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My question is actually prompted by this letter sent to cyclingnews:

http://www.cyclingnews.com/fitness/?id=2007/letters01-30#4

I was wondering if anyone knew of a sound way to estimate total energy expenditure for a ride using only heart rate zones, and the total amount of time spent in each. I know certain heart rate monitors have built in formulas for this, but I guess a lot of those are proprietary, and supposedly don't work very well. I was wondering if anyone know of a recent study or some other current method for doing this more accurately.

For example, Joe Friel's book mentions that you can gauge total cumulative workload by multiplying the minutes spent in a particular zone, by the value of the zone (e.g. 20 minutes in zone 1 and 30 minutes in zone 3 is 20x1 + 30x3 = 110). Now I figure this value is only useful in comparing workload from week to week, but perhaps there is a way to go from this figure to kcal?
 

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I have read that the aomunt of blood the heart pumps per beat is relatively constant, for any given person, but does vary from person to person.

If you assume a constant volume per stroke and that the blood is fully oxygenated (true for most aerobic zones), and no energy is supplied by anerobic metabolic cycles...

Then the oxygen consumed, would be proportional to the heart rate, and hence the total energy consumed by the body.

The total energy would include all of the work, not just work delivered to the pedals. (I believe that the (25% thermal efficiency) is for total energy consumed, and heart lungs and other motions can account for up to 15% of the total energy consumed.

All this said If one has a VO2 test just below Lacate Threshold, then ratioing the energy measured at this heart rate to any heart rate below it would seem realtivly useful to me.

Without this calibration step the results I believe would be accurate but not precise.

By that I mean the absolute value is not likely even close but comparing one work out to another should be okay.
 
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