Someone please explain a heart rate/calories question

jennhls

Hi, I don't know if this topic has come up before but it is something I have wondered for quite awhile and can't seem to wrap my head around so I am hoping someone can help me understand it.

How is it that these two people can burn such a different amount of calories based on their heart rate:

Person #1 ( an out of shape female runs 3 miles at the same pace as person 2 but because she is out of shape her heart rate is much higher):
female
age:40
weight:130
activity duration: 30 min
heart rate: 160
Calories burned: 335

Person #2 ( a female marathon runner runs 3 miles at the same pace as person 1 but because she is in shape her heart rate is much lower):
age:40
weight: 130
activity duration: 30 min
heart rate: 130
calories burned: 239

Nearly a 100 calorie difference. I see why one would be a bit higher. But a 100 calorie spread seems like a lot. They are covering the same distance and working the same muscles for the same amount of time. Why does heart rate make such a huge difference?

Wouldn't the calorie difference carry over as well for how many calories a person burned during the day when resting. Since a marathon runners resting heart rate can be quite low. They would also burn less calories all day long than a person with the same weight and age profile as an unfit person. This just goes against my reasoning and I can't make sense of it. I'm hoping someone will be able to explain this for me.

GetSoda

You've discovered why HRMs suck.

In short, heart rate has very little to do with calorie burn, and yet, it's how calorie burn is measured on a HRM.

So... it's because their heart rate is higher.
IF they did ABSOLUTELY NOTHING, and was simply laying down in bed, but had 160 bpm their calorie burn would read the same.

They probably aren't burning more calories than you.

RagtimeLady

The difference is conditioning. The out of shape person hits high heart rates more easily because they lack a number of elements which help the body deliver oxygen to the muscles efficiently, and the muscle cells lack the ability to metabolize oxygen, fat and carbs efficiently enough to keep up with the demands of the exercise. Just like a car engine that is not efficient will burn more gasoline, the out-of-shape person will burn more fuel for the same exertion as a fit person. They will also run out of steam a lot quicker and will not have the exercise tolerance.

On the other hand, the person who is the trained marathon runner has conditioned their body to deliver oxygen very efficiently - they have more red blood cells, more mitochondria in muscles, and the muscles are better at storing energy. While both people do the same amount of work, one "engine" is very efficient and burns less fuel (calories), while the other is inefficient and burns more fuel.

Make sense?

jennhls

Thanks for explaining it in that way. It makes sense but it still is frustrating knowing that I have to exercise a lot more to get the same burn as someone who isn't in shape.

Morgaath

What is the body fat of each person? On a person with a higher BF, it seems like the muscles would be working harder to move the same amount of weight.
Then there is the breathing, likely much faster rate (shallow breathes), as the body struggle to get oxygen around the system.
Basically, one person is being very efficient, while the other is burning more cals due to inefficiency.
This shows in the post workout as well, as the regular runner thinks it was a nice warm up, and the other person is sore and aching for the next 30 hrs.
Now, if you were both on a treadmill, and told it your weight, but it doesn't check your heart rate, it would give you the exact same number of cals burned, as it has no clue if one of you is more efficient or not.
Just my thoughts on it.

bwogilvie

Thanks for explaining it in that way. It makes sense but it still is frustrating knowing that I have to exercise a lot more to get the same burn as someone who isn't in shape.

That's actually not true. In most activities, two people of the same height and weight will burn approximately the same amount of calories when performing the same activity for the same amount of time. There are slight efficiency gains to be reached by proper form, but they aren't huge (swimming may be an exception, given how much resistance water offers).

Heart rate monitors use a formula derived from the average for a population. The reason that they tell you you're burning fewer calories as you get more fit is that *on average*, people whose hearts beat faster are burning more calories. That doesn't mean that's the case for any individual.

Riding a bike, for instance, is 20-25% efficient; in other words, 20-25% of the energy you put out goes into moving the bike forward. The rest is dissipated as heat. Two people of the same size, riding the same bike in the same position, who move the bike forward at the same speed for the same amount of time will have burned about the same amount of energy, with some variation depending on where they fall in the efficiency range. If one is a trained athlete with a big heart that can pump a lot of blood with each stroke, and the other is unconditioned, there might be a huge difference in their heart rate, and a typical HRM will say that the unconditioned rider is burning more calories, but that's not really true.

What differentiates an athlete from an untrained person is mostly not that they are more efficient but that they can put out more power, because they can get more oxygen to the muscles and they can recruit more muscle fibers for activity.

To take my own case as an example: a few years ago, cycling at 15 mph sent my heart rate up into the 160s. Now, I can cycle 15 mph on flat terrain with a heart rate in the 130s. I haven't become more efficient at cycling, and my fat mass really doesn't matter on flat ground; what has happened is that my cardiovascular system has gotten better at getting oxygen to the muscles, so my heart doesn't need to pump as much. My resting heart rate has also dropped from around 60 into the upper 40s; that doesn't mean that I consume less energy when lying down and not doing anything, simply that each heartbeat puts more oxygenated blood into circulation.

tl;dr: Your HRM says you're burning fewer calories, but that's not the case, other than the reduction caused by weight loss.

phjorg1

The problem is you are wrong. Calories burned will be the same. In shape or not... The heart beats faster because it can't deliver oxygen that well. Less oxygen per beat means more beats for same energy used. The in shape person needs less beats to deliver the same oxygen, and same energy used. Once you understand the cardio system and relationship between carbs and oxygen, you understand why heart rate really means nothing

The difference is conditioning. The out of shape person hits high heart rates more easily because they lack a number of elements which help the body deliver oxygen to the muscles efficiently, and the muscle cells lack the ability to metabolize oxygen, fat and carbs efficiently enough to keep up with the demands of the exercise. Just like a car engine that is not efficient will burn more gasoline, the out-of-shape person will burn more fuel for the same exertion as a fit person. They will also run out of steam a lot quicker and will not have the exercise tolerance.

On the other hand, the person who is the trained marathon runner has conditioned their body to deliver oxygen very efficiently - they have more red blood cells, more mitochondria in muscles, and the muscles are better at storing energy. While both people do the same amount of work, one "engine" is very efficient and burns less fuel (calories), while the other is inefficient and burns more fuel.

Make sense?

DopeItUp

Thanks for explaining it in that way. It makes sense but it still is frustrating knowing that I have to exercise a lot more to get the same burn as someone who isn't in shape.

Yes, however the difference is, since you are in shape you can go further, or with higher intensity (or both) and make up that calorie difference (if not exceed it). If you're both running the same speed and distance, and they are out of shape, they are working a LOT harder than you. Hence, the higher calorie burn.

I liked the engine efficiency analogy.

phjorg1

Again, that's myth. It will be the same calorie burn. You understand how vo2max works for calculating calorie burn right?? Once you do you understand why its the same calorie burn and why heart rate varied so much for equal calorie burn.

Thanks for explaining it in that way. It makes sense but it still is frustrating knowing that I have to exercise a lot more to get the same burn as someone who isn't in shape.

Yes, however the difference is, since you are in shape you can go further, or with higher intensity (or both) and make up that calorie difference (if not exceed it). If you're both running the same speed and distance, and they are out of shape, they are working a LOT harder than you. Hence, the higher calorie burn.

I liked the engine efficiency analogy.

cstigs84

OP's question demonstrates the flaw with heart rate monitors in relation to calorie expenditure. Those formulas are imperfect and not ideal to compare two people. Use it as a personal progress check but that's all it is good for. The two people would burn the same amount of kcals but the untrained individual is working closer to their threshold, hence the higher HR. The trained individual is able to do the same amount of work with fewer BPM(higher stroke volume). In your scenario, the work done is the same for both but the untrained person will *feel* as if they are working harder.

jennhls

OP's question demonstrates the flaw with heart rate monitors in relation to calorie expenditure. Those formulas are imperfect and not ideal to compare two people. Use it as a personal progress check but that's all it is good for. The two people would burn the same amount of kcals but the untrained individual is working closer to their threshold, hence the higher HR. The trained individual is able to do the same amount of work with fewer BPM(higher stroke volume). In your scenario, the work done is the same for both but the untrained person will *feel* as if they are working harder.

Seems there is some debate still on which way it works. I'm inclined to lean toward your explanation because it seems more logical to me. But mostly I ask because I don't want to over estimate on my calories burned. I do believe people who are less fit probably do burn a few more calories than I do, but not a 100 calorie difference per half hour. That to me is where the logic behind using a HRM to count calories burned seems flawed. I just don't know which way to adjust calories. If you take the example I showed above would the person who is less fit need to adjust their calorie burn down closer the the fit persons calorie burn. Or would the fit person adjust their calorie burn up closer to the person who is less fit?

What is the best way to determine calorie burn? Are MFP calories calculators accurate? Because right now I am pretty much ignoring my HRM and going with MFP calculators.

lsiberian

The differences are significant enough to really make a big difference besides a person who is fit will probably run faster and further in the same time as someone who isn't.

Heidi64

I'm so glad this got posted. Even after reading through the thread, I'm still a bit confused. Experts say to burn fat, you must reach a certain target heart rate, around 120, I believe? I'm thinking that if you have more difficulty getting your heart rate up to that range, you have a harder time losing weight. As with one of the previous posters, when I first started riding my bike, my heart rate and breathing skyrocketed at 8-10 mph. Now I ride in the 14-16 mph range and don't get much increase in my heart rate or breathing. So, I understand that my heart is beating more efficiently, but what does that mean in terms of weight loss if I can't hit that "target heart rate range"?

aliciarose511

While it is totally frustrating to have to work harder to burn more than someone who is out of shape while you are exercising, you also need to remember that since you are IN shape, you burn A LOT more at rest, because you probably have a much higher muscle mass.

mebepiglet123

It's sucks i know the fitter you are he harder you have to work, I was fit and had to work harder, than where I am now... That will change tho I'm sure

cstigs84

OP's question demonstrates the flaw with heart rate monitors in relation to calorie expenditure. Those formulas are imperfect and not ideal to compare two people. Use it as a personal progress check but that's all it is good for. The two people would burn the same amount of kcals but the untrained individual is working closer to their threshold, hence the higher HR. The trained individual is able to do the same amount of work with fewer BPM(higher stroke volume). In your scenario, the work done is the same for both but the untrained person will *feel* as if they are working harder.

Seems there is some debate still on which way it works. I'm inclined to lean toward your explanation because it seems more logical to me. But mostly I ask because I don't want to over estimate on my calories burned. I do believe people who are less fit probably do burn a few more calories than I do, but not a 100 calorie difference per half hour. That to me is where the logic behind using a HRM to count calories burned seems flawed. I just don't know which way to adjust calories. If you take the example I showed above would the person who is less fit need to adjust their calorie burn down closer the the fit persons calorie burn. Or would the fit person adjust their calorie burn up closer to the person who is less fit?

What is the best way to determine calorie burn? Are MFP calories calculators accurate? Because right now I am pretty much ignoring my HRM and going with MFP calculators.

Good thoughts and this is why HR is probably not the best variable to use in these formulas but it works fine for most people. This study(http://www.ncbi.nlm.nih.gov/pubmed/12868043) suggests using net HR(activity HR - resting HR) or HR reserve(100 x [(activity HR - resting HR)/(maximal HR - resting HR)]) rather than HR to calculate energy expenditure.

Ultimately there is no very accurate way to determine your calorie expenditure outside of a lab, but there isn't really a need for it either. As long as you have a rough estimate you are fine. That 100 kcals is not going to make a real difference in the big picture.

cstigs84

I'm so glad this got posted. Even after reading through the thread, I'm still a bit confused. Experts say to burn fat, you must reach a certain target heart rate, around 120, I believe? I'm thinking that if you have more difficulty getting your heart rate up to that range, you have a harder time losing weight. As with one of the previous posters, when I first started riding my bike, my heart rate and breathing skyrocketed at 8-10 mph. Now I ride in the 14-16 mph range and don't get much increase in my heart rate or breathing. So, I understand that my heart is beating more efficiently, but what does that mean in terms of weight loss if I can't hit that "target heart rate range"?

It is irrelevant in terms of weight loss. You will still be doing an equivalent amount of work but it will be easier for you as your VO2 max increases. If you want to continue to push up your VO2 max then you need to up the intensity as your body makes those improvements.

jennhls

The differences are significant enough to really make a big difference besides a person who is fit will probably run faster and further in the same time as someone who isn't.

The difference according to the calculator I used were quite significant. A hundred calories per half hour difference means a total of 400 calories over 2 hours of running which I do quite often.

3dogsrunning

The differences are significant enough to really make a big difference besides a person who is fit will probably run faster and further in the same time as someone who isn't.

A person who is more fit will probably run faster and further in the same time, however, assuming they do the same pace over the same course (same intensity), they will burn the same amount of calories.

As other's have mentioned, this is an issue with HRMs. They are less accurate for more fit individuals.

"Training status will also affect HRM data, as a less fit individual will elicit a higher HR than a more fit individual at any given VO2."
https://researchspace.auckland.ac.nz/bitstream/handle/2292/305/02whole.pdf?sequence=9

3dogsrunning

The differences are significant enough to really make a big difference besides a person who is fit will probably run faster and further in the same time as someone who isn't.

The difference according to the calculator I used were quite significant. A hundred calories per half hour difference means a total of 400 calories over 2 hours of running which I do quite often.

There are fairly reliable data tables for running. Check out some of these blogs. He covers data tables and how to make your calorie estimates more accurate with a HRM (scroll through)
http://www.myfitnesspal.com/blog/Azdak