The fuel utilisation test provides a detailed estimate of carbohydrate derived from glycogen and other glucose sources, plus fat use during exercise. Gas-exchange testing does not directly measure protein oxidation or identify the exact origin of every fuel molecule.
More data, better decisions. “No glycogen is used in Z1.” “No fat is used in Z5.” Are you sure? Fuel use is more nuanced.
This assessment helps estimate energy and nutrient needs during training or competition.
What should you eat beforehand, afterwards or at aid stations? Which supplements, if any, are useful?
Understanding how your body uses each energy system helps plan the fuels you may need at different intensities, personalising nutrition to support performance.
For the test, we use a Cortex Metalyzer 3B to assess respiratory gas exchange. Other measurements, such as heart rate, blood lactate, glucose and blood pressure, require suitable additional devices or sampling; not all are measured directly by the gas analyser.
After warming up, the athlete completes an incremental test with stages at different intensities.
Your sports nutritionist uses these estimates alongside other information to help prepare for competition.
