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Accuracy of Calories Burned??

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  • Accuracy of Calories Burned??

    I am skeptical as to the accuracy of the calories burned on my Garmin 705.

    I don't have a power meter, but I do use the HRM.

    I generally subtract 30% and figure that to be about right.

    Any thoughts?

  • #2
    If you dig around through some of the older posts you will see that this is a common issue with the 705. The addition of a power meter does not correct it. The two common solutions are decreasing your weight in the profile or reducing the calories burned figure by 30 to 40% as you are doing.
    AKA luv2climb.

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    • #3
      I did a ride on Sunday, and my 705 says I burned 1,801 cals
      I upload into Ascent, and the same ride in there says 3092 cals
      The ride was a VERY hilly 26 miles at 2578ft of total ascent.

      ?????

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      • #4
        Not sure if you're posing a question here. The 705 tends to overstate the caloric burn of a cycling activity. With that said, Ascent is showing an even greater discrepancy. I assume you are questioning the 705 vs. Ascent? Ascent performs its own calculations and you may wish to take that up on their forums.
        - Steve

        my GC digest

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        • #5
          Hi Steve,
          Sorry for not being clear.

          The point that I was trying to make, was that there are always discrepancies in calorie calculations. I think it's all to do the method of calc from one program compared to another. I don't believe there is a program that is 100% accurate. We are all striving for accuracy and absolute numbers, but I think that is a Utopian idea.

          Personally, and I've said it on here within a different thread on calories, is that it doesn't really matter what the numbers are, providing the figures are comparable from ride to ride.

          I am a member of the Ascent forum http://montebellosoftware.com/ascent_forum/? you will find me as "Mick F" on there. If you search through, you will find quite a few general queries regarding calorie calculations.

          How do you know that the 705 overstates the calories consumed? Surely this is a figure that will vary from person to person and ride to ride. You never know, it may be understating my figures? Is this possible? I'm not saying one calculation is right and one is wrong, it's just that there are different methods of calculating it, and we pick out the figure that means what we want it to mean.

          Sorry, I don't want to appear argumentative, please forgive me if you think I am.

          Regards,
          Mick.

          Comment


          • #6
            To your point, my Edge 705 consistently reports fewer calories burned than what the following calculator reports which is a heart-rate based calculation:

            http://www.braydenwm.com/calburn.htm

            So, I tend to believe that the 705 is more accurate than we think...

            Comment


            • #7
              I understood the intent of your post, SMICKF, and agree.
              The accuracy of the calorie algorithm isn't as important as its consistency so that trends can be clearly seen.
              Unlike others on here, I have actually found that the Garmin estimate closely matches online calorie counters and past HR monitors I have used so I was never very concerned about all of this.
              btw, from what I have seen, ASCENT looks fantastic.
              Actually thinking about jumping back into the Mac world (used to be a hardcore fanboy going back to 1984) just to have it on hand.
              Later . . . .

              Comment


              • #8
                Yes, Ascent is fantastic, and the best bit of software I've ever bought!

                I've just been on another hilly today. The ride I referred to before was on a very heavy bike with few gears, and the ride today was exactly the same, but on my lightweight 30 geared bike.

                Sunday's ride had 705 saying 1801c and Ascent 3092c - heavy bike
                Today's ride has 705 saying 1811c and Ascent 2001c - light bike

                I have my 705 set for 30lbs for one bike and 23lbs for the other.

                The good thing about Ascent, is that it analyses the ride more fully than the basic system in the 705. Consequently, Ascent knew that I was having a hard time with the heavy and difficult bike and an easy time with the lightweight with all the gears.

                I repeat, it was exactly the same ride - 26 miles - the heavy bike took a little over 3 hours, and today on the lightweight only 2 hours.

                I think I believe Ascent more than 705, but so what? They are just numbers!

                Comment


                • #9
                  I may be the only one - but I ride with both Polar and Edge 705. And since 2.90 my calorie values are very similar. before that it was way off compared between the two.

                  Quite frankly - I'm more concerned with other figures than calories anyways.

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                  • #10
                    Agreed, SEABEEGPS, I am also more concerned with other numbers than calories but I do like to know cuz I divide 540 into the grand total to find the "Big Mac Factor" so as to give my wife a bit of perspective on some of my longer rides.
                    Even so, I'll come home beat up but feeling like a million bucks and say something like, "Babe! I just finished a 14 Big Mac ride!", hoping for a big kiss or, at least, a high five but usually get nothing but an eye roll and a groan.

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                    • #11
                      Originally posted by ROBOTHEAD View Post
                      Even so, I'll come home beat up but feeling like a million bucks and say something like, "Babe! I just finished a 14 Big Mac ride!", hoping for a big kiss or, at least, a high five but usually get nothing but an eye roll and a groan.
                      That is so true! My kids care more than the spouse usually does.
                      AKA luv2climb.

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                      • #12
                        I weigh ~170, but hve my unit set for 110 and believe that the figures it gives me like that are more realistic.

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                        • #13
                          Actually the Garmin devices if setup correctly (Age, weight, height, bike weight and resting heart rate) are very accurate. I've compared the results with other units and also a sports nutritionist and all the results are very close to one another. Of course as others have mentioned it's not 100% accurate but a 5% error rate isn't too bad.

                          For riders who are serious about the stats I suggest you weigh yourself before rides and update the data on the unit as being lighter or heavier will change the calculations

                          Comment


                          • #14
                            Calorie calc variations between ROMs?

                            I recently went on a walk with my 705 and HRM, just to get used to my new device and check out the baseline data. It was a moderately quick walk lasting an hour. I'm ~170lbs, the unit was running software version 2.40.

                            I was a little surprised to see the unit credited me with almost 1000 calories burned, which is clearly not possible.

                            May I ask a couple of questions?

                            1- Should the 705 be expected to calculate calories burned for a person walking or running as opposed to riding?

                            2- I've updated my unit software to v3.10. Should I expect better accuracy as a result?

                            3- Are there plans to address this issue in future unit software releases?

                            Comment


                            • #15
                              Originally posted by JAMIELAING View Post
                              1- Should the 705 be expected to calculate calories burned for a person walking or running as opposed to riding?

                              2- I've updated my unit software to v3.10. Should I expect better accuracy as a result?

                              3- Are there plans to address this issue in future unit software releases?
                              1 - No. The unit is only set up for cycling.

                              2 - Not in my experience.

                              3 - No.

                              If you want the most accurate info for calories burned with ANY device you need to add a power meter and use the kilojoules burned. You can however lower your body weight on the Edge to get it closer to a correct figure.
                              AKA luv2climb.

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