As indicated in the text, the word aerobic means "with oxygen." Most daily activities are aerobic activities, which means oxygen is used by your muscles to produce energy for movement. But we also engage in short bursts of activity that are performed without oxygen; these are called anaerobic activities. The word anaerobic means "without 
oxygen." So, anaerobic activities refer to
explosive movements that require our muscles to produce energy without using oxygen. Some examples include the 100-yard dash, a shift in ice hockey, or sprinting to get to first base. Anaerobic activities can’t be continued for very long because your muscles have a limited amount of stored energy. Once you have finished anaerobic activity, your body will work aerobically to replace the lost energy.
Try this activity:
Using a safe surface in a place appropriate for running, sprint as fast as you can for 5 to 10 seconds. When you have finished the sprint, stop and tune in to your body. What is happening? The muscles of your body had to produce energy anaerobically (without oxygen), and now your body is working hard aerobically to replace that energy. You should be breathing harder and your heart rate should be higher than normal. This is your body working hard to move oxygenated blood to your muscles to help you to replace the energy you used during the anaerobic activity.
