PHYSIOLOGY OF AEROBIC
Aerobic exercise uses oxygen to produce most of the body's
energy needs. It also brings into play a fairly complex set of
To provide enough energy-producing oxygen to the muscles, the following events occur:
- Greater movement of air through the lungs.
- Increased movement of oxygen from the lungs into the blood stream.
- Increased delivery of oxygen-laden blood to the working muscles by the heart's accelerated pumping action.
- Regulation of the blood vessel's size to distribute blood away from inactive tissue to working muscle.
- Greater movement of oxygen from the blood into the muscle tissue.
- Accelerated return of veinous blood to the heart.
Correctly performed aerobic exercise, over time, causes positive
changes in the body's CR system. These changes allow the heart
and vascular systems to deliver more oxygen-rich blood to the
working muscles during exercise. Also, those muscles regularly
used during aerobic exercise undergo positive changes. By using
more oxygen, these changes let the muscles make and use more energy
during exercise and, as a result, the muscles can work longer
During maximum aerobic exercise, the trained person has an
increased maximum oxygen consumption (O2max). He is better able
to process oxygen and fuel and can therefore provide more energy
to the working muscles.
O2max, also called aerobic capacity, is the most widely accepted
single indicator of one's CR fitness level.
The best way to determine aerobic capacity is to measure it
in the laboratory. It is much easier, however, to estimate maximum
oxygen uptake by using other methods.
Aerobic exercise is the best types of activity for attaining and maintaining a low percentage of body fat.
In the presence of oxygen, muscle cells produce energy by
breaking down carbohydrates and fats. In fact, fats are only used
as an energy source when oxygen is present. Hence,
aerobic exercise is the best type of activity for attaining and
maintaining a low percentage of body fat.
A person's maximum aerobic capacity can be modified through
physical training. To reach very high levels of aerobic fitness,
one must train hard. The best way to improve CR fitness is to
participate regularly in a demanding aerobic exercise program.
Many factors can negatively affect one's ability to perform well aerobically. These include the following:
- Carbon monoxide from tobacco smoke or pollution.
- High altitude (reduced oxygen pressure).
- Illness (heart disease).
- Sedentary life-style.
Any condition that reduces the body's ability to bring in,
transport, or use oxygen reduces a person's ability to perform
aerobically. Inactivity causes much of the decrease in physical
fitness that occurs with increasing age. Some of this decrease
in aerobic fitness can be slowed by taking part in a regular exercise
Certain medical conditions also impair the transport of oxygen.
They include diseases of the lungs, which interfere with breathing,
and disabling heart conditions. Another is severe blocking of
the arteries which inhibits blood flow to the heart and skeletal
Smoking can lead to any or all of the above problems and can,
in the long and short term, adversely affect one's ability to
do aerobic exercise.