(a) In muscle: Glycogen breakdown supplies energy (ATP) via glycolysis.
Glycogen phosphorylase catalyzes the conversion of stored glycogen to glucose 1-phosphate, which is converted to glucose 6-phosphate, an intermediate in glycolysis.
During strenuous activity, skeletal muscle requires large quantities of glucose 6-phosphate.
In the liver: Glycogen breakdown maintains a steady level of blood glucose between meals (glucose 6-phosphate is converted to free glucose)