Fitness. Its Meaning and Significance
|"Aerobic fitness" refers
to endurance, or the ability to sustain work for prolonged periods.
This is usually experienced in the abilities to walk, run, climb uphill,
swim, etc. Most forms of sports, work, recreational and military activities
include elements of aerobic fitness. Generally speaking, any activity
which lasts less than 12 minutes is not fully aerobic. The term "aerobic"
implies that the oxygen necessary to accomplish the work is taken
up by the individual during the activity. Strenuous exercise lasting
less than 12 minutes includes substantial portions of
||anaerobic metabolism whereby
one uses energy sources stored in the body to perform the work. Since
the body's energy sources are limited, anaerobic work cannot last
long. Fast runs, lasting 10 to 15 seconds, are mostly accomplished
by anaerobic metabolism. With longer exercise time, more aerobic metabolism
is involved, and exercise lasting more than 12 minutes is mostly accomplished
by aerobic metabolism. Work is performed by the muscles which use
oxygen for the combustion of fat and carbohydrates creating the energy
necessary to move the body, or to move objects outside the body.
|In aerobic work, oxygen
is obtained from the air and is transferred from the lungs to the
blood and then to the muscles via the circulatory system. Maximal
oxygen uptake, or maximal aerobic power ( Vo2
max ) is the indicator of aerobic fitness. Vo2
max is determined by the measurement of oxygen uptake during the performance
of maximal work, typically while running on a treadmill or while cycling.
This is done by exercising for at least 12-minutes at submaximal loads,
after which the maximal effort is performed for one or two minutes.
Oxygen uptake during this time is measured, giving the value of Vo2
max. As Vo2 max increases, the level
of aerobic fitness also increases.
|| Aerobic fitness is dependent
upon age and sex and it can be improved by training. It is highest
at ages 18, 19 years in males and 15 to 20 years in females, and it
decreases with age in adulthood. In general, males have higher Vo2
max than females. The main reason for this is that aerobic fitness
is directly related to fat-free body weight, which consists mainly
of the weight of muscles in the body, and on the average, males have
a higher muscle mass than females. As with other physiological functions,
there are large individual differences in Vo2
max of people of the same sex and age. Some people show high Vo2
max without exercising because of genetic and other factors, while
other people who exercise regularly do not show high Vo2