Originally Posted by pacesetter
Hummm.... do you have evidence hrt is loosely related to cal burn?
Sure...it's the reason that top athletes are training with power meters. Heart rate can vary from ride to ride, depending on fitness levels, rest, etc. Two rides done at the same power can have different average heart rates. But, if they are done at the same power output (watts), they result in the same calories burned (assuming rider weight and bike weight are the same).
Power and calories burned are a function of the amount of physical work performed. Heart rate just tells you how hard your heart is working to produce the work. In general, higher levels of work result in higher heart rates, but not always. HRM's use this to help estimate calories, but they can be fooled by changes in heart rate, levels of training, amount of rest, and all the other things that can affect heart rate.