Fifty Plus (50+) - Calories burned?

A female friend who is 5' 3", approx. 140 lbs and 56 yrs. old and I ride together frequently. I am 5'9-10", 190 lbs and 65 yrs. old. On a typical 15 mph ride her HRM will indicate that she has burned about 60% of the calories that I have. I have referenced a variety of on-line charts, calculators, etc. They usually indicate that at 15 mph I'm burning 13-15 cals. per minute. These are all estimates of course but could the disparity be that much?

Depending on how you calculate it, you can get quite a bit of difference for the same person. With the weight difference between you, that is only going to be a wider range of values, so this seems as reasonable as any of the formulas I have seen.

I calculate calories in three different ways. 1) let the GPS do it. 2) Calculate using the standard met formula with a mod to take hills into account (my own creation). 3) use one of the many formulas to base calories on heart rate.

For an 18 mile ride on gravel with 1000 feet of climb, I get values ranging from around 1000 to 1400 calories using these three methods. Since this is more informational for me than anything I'm actually using to eat by, it does not bother me.

Today we rode 31 mi. on a very hilly route that, we discovered, had quite a few miles of dirt and chip seal road. Really slowed us down. We ended up doing it in 2:15:00. Her HRM showed her burning 867 cals. my formula is more like 1755. That's a typical disparity for us. I don't worry about it. I'm just surprised the difference is so great.

I really do not give much credence to any of the methods out there. They are estimates. One can make a better estimate by measuring CO2 production, but that is pretty much restricted to a laboratory setting and even then you have to make assumptions as to the fuel burned. Burning fat, carbohydrate or protein produces different results.

On the Tandem and me and my Co-Rider had the same Heart monitor. He is 45lbs heavier than me and I weigh 145lbs. So he is approximately 25% heavier than me and we set our monitors up to our own weight. He was showing 25 to 30% more calories burned than me so By ratio I reckon the monitors were about right. As to whether they were giving accurate readings- I would not like to say.

All I can state is that on the long rides we used to do- He was eating about twice the amount of Fuel than me and neither of us was gaining weight---or losing it from our norm.

Calorie computations are at best very rough estimates. The guy who writes Cyclistats software used to post frequently here, and he said that most folks burn around 40 calories per mile. I suggest you not concern yourself with calories burned.