above the surface while his lungs are fully inflated. (Fig. 2)

Floating and swimming also depend upon proper breathing. Due to
the energy output while in the water, more oxygen is needed by the
recruit during water activity than when he is out of the water. During
relative inactivity the volume of air which is exhaled or inhaled has
been approximated at 29 to 30 cubic inches. Obviously, when there is
an increase of physical exertion and, a greater. energy output, the ex-
change of oxygen in the lungs and blood stream must be carried on at a
faster rate and in a great quantity. For this reason, and also the fact
that water often blocks the nasal passage, mouth breathing is prescribed
for swimmers. Through mouth breathing while swimming the oxygen intake
can be increased from 25 to 30 cubic ee to about 200 to 225..cubic
inches. This will be sufficient to take care of the increased physical
activity, and to help maintain buoyancy. (Fig. 3)

The air is inhaled through the mouth and retained for about two
seconds. (Fig. 5) After the complete inhalation a full expiration should
follow. (Fig. 6) Inertia will maintain body buoyancy during the time
between this expiration and the next inhalation. Inertia is a physical
law that states that a tendency of a body at rest will be to remain at
rest, Or i7 in motion, to remain in motion. Therefore, if the recruit
is floating (at rest) and exhales, some lapse of time and considerable
force is required to start him sinking. However, by quickly inhaling,
he will eliminate the time element and, remain above the surface because
of the fresh supply of oxygen.

Besides maintaining buoyancy this oxygen intake is necessary to

help overcome the fatigue products which accumulate in the body. it

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