Sustained aerobic activity also increases the metabolism, the rate at which the body converts fuel to energy, so that more calories are used even while the body is resting. Muscle tissue, especially well toned muscle tissue, uses up far more calories than other kinds of tissue. Thus, it is may also be helpful to build or tone some muscle as a part of a weight control and fitness program. Depending on the body's current state, the muscle may develop naturally from aerobic exercise, or may be enhanced by a body building program. Fatty acids and amino acids require large amounts of oxygen to burn and produce energy, while glucose needs only a small amount.
Aerobic exercise is exercise in which the muscles use large amounts of oxygen supplied by the lungs.
For many people, the calculation for maximum target heart rate is 220 minus their age. The gold standard of fitness is called VO2-max. This is the body's ability to transport oxygen from the lungs through the bloodstream and to utilize oxygen to convert calories to energy. Anaerobic exercise is exercise in which little oxygen is utilized in the muscles to burn calories. The primary source of calories for anaerobic exercise is glucose.