Polar FT4 HRM Question

mlondon8509 · February 2013

So I just got my first heart rate monitor and I took it out for a spin yesterday. I ran for 45 minutes at about a 9:00 pace (inclusive of cool down). Based on MFP and the machine I was working on, it suggested my calorie burn should be around 620 for the session. According to my new HRM, I burned 758 calories. Now I had heard that MFP and machines tend to overestimate calorie burn, but I was unprepared to see the exact opposite. I should note that my average heart rate for the 45 minutes was 175 (93% of my alleged maximum, using 220-age), so the HRM assumed I was working exceptionally hard for 45 minutes. I guess my question is, if the HRM underestimates my maximum heart rate (it uses the 220-age formula), will it similarly overestimate my calories? Have others run into this issue and, if so, how do you "normalize" the calories burned for your unique maximum heart rate?

scribb · February 2013

I would go with what is on the HRM as long as all of your information you enered is correct. A good check would be to put on the HRM and take your HR the old fassion way. This will tell you if the HRM is accurate.

You can also chack it against the HRM on the treadmills.

imchicbad · February 2013

MFP calculations have been known to UNDER estimate your calories burned. I've had my POLAR FT4 for a month. I see no exaggeration. I do p90x and have calculated my TEDEE and burn using my HRM and it is perfect. I did stretching 1 hour and only reached 125 calories burned with 110 heart rate the highest but 80 was the steady reading, on my 1 hour weight lifting work out I burn little over 530 calories. So it sounds right to me.

ChristyRunStarr · February 2013

Agreed-I go with my HRM (I have a FT4 as well) and it's never failed me *knock on wood*. As long as you have your weight and info programed into it as well as the chest strap on right, you should be good to go and have no problems

mlondon8509 · February 2013

So my specific information inputed is correct. However, my question i more related to the fact that it is assuming my maximum heart rate is 189 (based on 220 minus my age). I have read that this equation can sometimes be off by as much as 30 bpm - which would make sense to me given I was at 93% of 189 on average for a 45 minute non-strenuous jog. If I actually have a higher maximum heart rate (lets say it is 200) that what the HRM is assuming, does this mean that the HRM is overestimating my level of work and my calorie expenditure.

Mokey41 · February 2013

MFP calculations have been known to UNDER estimate your calories burned. I've had my POLAR FT4 for a month. I see no exaggeration. I do p90x and have calculated my TEDEE and burn using my HRM and it is perfect. I did stretching 1 hour and only reached 125 calories burned with 110 heart rate the highest but 80 was the steady reading, on my 1 hour weight lifting work out I burn little over 530 calories. So it sounds right to me.

HRM's are not accurate for things like stretching or lifting because your HR isn't elevated enough. They're meant for steady state cardio that significantly raises your HR over an extended period of time. Using it for lower HR exercises will give exaggerated readings.

3dogsrunning · February 2013

MFP calculations have been known to UNDER estimate your calories burned. I've had my POLAR FT4 for a month. I see no exaggeration. I do p90x and have calculated my TEDEE and burn using my HRM and it is perfect. I did stretching 1 hour and only reached 125 calories burned with 110 heart rate the highest but 80 was the steady reading, on my 1 hour weight lifting work out I burn little over 530 calories. So it sounds right to me.

HRMs are not accurate for weightlifting nor are they for low intensity exercise (I believe under 120bpm but I stand to be corrected on that) activities like stretching. They are mean to estimate calories burned during steady state exercise. Intervals will also affect accuracy.

OP - here is a link to a spreadsheet with information on how to set it up to be most accurate.
http://www.myfitnesspal.com/topics/show/750920-spreadsheet-for-bmr-tdee-deficit-macro-calcs-hrm-zones

Also, a link to explain how to test for accuracy
http://www.myfitnesspal.com/topics/show/774337-how-to-test-hrm-for-how-accurate-calorie-burn-is

WhoTheHellIsBen · February 2013

I bring this up not to question your intelligence but because it's a fairly common over site by people. Have you checked to make sure all your settings are correct as well? Height, age, weight, sex, ect? Pounds not kgs? As long as all that is correct I'd say stick with the HRM

omma_to_3 · February 2013

I'm not sure how the possibly incorrect max HR would affect the readings. My max HR should be 182 according to formulas, but I know that it's really about 200. On my Polar, I can change it (and did). But I don't think you have that option on the FT4. I don't think it makes a big difference though - probably fairly minor.

What the reading does include though, is your BMR. So for me, I subtract that out of my readings before I record it. For example, my BMR (tested in a lab) burns about 65 calories per hour. So, for a 45 minute workout, I would subtract about 49 calories from the total reading.

mlondon8509 · February 2013

I'm not sure how the possibly incorrect max HR would affect the readings. My max HR should be 182 according to formulas, but I know that it's really about 200. On my Polar, I can change it (and did). But I don't think you have that option on the FT4. I don't think it makes a big difference though - probably fairly minor.

What the reading does include though, is your BMR. So for me, I subtract that out of my readings before I record it. For example, my BMR (tested in a lab) burns about 65 calories per hour. So, for a 45 minute workout, I would subtract about 49 calories from the total reading.

This makes great sense. Thank you.

Polar FT4 HRM Question

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