The usual Calorie question

[lorduintah]

EDGE 305 - I get 500 calories for a ride (Whiterock Lake, Dallas, TX - one lap)
iBIKE - usually close to 1/2 of this.

So is this typical for many - a delta to 2X??

Thanks for a sanity check -

Tom Anderson

[5am]

My Garmin 305 overestimates calories burned by more than half from my ibike. Always has. As I recall, Garmin uses speed, time ridden, and the rider weight. Numerous complaints have challenged the accuracy of the Garmin method. And have a look at this article from the NYT on how troublesome calorie counting devices can be when trying to get a handle on calories burned during exercise.

Putting Very Little Weight in Calorie Counting Methods

I'd stick with the ibike figure over Garmin. But even then, it probably is better to be conservative in calories burned estimates given the number of factors that can go into the calculation.

[racerfern]

Agreed. The Garmin grossly overestimates calories.

I use a number of programs to track my efforts. One of them is "Cyclistats" from http://www.shastasoftware.com. If you enter your ride data along with your weight, tire type, riding style and wind, its calorie and wattage averages are amazingly close to the iBike.

[lorduintah]

Thanks so far.

I was quite confident that Garmin was not using anything more than a first order approximation - way more factors involved than weight, and speed - does not even comprehend coasting - even with a Cadence sensor...nor wind resistance.

[chrispy]

I have a Garmin 205 and an iBike. The Garmin guesstimates calories burned pretty much on-par with the table that was published in Bicycling magazine a few years back--it's a simple table of speed and calories/minute per pound of rider weight, with an added term for calories per 100 feet of climbing per pound of rider weight.

One should be able to go from kiloJoules to calories, and then divide by efficiency (to compensate for calories lost as waste heat) and come up with a reasonable calorie burn. Efficiency typically ranges from 20% (0.20) to 25% (0.25).

[Site_Admin]

You're both right - Conrad Earnest at Cooper did a study on the Polar method, and found it to be about 84% correct, so that's a huge MoE. KJ's work better because you can get a better idea of how much work is needed to complete a task. We use a 25% conversion. A little high, I know, but still consistent.

There is some great information on PPonline.co.uk about how to get from absorbing 1g/min on carbs to about 1.8 g/min, which is huge. Do an internal search and have a look.