Originally Posted by
bobthib
From the Free Dictionary:
"Respiratory Quotient (RQ)the ratio of the volume of carbon dioxide gas (CO[SUB]2[/SUB]) given off by the body to the volume of oxygen (O[SUB]2[/SUB]) absorbed in the same time interval. The respiratory quotient may be expressed as
Determination of the RQ is important in research on the characteristics of gas exchange and metabolism in animals and plants.
Animals and humans. When carbohydrates are being oxidized in the organism and the requisite oxygen is available, the RQ is 1. In the oxidation of fats, the RQ is 0.7 and in the oxidation of proteins, 0.8."
The real "proof is in the pudding" for me. Riding for 1.5 hrs into a stiff wind at 85 - 90% HR and hardly puffing was really amazing. And that was at the end of the ride, miles 39 - 61, averaging 217 watts. No nutrition other than my drink (gatorade G2) and I was not tired and could have gone futher, but my grandson's parade was about to start. Not bad for an old man, even if I do say so myself.
The amount of oxygen used doesn't change for a given power level regardless of the ratio of carbs and fats being burned. The products of carbohydrate and fat oxidation are CO2 and H2O. If you burn fat you will produce less CO2 which but more H2O.
How are you measuring your power output? If you have a properly calibrated power meter you shouldn't need to rely on HR to determine your effort as HR can be influenced by many factors including hydration levels. After a long ride my HR is always higher for a given level of effort than at the beginning due to dehydration.