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Exercise Phys > (4A, Ch25) Thermal Stress > Flashcards

(4A, Ch25) Thermal Stress Flashcards

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1
Q

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

A

E. all of the above

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2
Q

What is the main cause of heat production?

A

Through muscle contraction

(NOTE: this is directly related to workout)

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3
Q

what are the 4 ways body heat can be lost?

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

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.

A

higher; lower

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5
Q

_____ is how a person perceives heat, taking into account humidity

A

heat sensation

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6
Q

On a day with low humidity, 85 degree Fahrenheit temperature, and bright sun, what is the primary means of heat exchange from the body to the environment during aerobic exercise (e.g. an hour run)?

A. heat lost in the breath
B. muscle contractions
C. evaporation of sweat
D. radiation
E. convection

A

C. evaporation of sweat

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7
Q

Main contributors to body heat (4)

A
  • solar radiation (AKA sunlight)
  • metabolic rate
  • physical activity
  • thermic effect of food
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8
Q

aerobic training _____ sweat NaCl concentration

A

decreases

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9
Q

Compared to exercise under temperate conditions, during exercise in hot conditions, blood flow to the skin is:

A. lower
B. higher
C. about the same

A

B. higher

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10
Q

What is a limiting factor in rehydration?

A

gastric emptying rate

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11
Q

Sodium in drink when rehydrating after exercise decreases urinary output. Why?

A

retains fluid AKA improving hydration

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12
Q

If core temp is constant, total heat loss is _____

A

the same

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13
Q

If core temps increases, ______ increases

A

sweating rate

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14
Q

Evaporative heat loss is more efficient in ____ temps

A

high temps

(increases w increasing temps)

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15
Q

Core temp and swimming

A

decreases, especially in winter when water temps are lower

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16
Q

Sodium in drink when rehydrating after exercise _____ urinary output

A

decreases

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17
Q

heat acclimation increases ____

A

performance

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18
Q

Dehydration impairs _____

A

aerobic performance

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19
Q

What is the effect of the following heat acclimatization response:

Inreased sweat output

A

Maximizes evaporative cooling

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20
Q

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

A

improves performance

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21
Q

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

A

Rest: remains the same

Maximal exercise: increases

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22
Q

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

A. convection
B. evaporation
C. radiation

A

A. convection

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

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23
Q

Which is greater?

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

A

A. maximal rate of sweating

(NOTE: up to 2L can be lost)

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24
Q

Who has a higher heart rate during low workload conditions?

A

Elderly

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25
What is the effect of the following heat acclimatization response: Lower threshold to begin sweating
evaporative cooling begins earlier
26
At low temperatures, a portion of VO2 goes towards _____
shiverign
27
_____ is water produced by oxygen consumption by the electron transport chain.
Metabolic water
28
Under conditions of low humidity, evaporative heat loss is greater than dry heat loss at... A. 10 degrees C B. 37 degrees C C. evaporative heat loss is never greater than dry heat loss D. evaporative heat loss is always greater than dry heat loss
B. 37 degrees C
29
Fluid loss during exercise is between _____ L per hour
1-2
30
At what air temperature would resting energy expenditure be greatest for someone wearing shorts and a t-shirt? 0 degrees C 20 degrees C 40 degrees C air temperature doesn't affect VO2
0 degrees C
31
When does humidity impair evaporation?
When it is high
32
Which statement about water loss and fluid replacement is false? A. The thirst mechanism always underestimates fluid loss during work in the heat and after work ends. B. You should take frequent drinks throughout the work period. C. If you drink 250 milliliters (about 1 cup) every 15 minutes, you can replace 1 liter per hour. D. If, during prolonged periods of work in the heat, weight loss exceeds 2 percent, the person should rehydrate before returning to work or exercise. E. Marathon runners are wise to drink as much as possible before the event and to drink as much as possible as frequently as possible during the event.
E. Marathon runners are wise to drink as much as possible before the event and to drink as much as possible as frequently as possible during the event.
33
Compared to exercise under temperate conditions, during exercise in hot conditions, maximal aerobic work rate is A. higher B. lower C. about the same
B. lower
34
Trained subjects lose ____ salt in sweat than untrained
less
35
Clothing _____ core temperature and skin temperature
increases
36
Compared to exercise under temperate conditions, during exercise in hot conditions, blood flow to skeletal muscle is: A. lower B. higher C. about the same
A. lower
37
Sweating rates are greater when it’s ____ and ______ why?
hot; humid sweat doesn't evaporate as rapidly, imparing ooling
38
DELETE Heat production amounts to evaporative heat loss
it is greater
39
Does dehydration have an effect on exercise other than aerobic exercise?
Does not affect strength or anaerobic performance
40
Relationship between evaporative and convective cooling
Inverse; as one increases, the other decreases
41
conduction vs convection
Conduction: heat transfer directly to solids (ex: muscle to skin contact) Convection: heat transfer to air/liquid (ex: heat transported in blood)
42
Convective cooling is more efficient in _____ temps
low (decreases w increasing temps)
43
A wet bulb globe temperature is a way of measuring....
heat stress using air temp to give an indication of heat conditions beyond air temp alone.
44
Increased blood flow to skin ______ aerobic performance
decreases
45
What does sweat rate depend on? (3)
- work rate - air temp - body size
46
As core temperature increases, _____ blood flow goes to the skin compared to muscles
more
47
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
A. metabolic heat production capacity (assuming a VO2 of 4 liters/min, each liter of O2 is equivalent to 5 kcal)
48
How long does it take to get the heat acclimatization benefits?
About 2 weeks
49
Aerobic training increases RBC count in the ____
later weeks
50
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)
A. when air temperature is equal to or greater than skin temperature
51
What types of events are impaired in the heat?
aerobic events
52
The ____ the aerobic workload, the ____ the core temperature
greater; greater
53
endurance, work capacity declines if you lose _____% of body weight through fluid loss
2
54
5 benefits of heat acclimatization
1. INCREASED sweating 2. DECREASED water loss 3. DECREASED salt concentration in sweat 4. INCREASED blood volume 5. INCREASED blood distribution
55
Risk of hyperthermia ______ with heat and humidity
increases
56
Effect of wind on convective and evaporative cooling
increases both
57
Fluid replacement limits the rise in _____ and _____
core temp; and HR increases
58
As sodium content increases, there is ____ retention of fluids (optimal: 50 mmol Na)
greater
59
While resting, how much body heat is produced?
Very minimal; it increases during exercise
60
When temps are high, blood flow to the ___ increases to aid in cooling, thus decreasing blood flow to _____
skin; the muscle
61
Aerobic training increases plasma volume in the ____
first weeks
62
If the air temperature on this day were higher than skin temperature, such as on a summer day in Arizona, there _____ be convective cooling
wouldn’t
63
What is the gastric emptying rate?
250 mL every 15 mins

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