Aerobic, or cardio, exercise uses oxygen to break down glycogen in your muscles for energy. The anaerobic system does not use oxygen to metabolize glycogen for energy. Aerobic fitness is generally associated with improved endurance, such as the ability to run a marathon or jog for an hour or more. Your anaerobic energy system is used primarily for short, intense physical exertion, such as lifting a heavy weight or sprinting. There are some disadvantages to sports performance when your physical exertion stimulates your muscles to use the anaerobic energy system.
Anaerobic Energy System
Weight lifting, jumping and sprinting are examples of exercise that rely on energy supplied by the anaerobic energy system. Exercise that consists of high-intensity exercise for a short period of time is anaerobic. A disadvantage of the anaerobic energy system is that energy stores are depleted quickly. Anaerobic metabolism also causes hydrogen ions to build up in the muscle tissues and lactic acid to accumulate in the blood, which causes the вЂњburnвЂќ you feel in your muscles. Because anaerobic metabolism takes place in the absence of oxygen, anaerobic glycolysis is catabolic, or destructive to muscle cells. A fully trained and conditioned athlete may be able to sustain anaerobic exercise for about one hour.
A significant disadvantage to anaerobic exercise is the accumulation of lactate in your blood and the build-up of hydrogen ions in your muscles. Once you enter the anaerobic energy system by rapid and intense exertion, the lactate is produced and then used for energy. Hydrogen ions are produced as a result of lactate metabolism, which irritates your muscle tissue. Hydrogen ions also limit muscle contractions. Hydrogen ions cause the feeling that your muscles are burning and ultimately results in muscle fatigue followed by muscle failure. If you have not conditioned your anaerobic energy system by participating in high-intensity exercise, you will reach muscle fatigue and failure rapidly, or at about 50 percent of your maximum exercise capacity.
Lactate is the waste product of anaerobic metabolism in your muscles. When you do aerobic exercise, your cardiorespiratory system can quickly remove lactate from your blood where it is used as an energy source by your muscles. As you increase the intensity of your exercise, your oxygen needs exceed your body's ability to take in oxygen and you enter the anaerobic energy system. At this point, lactate will build up rapidly in your blood. Once the levels of lactate exceed normal resting levels, you have reached your lactate threshold. You will begin to feel pain in your muscles and fatigue will follow. You can raise your lactate threshold by performing regular high-intensity interval exercise.
The anaerobic energy system provides energy for short bursts of exertion, but does not provide energy for endurance. Your anaerobic system will provide the energy necessary for short, high-intensity muscle contractions. Once you reach your lactate threshold, your muscles will not have the energy to continue. Anaerobic training can increase muscle power for short bursts, such as lifting a heavy weight or sprinting for 100 meters, but anaerobic training does not improve your endurance. Adenosine triphosphate (ATP) is synthesized in the muscles for rapid bursts of muscle contraction, but ATP is used up quickly, followed by fatigue and muscle failure. Anaerobic glycolysis can produce enough ATP for three to four minutes of sustained maximum effort or until you reach your lactate threshold and hydrogen ions inhibit muscle contraction.