make estimates based on the information you do have, such as weight, age, height, gender etc.

I did say using a HRM would still be an estimate, but probably a better one that online calculators alone. An online calculator would tell you that freewheeling down a hypothetical 20-mile hill for an hour would burn off 1,000 calories but a HRM would tell a slightly more accurate story. I've been using myfitnesspal for the last month or so and the calorie estimates for many of the exercises in their database are way above what my HRM tells me I've 'burned' off. I eat the exercise calories that my HRM tells me I've burned off and am losing weight at a rate of 1lb a week (which is what I'm aiming for), so my possibly-widly-innaccurate HRM is good enough for me!

 

[amaferanga]

How fast your heart beats during exercise is a reasonable indicator of how hard you're working (unless you find exercise terrifying and there's some strange adrenaline rush going on).

Well all I can say is that no HR-based calorie estimate gets close to the calorie estimation I get from my power meter. Interestingly, I actually get a more believable estimate of calories from my Garmin when I don't use the HR strap. But that's just me. There's so much variability in heart rate for a given power output that it's no wonder that any of these guesstimates is likely to be way off for a given individual.

People have been brainwashed by heart rate monitor manufacturers into thinking they give an accurate calorie estimate. They would say that though wouldn't they. I've not looked very hard, but I've never seen a peer reviewed publication that demonstrates an HR-based calorie formula giving a good estimate across the population.

 

[Rob3rt]

How fast your heart beats during exercise is a reasonable indicator of how hard you're working (unless you find exercise terrifying and there's some strange adrenaline rush going on). HRM aren't much good for estimating calories burned at rest or through static strength exercise. There are no doubt far more complex variables to consider, such as resting HR and how quickly you return the resting rate after exercising, as well as your body mass composition and efficiency rate. Unfortunately most of us can't always measure such things, but you can still make estimates based on the information you do have, such as weight, age, height, gender etc.

I did say using a HRM would still be an estimate, but probably a better one that online calculators alone. An online calculator would tell you that freewheeling down a hypothetical 20-mile hill for an hour would burn off 1,000 calories but a HRM would tell a slightly more accurate story. I've been using myfitnesspal for the last month or so and the calorie estimates for many of the exercises in their database are way above what my HRM tells me I've 'burned' off. I eat the exercise calories that my HRM tells me I've burned off and am losing weight at a rate of 1lb a week (which is what I'm aiming for), so my possibly-widly-innaccurate HRM is good enough for me!

Depends how you define "reasonable". Not trying to be pedantic, nor try to sell everyone a power meter, but having been training using power for a short while, it really is astonishing how large the variation in HR can be for a given work load day to day, or as a session progresses.

This whole debate comes up over and over again on this forum and it never gets anywhere, it would be best to just use the search function and read past debates rather than progress another one, unless you have anything particularly new to add.

 

[Sittingduck]

The trouble with power meters is that they are so flipping pricey!

Just take a reserved guesstimate or use an online calculator and reduce it be a certain percentage. Over time you can perhaps work out what that percentage is more likely to be, when you calculate the combined calorie deficit you have guesstimated and factor it against actual loss of weight (over a few weeks or months).

 

[chqshaitan]

the way I treat the heart rate monitors and calorie burn is that it gives you an idea (ie baseline) of how well you are doing over time.

Say for example you started to commute from home to work, which was 10 miles each way(figures for example only) and the first time you measured, you burned 500 calories, then you compared this against what you burned in 3 months time. and due to weight loss and getting fitter, you may only use 350.

This would then give you a good idea of how much fitter you were (relatively speaking). That's how I use it. Also good if you do other exercise as a comparison.

 

[Rob3rt]

The trouble with power meters is that they are so flipping pricey!

Just take a reserved guesstimate or use an online calculator and reduce it be a certain percentage. Over time you can perhaps work out what that percentage is more likely to be, when you calculate the combined calorie deficit you have guesstimated and factor it against actual loss of weight (over a few weeks or months).

They are, but my point wasn't to plug PM's, it was to highlight how variable HR is for a given effort, thus how flakey the measurements can be and why people shouldn't assume it right. As stated, you have to take it with a pinch of salt, it is an estimate (and not a particularly good one).

 

[Mr Haematocrit]

How does a power meter or a heart rate monitor detect how much oxygen you have used?

The direct relationship between how much oxygen you use and how much energy you use means that you need to measure this to determine calorie burn. Nothing else is accurate.

 

[Rob3rt]

How does a power meter or a heart rate monitor detect how much oxygen you have used?

The direct relationship between how much oxygen you use and how much energy you use means that you need to measure this to determine calorie burn. Nothing else is accurate.

It is called inference and it depends on the required accuracy, some circumstances will deem +/- 25% to be accurate, others +/- 2.5% to be inaccurate. There is no universal figure. As I explained previously, the way a PM estimates calorific burn is prone to error. The point re. power meters and HRM's is that the PM can tell you the watts delivered to the crank (with a known accuracy, provided it has been zero'd, calibrated correctly and that indeed you believe the spec sheet), or hub, the HR monitor can tell you how your heart responds to that stimulus at a given time. The main point being made by myself is that the way your HR responds to the stimulus varies considerably (enough to transition between zones) day to day, even hour to hour. So same stimulus from the cycling will result in a different response from the heart, due to other stimuli, such as temperature, illness etc. It is almost a 2nd order inference, depending how you look at it.

Some things can not be realistically or practically be measured in the field, so you take the next best thing, you give up accuracy for portability, affordability etc. I believe people refer to this as, compromise.

People get too fixated on absolute values IMO.

 

[Ningishzidda]

It is called inference and it depends on the required accuracy, some circumstances will deem +/- 25% to be accurate, others +/- 2.5% to be inaccurate. There is no universal figure.

Some things can not be realistically or practically be measured in the field, so you take the next best thing, you give up accuracy for portability, affordability etc. I believe people refer to this as, compromise.

People get too fixated on absolute values IMO.

+1
The most cost effective compromise is to go with 30 kCals per mile and hope to lose a bit of fat in the process.

 

[ColinJ]

I have a calories burned function on my gym bike. It bases its calculation on how fast I am pedalling. To me, that is like measuring heart rate. The thing is, there is no connection between the friction brake on the bike and the meter so it gives the same figure for free spinning as it does for pedalling at the same cadence against massive friction. Similarly, a heart rate monitor does not know why your heart rate is high, just that it is.

If you are working very hard, your heart rate will be high, but it does not follow that if your heart rate is high then you are working hard. My pulse rate is probably 120 bpm at the moment but all I am doing is sitting down typing on my laptop.