Chapter 5: Physiology and Fitness
- Demonstrate an awareness of and need for identifying
your personal limitations and strengths as a member of a search crew. (p.
- Describe how, in each of the following processes, the
human body loses heat:
- Radiation (p. 47)
- Conduction (p. 47)
- Convection (p. 48)
- Evaporation (p. 48)
- Respiration (p. 49)
- Describe the heat production and heat loss balance
equation of the human body. (p. 46)
- Describe the basic water and chemical needs of the
human body. (p. 45-46)
- List the average daily food and water requirements of
the human body in average, cold, and hot environments. (p. 44-46)
PowerPoint slides, Chapter 5
Selected Nutrition References
Liters-to-gallons conversion chart
II. Teaching Points
A. Food and nutrition (p. 44)
- It takes several hours for most foods to become
available to the body as energy:
“What you eat today is what you run on tomorrow.”
- Moral of the story: Eat well today in case you are
called out tomorrow.
- Humans in arctic or cold environments consume (burn)
more calories than those in warm climates¾perhaps
as much as 2,000 extra calories per day.
- This makes long-lasting, high-energy foods a more
critical factor in cold weather than other climates.
- Food should be eaten only when there is enough water
to drink. Do not eat if water is
B. Water and hydration (p. 45)
- The human body may be able to survive for as long as
a month without food but only for a matter of days without water.
- Two thirds of one’s body weight is water.
- Two thirds of this water is inside body cells and
the other one third is in the veins, body cavities, and other spaces.
- No other nutrient affects athletic or work
performance more than water.
- Decreases in normal levels:
- 1% decrease in normal levels triggers thirst.
- 10% drop impairs thinking and judgment.
- 20% loss is usually fatal.
- Water requirements:
- An inactive person requires a minimum of 1.2 liters
of water a day to keep all body systems functioning properly.
- Small levels of activity (walking, normal daily
actions) can easily double this requirement (2.4 liters).
- High humidity can again double the requirement (4.8
liters), as can physical exertion.
- It is not unusual to require 8 to 10 liters of
water per day under extreme conditions. Physical exertion under hot
desert conditions can cause the loss of 2 to 3 liters of water per hour
- To re-hydrate properly, drink water slowly until the
urine is a pale yellow color.
(Deep amber urine signifies dehydration whereas pale yellow
signifies adequate hydration).
- Sports drinks such as Gatorade® or an
equivalent can be used for re-hydration as well and will also help replace
electrolytes lost through sweating.
C. The heat balance equation (p.
- To maintain a normal body temperature one must:
- Control heat production¾proper
health and nutrition
- Control heat loss¾proper
- The body’s primary method of regulating temperature
involves adjusting the flow of heated blood between its core and
- Generally blood is pushed to the skin and extremities
for cooling and shunted to the core (brain, heart, lungs) to preserve
- The body produces heat:
- Through metabolism; and
- Through muscle movement; and
- May absorb heat from its environment
- To increase body temperature, isometric exercises and
the act of shivering are preferred over strenuous muscular activity
because they produce less perspiration.
D. Methods of heat transfer¾Loss
of heat to the environment. (p. 47)
- When heat escapes from bare skin or reaches the
outer layer of clothing
- The higher the temperature of the radiating
surface, the faster heat will be lost through this method.
- When heat is transferred from hot objects to cold
- The greater the temperature difference between the
two objects, the faster heat is conducted.
- As free moving air next to the body absorbs heat,
it expands and rises.
Immediately, new cooler air moves in and replaces this moving war
air. This is natural convection.
- To prevent convective heat loss, get out of the
- The majority of evaporative heat loss occurs
- Even without sweating, it is estimated
that one and one half (1½)pints of a
person’s daily water loss is due to “insensible perspiration” or the continuous,
imperceptible drying out of the skin.
- Respiratory heat loss is actually a form of
- In most cold circumstances, this manner of heat
loss is considered insignificant.
- In an extremely cold environment where any calorie
loss is important, the addition of a re-breather (scarf or improvised
thickness of material) that will preheat the inhaled air can
significantly reduce respiratory heat loss.
E. Admitting limitations (p. 55)
- You must make a realistic assessment of your physical
abilities without being nostalgic and recalling earlier athletic
- Knowing when to stay out of the field is a prime
example of when your brain becomes your primary survival tool.
- Admitting your physical limitations is preferred to finding
out about your lack of conditioning after a futile and dangerous attempt
at working in the field.
- When search and rescue personnel become disabled,
injured, or ill, focus is drawn away from the victim.
- It can also endanger fellow crew members.