Heart Rate Monitor math confusion...

petithamu

Hi all,

I've been on MFP actively since end of December and I love it! The support here has been amazing! Anyway, after much research and advise from others, I have purchased my first heart rate monitor. I bought a Polar FT40, the girly one so it's still nice and pretty on my wrist. I have been using it when I go for walks and when I do my 30 Day Shred with Jillian Michaels.

What I am confused about: I've been reading other blog posts on HRM and I've been told that I need to do some subtractions from the HRM reading at the end of my work out because I need to calculate the 'real exercise kcal burned' and not just 'all kcal burned' if that makes sense. Basically, I was told that I can work out the number by seeing how many calories I burn in a day naturally (1710), divide that by 24 hours then by 60 minutes which will give me kcal burned/per minute. I would then need to take that number and multiply the exercise minutes which would give me another number and I need to subtract that from the HRM reading. Um...sounded confusing...this is the formula:

(Daily burned/24hrs)/60minutes = kcal burned/per minute
(1710/24)/60 = 1.19 kcal/min

30 Day Shred is appx. 28 minutes
1.19 x 28 = 33.32kcal
HRM reading = 217 kcal
217 - 33.32 = 183.68kcal (true calories burned)

That is what I was told that I need to do to get the true kcal burned because I don't want to 'double count' the active calories burned that has already been incorporated by MFP.

And just to confuse you more...my question is...I don't wear HRM all day. I only start it when I start the exercise and I stop it the moment I finish the work out so theoretically, shouldn't my HRM reading is already accurate and is only calculating my exercise kcal?

I don't even know if I made sense...but if anyone can get an idea of what I'm asking...please do give me some advise...should I do the math equation or not?

Thanks!!

Tiffany

CricketClover

I understand what you are saying. I usually will subtract 100 calories per hour of exercise from what my HRM says. This morning I walked for 45 minutes and my HRM said 588 but I only posted that I burned 500 here on MFP just to play it safe when it comes to eating back those calories throughout the day. I think what people were trying to tell you is if you were just sitting down those 30 minutes of exercise then you would burn those many calories so you only need to count the exercise calories as extra calories burned.

staceyb_2003

Mine doesnt move unless i reach a certain burn rate though is that a good thing or a bad thing plus my HRm usually matches my WII active and wii fit give or take 10 either way sometimes so i usually just add what my HRM tells me

nuttynetty114

I have the same polar monitor. I have never heard of that befor. When I execise I put in what the heart rate montior calculates. That is what everyone I know does.

You should be able to hit the button at the end of your workout and it will display the workout out total time & calories.

gillleeman

I deduct my 'living and breathing' calories from my exercise calories. Roughly I burn 1.4 cals per min just living, so if I didn't deduct them and I exercise for an hour then thats 84 calories x 5 (I exercise 5 times a week) = 420 calories overeaten. Guess its not so important if you're a long way from goal, but thats a big chunk of calories if you're trying to lose the last 10 lbs or so.

petithamu

ohhhh I think I actually get it now...like the point of the math equation...at first I didn't really understand why!

Thanks for the explanation and I think I will do the subtractions...so I don't accidentally eat back too much of my exercise calories.

Tiffany

Azdak

You can do what you want, but I don't know that you need to spend that much time or effort thinking about it. We cannot estimate calories precisely enough that the 30-100 "resting" calories are all that significant.

Not to mention the fact that, if you are doing 30DS, you don't need to be all that concerned about "eating back" exercise calories because you don't really burn that many during the exercise.

TrainerRobin

You can do what you want, but I don't know that you need to spend that much time or effort thinking about it. We cannot estimate calories precisely enough that the 30-100 "resting" calories are all that significant.

Not to mention the fact that, if you are doing 30DS, you don't need to be all that concerned about "eating back" exercise calories because you don't really burn that many during the exercise.

Agreed. Too much work for too little of a margin. I'd just use the number of calories on your HRM, knowing that none of them are exact, and run with that.

SOAPBOX WARNING: More worthy of most folks' time, is keeping close track of their food intake. Between guesstimating, measuring versus weighing, that's the area that's more likely to be off. I've found that when I have clients who've hit a plateau, their food tracking is usually off. Sure, they may be writing things down, but they aren't necessarily recording accurately. I'll do a little exercise with them and have them "measure" a few foods and jot them down, using their measuring cup/guestimating method (whatever they do at home)., Then I "measure" the same foods (I weigh because I have found weighing foods on a kitchen scale is faster (& easier) than measuring by volume). There is often a 20% or more difference.
Stepping off my Soapbox.

adrienc

Thanks Robin and Azdak! I was wondering the same, and you're probably right: all this math is not worth it actually...