(4A, Ch25) Thermal Stress

Question 1

Which is greater?

A. metabolic heat production capacity (assuming a VO2 of 4 liters/min, each liter of O2 is equivalent to 5 kcal)

B. capacity for evaporative cooling (assuming maximal sweat rate of 30 ml/min, complete evaporation of the sweat, and a heat loss of 0.6 ml/ml of sweat that’s evaporated)

C. they’re the same, that’s why core temperature never changes

Answer 1

A. metabolic heat production capacity (assuming a VO2 of 4 liters/min, each liter of O2 is equivalent to 5 kcal)

Question 2

At low air temperatures (e.g. 40 degrees Fahrenheit), which is most important to body heat loss?

A. convection
B. evaporation
C. radiation

Answer 2

A. convection

(NOTE: not much sun–not much radiation; not hot out so not much evaporation)

Question 3

Convective cooling is least effective….

A. when air temperature is equal to or greater than skin temperature

B. when swimming in water cooler than body temperature

C. when it’s windy

D. when the air temperature is low (e.g. 40-50 degrees Fahrenheit)

Answer 3

A. when air temperature is equal to or greater than skin temperature

Question 4

Rise in core temperature during exercise is dependent on…

A. whether or not a person is wearing heavy uniform, pads, and helmet
B. whether or not it’s sunny
C. work intensity
D. whether or not it’s humid
E. all of the above

Answer 4

E. all of the above

Question 5

What does sweat rate depend on? (3)

Answer 5

• work rate
• air temp
• body size

Question 6

What does fluid replacement do in aerobic events under hot conditions?

Answer 6

improves performance

Question 7

During aerobic exercise under hot conditions, blood flow to the skin is ________ than under temperate conditions, so blood flow to skeletal muscle is _________ than under temperate conditions.

Answer 7

higher; lower

Question 8

Which is greater?

A. maximal rate of sweating
B. maximal rate of rehydration
C. they’re always the same

Answer 8

A. maximal rate of sweating

(NOTE: up to 2L can be lost)

Question 9

Heat production amounts to evaporative heat loss

Answer 9

it is greater

Question 10

When does humidity impair evaporation?

Answer 10

When it is high

Question 11

What happens to the core temperature at rest? At maximal exercise?

Answer 11

Rest: remains the same

Maximal exercise: increases

Question 12

While resting, how much body heat is produced?

Answer 12

Very minimal; it increases during exercise

Question 13

what are the 4 ways body heat can be lost?

Answer 13

1. radiation
2. conduction
3. convection
4. evaporation

Question 14

conduction vs convection

Answer 14

Conduction: heat transfer directly to solids

Convection: heat transfer to air/liquid

Question 15

Main contributors to body hear (4)

Answer 15

• solar radiation (AKA sunlight)
• metabolic rate
• physical activity
• thermic effect of food