<span>Aerobic exercise is sometimes known as "cardio" -- exercise that requires pumping of oxygenated blood by the heart to deliver oxygen to working muscles. </span><span>Examples of aerobic exercises include cardio machines, spinning, </span>running<span>, </span>swimming<span>, </span>walking, hiking, aerobics classes, dancing, cross country skiing, and kickboxing. Anaerobic ("without oxygen") exercise is the type where you get out of breath in just a few moments, like when you lift weights for improving strength, when you sprint, or when you climb a long flight of stairs. BUT, <span>Aerobic exercises can become anaerobic exercises if performed at a level of intensity that is too high.</span>