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Calories Burned-how determined?
Old 10-28-2013, 08:49 AM   #1
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Calories Burned-how determined?

For my birthday my DW bought me one of those heart rate monitor watches (Polar). This gives me all kinds of data relating to my daily workouts. The key for me is calories burned. This is determined by an algorithm based on average heart rate during the workout. So this results in a wide range of results depending on how I do in any given workout. For a 45 minute workout the calories can range from 600-800 generally higher on the elliptical vs the spinning bike. This confuses me as I thought the definition of a "calorie" was related to energy expended (eg the energy required to raise the temp of water one degree, or something). This watch seems to think a calorie is defined as how high my heart rate goes. I had to input an estimated fitness level (max VO2 level) so I am thinking the whole exercise is an approximation based on various fitness levels? A very fit person would burn fewer calories than someone doing the same workout who is not fit?

Has anyone else wondered about this? If so have you figured it out?
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Old 10-28-2013, 11:44 AM   #2
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It's been a long time since my heart rate watch fell apart, so I'm sure they've got more bells & whistles now (I don't remember inputting my fitness level).

The watch, in addition to tracking your pulse rate, communicates with the machine you are using. I believe the machines, themselves, use a pre-determined schedule of "X effort level = Y calories burned." So, if you are using more resistance on the elliptical, and maintaining a higher # of revolutions, that equates to more calories burned. Less resistance = burn fewer calories.

The machines also ask you to key in your sex and weight (the default weight usually seems to be 150 lbs on any machine I've ever used), and use that data to calculate how many calories a man who weighs 170 lbs (let's say) would be expected to burn, using this machine, at this effort level.

As for very fit people using fewer calories, well, I'm of the understanding that the more lean tissue you have, the more calories you use, just staying alive.

What I do not know, is whether "perceived effort" plays into the equation. Let's say you and I are the same sex, weigh the same, and you are more fit than I am. To you, exercise will seem easier than it does to me. I don't know if that means I am burning more calories, at the same REAL effort level, as you are.

Interesting questions.

Amethyst
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Old 10-28-2013, 02:08 PM   #3
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Originally Posted by Danmar View Post
For my birthday my DW bought me one of those heart rate monitor watches (Polar). This gives me all kinds of data relating to my daily workouts. The key for me is calories burned. This is determined by an algorithm based on average heart rate during the workout. So this results in a wide range of results depending on how I do in any given workout. For a 45 minute workout the calories can range from 600-800 generally higher on the elliptical vs the spinning bike. This confuses me as I thought the definition of a "calorie" was related to energy expended (eg the energy required to raise the temp of water one degree, or something). This watch seems to think a calorie is defined as how high my heart rate goes. I had to input an estimated fitness level (max VO2 level) so I am thinking the whole exercise is an approximation based on various fitness levels? A very fit person would burn fewer calories than someone doing the same workout who is not fit?

Has anyone else wondered about this? If so have you figured it out?
At best this would give a very approximate idea. Still, if you like you can use it to help you compare your exertion in one workout to workouts on other days, if the workout itself is similar.

I mainly use a Concept2 rower for indoor work, and I doubt it is very accurate as to the calories that I, haha, might use to go a certain distance, but IMO it is quite accurate in comparing my Monday workout to my Tuesday workout, in terms of the work I have expended actually on the machine. Rowing coaches use my machine, called the Erg, to compare one rowers work done in terms of spinning the fan to other rowers, and use these figures in combination with the individual rower's weights to rank power weight ratios for early boat makeups. The key is still seeking how the boat goes when differed individuals are inserted.

I have noticed that its calorie readout seems to be a simple extrapolation for the distance I traveled, with little or no attention paid to how fast or slowly I went, or how tight I set the baffle.

I believe that your device is mainly useful to help you stay out of trouble MI wise, while you work toward your goal of weight loss. BTW, this investigator below has a whole set of studies addressing fitness and weight loss, where he uses a target heart rate on a monitor to classify a workout as vigorous or moderate. So far at least, he has found that for more endpoints a longer workout at a slower pace is better for the metabolic health and weight goals that most of us are seeking. This is quite separate and perhaps somewhat opposed to the goals of a competitive athlete. Most of these studies are free to read and download on the web.

http://cardiology.medicine.duke.edu/...etails/0078469

Ha
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Old 10-28-2013, 02:46 PM   #4
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I also use a Polar heart rate monitor and my understanding is that along with heart rate and time it also uses your age, gender, and weight to calculate calories burned. All that information is entered during the initial setup.
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Old 10-28-2013, 03:04 PM   #5
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From the Livestrong website:

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ACCURACY OF OUTPUT
The American College of Sports Medicine and the "British Journal of Medicine" have put Polar's heart rate monitors to the test over the years. In these studies, the measurement of calories expended has a non-significant margin of error, meaning the difference between the control and the Polar monitor is not enough to skew your results. These studies revealed that entering your actual VO2 max and maximum heart rather than having it calculated by the formula, yields only a 12 percent overestimate of calorie expenditure versus a 33 percent overestimate. On average, Polar's heart rate monitors are 75 percent accurate.
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Old 10-28-2013, 03:59 PM   #6
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Thanks for the responses. Yes, I did enter my age, weight, gender. I also understand that the Polar monitor is apparently fairly accurate. I just don't really understand the definition of a cal. Does it depend on how hard it feels or how hard it actually is, to do a certain amount of work? Or as I suspect, given some background data, one is a good proxy for the other.
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Old 10-28-2013, 04:16 PM   #7
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I love my Polar heartrate monitor, although I really don't know how it determines calories used.

In my case, it vastly overestimates calories used. If I eat what it says I earned, in addition to my usual food intake for losing weight, I gain weight instead. (But then, I could probably gain weight just by looking at chocolate! )

Not a big deal, for me. Once I determined that I could still lose by ignoring the calories earned and sticking with a level of food intake consistent with weight loss, it just hasn't been a concern.
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Old 10-28-2013, 04:24 PM   #8
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By an amazing coincidence, the Globe and Mail has an article from Reuters on these things today.

Pricey wearable fitness gadgets are the new lapsed gym memberships - The Globe and Mail

How data driven are you, Danmar?
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Old 10-28-2013, 04:31 PM   #9
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Does it depend on how hard it feels or how hard it actually is, to do a certain amount of work?
A calorie is a measure of work. It really has nothing to do with how hard it feels, which is essentially the same as "how hard it is". Unless applied to the surface of a material, "hard" is not a physical term.

Imagine a 110# woman flying along on a treadmill, hardly breaking a sweat. Imagine another woman the same weight and age, who has been ill for some time and is trying to get back. Just getting out of a chair may feel very hard for her, but the gal tearing along on the treadmill hardly notices here effort. Who burns the most calories?

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Old 10-28-2013, 06:27 PM   #10
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Calories are really the least accurate measurement any of these watches can give you so try to find something else to measure. They are only guessing calories.

I have a Garmin for running and look at heart rate, distance, speed etc. Real measurements. I base my workouts on heart rate levels so that the 'effort' is the same each time. As I (hopefully) get fitter my speed will increase at the same heart rate (effort).

I personally like to calculate heart beats per mile when I get home. Something the watch does not do. When I am in top shape I can get under 1100 beats/mile on a long run.

Phil (training for Sacramento Marathon - Dec 8th)
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Old 10-28-2013, 06:44 PM   #11
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(But then, I could probably gain weight just by looking at chocolate! )
I still remember at age 21 when I was bemoaning how hard it was to gain weight. The police department at the time had a minimum weight of 145 and I weighed 140 despite five meals a day, milkshakes, pumping iron, etc.

My sister said "I hate you! You skip a meal and lose five pounds and if I even look at a piece of chocolate cake I gain five".

Of course now it is considerably easier to gain weight.
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Old 10-28-2013, 07:36 PM   #12
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Speaking of exercise and calorie burning......

Sex can be good, but not great, exercise: study - NY Daily News

Hmmm.......I wonder why the study from Quebec came up with a higher number than the study from Alabama?
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Old 10-28-2013, 08:08 PM   #13
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...This confuses me as I thought the definition of a "calorie" was related to energy expended (eg the energy required to raise the temp of water one degree, or something)...
Yes.

A calorie is the energy needed to raise 1 gram of water up 1 degree Celsius.

However, when it comes to dietary energy, we use the "large calorie" which is 1000 calories as defined above.

For a feel for the energy that we consume, or produce from food, the typical 2000-cal/day intake would bring to a boil from room temperature 26.7 liters or 7 US gal of water. This energy spread out over 24 hrs is about the same as a 100W bulb.

I am surprised that the expended calorie count could be estimated that well by the heart rate, meaning within 25% as noted by an earlier post.
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Old 10-28-2013, 08:17 PM   #14
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A calorie is a measure of work. It really has nothing to do with how hard it feels, which is essentially the same as "how hard it is". Unless applied to the surface of a material, "hard" is not a physical term.
This is pretty much correct.

A calorie is a unit of energy. Work = Force x distance which is in units of newtons-meters which can be directly converted to joules or calories.

Ideally the cardio machine should be able to give a very accurate measure of work since you are moving your weight over a distance or at least moving the foot pad through a rotational motion. The easiest way would be a measure of electrical energy generated in the machine. However, I doubt the machines are this sophisticated.

Your heart rate monitor is a very approximate measure of energy expended since it is an indirect measure of oxygen consumption.

Using it as a relative measure of one workout vs another workout is your best bet.
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Old 10-28-2013, 08:18 PM   #15
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Nope.....don't trust the calorie burns on the devices. Just too many variables. Size, sex, muscle mass, speed of effort, in/out of shape etc etc. I have a relative who posts her Garmin info on Facebook. The watch claims she loses about 800 calories running about 3.5 miles......ain't happening. An old rule that we used to use years ago......and I still think it's about as good as anything if you are on foot. You lose 100 calories a mile whether you are running or walking. Then with my adjustments.....if you are a good runner, in shape, you are likely losing less than 100 a mile. If you are heavier, out of shape....might be a little over 100. Now....if you are on a bike.....or rowing machine....that method is worth zilch.
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Old 10-28-2013, 08:51 PM   #16
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Human mechanical output can be measured very accurately with machines, not too differently than one using a dynamometer to measure the horsepower output of a car engine.

However, "flesh" motors are notoriously inefficient, and if we were to measure ourselves by the actual work that is produced, we would miss all the energy that was expended just to heat ourselves up and to make us sweat.

If you do not believe me, then consider that with 2,000 large calories, or 2 million calories, or 8.4 million Joules, a machine that is 100% efficient would be able to lift a 200-lb mass up 9.4 km or 5.8 miles!
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Old 10-28-2013, 09:15 PM   #17
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I don't pay any attention to calories burned when I use my Polar heart rate monitor, but I find the monitor extremely useful in warning me if my HR gets too high for too long. I also make sure that my HR comes down quickly after exertion. (recovery HR)

Researchers Find Heart Rate Worth a Thousand Words


Recently I was taking a course of herbal anti-inflammatory pills but after a week or so I was exercising and noticed that my HR shot up within the first minutes and didn't come down much when I eased off. I finished the hour long exercise session at a MUCH lower level of exertion because my HR was so high. I stopped the pills that day and haven't a problem since.
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Old 10-29-2013, 08:37 AM   #18
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By an amazing coincidence, the Globe and Mail has an article from Reuters on these things today.

Pricey wearable fitness gadgets are the new lapsed gym memberships - The Globe and Mail

How data driven are you, Danmar?
Thanks for the link. I have worn my polar since I got it 3 months ago anand don't think I will stop using it any time soon. I am quite data driven. I can tell you which days I worked out, what workout I did, cals burned, weight before and after, for the last 20 years. The polar monitor has helped me increase my workout intensity on spinning bikes because I can work harder to get my HR up as I know what it is. It also allows me to compare cals burned across various forms of exercise that I do (elliptical, spinning bikes, actual bikes, stationary bikes). I think this helps me do consistent workouts across the various equipment.
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Old 10-29-2013, 08:43 AM   #19
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A calorie is a measure of work. It really has nothing to do with how hard it feels, which is essentially the same as "how hard it is". Unless applied to the surface of a material, "hard" is not a physical term.

Imagine a 110# woman flying along on a treadmill, hardly breaking a sweat. Imagine another woman the same weight and age, who has been ill for some time and is trying to get back. Just getting out of a chair may feel very hard for her, but the gal tearing along on the treadmill hardly notices here effort. Who burns the most calories?

Ha
Sorry for the loose use of the word "hard". I should have used difficult. Yes, I agree with your analysis. My experience is that after a week or two of difficult workouts, it gets more difficult to get my heart rate elevated. This results in fewer cals indicated as burned. Obviously, I am doing the same work and am burning the same cals but if feels easier and shows less cals. Another example: if it is particularly warm or humid during my workout, my heart rate will go higher, thus indicating more cals. Doubtful.
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Old 10-29-2013, 08:52 AM   #20
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Nope.....don't trust the calorie burns on the devices. Just too many variables. Size, sex, muscle mass, speed of effort, in/out of shape etc etc. I have a relative who posts her Garmin info on Facebook. The watch claims she loses about 800 calories running about 3.5 miles......ain't happening. An old rule that we used to use years ago......and I still think it's about as good as anything if you are on foot. You lose 100 calories a mile whether you are running or walking. Then with my adjustments.....if you are a good runner, in shape, you are likely losing less than 100 a mile. If you are heavier, out of shape....might be a little over 100. Now....if you are on a bike.....or rowing machine....that method is worth zilch.
I think the devices have improved quite a bit. Research seems to indicate the Polar monitors are fairly accurate. It seems very consistent with ellipticals and stationary bikes which show HR. Also, the device knows my weight, gender, age, and fitness level(maxVO2) which I believe makes the cal determination fairly accurate.
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