Lecture 17

Question 1

major drivers for heat stress in exercise

Answer 1

exercise duration and intensity

Question 2

normally the least important avenue for heat exchange in exercise is …

Answer 2

normally conduction is least important

Question 3

the most important avenue for heat exchange in exercise is

Answer 3

evaporation

Question 4

muscles can warm rapidly by how much ? during endurance and resistance exercise

Answer 4

2-3 degrees

Question 5

what happens to the force and fatigue rate of hot muscles

WHY?

Answer 5

hot muscles can produce less force

and fatigue faster

increased glycogenolysis

Question 6

what is the optimal temperature for swimming

Answer 6

around 27 degrees

Question 7

what does exercise performance in the heat depend on

Answer 7

• exercise intensity
• clothing
• body composition
• body size
• exercise mode

Question 8

what are two factors that lead to heat stress

Answer 8

exercise and environment

Question 9

why does thermoregulation reduce exercise capacity

Answer 9

because you are having to thermoregulate and having to serve the metabolism of exercise

Question 10

is thermoregulatory power finite

Answer 10

yes, it is limited by other effects of exercise on the body

Question 11

when is heat stroke more likely to be fatal

Answer 11

when you were exercising

Question 12

what temperature is the peak skin blood flow and sweat rate

Answer 12

38 degrees

Question 13

temperature tolerance limit for moderately trained

Answer 13

39 degrees

Question 14

temperature tolerance limit for many athletes, where increased cell permeabilities occurs

Answer 14

40 degrees

Question 15

what temperature are some athletes able to tolerate

Answer 15

42 degrees

Question 16

if no heat was dissipated what would the core temperature rise by in the body on active day

Answer 16

around 100 degrees

Question 17

what is the main way our bodies gain heat

Answer 17

metabolism

Question 18

other ways that our bodies gain heat

Answer 18

• radiation
• convection
• conduction

Question 19

methods of heat loss

Answer 19

• evaporation (skin and respiratory)
• radiation
• convection
• conduction

Question 20

what is heat production directly related to (equation)

Answer 20

work rate

heat production = metabolic rate - work rate

Question 21

what does the capacity of environment to absorb heat depend on (5)

Answer 21

• water vapour pressure (absolute humidity)
• radiant temperature
• air movement (relative to the skin surface)
• resistance to heat transfer (clothing, posture)
• ambient temperature (dry bulb)

Question 22

what is the most common way to represent the environmental effect in sport

Answer 22

Wet Bulb Globe Temperature (WBGT)

Question 23

why are hot or humid environments stressful

Answer 23

harder to offload heat, especially if low evaporative capacity

Question 24

what is the big picture of the physiological demands of exercise (where does blood flow need to be increased and what needs to be maintained)

Answer 24

• need increased muscle blood flow
• also need increase skin blood flow and sweating
• maintain arterial pressure
• adequate blood supply to other tissues

Question 25

why does a warmer periphery occur in exercise in the heat

Answer 25

• increased skin blood flow and sweating
• increased blood osmolarity

Question 26

why does blood osmolarity increase during exercise in the heat

Answer 26

because you sweat which causes loss of body water, so concentration of solutes in the blood increases

Question 27

why is there a reduction in central blood volume during exercise in the heat

Answer 27

because there is a greater accumulation in the periphery

Question 28

what happens to heart rate and stroke volume when exercising in the heat, to maintain cardiac output and mean arterial pressure

Answer 28

increased heart rate and decreased stroke volume

Question 29

what happens to the amount of stress hormones when exercising in the heat

Answer 29

increase = have to activate the sympathetic nervous system more

Question 30

what does offloading heat effectively require

Answer 30

requires evaporating water (sweat) off skin

Question 31

what does dehydration cause in terms of heat loss and exercise tolerance

Answer 31

decreases both heat loss and exercise tolerance

Question 32

what is evaporation for heat loss governed by and why

Answer 32

absolute humidity

• harder for sweat to evaporate from skin when the air surrounding is moist