Liver glycogen is a major source of carbohydrates for your muscles to burn when you’re running. The glycogen molecule is just a big long chain of glucose molecules which is optimized for long-term storage.
When your body needs carbs during a run during a run, your liver can break down glycogen into glucose, shuttle it into the bloodstream, and send it to your active muscles to be burned for energy.
Stored glycogen in your liver is particularly important for running the marathon and ultra distance races, since the glycogen that's locally in your muscles isn’t sufficient to get you to the finish line. But exactly how much glycogen do you store in your liver? And can training increase this amount?