Heat And Performance

Question 1

What does heat stress impair?

Answer 1

Endurance

Aerobic

Question 2

What has been shown to be associated with heat stress and hyperthermia?

Answer 2

Reduction in time to exhaustion during constant work rate exercise

Progressive decrease in work rate during self-paced exercise (i.e., time trial)

Reduced maximal aerobic power (i.e., VO2max)

Note: associated with rise in mean body temperature, rather than the ambient conditions per se.

Question 3

What is reached at a lower work rate when exercising under heat stress conditions compared to cool conditions?

Answer 3

HRmax

HRmax is reached at a lower work rate as compared to cool conditions

Question 4

What leads to a decrease in maximal cardiac output when exercising under heat stress conditions?

Answer 4

Lower stroke volume

Coupled with a lower stroke volume, leads to decrease in maximal cardiac output

Question 5

What is forced to a functional limit when exercising under heat stress conditions?

Answer 5

Cardiovascular system

Thus, forcing the cardiovascular system to a functional limit

Question 6

What are the effects of prolonged exercise in the heat on skeletal muscle?

Answer 6

Increases muscle glycogen utilization and anaerobic metabolism, causing greater accumulation of ammonia and muscle lactate.

Though not all studies support this assertion.

Question 7

Summary: Physiological demands of Exercise in the he

Answer 7

Need 1 muscle blood flow
Then need 1 skin blood flow
Offload heat to prevent hyperthermia
But, also need to maintain: arterial pressure, adequate blood supply to other tissues (especially CNS)
Heat stress makes it more difficult to meet these multiple demands!

OneDrive
Searen

Question 8

Exercising heat stress maximizes conflict between

Answer 8

body’s homeostatic requirements & mechanisms

Question 9

Order of priority for regulation during exercise 1

Answer 9

Blood Pressure

Effects may limit sustainable power

Question 10

Order of priority for regulation during exercise 2

Answer 10

Metabolism (perfusing active muscle)

Not usually observed to be the limiting performance factor in heat

Question 11

Order of priority for regulation during exercise 3

Answer 11

Body Temperature

Consequences can prove fatal

Contributes to ex. intolerance.

Motivation - risk for heat injury

Question 12

Possible heat-related mechanisms contributing to sprint improvements

Answer 12

• Faster rate of PCr utilisation
• Greater ATP turnover and adenine nucleotide degradation
• Accelerated muscle fibre conduction velocity

15-81-910

Question 13

Effect of core temperature on repeat sprint performance in hot environments

Answer 13

Repeat sprint performance improves in hot environments as long as core temperature is lower than 38.5 ° C

Elevated body core temperature impairs repeat sprint performance

Question 14

Impairment of central nervous system functioning due to heat stress

Answer 14

Heat-related reductions in CO and O2 delivery to exercising muscle

5

Question 15

What does heat acclimation do to total body water?

Answer 15

Heat acclimation increases total body water.

Question 16

What is the result of heat acclimation on plasma volume?

Answer 16

Rapid increase in plasma volume expansion.

Question 17

What happens to fluid regulatory hormones & proteins during heat acclimation?

Answer 17

Increase secretion or renal sensitivity to fluid regulatory hormones & proteins (aldosterone, vasopressin, albumin).

Question 18

How does heat acclimation affect renal retention of water and electrolytes?

Answer 18

Increasing renal retention of water and electrolytes.

Question 19

What effect does heat acclimation have on the intravascular space?

Answer 19

Changing the oncotic pressure and drawing fluid into the intravascular space.

Question 20

What does heat acclimation increase?

Answer 20

Total body water

Heat acclimation increases total body water

Question 21

What leads to a rapid increase in plasma volume expansion?

Answer 21

Increase secretion or renal sensitivity to fluid regulatory hormones & proteins (aldosterone, vasopressin, albumin)

Rapid increase in plasma volume expansion

Question 22

What does increasing renal retention of water and electrolytes result in?

Answer 22

Changing the oncotic pressure and drawing fluid into the intravascular space

Increasing renal retention of water and electrolytes

Question 23

Heat adaptation of metabolism may alter substrate metabolism via:

Answer 23

glycogen sparing

Question 24

Heat adaptation of metabolism may alter substrate metabolism via:

Answer 24

Increasing lactate threshold

Question 25

Heat adaptation of metabolism may alter substrate metabolism via:

Answer 25

Reduce lactate concentrations during exercise

Question 26

Heat adaptation of metabolism may alter substrate metabolism via:

Answer 26

Improved economy

39