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Old 08-22-07, 11:14 AM   #1
Smorgasbord42
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Garmin Calorie Counting - Inaccurate?

I have a new Garmin 305 Edge with Cadence (not Heart Rate). After about an hour and 18 miles it's telling me I burned over 800 calories. That seems way high given that the terrain was pretty level with only a few short hills (and I went to a destination and then back along the same path).

How is Garmin figuring the calories? Would adding the HRM make it more accurate?
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Old 08-22-07, 11:50 AM   #2
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How is Garmin figuring the calories? Would adding the HRM make it more accurate?
I have the HRM for the Garmin. The Garmin seems at least 20% to 25% high, IMHO. I download the Garmin into SportTracks, and then let SportTracks recalculate the calories. I think that's much closer.
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Old 08-22-07, 06:14 PM   #3
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I have the HRM for the Garmin. The Garmin seems at least 20% to 25% high, IMHO. .
It seems to use about 50 calories a mile. I think 30-40 is more accurate, depending on rider weight, terrain, etc.
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Old 08-22-07, 07:15 PM   #4
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Garmin Calories ...heh, just turn that function off.

I have the heart rate and cadence model, and given that it has all the data to calculate calories semi accuratly, it instead chooses to ignore heartrate and cadence. And uses the brainiac idea of basing calories purely on speed.

So if your climbing UP a 10 mile long mountain road at 6 mph standing and hammering all the way, on the verge of passing out from effort, it says you used 100 calores. Now come down the same road, at 50 mph, not even turning the pedals, and it'll say you burned 3000 calories.

Basically its garbage, but averages out I suppose over long trips.
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Old 08-22-07, 09:21 PM   #5
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Yeah, I drove my car with the bike in it and the Garmin on. Although the crank wasn't turning, it said I was burning all kinds of calories coasting around at 55 MPH. Bummer.
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Old 08-22-07, 11:51 PM   #6
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Originally Posted by Jarery View Post
Garmin Calories ...heh, just turn that function off.

I have the heart rate and cadence model, and given that it has all the data to calculate calories semi accuratly, it instead chooses to ignore heartrate and cadence. And uses the brainiac idea of basing calories purely on speed.

So if your climbing UP a 10 mile long mountain road at 6 mph standing and hammering all the way, on the verge of passing out from effort, it says you used 100 calores. Now come down the same road, at 50 mph, not even turning the pedals, and it'll say you burned 3000 calories.

Basically its garbage, but averages out I suppose over long trips.
I don't know... it seems accurate to me... Take for example:

My commute to work: 13 miles, 40 minutes, avg speed 19.4 mph, ascents 359 ft, descents 1588 ft
Total calories: 456

My commute to home: 13 miles, 67 minutes, avg speed 11.7 mph, ascents 1604 ft, descents 423 ft
Total calories: 1070
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Old 08-23-07, 06:43 AM   #7
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the edge 305 calorie calculations is in no way accurate. its a well established fact that the formula garmin uses puts more emphasis on average speed then HR, CAD, or elevation changes. a quick search for "calories" over at the MB forum will tell you all you need to know.

MB Forum

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Old 08-23-07, 09:15 AM   #8
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the edge 305 calorie calculations is in no way accurate. its a well established fact that the formula garmin uses puts more emphasis on average speed then HR, CAD, or elevation changes. a quick search for "calories" over at the MB forum will tell you all you need to know.

MB Forum

later.
I know that my experience is only that, my experience... however, what you're telling me is that garmin puts more emphasis on average speed then HR, CAD or elevation changes. According to the data that I'm getting, that is not the case. Look at my stats above... it doesn't coincide. In fact, it's the opposite. My commute to work has a greater average speed then going home and it's mostly downhill. According to your statement, I should be buring more calories going to work then going home not the other way around.

I recently got my garmin edge 305... who know, maybe the latest firmware adjusted how it's calculating the calories.
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Old 09-09-07, 07:00 PM   #9
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Quote:
Originally Posted by Jarery View Post
Garmin Calories ...heh, just turn that function off.

I have the heart rate and cadence model, and given that it has all the data to calculate calories semi accuratly, it instead chooses to ignore heartrate and cadence. And uses the brainiac idea of basing calories purely on speed.

So if your climbing UP a 10 mile long mountain road at 6 mph standing and hammering all the way, on the verge of passing out from effort, it says you used 100 calores. Now come down the same road, at 50 mph, not even turning the pedals, and it'll say you burned 3000 calories.

Basically its garbage, but averages out I suppose over long trips.
i am not sure the calculation as accurate as it could be (given the device "knows" one's cadence, HR, grade, weight, speed, etc.), but i know that what you are saying above is not true.

for example, when i bike up a 6 mile mountain pass with ~2,300' elevation gain (@ ~6mph), it reports that I burned 925 calories. this is for the ascent, only.

when i do the same trip but look at the data for the ascent AND descent, (6 miles down -- obviously -- at ~30-50 mph, almost exclusively coasting & braking) it reports that i burned 987 calories...total.

it's doing some type of calculation. whether it is the most accurate is another matter.
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Old 09-09-07, 08:21 PM   #10
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When I do cardio exercises in the gym the eliptical trainer or the treadmill
put me in the range of 600 to 900 per hour. Given that as a standard my
Forerunner 301 is in the same range and it does vary as my perception of
the work I have done. I would say that it is an instrument that gives a
repeatable indication of work and is of value for training.

By themselves heartrate and cadence are not indicators of work.
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Old 09-09-07, 08:38 PM   #11
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I have a Garmin and a Powertap. (Yeah I'm a stats junkie). I reasonably trust the powertap calorie measurement since its measuring actual work done.

The powertap consistently reports 1/2 the calories the garmin does. So, whenever I ride without the powertap and just the garmin, I cut the calorie count in half.
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