heart rate monitor vs excerise "calories"

your hrm is the one that is accurate. this site uses averages for calories burned. When you add your exercise, you can manually enter the number of calories that your hrm says you burned instead of changing the minutes that you exercised.

Work = force x distance. ( check a physics textbook if you don't believe me)

The exercise machine is more accurate, because it is actually measuring work. Calories (you can convert from joules) is the unit used to measure work.

Heart rate monitors do not actually measure the work that you are doing. It is a component of your physiologic response to work, which is dependent on many variables, including your level of fitness. If two subjects, one deconditioned, and the second fit, walked he same distance over the same terrain, they would burn the same amount of calories, although the fit person would have a lower heart rate. This has to do with a more efficient heart with a higher stroke volume (more blood pumped per beat), thus necessitating fewer beats per minute to deliver the same amount of tissue to the muscles.

In addition, there are medications which affect heart rate. For example, a person taking B-blockers may not be able to mount a tachycardic response to exercise, even though they are doing the same amount of work. This does not make the amount of work they die (ie: calorie burnes) any less.

I hope this helps.

J. Coleman, MD

I think your weight factors into calories burned.

Your gait factors into it, but if they walked in exactly the same way, then yes, they would burn the same # of calories.

Heart rate is NOT a unit of work, calories are. There is no consistent way to convert heart rate into calories (units of work). the heart rate response to exercise id dependent upon multiple physiologic variables.

When we do exercise studies at the hospital (I'm a pulmonologist), we use a cycle ergotomer instead of a treadmill so that we can standardize the amount of external work (this takes weight out of the equation). If we set the cycle to the same resistance and have them cycle at the same rpm, then both Joes are doing the SAME amount of work, although 300lb Joe will have a higher heart rate.

J. Coleman, MD

Do you have any articles or anything to back that up? I have ALWAYS heard that two people who are different weight will burn a different amount of calories. If not then why do heavier people lose weight so much faster? Is it not because they are carrying the extra weight around in everyday activities and are burning more calories because of it?

You can consult any physics textbook to understand what a calorie is and what it measures. It's important to understand what "work" really is.

For exercise physiology, I prefer Wasserman's " Principle's of Exercise Testing and Interpretation". Probably not available at your local library but if you live near a medical school you might be in luck.

Happy reading :flowerforyou:

I think I understand what you are saying is the heart rate monitor assumes that if you have a heart rate of x that you are doing y amount of work. However different factors (you listed medication) can affect what that heart rate is so it is not necesarily a good indicator of how much work you are doing.

The exercise machine is calculating the calories based on W=F*D or W= Mass x acceleration *distance. So if you input your weight it is more accurate that the HRM?

I have noticed that too. But, I leave my monitor on until I get home from the gym. So those extra 100 or so calories I burned after I was done working out do not count either.
But you can change the calorie amount also.

Science geek time!
work done does = force x distance, but 300 lb. Joe Shmoe has to apply more force to move the extra weight when running a mile, so 300 lb. Joe Shmoe would do three times as much work as 100 lb. Joe FitShmoe.
However, on an exercise bike a lot of the weight factor is taken out of the equation, as both Joes push against a set resistance instead of lifting their bodies (assuming both Joes ride in a seated position).

But pumping the pedals is not the only work done on the exercise bike. Calories are a measure of energy, and that energy can also be in the form of heat. 300 lb Joe Shmoe produces a lot more heat while riding the bike than 100 lb. Joe Fitshmoe. That heat is produced by the burning of calories. Calories a burnt and heat is produced by the pumping of the heart, the flexing of the muscles, the dilating of blood vessels, the increased use of the diaphragm as you breathe heavier, etc.
:yawn: Still with me?
So, what MFP tells you are the calories burnt, what the exercise equipment tells you, and what the HRM tells you are all going to be estimates, since none of them can measure every factor.
For myself I just make sure I have my base calories and then lowball my exercise calories in hopes of being happily surprised on measuring day :happy:

this is a fascinating discussion...
I have been thinking about getting a HRM for use in the gym and to help track my fitness progress. I'm woefully out of shape and happen to be a data nerd, so I figure the more data I have about my progress the more to motivate me to continue.

I'm wondeirng now if a HRM is really a wise investment, if I should really be using the machine calculations. Another thing that I have noticed is that different machines give you a different answer even though you exercise at roughly the same pace and for the same distance/time. I don't understand that either.

Would love more info...




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I've been testing my HRM this week and have been comparing the read out to what I've found and have been using on MFP since mid-Nov. Some are roughly the same, some are not. It's hard to tell what LIGHT, MODERATE and VIGOROUS mean to each individual's work out style.

MFP = 60 min of soccer (general, casual) has me burning 553 cal. I run my bu tt off during the games and thought this was a good number. My HRM on Monday said I burned 776. I then took out my REST HR of aprox 70 which left me at 706. I think this is more accurate, cause I have NEVER run this hard in my life. I know it's no longer "casual".

MFP = 40 min stationary bike (moderate effort) has me burning 349 cal. Last night I wore my HRM and got on my bike, which is a road bike on an indoor trainer, and in 40 min I burned 352 minus my rest rate left me at 320. Lower. Not by much, but lower.

I think it's best to get a HRM because MFP is just an estimate. Based on your height, weight, age, you may be burning more or less. Just me 2 cents.

this is a fascinating discussion...
I have been thinking about getting a HRM for use in the gym and to help track my fitness progress. I'm woefully out of shape and happen to be a data nerd, so I figure the more data I have about my progress the more to motivate me to continue.

I'm wondeirng now if a HRM is really a wise investment, if I should really be using the machine calculations. Another thing that I have noticed is that different machines give you a different answer even though you exercise at roughly the same pace and for the same distance/time. I don't understand that either.

Would love more info...

I would still get the HRM, both to monitor the intensity of your work outs and measure your recovery after your work out. If your goal is weight loss / general fitness, you will lose weight more efficiently working in an aerobic range of heart heart, so your HRM will tell you when you're overdoing it (or not pushing hard enough). The rate of recovery to your resting HR is a good indication of fitness, so continue to monitor HR when you are finished your work out to track your improvement in fitness.

My beef on the calorie calculations from your heart rate monitor is when I read posts from people who get on an elliptical machine and put their heart rate through the roof, then get off and sit on the floor to stretch and think they're still burning a ton of calories while stretching ( or driving home from the gym) because their HR stays elevated, when in fact it is really an indication that they aren't fit enough to recover from their work out in a timely manner.

Of course, the calorie count on the machine assumes you are actually doing the work on the machine. Every time I go to the gym, you see people (you know who you are) on the treadmill with the incline and the speed cranked up, and they have their upper body draped over the console to hold themselves up and their legs are just flailing free because they can't keep up with the pace. Obviously, they are not burning the same calories as they would if they let go and actually worked hard enough to avoid getting flung off the back! (The same is true for all you people on the ellipticals who brace your arms on the side rails to take your weight off your legs - hello - isn't that the point of being there?)

I think what she is saying is they take weight out of the equation because weight composition is a factor also. Two 200 lb people will not burn the same amount of calories if one has 50% body fat and one has 10%. That is why they always tell you exercise calculators are not accurate for the very obese or very muscular or short or tall or people in people in high elevation or very hot places..

You can consult any physics textbook to understand what a calorie is and what it measures. It's important to understand what "work" really is.

For exercise physiology, I prefer Wasserman's " Principle's of Exercise Testing and Interpretation". Probably not available at your local library but if you live near a medical school you might be in luck.

Happy reading :flowerforyou:

I think I understand what you are saying is the heart rate monitor assumes that if you have a heart rate of x that you are doing y amount of work. However different factors (you listed medication) can affect what that heart rate is so it is not necesarily a good indicator of how much work you are doing.

The exercise machine is calculating the calories based on W=F*D or W= Mass x acceleration *distance. So if you input your weight it is more accurate that the HRM?

Which is why I would assume that even on a bike machine you would enter your weight, so it would tell you that yes, Joe weighing more, is actually burning more calories.

Your gait factors into it, but if they walked in exactly the same way, then yes, they would burn the same # of calories.

Heart rate is NOT a unit of work, calories are. There is no consistent way to convert heart rate into calories (units of work). the heart rate response to exercise id dependent upon multiple physiologic variables.

When we do exercise studies at the hospital (I'm a pulmonologist), we use a cycle ergotomer instead of a treadmill so that we can standardize the amount of external work (this takes weight out of the equation). If we set the cycle to the same resistance and have them cycle at the same rpm, then both Joes are doing the SAME amount of work, although 300lb Joe will have a higher heart rate.

J. Coleman, MD

Soooo, would my nike + be a better guide for calories burned when I run vs. my hrm? Just so you know I hate math and this discussion caused my eyes to glaze over as I was reading. :embarassed:

Science geek time!
work done does = force x distance, but 300 lb. Joe Shmoe has to apply more force to move the extra weight when running a mile, so 300 lb. Joe Shmoe would do three times as much work as 100 lb. Joe FitShmoe.
However, on an exercise bike a lot of the weight factor is taken out of the equation, as both Joes push against a set resistance instead of lifting their bodies (assuming both Joes ride in a seated position).

But pumping the pedals is not the only work done on the exercise bike. Calories are a measure of energy, and that energy can also be in the form of heat. 300 lb Joe Shmoe produces a lot more heat while riding the bike than 100 lb. Joe Fitshmoe. That heat is produced by the burning of calories. Calories a burnt and heat is produced by the pumping of the heart, the flexing of the muscles, the dilating of blood vessels, the increased use of the diaphragm as you breathe heavier, etc.
:yawn: Still with me?
So, what MFP tells you are the calories burnt, what the exercise equipment tells you, and what the HRM tells you are all going to be estimates, since none of them can measure every factor.
For myself I just make sure I have my base calories and then lowball my exercise calories in hopes of being happily surprised on measuring day :happy:

I do the same (lowballing calories burned) but great explanation. :bigsmile:

i love this thread