How it works
Ever wondered how much of the carbohydrates you consume during training and racing are actually used by your muscles?
With the ExoAnalytics Exogenous Carbohydrate Oxidation Test, we can now measure it directly. Grounded in science and used by some of the best endurance athletes in the world, this test allows you to know your personalised fuelling strategy.
All it takes is for you to follow our 90 minute indoor exercise test protocol.
The process
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Order
Select the week which you would like to perform the test (subject to availability)
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Test
We will send everything you need to prepare for and complete your home test. All you need is an indoor bike or treadmill
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Return
Ship your breath samples and metabolic mask back to us in the pre-paid return box
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Results
We'll analyse the samples and email your personalised fuelling report including how many grams of carbohydrate you can oxidise per hour
The Science Behind the Method: Carbon-13 Stable Isotope Testing
Curious about how we can measure how much of your sports drink or gel actually powers your muscles during endurance events? Our exogenous carbohydrate oxidation testing uses cutting-edge carbon-13 (13C) stable isotope technology—a gold standard in sports science for decades.
How does it work?
Most carbon atoms found in nature are the isotope 12C, making up about 98.9% of all carbon. In contrast, only around 1.1% of carbon exists as 13C, which has an additional neutron.
By enriching carbohydrates with 13C, we can use this rare, naturally occurring isotope as a marker and can distinguish the ingested carbs from those already present in your body. When athletes consume these labeled carbs, the 13C can be precisely detected in their breath as CO₂. This allows us to measure exactly how much of the ingested carbohydrate is being used for energy—helping you optimise fuelling strategies and maximise performance.
Science you can trust
This method isn’t new—it's been validated in published studies for decades and is widely considered the reference standard for assessing exogenous carbohydrate oxidation in both research and elite athletic practice.
