b. Breathing is the process by which air is moved into and out of the lungs. The
skeletal muscles of the rib cage and the abdominal cavity produce the various muscular
actions of breathing.
c. The interior pressures of the trunk must be increased by the muscles of the
trunk wall for two purposes:
(1) Evacuation of substances from the body.
(2) Stabilization so that the trunk can act as a base for work of the upper
d. Skeletal muscles can also produce a more or less continuous contraction to
immobilize an area of the body. This occurs around painful areas, such as inflamed
joints or fractures. This muscular response is called splinting.
5-20. EFFECTS OF EXERCISE OR THE LACK OF IT
a. Atrophy. Whether by choice or as a result of injury or illness, a skeletal
muscle may not be used. Without use, the striated muscle tissue tends to be lost. The
general process in which muscle or another type of tissue decreases is called atrophy.
Where the muscle tissue has been, there is an invasion of FCT and fat.
A = without
TROPHY = growth
b. Hypertrophy. When a muscle is exercised to capacity, the muscle responds
by increasing in mass. The increased mass results from an increase in the diameter of
the individual muscle fibers. The number of muscle fibers does not increase. This
general process is called hypertrophy.
c. Types of Exercises.
(1) Isometric. An activity in which a muscle produces tension without a
change in length is called an isometric exercise.
ISO = same
METRIC = measurement
For example, if you clasp your hands together and pull without actually moving them,
you are participating in an isometric exercise. It has been shown that isometric
exercises build muscle strength rapidly. On the other hand, the skeletomuscular system
may still lack range of motion.