Heart rate monitor confusion wrt calories burned

davert123

Hiya

I'm confused over the data I am getting from my polar hrm. A few weeks ago I was given the all clear from the doc regarding a knee injury so I've gone back to exercise. Over the last 2 months my weight hasn't really moved down much (Which I expected due to holidays etc.) but the amount of calories I have burned during exercise has dropped loads. For example my polar used to inform me that a very uphill bike ride burned 800 calories. Now its 500 ? I have got a lot fitter. My RHR has dropped significantly and so as my HR during exercise. I always thought getting fitter meant I would be able to burn more calories with increased output but it seems that it results in me burning fewer because. Does anyone understand what is going on or could point me in the right direction. Either way doesn't really bother me because my goal is to get cardiovascularly fit but I also want to understand what is going on :-)

Cheers

WhatMeRunning

I'm a bit curious too. I've been burning fewer calories on my runs. I am running longer, but my HR doesn't peak as high as before, because I am in better shape. I believe we are supposed to push "harder", but I am honestly pushing about as hard as I can right now based on my strength levels.

I guess this is a very "first world" sort of problem.

I still burn a lot...just not as much as before, unless I simply add more "time".

h7463

Hi there!

Yes, the good news is, your HRM isn't broken, you probably got fitter. The bad news: In order to burn the same number of calories as before, you'll have to work harder.....lol

Spice up your exercise routine. Find something else that your body isn't used to, and mix it in with your bike rides. A surprised body will start burning more again! That's a lot of trial and error speaking here......

Happy training! :flowerforyou:

SteveTries

With regard to improved fitness levels burning less calories.......yes and no.

Yes.....If you are doing the same 15km bike ride route in 30mins now that you are fitter, then certainly the stress on your body is lower and the caloric burn therefore lesser.

No......If you are doing the same effort for 30 miins now that you did then, I'd expect the calorie burn to be in the same ball park as before. The key is in the effort. If you were doing 80% of max HR before for 30 mins then 80% now for 30 is the same amount of stress. You're probably able to cycle further in that 30 mins than you used to for the same effort.

Does that make sense?

The level of calorie drop you report seems unusually large to me. Have you changed any of the settings on the Polar? If you've altered your weight downwards and/or your working heart range, then this can have a large effect.

h7463

With regard to improved fitness levels burning less calories.......yes and no.

Yes.....If you are doing the same 15km bike ride route in 30mins now that you are fitter, then certainly the stress on your body is lower and the caloric burn therefore lesser.

No......If you are doing the same effort for 30 miins now that you did then, I'd expect the calorie burn to be in the same ball park as before. The key is in the effort. If you were doing 80% of max HR before for 30 mins then 80% now for 30 is the same amount of stress. You're probably able to cycle further in that 30 mins than you used to for the same effort.

Does that make sense?

The level of calorie drop you report seems unusually large to me. Have you changed any of the settings on the Polar? If you've altered your weight downwards and/or your working heart range, then this can have a large effect.

I've been keeping nutrition and workout logs for nearly 3 years now, and out of experience I can say, nothing ever is really unusual. We just usually don't know our bodies as well as we could.
Using 2 different Polar HRMs (FT7 and H7), i have noticed some ups and downs myself, and started writing down little things that I remembered about my mood, weather, stress, lingering cold....etc.... I cross-referenced them with my HRM results, and BAM...that's what made the difference.
My advise would be, not to mourn the old calorie burn numbers, but monitor the consistency of the results. Look for a 'ball park' number, instead of crunching every single calorie. After all, most of the food intake is a guess at best, too.
As long as you are feeling good, strong, and healthy in body and mind, you are making progress!

Good luck!

davert123

I just want to say thanks to all of you for your great answers. I was surprised but after reading all of this it does sound normal. I guess I just need to get used to the dropping calories and up the effort a bit more sometimes to keep improving and burning more. Its a little frustrating but that is the way it is I suppose :-) Cheers

jjaylynn

I've read that if you "confuse" the muscles it will do exactly that! I mix it up by walking, running and throw spinning in the mix. My first choice is running but I hit a plateau. The spinning helped rev things up it seems. Also, changing the time of day I work out I think has helped. Just a guess based on things I've read.

davert123

I've read that if you "confuse" the muscles it will do exactly that! I mix it up by walking, running and throw spinning in the mix. My first choice is running but I hit a plateau. The spinning helped rev things up it seems. Also, changing the time of day I work out I think has helped. Just a guess based on things I've read.

Thanks for this. It makes sense from what I've read about fitness in regard to triathlons. There seem to be many systems involved in fitness and one of them is around the set of muscles that are working so if I move off my bike onto my feet then my muscles associated with running would be less "fit" and therefore consume more calories. I think I may give this a go :-). I haven't tried changing the times of my sessions but that makes sense as well so I will definitely play around with things :-) Thanks for the advice

Azdak

What you are experiencing is a HRM anomaly, not a change in physiology.

Steady state cardio exercises have relatively fixed energy costs, based on workload and weight. However, HR is a relative measure, not a fixed one. With training, your max fitness level improves, but max HR does not. If you do the same workload, HR will decrease because that workload is now a smaller percentage of your aerobic max. If body weight is the same, then calories burned for that workload are still the same. However, since the HRM has no idea that your aerobic max has changed, it thinks the lower HR is due to you exercising at a lower workload.

if you have an HRM that allows you to input VO2 max manually, you can change that number to reflect the higher fitness level. If not, then I don't know what people do.

At any rate, you probably aren't burning fewer calories, your HRM settings are just off.

Azdak

I've read that if you "confuse" the muscles it will do exactly that! I mix it up by walking, running and throw spinning in the mix. My first choice is running but I hit a plateau. The spinning helped rev things up it seems. Also, changing the time of day I work out I think has helped. Just a guess based on things I've read.

It is necessary to vary the training stimulus (in a planned and controlled way) to continue making training improvement, and cross-training can be helpful for the recreational athlete to avoid excessive fatigue and injury, but the idea of "muscle confusion" is just marketing gibberish--a concept that was concocted to sell second-rate workout videos.

Azdak

I've read that if you "confuse" the muscles it will do exactly that! I mix it up by walking, running and throw spinning in the mix. My first choice is running but I hit a plateau. The spinning helped rev things up it seems. Also, changing the time of day I work out I think has helped. Just a guess based on things I've read.

Thanks for this. It makes sense from what I've read about fitness in regard to triathlons. There seem to be many systems involved in fitness and one of them is around the set of muscles that are working so if I move off my bike onto my feet then my muscles associated with running would be less "fit" and therefore consume more calories. I think I may give this a go :-). I haven't tried changing the times of my sessions but that makes sense as well so I will definitely play around with things :-) Thanks for the advice

Randomly changing activities will not consume more calories. Actually, just the opposite will occur. A less fit or untrained body will burn fewer calories because mechanical limitations prevent it from pushing to a higher workload.

The concept of "muscle confusion" is a pernicious lie that will lower the overall quality of your routine.

alereck

For you to keep progressing you have to keep pushing harder and harder. I don't do any cardio but it would make sense to me that it would work much like lifting weights. If I keep lifting the same 15 lbs dumbells for bicep curls for a year I will get little progress compared to increasing the weight along the way.

MeanderingMammal

I'm confused over the data I am getting from my polar hrm

Update your weight on the settings periodically.

jjaylynn

Re: "Randomly changing activities will not consume more calories. Actually, just the opposite will occur. A less fit or untrained body will burn fewer calories because mechanical limitations prevent it from pushing to a higher workload.

The concept of "muscle confusion" is a pernicious lie that will lower the overall quality of your routine."


I disagree with that , based on my personal experience and one other. Adding other activites and varying the times doesn't make one "less fit" After hitting a plateau AND changing it up has worked for "me", I'm more fit than before sinceI work differing muscle groups instead of "just" running. But everyone is different.

MeanderingMammal

Re: "Randomly changing activities will not consume more calories. Actually, just the opposite will occur. A less fit or untrained body will burn fewer calories because mechanical limitations prevent it from pushing to a higher workload.

The concept of "muscle confusion" is a pernicious lie that will lower the overall quality of your routine."

I disagree with that , based on my personal experience and one other. Adding other activites and varying the times doesn't make one "less fit" After hitting a plateau AND changing it up has worked for "me", I'm more fit than before sinceI work differing muscle groups instead of "just" running. But everyone is different.

Do you mean that you've added other activities in a structured way, that leads to complementary effects, or do you mean that you randomly added stuff to generate muscle confusion?

Notwithstanding that much of this is about delivering desired outcomes.

For the former I'd be thinking running plus cycling, plus swimming, as each of these disciplines helps compensate for the weaknesses inherent in only doing one of the three, similarly resistance training in addition to any one of those disciplines is going to deliver both performance improvements and a wider range of benefits.

On the other hand doing a random collection of rowing machine one week, elliptihell the following week then dreadmill the week after that isn't going to lead to effective progression.

Taking running as an example, the ability to run continuously for an hour means a decent amount of calorie expenditure, although that's not really the point of running for an hour. Getting to the stage of being able to run for an hour took about 16 weeks of sustained progressive training. Changing disciplines to confuse the muscles wouldn't have led to the ability to sustain the required level of effort in any discipline. That said, my calorie expenditure by minute is significantly less now that I can run for that hour, given that my running form is significantly better than it was when I started.

As Adzak identifies, the term muscle confusion was invented by marketing filth to sell products, it doesn't have a basis in sports science.

Azdak

That said, my calorie expenditure by minute is significantly less now that I can run for that hour, given that my running form is significantly better than it was when I started.

It may be a little less, but likely not "significantly" less.

When one starts a new activity (in this case, running), there is an initial period of adaptation. Meaning that the body has to learn the basics of how to do the movement, and, internally, the body has to learn to shunt blood flow and make some other neural adaptations. During this initial time (which is short), the body will not have a consistent, stable response to the exercise.

If one uses these workouts as a "benchmark" for comparison, then, yes, the difference will seem dramatic. Often with a new exercise, esp if somewhat strenuous, HR will skyrocket, the body feels out of control, and an HRM will show you burned 1,000,000 calories. But these are not real numbers and cannot use them as a reference. When researchers want to study the effects of a new exercise machine, or to compare the effects of two or more machines, the subjects always go through a habituation process, so that the entry data is consistent.

Studies on the effects of mechanical efficiency have shown only a small effect over a long period of time--on the order of 3%-6% over several years for trained athletes. Heart rate may drop more dramatically, and that can affect HRM readings, but actual VO2 and calorie burn will not change that much.

And even if "mechanical efficiency" does play a larger role, there is no reason why calorie burn has to decrease for the individual. If one has become, for example, 10% more "efficient", then one, by definition, has the capability to run 10% faster to compensate (at the same perceived exertion level).

In other words, if someone is running at "X" miles per hour and that speed results in a calorie burn of 500 per hour, and after 5 years their economy of form has improved by 10% (meaning they are now burning 10% fewer calories running at "X" mph), then they must be able to now run at "X" mph + 10% at the same level of perceived exertion. This would increase calorie burn to what it was before.

If improved efficiency lowers calorie burn, it's because it has also lowered exertion level. If you are moving more efficiently, then you aren't working as hard. But you are not restricted to that level of effort. If running at 6 mph represented a 70% effort, and the person was comfortable working at that level, and mechanical efficiency reduced that to a 62% effort, why would the person just stay at 62%? They would certainly notice the difference. The logical thing to do would be to increase workload so that you were back at a 70% effort. And by increasingly workload, one would burn more calories.

davert123

What you are experiencing is a HRM anomaly, not a change in physiology.

Steady state cardio exercises have relatively fixed energy costs, based on workload and weight. However, HR is a relative measure, not a fixed one. With training, your max fitness level improves, but max HR does not. If you do the same workload, HR will decrease because that workload is now a smaller percentage of your aerobic max. If body weight is the same, then calories burned for that workload are still the same. However, since the HRM has no idea that your aerobic max has changed, it thinks the lower HR is due to you exercising at a lower workload.

if you have an HRM that allows you to input VO2 max manually, you can change that number to reflect the higher fitness level. If not, then I don't know what people do.

At any rate, you probably aren't burning fewer calories, your HRM settings are just off.

Just wanted to say thanks for all of your advice here. and in other posts in the thread. After reading what you said I looked at my hrm and looked at the fitness test it does. I ran it when I first got it 2 months ago and then last month but nothing had changed (last month i was "coming down" off pain killters at the time so I'm guessing my heart rate was a little high. I ran it again and it predicts that my vo2max figure has increased from 40 to 46. The hrm automatically adjusted its internal settings and low and behold my calorie burn has jumped back to nearly where it was at the start :-) The figures appear to correlate with the gym equipment I use as well as on line databases so they do appear to be reasonably accurate (or at least guessing the same as other guesses). Just wanted to say thanks for your help here. I was starting to seriously under eat because of this. - perhaps by 500 calories a day added on to my already large deficit so I was really undergoing it. Without your help here i would have continued so thank you :-)