People who engage in even moderate exercise live longer than those who do not. The body's muscle cells and tissues respond to lack of exercise by atrophy Aerobic activity and the heart 381 Aerobic exercise is sustained vigorous activity. Such exercise increases blood volume and number of red blood cells. Such exercise builds lean tissue, and improves body composition. While resting, Fats provide about half the body's needed energy, Carbohydrates provide most of the remainder.
Amino acids contribute a few percent.
At the beginning of exercise, Glucose alone is mobilized for the extra energy burst. Then as activity continues, fats and other stored carbohydrates begin to be available to the muscles from the blood. Glucose as fuel for activity 382 Liver and muscle store glucose as glycogen. Liver also makes glucose. Liver glycogen is circulated.