Endurance exercise training produces numerous metabolic and cardiovascular effects. Metabolic adaptations include an increase in oxidative capacity of skeletal muscle (greater number and size of mitochondria); an increase in skeletal muscle myoglobin concentration; a greater ability to oxidize fatty acids for energy; and an increase in stored glycogen. Cardiovascular effects of training include a decrease in resting heart rate and heart rate response to submaximal exercise; an increase in resting and exercise stroke volume; an increase in maximal cardiac output; an increase in VO2max; and an increase in arteriovenous oxygen difference. Aerobic exercise training contributes to cardiovascular fitness, because it beneficially alters the coronary artery disease risk profile. An inverse relationship exists between physical fitness and resting heart rate, body weight, percent body fat, serum cholesterol, triglycerides, glucose, and systolic blood pressure. In addition, exercise training increases the high-density lipoprotein fraction of total cholesterol. Endurance exercise is any activity that uses large muscle groups, can be performed continuously, and is rhythmic and aerobic in nature. To develop and maintain cardiovascular fitness, this exercise should be performed at a frequency of 3 to 5 days per week, an intensity of 60% to 90% HRmax or 50% to 85% HRmax reserve, and a duration of 20 to 60 minutes.