Glucose will be the outside sourcing when you are training.
Explanation:
The gylcogen stored in the liver is the source of energy and carbohydrate when you are starving or on strenous exercise or training.
The glucose is the most readily accepted energy form by the body as it easily travels the blood streams.
The body replenishes the glycogen stored by converting it into glucose but when the glycogen level decreases during exercise the glucose should be taken while training to prevent hypoglycemia.
