A large polysaccharide similar to amylopectin, the difference being it is more highly branched. GLycogen is the main storage form of carbohydrates in humans and other animals. Glycogen is stored in the liver and muscles. After a high carbohydrate meal, the muscles can increase 1-2% in size as a result of accomodating glycogen stores. Glycogen is a very efficient means of storing carbohydrates because of its construction. Glycogen is made from repeatig linked glucose residues in a linear pattern, with branch points for more glucose, giving the structure a somewhat "tree-branch" like appearance.