During intense exercise, your body enters the anaerobic zone when your heart rate increases and the oxygen demands of your muscles exceed your ability to consume oxygen. When this happens, your body adapts by producing energy anaerobically. Since oxygen is the main driving force of every biological process in your body, you can't sustain anaerobic exercise for long periods of time, but you can get significant benefits from short-burst anaerobic training.
Some of the factors that can influence how long you can sustain a continuous period of anaerobic exercise include age, body composition and your level of conditioning. Typically, the average person is only capable of working anaerobically for one to three minutes at a time. Pushing yourself past this zone can maximize damage to muscle tissue and minimize positive effects from your workout.
When your body's need for oxygen exceeds its ability to supply it, you're pushed into the anaerobic zone by way of an oxygen deficit. To compensate, your muscles break down glycogen stores to produce immediate contractions. The more intense your exercise and the longer you keep up a continuous round of anaerobic training without rest, the more anaerobic contractions you'll create.
Just because your body adapts to anaerobic training by producing energy through a different process doesn't mean you can keep it up for long. A byproduct of the breakdown of glycogen stores is the buildup of lactic acid, which slows your muscles down and causes a burning sensation as you work. This is a defense mechanism for your body designed to prevent extreme exertion due to repeated muscle contractions.
You may wonder why you should bother with anaerobic training if you can only sustain it for one to three minutes at a time. Interval training represents an ideal way to get the most out of high-intensity workouts. By alternating between periods of high and low intensity, you can get repeated benefits from anaerobic training without being overcome with an oxygen deficit, since you recover between rounds. In addition to increasing your tolerance of lactic acid during exercise, interval training burns a significant number of calories and allows you to get results in a shorter period of time.
- Scientific American: Why Does Lactic Acid Build Up in Muscles? And Why Does it Cause Soreness?
- The Japanese Journal of Clinical Pathology: Analysis of Factors Affecting Anaerobic Threshold in Healthy Subjects
- San Diego State University: Oxygen Consumption (V02)
- American Council on Exercise: Fit Facts -- Interval Training
- University of New Mexico: Lactate Threshold Training
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