What Is Aerobic and Anaerobic Exercise

The body uses two different systems to supply energy to muscles:

– Aerobic system: Carbohydrates and fat are used with oxygen and metabolized to carbon dioxide and water.
– Anaerobic system: Carbohydrates are used for energy production without oxygen and metabolized to lactic acid.

At lower training intensities, your muscles' use of oxygen matches your oxygen intake. This kind of activity can be sustained for long periods of time. At high intensities, however, your heart and lungs cannot supply enough oxygen to keep up with the demands of your muscles. As a result, your muscles begin to work anaerobically.

The problem with anaerobic energy production is that after a few seconds, waste products like lactate rapidly build up. Lactate blocks fat metabolism and forces the body to stop the exercise. The metabolic turning point at which the body shifts from the aerobic to the anaerobic energy system is called the anaerobic threshold (AT).

Your Anaerobic Threshold (AT) is the exercise intensity at which you begin to go anaerobic and build up lactate. If you want to improve your performance, it's useful to train for short periods (three to five minutes) at a heart rate just below your AT in order to raise it.

If you're out of shape, your AT might be at 70-80% or less of your maximum heart rate. However, if your training progresses intensively, your AT will increase, so that in very fit competitive athletes it might be at 90% of their maximum heart rate.

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