what are the mechanisms of heat loss?

1. radiation

2. convection

3. conduction

4. evaporation

what is radiation?

the exchange of electromagnetic energy waves from one object and absorbed by another

what the manhattan effect?

@ room tem and naked. 60% of heat loss will be because of radiation

what is conduction ?

when two surfaces with differing temps are indirect contact.

what are insulators?

why is heat conduction in wter 25x greater than in air?

dont conduct heat readily - air and water is an excellent insulator.

the rate of conductive heat exchange in related to the thickness of the insulating substance.

what is convection ?

what is the wind chill index?

one of the media be moving as occurs with fluid or gaseous mediums..

gives the equivalent still air temp for a particular ambient temp at differnt wind velocities

what is important in determining convective heat oss btween win and air?

temp gradient and air velocity

what is evaporation?

transfer of heat from the body surface through the change of liquid water on the skin to vapour

what are the two primary physiological response used by humans to defend agains the cold?

explain

1. increase metabolic rate: voluntary - exercise -- increases 10-20x the basal rate

involuntary -- shivering - increase basal by 3-4x

2. increase tissue insulation: vasoconstriction of peripheral blood vessels and shunting blood into deeper vessels

superficial dont constrict ; like the heat loss from the head

what are the factors that affect response to cold?

1. skinfold thickness -- the ticker the better
2. gender -- females have more fat = better insulation
3. clothing -- thickness of clothes traps heat

what is hypothermia ?

what does body core mean?

where do you lose heat the most?

body core goes below 35

body cores means brain heart lungs liver and kidneys

critical areas ; head and neck, sides of chest and groin

when will you stop shivering?

if core temp goes below 32-34

what are the factors that are associated with hypothermia?

1. immersion in cold water or wet clothes

2. wind

3. physical exhaustion

4. inadequate clothes for cold weather

5. lower % of body fat

6. hyopglycemia

7. alcohol consumption - decreases blood flow to skin

what is hypoglycemia?

no shivering

what happens during hypothermia?

oxyhemoglobing curve shifts to the left --> increase hemoglobin affinity for o2 --> less o2 to the tissues --> body tissues shift to anaerobic --> hypoxia of the har and brain plus metabolic acidosis--> depressed brain function and Q --> ventricular fibrilation and death

what happens when you get a frostbite?

it is the freezing of superficial tissues when the temp is -2 -6

many people dont know they are frostbit because sensory nerves are blocked and skin is numb

explain cold exposure and and the respiratory tract

inhaled air enters the upper respiratory passage - warmed to 37 and is saturated with water

** you cant freeze ur lungs when exercising in the cold

if the air is cold, you can cause the rp to be come dry and have irritation of the throat

what are the effectos of cold on performance?

explain them

1. cardivascular endurance -- vo2mx decreeased because hr shift to the left

look at diagram.. find it...

reduce blood flow --- more anaerobic metabolism

2. strength, power and flexibility

what decreases with strength power and flexibility in the cold?

• strength and power
• nerve condunction velocity
• reaction time
• manual dextrity
• flexibility

name those cold injuries

hypothermia

frostbite

cold exposure to respiratory tract