"A person who maintains aerobic fitness may delay biological aging by up to 12 years, a new analysis shows. Jogging and other types of aerobic exercise improve the body's oxygen consumption and its use in generating energy (metabolism). However, a steady decline in maximal aerobic power begins in middle age, decreasing about 5 ml/ (kg. min) every decade, according to the information in the analysis. When maximal aerobic power falls below about 18 ml in men and 15 ml in women, it becomes difficult to do any activity without experiencing major fatigue. A typical 60-year-old sedentary man has a maximal aerobic power of about 25 ml, nearly half of what it was at age 20. But research shows that a long period of relatively high-intensity aerobic exercise can increase maximal aerobic power by 25 percent (about 6 ml), which equals 10 to 12 biological years."