Calories burnt?

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SimonLondon
SimonLondon Posts: 350
in Fitness and Exercise
Having read all over the place that the calorie counter on the elliptical trainer can be way off I went and got myself a HRM (Polar RS400) and blow me down if it didn't give me the EXACT same reading as the elliptical trainer (heart beat, calories burnt etc).

If I have two seperate devices both giving me indentical readings is it safe to assume that they are going to be pretty accurate?

After a 35 minute (very intense) session both said I had burnt 620 calories whereas the MFP for 35 minutes shows half of that.

Which do I go with?

Replies

  • SHBoss1673
    SHBoss1673 Posts: 7,161 Member
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    mfp is what I would call a guestimate. While even an HRM is going to have a margin for error of around 5 to 10% that's going to be far closer to actual than MFP is.
  • kdiamond
    kdiamond Posts: 3,329 Member
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    Are you trying to lose a good amount of weight? If so I would stick with what MFP says and have a little calorie shortage. As long as you aren't going under 1200 cals a day you aren't going to put yourself into starvation mode and you might jump start your loss a little bit. I doubt a couple hundred calories is going to make a difference in the long run anyway. If you're hungrier, just eat something else.
  • kajaknowers
    kajaknowers Posts: 113 Member
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    http://www.healthstatus.com/calculate/cbc

    Check this website out as it calculate the calories burned according to your weight....I used to go by this and it seemed to make sure I kept on track with my weight. Hope it helps
  • Azdak
    Azdak Posts: 8,281 Member
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    No, you cannot make that assumption. It just means that on that machine they both coincide.

    To get the most accurate information from your RS400, you need to determine the following input data as accurately as possible:

    1. Resting heart rate

    2. Maximum heart rate

    3. VO2 Max (maximal oxygen uptake)


    #1 is easy to measure.

    #2 can be tricky

    #3 can be difficult

    You can start on #2 by using a formula to estimate HRmax. Use 266-age as a starting point. Use the HR reserve (or the Polar Own Zone protocol) to determine your target zones for various intensities. Figure out a 60% of HR reserve training rate and a 75% of HR reserve training rate.

    Now, do your workout and compare the calculated HR numbers to your feelings of perceived exertion. 60% still feel relatively easy--it's real exercise, but you can carry out a conversation without real difficulty. 75% is difficult--you have trouble talking and must really focus to maintain the effort.

    If your true HR numbers at those intensities are significantly different than your calculated numbers, I would adjust your HRmax upward.

    VO2 max is trickier, since most people have little or no idea about what these numbers mean or how to estimate the aerobic intensity of various activities. Polar has a "fitness test" that is based on your resting HR, but I don't have much confidence in that. If you have access to a Life Fitness 95 series treadmill, they have a 5 min submax fitness test that I have used and seems to come up with numbers that are in the ballpark. However, submax tests will underestimate your fitness if you have a higher than average HR max. There are other field tests that can be used to estimate VO2 max (1-mile run, Cooper 12 min test)--but they require a good ability to properly pace yourself.

    The more you can find out about your physiologic parameters, the more accurate your HRM will be when you estimate calorie burn during steady-state aerobic exercise.

    Sorry if this sounds complicated, but that's that way it works. Don't blame me--blame the manufacturers who gloss over the details.....

    At least you do have a good HRM--the RS400 is a nice model.
  • caropowell
    caropowell Posts: 31 Member
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    I have the Polar RS300X and really like it. The Polar HRM actually transmits the information it receives to a lot of the exercise machines, so I'm guessing that the heart rate the elliptical machine was showing you was based on the data it received from your HRM. This probably explains some of the correlation.

    I have to agree strongly with Azdak regarding the VO2 Max and the fit test on the Polar HRMs. I am about 40 lbs over the high end of my recommended "healthy weight" range. I am a VERY slow jogger and can't yet quite jog 3 miles without walking. According to my HRM's fit test based on resting HR, I am in the "elite" category. When I accepted that reading, all of a sudden, my calorie estimates were increased by about 1/3 to 1/2 because my HRM assumed that if I was working out that hard and was "elite" I must be doing some SERIOUS exercise. Anyhow, much as I enjoyed seeing those high calorie burns, I knew they weren't realistic so I adjusted my VO2 Max down to something more reasonable and am back to getting more realistic calorie burns.


    Good luck!
  • SimonLondon
    SimonLondon Posts: 350
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    Wow thanks so much for such excellent responses.

    Azdak - you're right, I only understand some of what you're saying but I do have some answers :)

    I worked out yesterday that my Fat burning HR is between 108 and 168.

    During this session I had a HR of 155-165 during each 2 min cooldown (I was still pushing on the cooldown) and between 175 and 180 during each 1 minute intense push.

    This was my first attempt at an intensive session but at the end of this session I felt like I had a much better workout than a normal, steady session. Given that I worked a lot harder than normal it did seem strange to use the same MFP results.

    Fitness is so confusing :)
  • Azdak
    Azdak Posts: 8,281 Member
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    I have the Polar RS300X and really like it. The Polar HRM actually transmits the information it receives to a lot of the exercise machines, so I'm guessing that the heart rate the elliptical machine was showing you was based on the data it received from your HRM. This probably explains some of the correlation.

    I have to agree strongly with Azdak regarding the VO2 Max and the fit test on the Polar HRMs. I am about 40 lbs over the high end of my recommended "healthy weight" range. I am a VERY slow jogger and can't yet quite jog 3 miles without walking. According to my HRM's fit test based on resting HR, I am in the "elite" category. When I accepted that reading, all of a sudden, my calorie estimates were increased by about 1/3 to 1/2 because my HRM assumed that if I was working out that hard and was "elite" I must be doing some SERIOUS exercise. Anyhow, much as I enjoyed seeing those high calorie burns, I knew they weren't realistic so I adjusted my VO2 Max down to something more reasonable and am back to getting more realistic calorie burns.


    Good luck!

    Good job on your last paragraph--even if you don't get it exactly right, you are using the correct reasoning.

    First paragraph--doesn't make any difference where the heart rate monitoring takes place. Heart rate is heart rate. HRMs do not measure calories--they measure heart rate and use computer sensing and mathematical calculations to *estimate* caloric burn. Exercise machines do the exact same thing--they just use different research and different calculations. The heart rate receiver on a cardio piece is a Polar receiver--it is a separate module that is plugged into the display circuit board of the equipment. All the machine receives is the heart rate transmission signal. Once the machine receives the raw data, it uses it's own internal "brain" to estimate the calories, based on equations stored in the machine's memory.

    As I have said several times, calculating calories on ellipticals/cross trainers is the most difficult of the standard cardio machines. There are well-established equations for treadmill walking/running, stair climbing, and cycling to predict energy expenditure. These are not 100% accurate, but they should be relatively consistent. Since every manufacturer has their own movement design for an elliptical, they must determine a unique calculating method for each machine. Some just use algorithms from previous models, some extrapolate calculations from related movements or research, some contract with a local college to have them do the testing. One manufacturer--Life Fitness--has their own biomechanical lab in house and they do VO2 testing and develop specific equations for each new machine they design. There is still some variability, since it is only practical to test 50-75 subjects, but they are probably the most accurate of any cardio machines. (For 95 level cross trainers manufactured after about 2006).
  • SimonLondon
    SimonLondon Posts: 350
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    Azdak, Your replies are clear and in-depth. It's people like you who make this community work so well!

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