The Navy SEAL Physical Fitness Guide - Human Performance

The Navy SEAL Physical Fitness Guide 229

" Caffeine

This section will discuss only those agents which are illegal and can produce
harmful effects.

Amphetamines

One class of stimulants is the Amphetamines. The term amphetamine also includes
methylamphetamine, dimethyl-amphetamine, and benzylamphetamine which are
metabolized to amphetamine after ingestion. In the 1960's, these drugs were widely used
by athletes in the belief that they improved strength and endurance. Stimulants such as
amphetamines and many over-the-counter amphetamine “look alikes” have pronounced
effects throughout the body. Taking these agents will result in the physiologic and
psychological effects noted in Table 13-4 and Table 13-5. As can be seen, these effects are
the same ones which occur normally without stimulants when you are asked to undertake
dangerous missions.

Amphetamines can mask symptoms of fatigue. They may restore reaction time in a
weary athlete, but cannot improve reaction time or diligence in a well rested and motivated
athlete. The potential beneficial effect is most marked when performance is reduced by
fatigue or lack of sleep.

Table 13-4. Reported Physiologic Effects of

Amphetamines

Increases heart rate

Increases cardiac output

Elevates blood pressure

Increases conversion of glycogen to glucose

Elevates serum glucose

Elevates serum free fatty acids

Dilates blood vessels in muscles

Constricts blood vessels in the skin

Increases muscle cell excitability