The Training Effect is a physical phenomenon
known to athletes. When a person exercises at a certain level
for a certain duration over a certain number of weeks, their body
will elevate its metabolism to a higher level - it will continue
at this level as long as a certain amount of exercise is performed
each couple of days. This effect was discovered by Dr. Kenneth
H. Cooper for the United States Air Force in the late 1960s. Dr.
Cooper coined the term "Training Effect" for this.
The measured effects were that muscles of respiration
were strengthened, the heart was strengthened, blood pressure
was sometimes lowered and the total amount of blood and number
of red blood cells increased, making the blood a more efficient
carrier of oxygen. VO2 Max was increased.
The exercise necessary can be accomplished by
exercise in a wide variety of schedules - Dr. Cooper
found it best to award "points" for each amount of exercise
(as laid out in the detailed tables in his classic 1968 book "Aerobics"
ISBN 0553209922, reprinted and expanded several times) and require
30 points a week to maintain the Training Effect.
As it would be foolish for someone unconditioned
to attempt 30 points in their first week, Dr. Cooper instead recommends
a "12-minute test" (the Cooper test) followed by adherence
to the appropriate starting-up schedule in his book. As always,
he recommends that a physical exam should precede any exercise
program. (A newly-recognized effect is that of Exercise hypertension,
for which there is a medical test.)