One of the things that define the best endurance athletes in the world, is their ability to maintain a high amount of power, but still use fat as their primary energy source. This makes them able to go fast for a long time, but still be able to save energy for a huge power surge in the final. Another thing is their recovery from day to day.  

What makes this possible is that they have a high aerobic threshold (AeT). Most people will know the anaerobic threshold, where the build-up of lactic acid becomes too large for the body to handle, and you will begin to suffer.  

The AeT marks the place where you begin to use carbohydrates as an energy source, along with fat. This means that whenever you’re riding above your AeT, you need to keep eating to keep pushing. So, endurance athletes have a lot to gain from pushing their AeT as high as possible, as that will make you able to ride on fat for longer. 

When you are riding below the AeT, your body works completely aerobically, which means it produces energy by breaking down fatty acids using oxygen.  

How good you are using aerobic or anaerobic processes is a genetic thing, sure. But you can nudge it by how you distribute your time in different training zones.  

The best endurance athletes in the world use more than 80% of their training time below their AeT. When you work below AeT your increase your ability to transport oxygen to the muscles. You do this because you increase the number of mitochondria in addition to strengthening your capillary network, the network of your smallest blood vessels that lead blood into the muscles. 

The professional athletes also spend a lot of time just above and just below the AeT, since this is the area where you burn the biggest amount of fat. Spending a lot of time here is also how you increase your AeT, in the same way sweetspot intervals increase your anaerobic threshold.  

Even though the AeT is this important for Endurance athletes like cyclist and runners, the anaerobic threshold is still the most commonly talked of, and used threshold. No external test methods like 20 minutes FTP test, the step tests on ZWIFT and trainerroad can measure the AeT. To find your AeT you need a Vo2max, Lactate or GRASPOR threshold test to find this important threshold.  

Read our part about Threshold testing and learn more about how GRASPOR can help you define the anaerobic threshold, and your aerobic threshold (AeT) and your training zones for optimal training.