How Does Aerobic Exercise Work?

Aerobic exercise is any activity that uses your major muscle groups and raises your heart and respiration rates for an extended period--usually 20 minutes, or more.
The exercise is not so taxing that your body's need for oxygen exceeds what is supplied by your lungs and circulatory system, as in anaerobic exercise.
Jogging is an example of aerobic exercise, while sprinting--an anaerobic activity--is not. Done regularly, aerobic exercise improves the body's ability to use oxygen and increases the efficiency of the cardiovascular system. The heart becomes stronger, lung function is optimized, your whole body becomes more toned and muscles use oxygen and energy more efficiently.
As a result of these physiological phenomena, aerobic capacity and endurance increase. Along the way, calories are burned and mood elevating benefits are reaped.

The Heart Becomes Stronger and More Efficient

When you exercise aerobically three to five times a week, causing your heart rate to reach and sustain a calculated target rate, your heart responds to the demand by becoming bigger and stronger. The heart is then able to pump more blood with each contraction. As a result, the heart can move blood through your body with fewer contractions and your resting heart rate is reduced. Also, the rest of the muscles of your body receive oxygen more quickly.

Lungs Function is Optimized

While aerobic exercise has not been shown to appreciably affect lung capacity, it does strengthen breathing muscles and help mitigate chronic lung problems.
Conditions such as asthma and emphysema respond well to regular aerobic exercise at an appropriate level.
Also, lung damage from air pollution also seems to be reduced somewhat by regular aerobic activity. As a result, the body is better able to make maximum use of the oxygen the lungs take in.

The Circulatory System Expands

The number of red blood cells that deliver oxygen from the lungs to your muscles increases with regular aerobic exercise. Also, as neovascularization of the muscles occurs, additional microvascular pathways grow within the muscles to bring more red blood cells to the muscle tissue. This means more oxygen is available for use by your muscles and they can perform at an aerobic level longer.

Muscles Use Energy More Efficiently

Muscle cells store energy in the form of glycogen, a complex sugar molecule made up of many glucose molecules, which are a simple sugar. However, the muscle cannot use glycogen in its complex form; the glycogen must be broken down into single glucose units. In both aerobic and anaerobic exercise, glycogen combines with oxygen from the red blood cells and is broken down. In aerobic exercise the process is much more efficient because more oxygen is available. Consequently, the muscle can perform longer and will eventually burn fat for energy, once glucose stores are depleted.

Muscles Become Bigger and Stronger

As muscles are repeatedly stressed by exercise they become larger. Eventually a leaner body results from increased muscle mass along and increased use of body fat for energy. Developing more lean muscle tissue increases metabolism and weight loss.

Calories are Burned and Endorphins Elevate Mood

The fat calories burned during aerobic activity add up quickly, which is why aerobic exercise is a staple of weight-loss regimens. Endorphins, the body's natural pain killers, are released when you get a good aerobic work out, giving you an increased sense of well-being

Resources

• Starting an Exercise Program
• Mayo Clinic: Target Heart Rate Calculator
• New York Times: Exercise's Effects on the Lungs