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Old 06-21-12, 04:47 PM
  #7  
gregf83 
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Most of the energy you expend goes into overcoming wind resistance. If you were the same height and rode in the same riding positions i.e. drops or hoods and didn't draft off of each other unevenly then the total work you did should be the same.

To determine how many calories you burned you divide the total work by your efficiency. Efficiency of riders can vary between about 18-24% with most people falling in the 20-22% range. If one of you had a 20% efficiency and the other 22% you would expect a 10% difference in the total calories burned.

The 20% difference you noticed could be due to errors in HR/calorie algorithms, differences in riding positions and/or different amounts of time spent drafting. You would need powermeters if you want more accurate numbers.
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