Anaerobic exercise involves short, intense bursts that burn stored glycogen as fuel, explains Barbara Gibson of Fitness 19. During anaerobic exercise, no oxygen is present and lactic acid builds within the tissues. Once all of the glycogen is spent and lactic acid levels peak, discomfort and fatigue set in.
During aerobic exercise, a long-term effort is sustained as the body delivers oxygen to the muscles to use as fuel. Gibson compares aerobic and anaerobic exercises using the examples of marathon running versus sprinting. Marathon running is a sustained effort that requires aerobic respiration, where oxygen is delivered to the muscles over the lengthy exercise duration. Sprinting, however, requires a short, powerful burst where the body is unable to deliver oxygen quickly. Instead, the muscles use stored glycogen to fuel the quick explosions of activity. Gibson explains that anaerobic exercises help build lean muscle mass, increase endurance and train the body to burn calories more efficiently.