The relationship between heart rate and calories burned?

Azdak

Calories burned are measured indirectly as a function of oxygen consumption. Heart rate is an indicator of oxygen consumption in that when you need more oxygen to your muscles and other cells, your heartrate goes up to deliver that oxygen where it needs to be. If the caloric need is high (ie you're burning lots of calories to perform the required task) then oxygen demand is high. If oxygen demand is high, then heartrate goes up. Since you can't measure your oxygen consumption or caloric need directly, you can measure your heart rate and get a decently accurate idea of what's going on. And there's no two ways about it, the most accurate way to actually accomplish this is with a heart rate monitor. Cardio machines that give you calories burned only use an algorithm based on broad range average estimates in the general population. Odds are excellent they are wildly inaccurate.

Well, it was a good start. Actually, it is the HRMs who use the algorithms based on a broad range of estimates in the general population. And, yes, the odds are excellent that HRMs will be inaccurate.

During steady-state aerobic exercise -- and ONLY steady-state aerobic exercise -- there is a relationship between heart rate and oxygen uptake, so changes in heart rate can be used to estimate oxygen uptake, and, thus, calories burned.

However.....a number of conditions must be present for that estimate to be in the ballpark.

1. The activity must be a steady-state aerobic activity with a minimum intensity of 40% of VO2 max.

2. The HRM must be programmed with the user's ACTUAL max HR.

3. The HRM must be programmed with the user's ACTUAL VO2 max.

4. The HRM must be programmed with the other data that HRMs ask for.

5. Heart rate must not be affected by thermal stress, anxiety, medication, cardiovascular drift, illness or any other external factor.

6. The HRM must be a quality instrument with well-researched and validated algorithms.

If all those conditions are met, and HRM might be 85% accurate.

Since few people (except me) has all of those factors correctly entered into their HRMs, the calorie accuracy is considerably lower.

Machines measure ACTUAL workload--they don't have to estimate the workload. They then use energy predicting equations, based on aerobic workload, to estimate calories.

For activities such as walking, where the existing energy prediction equations are simple and accurate, the machine calorie counts are as accurate as you can get (assuming no handrail support). For other machines, such as cross trainers, the equations are often extrapolated from other activities (such as walking or running), and so the calorie counts are much less accurate and almost always overestimate.

A blanket statement such as "the most accurate way to accomplish this( i.e. calorie estimate) is with a heart rate monitor" is not supported by facts.

Azdak

If oxygen demand is high, then heartrate goes up. Since you can't measure your oxygen consumption or caloric need directly, you can measure your heart rate and get a decently accurate idea of what's going on. And there's no two ways about it, the most accurate way to actually accomplish this is with a heart rate monitor.

Unless the HRM contains the data to measure an individuals current fitness level then the calorie counts are basically wild guesses.

Two individuals of equal weight may be exercising, one with a heartrate of 130 and the other with a heartrate of 160. Is one working harder or is he just out of shape? If they are both doing the same exercise at the same workload the calorie burn ought to be the same, no matter what their heartrate is.

A person who is aerobically fit will have a heart with a much larger stroke volume than a person not fit. That means that his heart does not have to beat as fast as the other person's to supply the exact same oxygen demand.

People who think that their calorie counts go down as they get in shape and their heartrates drop are wrong. Normalizing for weight the calorie count stays the same for equal workload. If the HRM says the calorie count is down then that should be an indication that the HRM calorie count is wrong.

The truth is that as a person becomes aerobically fit they ought to be able to produce increasing calorie burns in equal time because they will be able to exercise at increasing levels of workload at the same exercise intensity without an increase in heartrate.

If the HRM is not reflecting this then the HRM is simply wrong.

And this is the key issue with being obsessed with exact calorie burns. It doesn't exist. When you factor in EPOC it is even less precise. And HRMs are usless for measuring the burn from anaerobic activites like weight training.

It's just not that critical. Eat in a reasonable deficit and work out regularly (4 to 5 times per week) with a varied program (some cardio, some strength). Give it a few weeks and adjust accordindy. You'll never know exactly your burns and your calorie intake. It is unproductive to obsess over things you can't control.

For the most part, I agree. I use machine calorie counts, not for my eating plan, but as a reliable way to track the total amount of aerobic work performed in an exercise workout. For that purpose, they are excellent, but is a workout score, not a precise energy estimate for my eating plan.

Azdak

Unless the HRM contains the data to measure an individuals current fitness level then the calorie counts are basically wild guesses.

Two individuals of equal weight may be exercising, one with a heartrate of 130 and the other with a heartrate of 160. Is one working harder or is he just out of shape? If they are both doing the same exercise at the same workload the calorie burn ought to be the same, no matter what their heartrate is.

A person who is aerobically fit will have a heart with a much larger stroke volume than a person not fit. That means that his heart does not have to beat as fast as the other person's to supply the exact same oxygen demand.

People who think that their calorie counts go down as they get in shape and their heartrates drop are wrong. Normalizing for weight the calorie count stays the same for equal workload. If the HRM says the calorie count is down then that should be an indication that the HRM calorie count is wrong.

The truth is that as a person becomes aerobically fit they ought to be able to produce increasing calorie burns in equal time because they will be able to exercise at increasing levels of workload at the same exercise intensity without an increase in heartrate.

If the HRM is not reflecting this then the HRM is simply wrong.

So would you say that a HRM that measures resting HR likely be more accurate? My HRM had me lie still for a while when I first got it, and then redo it every so often. A more fit person would have a lower resting HR and then the HRM can take that into account.

It may or it may not. The relationship between resting heart rate and fitness level is a lot more tenuous than Polar would lead you to believe.

An initial decrease for someone starting a fitness program MAY reflect an improvement in conditioning, but the lack of a substantial decrease does not mean that no conditioning has taken place.

And you cannot "rank" resting heart rate levels--e.g. 55-60 = "super" fit, 61-65 = "fit", etc. The longer one exercises, the less relevant resting HR is as an indicator of anything.

Even at my highest weight and lowest fitness level a few years ago, my resting HR was still around 55-56, only 10%-15% higher than my "fit" level.

Azdak

For the first time in my life I am exercising every day of the week. I aim for at least 30-45 minutes of something- elliptical, swimming laps, horseback riding, or walking the dogs. And it's going great!

But I am seriously confused about the relationship between heart rate and calories burned... and how to get the most accurate calories burned count for my work out.

It seems to me that every work out there are lots of variables. For example, today on the elliptical I could give you all of this information:

45 minutes, HR avg 140, 3.55 miles, resistance level 5, incline 5.
The machine says I burned 390 calories, mapmyfitness (where I log my workouts) says 408, and this calculator* says 359 calories. (This example just has a calorie difference of 50 calories, but when it's swimming or zumba or yoga it gets loads more confusing.)

Now yesterday, I did the same thing, but a little bit harder- steeper incline, more resistance. My heart rate average only went up one or two beats per minute. So basically, I got the same calorie count.

So what's the deal? Do calories burned have everything to do with heart rate and duration and nothing to do with how far you went or the intensity of your work out?

If I do anything that gives me an average heart rate of 140 for 45 minutes will my calorie burn be the same? And what about workouts that don't raise your heart rate, but still kick your bum, like weight training?

Is there some magic formula out there that I could plug my overload of information into and get an accurate calories burned count?

PS. I sense that a lot of you are about to tell me to get a HRMonitor. I think this would be a good idea as well, but I can't afford one at the moment. I use the HR monitors at the gym on the machines, and am looking for ways to get the most accurate calories burned count without having a HRM.


* http://www.shapesense.com/fitness-exercise/calculators/heart-rate-based-calorie-burn-calculator.aspx

What you describe is one of the biggest shortcomings of HRMs.

With exercise training, one achieves an increase in their VO2max, or maximum aerobic fitness level. That means that one can perform a higher workload at any given submaximal heart rate.

However, a heart rate calculator doesn't know your fitness level has increased unless you tell it. And since it is not that easy to actually measure VO2 max, that number is often not changed.

Exercise workloads have essentially fixed energy costs. In other words, running at 6.0 mph requires about 10 METs (MET is a measure of aerobic intensity). It doesn't make any difference who is doing the activity--the cost is still 10 METs.

If someone is running at 10 METs and has a heart rate of 150, after a period of training it is likely that the person will now be able to run 6.5 mph at a heart rate of 150. Running at 6.5 mph has a higher energy cost than running at 6.0 mph and thus will have a higher calorie burn (assuming no change in weight).

However, an unchanged HRM or heart rate calculator just knows that the heart rate was the same -- 150-- and so it spits back the same number. It's sill using the old "scale".

If you have an HRM that allows manual entry of VO2max (Polar FT40 or FT60, for example), you can go in and change that number if it goes up. If you change your VO2 max, the HRM now has a new "scale" and now it will give you a different (and higher) calorie number when you are working at a heart rate of 150.

mmapags

If oxygen demand is high, then heartrate goes up. Since you can't measure your oxygen consumption or caloric need directly, you can measure your heart rate and get a decently accurate idea of what's going on. And there's no two ways about it, the most accurate way to actually accomplish this is with a heart rate monitor.

Unless the HRM contains the data to measure an individuals current fitness level then the calorie counts are basically wild guesses.

Two individuals of equal weight may be exercising, one with a heartrate of 130 and the other with a heartrate of 160. Is one working harder or is he just out of shape? If they are both doing the same exercise at the same workload the calorie burn ought to be the same, no matter what their heartrate is.

A person who is aerobically fit will have a heart with a much larger stroke volume than a person not fit. That means that his heart does not have to beat as fast as the other person's to supply the exact same oxygen demand.

People who think that their calorie counts go down as they get in shape and their heartrates drop are wrong. Normalizing for weight the calorie count stays the same for equal workload. If the HRM says the calorie count is down then that should be an indication that the HRM calorie count is wrong.

The truth is that as a person becomes aerobically fit they ought to be able to produce increasing calorie burns in equal time because they will be able to exercise at increasing levels of workload at the same exercise intensity without an increase in heartrate.

If the HRM is not reflecting this then the HRM is simply wrong.

And this is the key issue with being obsessed with exact calorie burns. It doesn't exist. When you factor in EPOC it is even less precise. And HRMs are usless for measuring the burn from anaerobic activites like weight training.

It's just not that critical. Eat in a reasonable deficit and work out regularly (4 to 5 times per week) with a varied program (some cardio, some strength). Give it a few weeks and adjust accordindy. You'll never know exactly your burns and your calorie intake. It is unproductive to obsess over things you can't control.

For the most part, I agree. I use machine calorie counts, not for my eating plan, but as a reliable way to track the total amount of aerobic work performed in an exercise workout. For that purpose, they are excellent, but is a workout score, not a precise energy estimate for my eating plan.

Yes. And I think that is one of the drawback of the otherwise well designed site here. It creates a mentality of earning more food to eat in some.

zlauerMom

If oxygen demand is high, then heartrate goes up. Since you can't measure your oxygen consumption or caloric need directly, you can measure your heart rate and get a decently accurate idea of what's going on. And there's no two ways about it, the most accurate way to actually accomplish this is with a heart rate monitor.

Unless the HRM contains the data to measure an individuals current fitness level then the calorie counts are basically wild guesses.

Two individuals of equal weight may be exercising, one with a heartrate of 130 and the other with a heartrate of 160. Is one working harder or is he just out of shape? If they are both doing the same exercise at the same workload the calorie burn ought to be the same, no matter what their heartrate is.

A person who is aerobically fit will have a heart with a much larger stroke volume than a person not fit. That means that his heart does not have to beat as fast as the other person's to supply the exact same oxygen demand.

People who think that their calorie counts go down as they get in shape and their heartrates drop are wrong. Normalizing for weight the calorie count stays the same for equal workload. If the HRM says the calorie count is down then that should be an indication that the HRM calorie count is wrong.

The truth is that as a person becomes aerobically fit they ought to be able to produce increasing calorie burns in equal time because they will be able to exercise at increasing levels of workload at the same exercise intensity without an increase in heartrate.

If the HRM is not reflecting this then the HRM is simply wrong.

I've used a heartrate monitor for years and I don't understand why so many people think it is so much more accurate than any machine's calculation of calories burned. Many of the very best HRM won't even give you a calories burned unless you've input what activity you are doing, your resting HR, your max HR (and please don't use the formula for this), and you use the GPS feature. So they won't guess at treadmill and weightlifting calorie counts.

When I was in marathon training, I would go for a 5 mile run and record my HR. Three days later doing the exact same run but on a much hotter day, my HR would be much higher. Did I burn more calories? No, the increased temp made my HR higher to begin with.

I love using my HR monitor for workouts to keep track of my cardio-vascular improvement or maintenance overtime, or to make sure I don't workout too hard on hot days. The HRM for calories burned, I'd put those numbers on par with gym equipment where you input sex, height, weight, age.

NutellaAddict

Polar FT4 with the chest strap as others have mentioned!!!!

Timshel_

Does anyone want to recommend a HR Monitor that is good for machine cardio and reasonably priced?

I bought a $30 Garmin unit last year and it has been durable and functional. It is ANT+ and depending on what equipment is out there or what you pair it with, BLE ( Bluetooth) are more efficient energy wise in some instances.

Cyclink

Heart rate is an indicator of oxygen consumption in that when you need more oxygen to your muscles and other cells, your heartrate goes up to deliver that oxygen where it needs to be.

Yes and no.

In a strictly exercise context, that is true. However, it ignores that your heart rate only measures how many times per minute your heart beats, which has only a slight correlation with oxygen consumption. You could more generically say that your heart rate rises in response to stress on your body, whether from exercise, fear, anxiety, dehydration, or a number of other sources.

Providing you calorie numbers on heart rate devices make for a brilliant marketing gimmick with little real validated information.

Timshel_

When I was in marathon training, I would go for a 5 mile run and record my HR. Three days later doing the exact same run but on a much hotter day, my HR would be much higher. Did I burn more calories? No, the increased temp made my HR higher to begin with.

I don't believe that is accurate. Because the body is working harder to oxygenate muscle and circulate blood, you would be burning more calories - albeit not a huge difference in what I see. Maybe 100-150 calories over an hour for me. That is based on my studies years ago in college so I am not sure there isn't conflicting opinions.

Overla a HR measure the exertion of your body to perform work, expressed by the heart pumping to supply oxygenated blood to muscle as well as help cool you down. The higher your HR, the more exertion, the more calories burned.

tnhiker865

One key factor to include when relating HR to calorie burn is an individual's personal VO2Max. Simply stated, VO2Max is the ability of one's body to utilize oxygen for producing energy that can be used by the muscles. VO2Max is typically expressed in terms that factor-in body weight. People who are not very fit typically have lower VO2Max scores. Even when lesser fit persons' heart rates are elevated, they may not be burning as many calories as a more fit person with the same heart rate and body weight. Knowing your VO2Max score is important if you want to use heart rate as a method of estimating calorie burn. And note, your VO2Max scores will most likely increase as you become more fit. Here's a good website where you can read more about VO2Max and along with several other related factors regarding heart rate and calorie burn: http://www.shapesense.com/fitness-exercise/calculators/vo2max-calculator.aspx#restingheartrate. Note that this website also provides a few different self-tests you can conduct to estimate your personal VO2Max score.