the oxygen intake is sufficient to meet the output of energy, a "steady
state" of muscular functioning will be reached..* This means that a
swimmer who keeps the flow of oxygen consistently replenished can
endure great swimming effort. The recruits should be given drills
and breathing exercises both on land and in the water. Deep breathing
exercises out of water to develop facility for large intake of oxygen
are especially recommended. ‘The breathing exercises should be practiced
daily.

The above mentioned law of inertia depends on force and time. In
other words, a body at rest will tend to remain at rest. apeecs: if
a great deal of force is applied to that body its state of rest will
be changed. Let us examine this in relation to water activity. If
we throw a block of wood in the water, it will bob up and down until
it stabilizes. In order to change this position of stability some
force must be applied to the block in order to push it below the sur-

face of the water. If, however, we place the block of wood carefully

in the water to the proper depth, it will not bob up and down.

*Physiologically it is impossible for a muscle to function without
oxygen. Experimentation on fatigue has clearly demonstrated the
importance of oxygen to man during strenuous, active work. In labora-
tory experiments a muscle electrically stimulated by a succession of
shocks to simulate work, was at the same time deprived of an adequate ©
supply of oxygen. The muscle soon lost its ability to work and ceased
functioning. Another muscle similiarly stimulated, but with oxygen ad-
equately supplied weakened at first and finally reached a "steady state".
In this "steady state" the muscle breakdown was balanced by the muscle
recovery. In other words the oxygen-supplied muscle was not fatigued as
in the case of the non-oxygen supplied muscle, but endured even through
strenuous work.

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