Exercise Physiology
Two kinds
of exercise are recognized : isotonic and isometric.
Isotonic
exercise involves moving a muscle through a long
distance against low resistance, as in
running, swimming, or gymnastics.
In isometric
exercise, on the other hand, muscles are moved
through a short distance against a high
resistance, as in pushing or pulling an
immovable object.
Isometric
exercise is best for developing large muscles, whereas
isotonic exercise has beneficial effects on the
cardiovascular system. It increases the amount of blood
that the heart can pump and causes proliferation of small
blood vessels that carry oxygen to the muscles. These
changes make possible longer sustained activity. Neither
kind of exercise increases the number of muscle fibers,
but both types—and especially isometric exercise—increase
the thickness of the muscle fibers and their ability to
store glycogen, the fuel for muscular activity.
 
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