Elite endurance athletes have the ability to consume large amounts of fat at high intensities while also efficiently burning large amounts of carbohydrates. This capability is created through the training they do.
Simply put, endurance performance relies on our ability to convert fuel to energy. Our muscles have two fuel sources: fat and carbohydrate. We break these fuel sources down to create the energy that propels us forward. At low intensities, fat is the preferred fuel source. It is 3-4x more efficient than carbohydrates, and every person stores 1 weeks worth of ready to use fat. Fat is efficient and abundant!
As intensity increases, using fat to meet our energy demands is compromised. We must switch to using carbohydrates, a less efficient and scarcer fuel source in order to meet our energy demands. Training our muscles to efficiently consume carbs is fundamental to endurance performance.

The key to becoming a better endurance athlete is maximizing the ability to consume all of our available fuel resources as efficiently as possible. The guide below lays out the framework by which you can accomplish this in your training!