Carbohydrate and fat oxidation

The aerobic system, respiratory quotient, the crossover concept and the intensity of peak fat oxidation.

The outline, topic by topic

Each topic is weighted the way the exam weighs it.

Aerobic system: what is it?
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ATP made in mitochondria by oxidising carbohydrate and fat.
Slow to start, but almost unlimited.
An RQ of 0.95 is measured during exercise. Which fuel dominates?
- Carbohydrate
- Fat
- Protein
- Equal amounts
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Carbohydrate
The closer RQ gets to 1, the more carbohydrate dominates.
Respiratory quotient: what is it?
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CO2 produced over O2 used: 0.7 for fat, 1.0 for carbohydrate.
It shows which fuel dominates.
Why does carbohydrate dominate at high intensity despite smaller stores?
- Fat is toxic during exercise
- They yield ATP faster and with less oxygen per ATP
- Fat only oxidises at rest
- The liver blocks fat
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They yield ATP faster and with less oxygen per ATP
ATP rate matters most as intensity rises.