Type of calories being burned when Anaerobic and Aerobic energy systems activated?

[MuscleXtreme]

I'm trying to get a better grasp of how calories are being burned when the different energy systems are activated.

From what I understand, during the Anaerobic system, the body is predominately using glycogen for fuel. Would this mean that simple sugars are being broken down and used first; such as the monosaccharides: fructose, sucrose, etc. Thus carbohydrates are being used predominately during the Anaerobic system; but at what percentage to fats and protein?

The aerobic system I'm more at a loss for. From what I read the body will start burning fat cells after a sustained length of time of 40 minutes? Does this mean that carbohydrates are being burned up until that point or is it a mixture of both fat/carbs being burned? If so does anyone know at what percentage?

Thanks for the help!

[Andrew_S]

It may help to look up information on the respiratory exchange ratio. It gives an idea of the balance between the substrates being used depending on demand. So sitting down and doing nothing, mostly fat, when active with a greater amount of energy required, more carbohydrate. As far as my understanding, no energy pathway is going to work in isolating. All are active, it just depends on the degree...what one is primary. Fitness level plays a role too...endurance trained athletes able to spare more glycogen/use more lipids to supply ATP, etc...and on and on.

[MuscleXtreme]

It may help to look up information on the respiratory exchange ratio. It gives an idea of the balance between the substrates being used depending on demand. So sitting down and doing nothing, mostly fat, when active with a greater amount of energy required, more carbohydrate. As far as my understanding, no energy pathway is going to work in isolating. All are active, it just depends on the degree...what one is primary. Fitness level plays a role too...endurance trained athletes able to spare more glycogen/use more lipids to supply ATP, etc...and on and on.

Cool thanks man. I'll look into respiratory exchange ratios; thanks for the tip!

[ArchangelEST]

[Andrew_S]

Indirect calorimetry is the "tool" used to get that information at a basic level.